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20.5: Circulatory Pathways

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    765
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    Learning Objectives

    • Identify the vessels through which blood travels within the pulmonary circuit, beginning from the right ventricle of the heart and ending at the left atrium
    • Create a flow chart showing the major systemic arteries through which blood travels from the aorta and its major branches, to the most significant arteries feeding into the right and left upper and lower limbs
    • Create a flow chart showing the major systemic veins through which blood travels from the feet to the right atrium of the heart

    Virtually every cell, tissue, organ, and system in the body is impacted by the circulatory system. This includes the generalized and more specialized functions of transport of materials, capillary exchange, maintaining health by transporting white blood cells and various immunoglobulins (antibodies), hemostasis, regulation of body temperature, and helping to maintain acid-base balance. In addition to these shared functions, many systems enjoy a unique relationship with the circulatory system. Figure \(\PageIndex{1}\) summarizes these relationships.

    As you learn about the vessels of the systemic and pulmonary circuits, notice that many arteries and veins share the same names, parallel one another throughout the body, and are very similar on the right and left sides of the body. These pairs of vessels will be traced through only one side of the body. Where differences occur in branching patterns or when vessels are singular, this will be indicated. For example, you will find a pair of femoral arteries and a pair of femoral veins, with one vessel on each side of the body. In contrast, some vessels closer to the midline of the body, such as the aorta, are unique. Moreover, some superficial veins, such as the great saphenous vein in the femoral region, have no arterial counterpart. Another phenomenon that can make the study of vessels challenging is that names of vessels can change with location. Like a street that changes name as it passes through an intersection, an artery or vein can change names as it passes an anatomical landmark. For example, the left subclavian artery becomes the axillary artery as it passes through the body wall and into the axillary region, and then becomes the brachial artery as it flows from the axillary region into the upper arm (or brachium). You will also find examples of anastomoses where two blood vessels that previously branched reconnect. Anastomoses are especially common in veins, where they help maintain blood flow even when one vessel is blocked or narrowed, although there are some important ones in the arteries supplying the brain.

    2119_Pulmonary_Circuit.jpg
    Figure \(\PageIndex{2}\): Pulmonary Circuit. Blood exiting from the right ventricle flows into the pulmonary trunk, which bifurcates into the two pulmonary arteries. These vessels branch to supply blood to the pulmonary capillaries, where gas exchange occurs within the lung alveoli. Blood returns via the pulmonary veins to the left atrium.
    Table \(\PageIndex{1}\): Pulmonary Arteries and Veins
    Vessel Description
    Pulmonary trunk Single large vessel exiting the right ventricle that divides to form the right and left pulmonary arteries
    Pulmonary arteries Left and right vessels that form from the pulmonary trunk and lead to smaller arterioles and eventually to the pulmonary capillaries
    Pulmonary veins Two sets of paired vessels—one pair on each side—that are formed from the small venules, leading away from the pulmonary capillaries to flow into the left atrium

    Overview of Systemic Arteries

    Blood relatively high in oxygen concentration is returned from the pulmonary circuit to the left atrium via the four pulmonary veins. From the left atrium, blood moves into the left ventricle, which pumps blood into the aorta. The aorta and its branches—the systemic arteries—send blood to virtually every organ of the body (Figure \(\PageIndex{3}\)).

    2120_Major_Systemic_Artery.jpg
    Figure \(\PageIndex{3}\): Systemic Arteries. The major systemic arteries shown here deliver oxygenated blood throughout the body.

    The Aorta

    The aorta is the largest artery in the body (Figure \(\PageIndex{4}\)). It arises from the left ventricle and eventually descends to the abdominal region, where it bifurcates at the level of the fourth lumbar vertebra into the two common iliac arteries. The aorta consists of the ascending aorta, the aortic arch, and the descending aorta, which passes through the diaphragm and a landmark that divides into the superior thoracic and inferior abdominal components. Arteries originating from the aorta ultimately distribute blood to virtually all tissues of the body. At the base of the aorta is the aortic semilunar valve that prevents backflow of blood into the left ventricle while the heart is relaxing. After exiting the heart, the ascending aorta moves in a superior direction for approximately 5 cm and ends at the sternal angle. Following this ascent, it reverses direction, forming a graceful arc to the left, called the aortic arch. The aortic arch descends toward the inferior portions of the body and ends at the level of the intervertebral disk between the fourth and fifth thoracic vertebrae. Beyond this point, the descending aorta continues close to the bodies of the vertebrae and passes through an opening in the diaphragm known as the aortic hiatus. Superior to the diaphragm, the aorta is called the thoracic aorta, and inferior to the diaphragm, it is called the abdominal aorta. The abdominal aorta terminates when it bifurcates into the two common iliac arteries at the level of the fourth lumbar vertebra. See Figure \(\PageIndex{4}\) for an illustration of the ascending aorta, the aortic arch, and the initial segment of the descending aorta plus major branches; Table \(\PageIndex{2}\) summarizes the structures of the aorta.

    2121_Aorta.jpg
    Figure \(\PageIndex{4}\): Aorta. The aorta has distinct regions, including the ascending aorta, aortic arch, and the descending aorta, which includes the thoracic and abdominal regions.
    Table \(\PageIndex{2}\): Components of the Aorta
    Vessel Description
    Aorta Largest artery in the body, originating from the left ventricle and descending to the abdominal region, where it bifurcates into the common iliac arteries at the level of the fourth lumbar vertebra; arteries originating from the aorta distribute blood to virtually all tissues of the body
    Ascending aorta Initial portion of the aorta, rising superiorly from the left ventricle for a distance of approximately 5 cm
    Aortic arch Graceful arc to the left that connects the ascending aorta to the descending aorta; ends at the intervertebral disk between the fourth and fifth thoracic vertebrae
    Descending aorta Portion of the aorta that continues inferiorly past the end of the aortic arch; subdivided into the thoracic aorta and the abdominal aorta
    Thoracic aorta Portion of the descending aorta superior to the aortic hiatus
    Abdominal aorta Portion of the aorta inferior to the aortic hiatus and superior to the common iliac arteries

    Coronary Circulation

    The first vessels that branch from the ascending aorta are the paired coronary arteries (see Figure20.5.4), which arise from two of the three sinuses in the ascending aorta just superior to the aortic semilunar valve. These sinuses contain the aortic baroreceptors and chemoreceptors critical to maintain cardiac function. The left coronary artery arises from the left posterior aortic sinus. The right coronary artery arises from the anterior aortic sinus. Normally, the right posterior aortic sinus does not give rise to a vessel.

    The coronary arteries encircle the heart, forming a ring-like structure that divides into the next level of branches that supplies blood to the heart tissues. (Seek additional content for more detail on cardiac circulation.)

    Aortic Arch Branches

    There are three major branches of the aortic arch: the brachiocephalic artery, the left common carotid artery, and the left subclavian (literally “under the clavicle”) artery. As you would expect based upon proximity to the heart, each of these vessels is classified as an elastic artery.

    The brachiocephalic artery is located only on the right side of the body; there is no corresponding artery on the left. The brachiocephalic artery branches into the right subclavian artery and the right common carotid artery. The left subclavian and left common carotid arteries arise independently from the aortic arch but otherwise follow a similar pattern and distribution to the corresponding arteries on the right side (see Figure \(\PageIndex{2}\)).

    Each subclavian artery supplies blood to the arms, chest, shoulders, back, and central nervous system. It then gives rise to three major branches: the internal thoracic artery, the vertebral artery, and the thyrocervical artery. The internal thoracic artery, or mammary artery, supplies blood to the thymus, the pericardium of the heart, and the anterior chest wall. The vertebral artery passes through the vertebral foramen in the cervical vertebrae and then through the foramen magnum into the cranial cavity to supply blood to the brain and spinal cord. The paired vertebral arteries join together to form the large basilar artery at the base of the medulla oblongata. This is an example of an anastomosis. The subclavian artery also gives rise to the thyrocervical artery that provides blood to the thyroid, the cervical region of the neck, and the upper back and shoulder.

    The common carotid artery divides into internal and external carotid arteries. The right common carotid artery arises from the brachiocephalic artery and the left common carotid artery arises directly from the aortic arch. The external carotid artery supplies blood to numerous structures within the face, lower jaw, neck, esophagus, and larynx. These branches include the lingual, facial, occipital, maxillary, and superficial temporal arteries. The internal carotid artery initially forms an expansion known as the carotid sinus, containing the carotid baroreceptors and chemoreceptors. Like their counterparts in the aortic sinuses, the information provided by these receptors is critical to maintaining cardiovascular homeostasis (Figure \(\PageIndex{5}\)).

    2123_Arteries_of_the_Brain.jpg
    Figure \(\PageIndex{6}\): Arteries Serving the Brain. This inferior view shows the network of arteries serving the brain. The structure is referred to as the arterial circle or circle of Willis.
    Aortic Arch Branches and Brain Circulation
    Vessel Description
    Brachiocephalic artery Single vessel located on the right side of the body; the first vessel branching from the aortic arch; gives rise to the right subclavian artery and the right common carotid artery; supplies blood to the head, neck, upper limb, and wall of the thoracic region
    Subclavian artery The right subclavian artery arises from the brachiocephalic artery while the left subclavian artery arises from the aortic arch; gives rise to the internal thoracic, vertebral, and thyrocervical arteries; supplies blood to the arms, chest, shoulders, back, and central nervous system
    Internal thoracic artery Also called the mammary artery; arises from the subclavian artery; supplies blood to the thymus, pericardium of the heart, and anterior chest wall
    Vertebral artery Arises from the subclavian artery and passes through the vertebral foramen through the foramen magnum to the brain; joins with the internal carotid artery to form the arterial circle; supplies blood to the brain and spinal cord
    Thyrocervical artery Arises from the subclavian artery; supplies blood to the thyroid, the cervical region, the upper back, and shoulder
    Common carotid artery The right common carotid artery arises from the brachiocephalic artery and the left common carotid artery arises from the aortic arch; each gives rise to the external and internal carotid arteries; supplies the respective sides of the head and neck
    External carotid artery Arises from the common carotid artery; supplies blood to numerous structures within the face, lower jaw, neck, esophagus, and larynx
    Internal carotid artery Arises from the common carotid artery and begins with the carotid sinus; goes through the carotid canal of the temporal bone to the base of the brain; combines with the branches of the vertebral artery, forming the arterial circle; supplies blood to the brain
    Arterial circle or circle of Willis An anastomosis located at the base of the brain that ensures continual blood supply; formed from the branches of the internal carotid and vertebral arteries; supplies blood to the brain
    Anterior cerebral artery Arises from the internal carotid artery; supplies blood to the frontal lobe of the cerebrum
    Middle cerebral artery Another branch of the internal carotid artery; supplies blood to the temporal and parietal lobes of the cerebrum
    Ophthalmic artery Branch of the internal carotid artery; supplies blood to the eyes
    Anterior communicating artery An anastomosis of the right and left internal carotid arteries; supplies blood to the brain
    Posterior communicating artery Branches of the posterior cerebral artery that form part of the posterior portion of the arterial circle; supplies blood to the brain
    Posterior cerebral artery Branch of the basilar artery that forms a portion of the posterior segment of the arterial circle of Willis; supplies blood to the posterior portion of the cerebrum and brain stem
    Basilar artery Formed from the fusion of the two vertebral arteries; sends branches to the cerebellum, brain stem, and the posterior cerebral arteries; the main blood supply to the brain stem

    Thoracic Aorta and Major Branches

    The thoracic aorta begins at the level of vertebra T5 and continues through to the diaphragm at the level of T12, initially traveling within the mediastinum to the left of the vertebral column. As it passes through the thoracic region, the thoracic aorta gives rise to several branches, which are collectively referred to as visceral branches and parietal branches (Figure \(\PageIndex{7}\)). Those branches that supply blood primarily to visceral organs are known as the visceral branches and include the bronchial arteries, pericardial arteries, esophageal arteries, and the mediastinal arteries, each named after the tissues it supplies. Each bronchial artery (typically two on the left and one on the right) supplies systemic blood to the lungs and visceral pleura, in addition to the blood pumped to the lungs for oxygenation via the pulmonary circuit. The bronchial arteries follow the same path as the respiratory branches, beginning with the bronchi and ending with the bronchioles. There is considerable, but not total, intermingling of the systemic and pulmonary blood at anastomoses in the smaller branches of the lungs. This may sound incongruous—that is, the mixing of systemic arterial blood high in oxygen with the pulmonary arterial blood lower in oxygen—but the systemic vessels also deliver nutrients to the lung tissue just as they do elsewhere in the body. The mixed blood drains into typical pulmonary veins, whereas the bronchial artery branches remain separate and drain into bronchial veins described later. Each pericardial artery supplies blood to the pericardium, the esophageal artery provides blood to the esophagus, and the mediastinal artery provides blood to the mediastinum. The remaining thoracic aorta branches are collectively referred to as parietal branches or somatic branches, and include the intercostal and superior phrenic arteries. Each intercostal artery provides blood to the muscles of the thoracic cavity and vertebral column. The superior phrenic artery provides blood to the superior surface of the diaphragm. Table lists the arteries of the thoracic region.

    2124_Thoracic_Abdominal_Arteries.jpg
    Figure \(\PageIndex{7}\): Arteries of the Thoracic and Abdominal Regions. The thoracic aorta gives rise to the arteries of the visceral and parietal branches.
    Arteries of the Thoracic Region
    Vessel Description
    Visceral branches A group of arterial branches of the thoracic aorta; supplies blood to the viscera (i.e., organs) of the thorax
    Bronchial artery Systemic branch from the aorta that provides oxygenated blood to the lungs; this blood supply is in addition to the pulmonary circuit that brings blood for oxygenation
    Pericardial artery Branch of the thoracic aorta; supplies blood to the pericardium
    Esophageal artery Branch of the thoracic aorta; supplies blood to the esophagus
    Mediastinal artery Branch of the thoracic aorta; supplies blood to the mediastinum
    Parietal branches Also called somatic branches, a group of arterial branches of the thoracic aorta; include those that supply blood to the thoracic wall, vertebral column, and the superior surface of the diaphragm
    Intercostal artery Branch of the thoracic aorta; supplies blood to the muscles of the thoracic cavity and vertebral column
    Superior phrenic artery Branch of the thoracic aorta; supplies blood to the superior surface of the diaphragm

    Abdominal Aorta and Major Branches

    After crossing through the diaphragm at the aortic hiatus, the thoracic aorta is called the abdominal aorta (see Figure \(\PageIndex{7}\)). This vessel remains to the left of the vertebral column and is embedded in adipose tissue behind the peritoneal cavity. It formally ends at approximately the level of vertebra L4, where it bifurcates to form the common iliac arteries. Before this division, the abdominal aorta gives rise to several important branches. A single celiac trunk (artery) emerges and divides into the left gastric artery to supply blood to the stomach and esophagus, the splenic artery to supply blood to the spleen, and the common hepatic artery, which in turn gives rise to the hepatic artery proper to supply blood to the liver, the right gastric artery to supply blood to the stomach, the cystic artery to supply blood to the gall bladder, and several branches, one to supply blood to the duodenum and another to supply blood to the pancreas. Two additional single vessels arise from the abdominal aorta. These are the superior and inferior mesenteric arteries. The superior mesenteric artery arises approximately 2.5 cm after the celiac trunk and branches into several major vessels that supply blood to the small intestine (duodenum, jejunum, and ileum), the pancreas, and a majority of the large intestine. The inferior mesenteric artery supplies blood to the distal segment of the large intestine, including the rectum. It arises approximately 5 cm superior to the common iliac arteries.

    In addition to these single branches, the abdominal aorta gives rise to several significant paired arteries along the way. These include the inferior phrenic arteries, the adrenal arteries, the renal arteries, the gonadal arteries, and the lumbar arteries. Each inferior phrenic artery is a counterpart of a superior phrenic artery and supplies blood to the inferior surface of the diaphragm. The adrenal artery supplies blood to the adrenal (suprarenal) glands and arises near the superior mesenteric artery. Each renal artery branches approximately 2.5 cm inferior to the superior mesenteric arteries and supplies a kidney. The right renal artery is longer than the left since the aorta lies to the left of the vertebral column and the vessel must travel a greater distance to reach its target. Renal arteries branch repeatedly to supply blood to the kidneys. Each gonadal artery supplies blood to the gonads, or reproductive organs, and is also described as either an ovarian artery or a testicular artery (internal spermatic), depending upon the sex of the individual. An ovarian artery supplies blood to an ovary, uterine (Fallopian) tube, and the uterus, and is located within the suspensory ligament of the uterus. It is considerably shorter than a testicular artery, which ultimately travels outside the body cavity to the testes, forming one component of the spermatic cord. The gonadal arteries arise inferior to the renal arteries and are generally retroperitoneal. The ovarian artery continues to the uterus where it forms an anastomosis with the uterine artery that supplies blood to the uterus. Both the uterine arteries and vaginal arteries, which distribute blood to the vagina, are branches of the internal iliac artery. The four paired lumbar arteries are the counterparts of the intercostal arteries and supply blood to the lumbar region, the abdominal wall, and the spinal cord. In some instances, a fifth pair of lumbar arteries emerges from the median sacral artery.

    The aorta divides at approximately the level of vertebra L4 into a left and a right common iliac artery but continues as a small vessel, the median sacral artery, into the sacrum. The common iliac arteries provide blood to the pelvic region and ultimately to the lower limbs. They split into external and internal iliac arteries approximately at the level of the lumbar-sacral articulation. Each internal iliac artery sends branches to the urinary bladder, the walls of the pelvis, the external genitalia, and the medial portion of the femoral region. In females, they also provide blood to the uterus and vagina. The much larger external iliac artery supplies blood to each of the lower limbs. Figure \(\PageIndex{8}\) shows the distribution of the major branches of the aorta into the thoracic and abdominal regions. Figure \(\PageIndex{9}\) shows the distribution of the major branches of the common iliac arteries. Table summarizes the major branches of the abdominal aorta.

    2126_Iliac_Artery_Branches_Chart.jpg
    Figure \(\PageIndex{9}\): Major Branches of the Iliac Arteries. The flow chart summarizes the distribution of the major branches of the common iliac arteries into the pelvis and lower limbs. The left side follows a similar pattern to the right.
    Vessels of the Abdominal Aorta
    Vessel Description
    Celiac trunk Also called the celiac artery; a major branch of the abdominal aorta; gives rise to the left gastric artery, the splenic artery, and the common hepatic artery that forms the hepatic artery to the liver, the right gastric artery to the stomach, and the cystic artery to the gall bladder
    Left gastric artery Branch of the celiac trunk; supplies blood to the stomach
    Splenic artery Branch of the celiac trunk; supplies blood to the spleen
    Common hepatic artery Branch of the celiac trunk that forms the hepatic artery, the right gastric artery, and the cystic artery
    Hepatic artery proper Branch of the common hepatic artery; supplies systemic blood to the liver
    Right gastric artery Branch of the common hepatic artery; supplies blood to the stomach
    Cystic artery Branch of the common hepatic artery; supplies blood to the gall bladder
    Superior mesenteric artery Branch of the abdominal aorta; supplies blood to the small intestine (duodenum, jejunum, and ileum), the pancreas, and a majority of the large intestine
    Inferior mesenteric artery Branch of the abdominal aorta; supplies blood to the distal segment of the large intestine and rectum
    Inferior phrenic arteries Branches of the abdominal aorta; supply blood to the inferior surface of the diaphragm
    Adrenal artery Branch of the abdominal aorta; supplies blood to the adrenal (suprarenal) glands
    Renal artery Branch of the abdominal aorta; supplies each kidney
    Gonadal artery Branch of the abdominal aorta; supplies blood to the gonads or reproductive organs; also described as ovarian arteries or testicular arteries, depending upon the sex of the individual
    Ovarian artery Branch of the abdominal aorta; supplies blood to ovary, uterine (Fallopian) tube, and uterus
    Testicular artery Branch of the abdominal aorta; ultimately travels outside the body cavity to the testes and forms one component of the spermatic cord
    Lumbar arteries Branches of the abdominal aorta; supply blood to the lumbar region, the abdominal wall, and spinal cord
    Common iliac artery Branch of the aorta that leads to the internal and external iliac arteries
    Median sacral artery Continuation of the aorta into the sacrum
    Internal iliac artery Branch from the common iliac arteries; supplies blood to the urinary bladder, walls of the pelvis, external genitalia, and the medial portion of the femoral region; in females, also provides blood to the uterus and vagina
    External iliac artery Branch of the common iliac artery that leaves the body cavity and becomes a femoral artery; supplies blood to the lower limbs

    Arteries Serving the Upper Limbs

    As the subclavian artery exits the thorax into the axillary region, it is renamed the axillary artery. Although it does branch and supply blood to the region near the head of the humerus (via the humeral circumflex arteries), the majority of the vessel continues into the upper arm, or brachium, and becomes the brachial artery (Figure \(\PageIndex{10}\)). The brachial artery supplies blood to much of the brachial region and divides at the elbow into several smaller branches, including the deep brachial arteries, which provide blood to the posterior surface of the arm, and the ulnar collateral arteries, which supply blood to the region of the elbow. As the brachial artery approaches the coronoid fossa, it bifurcates into the radial and ulnar arteries, which continue into the forearm, or antebrachium. The radial artery and ulnar artery parallel their namesake bones, giving off smaller branches until they reach the wrist, or carpal region. At this level, they fuse to form the superficial and deep palmar arches that supply blood to the hand, as well as the digital arteries that supply blood to the digits. Figure \(\PageIndex{11}\) shows the distribution of systemic arteries from the heart into the upper limb. Table summarizes the arteries serving the upper limbs.

    2128_Thoracic_Upper_Limb_Arteries_Chart.jpg
    Figure \(\PageIndex{11}\): Major Arteries of the Upper Limb. The flow chart summarizes the distribution of the major arteries from the heart into the upper limb.
    Arteries Serving the Upper Limbs
    Vessel Description
    Axillary artery Continuation of the subclavian artery as it penetrates the body wall and enters the axillary region; supplies blood to the region near the head of the humerus (humeral circumflex arteries); the majority of the vessel continues into the brachium and becomes the brachial artery
    Brachial artery Continuation of the axillary artery in the brachium; supplies blood to much of the brachial region; gives off several smaller branches that provide blood to the posterior surface of the arm in the region of the elbow; bifurcates into the radial and ulnar arteries at the coronoid fossa
    Radial artery Formed at the bifurcation of the brachial artery; parallels the radius; gives off smaller branches until it reaches the carpal region where it fuses with the ulnar artery to form the superficial and deep palmar arches; supplies blood to the lower arm and carpal region
    Ulnar artery Formed at the bifurcation of the brachial artery; parallels the ulna; gives off smaller branches until it reaches the carpal region where it fuses with the radial artery to form the superficial and deep palmar arches; supplies blood to the lower arm and carpal region
    Palmar arches (superficial and deep) Formed from anastomosis of the radial and ulnar arteries; supply blood to the hand and digital arteries
    Digital arteries Formed from the superficial and deep palmar arches; supply blood to the digits

    Arteries Serving the Lower Limbs

    The external iliac artery exits the body cavity and enters the femoral region of the lower leg (Figure \(\PageIndex{12}\)). As it passes through the body wall, it is renamed the femoral artery. It gives off several smaller branches as well as the lateral deep femoral artery that in turn gives rise to a lateral circumflex artery. These arteries supply blood to the deep muscles of the thigh as well as ventral and lateral regions of the integument. The femoral artery also gives rise to the genicular artery, which provides blood to the region of the knee. As the femoral artery passes posterior to the knee near the popliteal fossa, it is called the popliteal artery. The popliteal artery branches into the anterior and posterior tibial arteries.

    The anterior tibial artery is located between the tibia and fibula, and supplies blood to the muscles and integument of the anterior tibial region. Upon reaching the tarsal region, it becomes the dorsalis pedis artery, which branches repeatedly and provides blood to the tarsal and dorsal regions of the foot. The posterior tibial artery provides blood to the muscles and integument on the posterior surface of the tibial region. The fibular or peroneal artery branches from the posterior tibial artery. It bifurcates and becomes the medial plantar artery and lateral plantar artery, providing blood to the plantar surfaces. There is an anastomosis with the dorsalis pedis artery, and the medial and lateral plantar arteries form two arches called the dorsal arch (also called the arcuate arch) and the plantar arch, which provide blood to the remainder of the foot and toes. Figure \(\PageIndex{13}\) shows the distribution of the major systemic arteries in the lower limb. Table summarizes the major systemic arteries discussed in the text.

    2130_Lower_Limb_Arteries_Chart.jpg
    Figure \(\PageIndex{13}\): Systemic Arteries of the Lower Limb. The flow chart summarizes the distribution of the systemic arteries from the external iliac artery into the lower limb.
    Arteries Serving the Lower Limbs
    Vessel Description
    Femoral artery Continuation of the external iliac artery after it passes through the body cavity; divides into several smaller branches, the lateral deep femoral artery, and the genicular artery; becomes the popliteal artery as it passes posterior to the knee
    Deep femoral artery Branch of the femoral artery; gives rise to the lateral circumflex arteries
    Lateral circumflex artery Branch of the deep femoral artery; supplies blood to the deep muscles of the thigh and the ventral and lateral regions of the integument
    Genicular artery Branch of the femoral artery; supplies blood to the region of the knee
    Popliteal artery Continuation of the femoral artery posterior to the knee; branches into the anterior and posterior tibial arteries
    Anterior tibial artery Branches from the popliteal artery; supplies blood to the anterior tibial region; becomes the dorsalis pedis artery
    Dorsalis pedis artery Forms from the anterior tibial artery; branches repeatedly to supply blood to the tarsal and dorsal regions of the foot
    Posterior tibial artery Branches from the popliteal artery and gives rise to the fibular or peroneal artery; supplies blood to the posterior tibial region
    Medial plantar artery Arises from the bifurcation of the posterior tibial arteries; supplies blood to the medial plantar surfaces of the foot
    Lateral plantar artery Arises from the bifurcation of the posterior tibial arteries; supplies blood to the lateral plantar surfaces of the foot
    Dorsal or arcuate arch Formed from the anastomosis of the dorsalis pedis artery and the medial and plantar arteries; branches supply the distal portions of the foot and digits
    Plantar arch Formed from the anastomosis of the dorsalis pedis artery and the medial and plantar arteries; branches supply the distal portions of the foot and digits

    Overview of Systemic Veins

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    Visit this site for a brief online summary of the veins.

    Figure \(\PageIndex{14}\): Major Systemic Veins of the Body. The major systemic veins of the body are shown here in an anterior view.

    The right atrium receives all of the systemic venous return. Most of the blood flows into either the superior vena cava or inferior vena cava. If you draw an imaginary line at the level of the diaphragm, systemic venous circulation from above that line will generally flow into the superior vena cava; this includes blood from the head, neck, chest, shoulders, and upper limbs. The exception to this is that most venous blood flow from the coronary veins flows directly into the coronary sinus and from there directly into the right atrium. Beneath the diaphragm, systemic venous flow enters the inferior vena cava, that is, blood from the abdominal and pelvic regions and the lower limbs.

    The Superior Vena Cava

    The superior vena cava drains most of the body superior to the diaphragm (Figure \(\PageIndex{15}\)). On both the left and right sides, the subclavian vein forms when the axillary vein passes through the body wall from the axillary region. It fuses with the external and internal jugular veins from the head and neck to form the brachiocephalic vein. Each vertebral vein also flows into the brachiocephalic vein close to this fusion. These veins arise from the base of the brain and the cervical region of the spinal cord, and flow largely through the intervertebral foramina in the cervical vertebrae. They are the counterparts of the vertebral arteries. Each internal thoracic vein, also known as an internal mammary vein, drains the anterior surface of the chest wall and flows into the brachiocephalic vein.

    The remainder of the blood supply from the thorax drains into the azygos vein. Each intercostal vein drains muscles of the thoracic wall, each esophageal vein delivers blood from the inferior portions of the esophagus, each bronchial vein drains the systemic circulation from the lungs, and several smaller veins drain the mediastinal region. Bronchial veins carry approximately 13 percent of the blood that flows into the bronchial arteries; the remainder intermingles with the pulmonary circulation and returns to the heart via the pulmonary veins. These veins flow into the azygos vein, and with the smaller hemiazygos vein (hemi- = “half”) on the left of the vertebral column, drain blood from the thoracic region. The hemiazygos vein does not drain directly into the superior vena cava but enters the brachiocephalic vein via the superior intercostal vein.

    The azygos vein passes through the diaphragm from the thoracic cavity on the right side of the vertebral column and begins in the lumbar region of the thoracic cavity. It flows into the superior vena cava at approximately the level of T2, making a significant contribution to the flow of blood. It combines with the two large left and right brachiocephalic veins to form the superior vena cava.

    Table summarizes the veins of the thoracic region that flow into the superior vena cava.

    2132_Thoracic_Abdominal_Veins.jpg
    Figure \(\PageIndex{15}\): Veins of the Thoracic and Abdominal Regions. Veins of the thoracic and abdominal regions drain blood from the area above the diaphragm, returning it to the right atrium via the superior vena cava.
    Veins of the Thoracic Region
    Vessel Description
    Superior vena cava Large systemic vein; drains blood from most areas superior to the diaphragm; empties into the right atrium
    Subclavian vein Located deep in the thoracic cavity; formed by the axillary vein as it enters the thoracic cavity from the axillary region; drains the axillary and smaller local veins near the scapular region and leads to the brachiocephalic vein
    Brachiocephalic veins Pair of veins that form from a fusion of the external and internal jugular veins and the subclavian vein; subclavian, external and internal jugulars, vertebral, and internal thoracic veins flow into it; drain the upper thoracic region and lead to the superior vena cava
    Vertebral vein Arises from the base of the brain and the cervical region of the spinal cord; passes through the intervertebral foramina in the cervical vertebrae; drains smaller veins from the cranium, spinal cord, and vertebrae, and leads to the brachiocephalic vein; counterpart of the vertebral artery
    Internal thoracic veins Also called internal mammary veins; drain the anterior surface of the chest wall and lead to the brachiocephalic vein
    Intercostal vein Drains the muscles of the thoracic wall and leads to the azygos vein
    Esophageal vein Drains the inferior portions of the esophagus and leads to the azygos vein
    Bronchial vein Drains the systemic circulation from the lungs and leads to the azygos vein
    Azygos vein Originates in the lumbar region and passes through the diaphragm into the thoracic cavity on the right side of the vertebral column; drains blood from the intercostal veins, esophageal veins, bronchial veins, and other veins draining the mediastinal region, and leads to the superior vena cava
    Hemiazygos vein Smaller vein complementary to the azygos vein; drains the esophageal veins from the esophagus and the left intercostal veins, and leads to the brachiocephalic vein via the superior intercostal vein

    Veins of the Head and Neck

    Blood from the brain and the superficial facial vein flow into each internal jugular vein (Figure \(\PageIndex{16}\)). Blood from the more superficial portions of the head, scalp, and cranial regions, including the temporal vein and maxillary vein, flow into each external jugular vein. Although the external and internal jugular veins are separate vessels, there are anastomoses between them close to the thoracic region. Blood from the external jugular vein empties into the subclavian vein. Table summarizes the major veins of the head and neck.

    Major Veins of the Head and Neck
    Vessel Description
    Internal jugular vein Parallel to the common carotid artery, which is more or less its counterpart, and passes through the jugular foramen and canal; primarily drains blood from the brain, receives the superficial facial vein, and empties into the subclavian vein
    Temporal vein Drains blood from the temporal region and flows into the external jugular vein
    Maxillary vein Drains blood from the maxillary region and flows into the external jugular vein
    External jugular vein Drains blood from the more superficial portions of the head, scalp, and cranial regions, and leads to the subclavian vein

    Venous Drainage of the Brain

    Circulation to the brain is both critical and complex (see Figure \(\PageIndex{16}\)). Many smaller veins of the brain stem and the superficial veins of the cerebrum lead to larger vessels referred to as intracranial sinuses. These include the superior and inferior sagittal sinuses, straight sinus, cavernous sinuses, left and right sinuses, the petrosal sinuses, and the occipital sinuses. Ultimately, sinuses will lead back to either the inferior jugular vein or vertebral vein.

    Most of the veins on the superior surface of the cerebrum flow into the largest of the sinuses, the superior sagittal sinus. It is located midsagittally between the meningeal and periosteal layers of the dura mater within the falx cerebri and, at first glance in images or models, can be mistaken for the subarachnoid space. Most reabsorption of cerebrospinal fluid occurs via the chorionic villi (arachnoid granulations) into the superior sagittal sinus. Blood from most of the smaller vessels originating from the inferior cerebral veins flows into the great cerebral vein and into the straight sinus. Other cerebral veins and those from the eye socket flow into the cavernous sinus, which flows into the petrosal sinus and then into the internal jugular vein. The occipital sinus, sagittal sinus, and straight sinuses all flow into the left and right transverse sinuses near the lambdoid suture. The transverse sinuses in turn flow into the sigmoid sinuses that pass through the jugular foramen and into the internal jugular vein. The internal jugular vein flows parallel to the common carotid artery and is more or less its counterpart. It empties into the brachiocephalic vein. The veins draining the cervical vertebrae and the posterior surface of the skull, including some blood from the occipital sinus, flow into the vertebral veins. These parallel the vertebral arteries and travel through the transverse foramina of the cervical vertebrae. The vertebral veins also flow into the brachiocephalic veins. Table summarizes the major veins of the brain.

    2133_Head_and_Neck_Veins.jpg
    Figure \(\PageIndex{16}\): Veins of the Head and Neck. This left lateral view shows the veins of the head and neck, including the intercranial sinuses.
    Major Veins of the Brain
    Vessel Description
    Superior sagittal sinus Enlarged vein located midsagittally between the meningeal and periosteal layers of the dura mater within the falx cerebri; receives most of the blood drained from the superior surface of the cerebrum and leads to the inferior jugular vein and the vertebral vein
    Great cerebral vein Receives most of the smaller vessels from the inferior cerebral veins and leads to the straight sinus
    Straight sinus Enlarged vein that drains blood from the brain; receives most of the blood from the great cerebral vein and leads to the left or right transverse sinus
    Cavernous sinus Enlarged vein that receives blood from most of the other cerebral veins and the eye socket, and leads to the petrosal sinus
    Petrosal sinus Enlarged vein that receives blood from the cavernous sinus and leads into the internal jugular veins
    Occipital sinus Enlarged vein that drains the occipital region near the falx cerebelli and leads to the left and right transverse sinuses, and also the vertebral veins
    Transverse sinuses Pair of enlarged veins near the lambdoid suture that drains the occipital, sagittal, and straight sinuses, and leads to the sigmoid sinuses
    Sigmoid sinuses Enlarged vein that receives blood from the transverse sinuses and leads through the jugular foramen to the internal jugular vein

    Veins Draining the Upper Limbs

    The digital veins in the fingers come together in the hand to form the palmar venous arches (Figure \(\PageIndex{17}\)). From here, the veins come together to form the radial vein, the ulnar vein, and the median antebrachial vein. The radial vein and the ulnar vein parallel the bones of the forearm and join together at the antebrachium to form the brachial vein, a deep vein that flows into the axillary vein in the brachium.

    The median antebrachial vein parallels the ulnar vein, is more medial in location, and joins the basilic vein in the forearm. As the basilic vein reaches the antecubital region, it gives off a branch called the median cubital vein that crosses at an angle to join the cephalic vein. The median cubital vein is the most common site for drawing venous blood in humans. The basilic vein continues through the arm medially and superficially to the axillary vein.

    The cephalic vein begins in the antebrachium and drains blood from the superficial surface of the arm into the axillary vein. It is extremely superficial and easily seen along the surface of the biceps brachii muscle in individuals with good muscle tone and in those without excessive subcutaneous adipose tissue in the arms.

    The subscapular vein drains blood from the subscapular region and joins the cephalic vein to form the axillary vein. As it passes through the body wall and enters the thorax, the axillary vein becomes the subclavian vein.

    Many of the larger veins of the thoracic and abdominal region and upper limb are further represented in the flow chart in Figure \(\PageIndex{18}\). Table summarizes the veins of the upper limbs.

    2135_Veins_Draining_into_Superior_Vena_Cava_Chart.jpg
    Figure \(\PageIndex{18}\): Veins Flowing into the Superior Vena Cava. The flow chart summarizes the distribution of the veins flowing into the superior vena cava.
    Veins of the Upper Limbs
    Vessel Description
    Digital veins Drain the digits and lead to the palmar arches of the hand and dorsal venous arch of the foot
    Palmar venous arches Drain the hand and digits, and lead to the radial vein, ulnar veins, and the median antebrachial vein
    Radial vein Vein that parallels the radius and radial artery; arises from the palmar venous arches and leads to the brachial vein
    Ulnar vein Vein that parallels the ulna and ulnar artery; arises from the palmar venous arches and leads to the brachial vein
    Brachial vein Deeper vein of the arm that forms from the radial and ulnar veins in the lower arm; leads to the axillary vein
    Median antebrachial vein Vein that parallels the ulnar vein but is more medial in location; intertwines with the palmar venous arches; leads to the basilic vein
    Basilic vein Superficial vein of the arm that arises from the median antebrachial vein, intersects with the median cubital vein, parallels the ulnar vein, and continues into the upper arm; along with the brachial vein, it leads to the axillary vein
    Median cubital vein Superficial vessel located in the antecubital region that links the cephalic vein to the basilic vein in the form of a v; a frequent site from which to draw blood
    Cephalic vein Superficial vessel in the upper arm; leads to the axillary vein
    Subscapular vein Drains blood from the subscapular region and leads to the axillary vein
    Axillary vein The major vein in the axillary region; drains the upper limb and becomes the subclavian vein

    The Inferior Vena Cava

    Other than the small amount of blood drained by the azygos and hemiazygos veins, most of the blood inferior to the diaphragm drains into the inferior vena cava before it is returned to the heart (see Figure \(\PageIndex{15}\)). Lying just beneath the parietal peritoneum in the abdominal cavity, the inferior vena cava parallels the abdominal aorta, where it can receive blood from abdominal veins. The lumbar portions of the abdominal wall and spinal cord are drained by a series of lumbar veins, usually four on each side. The ascending lumbar veins drain into either the azygos vein on the right or the hemiazygos vein on the left, and return to the superior vena cava. The remaining lumbar veins drain directly into the inferior vena cava.

    Blood supply from the kidneys flows into each renal vein, normally the largest veins entering the inferior vena cava. A number of other, smaller veins empty into the left renal vein. Each adrenal vein drains the adrenal or suprarenal glands located immediately superior to the kidneys. The right adrenal vein enters the inferior vena cava directly, whereas the left adrenal vein enters the left renal vein.

    From the male reproductive organs, each testicular vein flows from the scrotum, forming a portion of the spermatic cord. Each ovarian vein drains an ovary in females. Each of these veins is generically called a gonadal vein. The right gonadal vein empties directly into the inferior vena cava, and the left gonadal vein empties into the left renal vein.

    Each side of the diaphragm drains into a phrenic vein; the right phrenic vein empties directly into the inferior vena cava, whereas the left phrenic vein empties into the left renal vein. Blood supply from the liver drains into each hepatic vein and directly into the inferior vena cava. Since the inferior vena cava lies primarily to the right of the vertebral column and aorta, the left renal vein is longer, as are the left phrenic, adrenal, and gonadal veins. The longer length of the left renal vein makes the left kidney the primary target of surgeons removing this organ for donation. Figure \(\PageIndex{19}\) provides a flow chart of the veins flowing into the inferior vena cava. Table summarizes the major veins of the abdominal region.

    2140_FlowChart_Veins_into_VenaCava.jpg
    Figure \(\PageIndex{19}\): Venous Flow into Inferior Vena Cava. The flow chart summarizes veins that deliver blood to the inferior vena cava.
    Major Veins of the Abdominal Region
    Vessel Description
    Inferior vena cava Large systemic vein that drains blood from areas largely inferior to the diaphragm; empties into the right atrium
    Lumbar veins Series of veins that drain the lumbar portion of the abdominal wall and spinal cord; the ascending lumbar veins drain into the azygos vein on the right or the hemiazygos vein on the left; the remaining lumbar veins drain directly into the inferior vena cava
    Renal vein Largest vein entering the inferior vena cava; drains the kidneys and flows into the inferior vena cava
    Adrenal vein Drains the adrenal or suprarenal; the right adrenal vein enters the inferior vena cava directly and the left adrenal vein enters the left renal vein
    Testicular vein Drains the testes and forms part of the spermatic cord; the right testicular vein empties directly into the inferior vena cava and the left testicular vein empties into the left renal vein
    Ovarian vein Drains the ovary; the right ovarian vein empties directly into the inferior vena cava and the left ovarian vein empties into the left renal vein
    Gonadal vein Generic term for a vein draining a reproductive organ; may be either an ovarian vein or a testicular vein, depending on the sex of the individual
    Phrenic vein Drains the diaphragm; the right phrenic vein flows into the inferior vena cava and the left phrenic vein empties into the left renal vein
    Hepatic vein Drains systemic blood from the liver and flows into the inferior vena cava

    Veins Draining the Lower Limbs

    The superior surface of the foot drains into the digital veins, and the inferior surface drains into the plantar veins, which flow into a complex series of anastomoses in the feet and ankles, including the dorsal venous arch and the plantar venous arch (Figure \(\PageIndex{20}\)). From the dorsal venous arch, blood supply drains into the anterior and posterior tibial veins. The anterior tibial vein drains the area near the tibialis anterior muscle and combines with the posterior tibial vein and the fibular vein to form the popliteal vein. The posterior tibial vein drains the posterior surface of the tibia and joins the popliteal vein. The fibular vein drains the muscles and integument in proximity to the fibula and also joins the popliteal vein. The small saphenous vein located on the lateral surface of the leg drains blood from the superficial regions of the lower leg and foot, and flows into to the popliteal vein. As the popliteal vein passes behind the knee in the popliteal region, it becomes the femoral vein. It is palpable in patients without excessive adipose tissue.

    Close to the body wall, the great saphenous vein, the deep femoral vein, and the femoral circumflex vein drain into the femoral vein. The great saphenous vein is a prominent surface vessel located on the medial surface of the leg and thigh that collects blood from the superficial portions of these areas. The deep femoral vein, as the name suggests, drains blood from the deeper portions of the thigh. The femoral circumflex vein forms a loop around the femur just inferior to the trochanters and drains blood from the areas in proximity to the head and neck of the femur.

    As the femoral vein penetrates the body wall from the femoral portion of the upper limb, it becomes the external iliac vein, a large vein that drains blood from the leg to the common iliac vein. The pelvic organs and integument drain into the internal iliac vein, which forms from several smaller veins in the region, including the umbilical veins that run on either side of the bladder. The external and internal iliac veins combine near the inferior portion of the sacroiliac joint to form the common iliac vein. In addition to blood supply from the external and internal iliac veins, the middle sacral vein drains the sacral region into the common iliac vein. Similar to the common iliac arteries, the common iliac veins come together at the level of L5 to form the inferior vena cava.

    Figure \(\PageIndex{21}\) is a flow chart of veins flowing into the lower limb. Table summarizes the major veins of the lower limbs.

    2137_Lower_Limb_Veins_Chart.jpg
    Figure \(\PageIndex{21}\): Major Veins of the Lower Limb. The flow chart summarizes venous flow from the lower limb.
    Veins of the Lower Limbs
    Vessel Description
    Plantar veins Drain the foot and flow into the plantar venous arch
    Dorsal venous arch Drains blood from digital veins and vessels on the superior surface of the foot
    Plantar venous arch Formed from the plantar veins; flows into the anterior and posterior tibial veins through anastomoses
    Anterior tibial vein Formed from the dorsal venous arch; drains the area near the tibialis anterior muscle and flows into the popliteal vein
    Posterior tibial vein Formed from the dorsal venous arch; drains the area near the posterior surface of the tibia and flows into the popliteal vein
    Fibular vein Drains the muscles and integument near the fibula and flows into the popliteal vein
    Small saphenous vein Located on the lateral surface of the leg; drains blood from the superficial regions of the lower leg and foot, and flows into the popliteal vein
    Popliteal vein Drains the region behind the knee and forms from the fusion of the fibular, anterior, and posterior tibial veins; flows into the femoral vein
    Great saphenous vein Prominent surface vessel located on the medial surface of the leg and thigh; drains the superficial portions of these areas and flows into the femoral vein
    Deep femoral vein Drains blood from the deeper portions of the thigh and flows into the femoral vein
    Femoral circumflex vein Forms a loop around the femur just inferior to the trochanters; drains blood from the areas around the head and neck of the femur; flows into the femoral vein
    Femoral vein Drains the upper leg; receives blood from the great saphenous vein, the deep femoral vein, and the femoral circumflex vein; becomes the external iliac vein when it crosses the body wall
    External iliac vein Formed when the femoral vein passes into the body cavity; drains the legs and flows into the common iliac vein
    Internal iliac vein Drains the pelvic organs and integument; formed from several smaller veins in the region; flows into the common iliac vein
    Middle sacral vein Drains the sacral region and flows into the left common iliac vein
    Common iliac vein Flows into the inferior vena cava at the level of L5; the left common iliac vein drains the sacral region; formed from the union of the external and internal iliac veins near the inferior portion of the sacroiliac joint

    Hepatic Portal System

    The liver is a complex biochemical processing plant. It packages nutrients absorbed by the digestive system; produces plasma proteins, clotting factors, and bile; and disposes of worn-out cell components and waste products. Instead of entering the circulation directly, absorbed nutrients and certain wastes (for example, materials produced by the spleen) travel to the liver for processing. They do so via the hepatic portal system (Figure \(\PageIndex{22}\)). Portal systems begin and end in capillaries. In this case, the initial capillaries from the stomach, small intestine, large intestine, and spleen lead to the hepatic portal vein and end in specialized capillaries within the liver, the hepatic sinusoids. You saw the only other portal system with the hypothalamic-hypophyseal portal vessel in the endocrine chapter.

    The hepatic portal system consists of the hepatic portal vein and the veins that drain into it. The hepatic portal vein itself is relatively short, beginning at the level of L2 with the confluence of the superior mesenteric and splenic veins. It also receives branches from the inferior mesenteric vein, plus the splenic veins and all their tributaries. The superior mesenteric vein receives blood from the small intestine, two-thirds of the large intestine, and the stomach. The inferior mesenteric vein drains the distal third of the large intestine, including the descending colon, the sigmoid colon, and the rectum. The splenic vein is formed from branches from the spleen, pancreas, and portions of the stomach, and the inferior mesenteric vein. After its formation, the hepatic portal vein also receives branches from the gastric veins of the stomach and cystic veins from the gall bladder. The hepatic portal vein delivers materials from these digestive and circulatory organs directly to the liver for processing.

    Because of the hepatic portal system, the liver receives its blood supply from two different sources: from normal systemic circulation via the hepatic artery and from the hepatic portal vein. The liver processes the blood from the portal system to remove certain wastes and excess nutrients, which are stored for later use. This processed blood, as well as the systemic blood that came from the hepatic artery, exits the liver via the right, left, and middle hepatic veins, and flows into the inferior vena cava. Overall systemic blood composition remains relatively stable, since the liver is able to metabolize the absorbed digestive components.

    2138_Hepatic_Portal_Vein_System.jpg
    Figure \(\PageIndex{22}\): Hepatic Portal System. The liver receives blood from the normal systemic circulation via the hepatic artery. It also receives and processes blood from other organs, delivered via the veins of the hepatic portal system. All blood exits the liver via the hepatic vein, which delivers the blood to the inferior vena cava. (Different colors are used to help distinguish among the different vessels in the system.)

    Chapter Review

    The right ventricle pumps oxygen-depleted blood into the pulmonary trunk and right and left pulmonary arteries, which carry it to the right and left lungs for gas exchange. Oxygen-rich blood is transported by pulmonary veins to the left atrium. The left ventricle pumps this blood into the aorta. The main regions of the aorta are the ascending aorta, aortic arch, and descending aorta, which is further divided into the thoracic and abdominal aorta. The coronary arteries branch from the ascending aorta. After oxygenating tissues in the capillaries, systemic blood is returned to the right atrium from the venous system via the superior vena cava, which drains most of the veins superior to the diaphragm, the inferior vena cava, which drains most of the veins inferior to the diaphragm, and the coronary veins via the coronary sinus. The hepatic portal system carries blood to the liver for processing before it enters circulation. Review the figures provided in this section for circulation of blood through the blood vessels.

    Review Questions

    Q. The coronary arteries branch off of the ________.

    A. aortic valve

    B. ascending aorta

    C. aortic arch

    D. thoracic aorta

    Answer: B

    Q. Which of the following statements is true?

    A. The left and right common carotid arteries both branch off of the brachiocephalic trunk.

    B. The brachial artery is the distal branch of the axillary artery.

    C. The radial and ulnar arteries join to form the palmar arch.

    D. All of the above are true.

    Answer: C

    Q. Arteries serving the stomach, pancreas, and liver all branch from the ________.

    A. superior mesenteric artery

    B. inferior mesenteric artery

    C. celiac trunk

    D. splenic artery

    Answer: C

    Q. The right and left brachiocephalic veins ________.

    A. drain blood from the right and left internal jugular veins

    B. drain blood from the right and left subclavian veins

    C. drain into the superior vena cava

    D. all of the above are true

    Answer: D

    Q. The hepatic portal system delivers blood from the digestive organs to the ________.

    A. liver

    B. hypothalamus

    C. spleen

    D. left atrium

    Answer: A

    Critical Thinking Questions

    Q. Identify the ventricle of the heart that pumps oxygen-depleted blood and the arteries of the body that carry oxygen-depleted blood.

    A. The right ventricle of the heart pumps oxygen-depleted blood to the pulmonary arteries.

    Q. What organs do the gonadal veins drain?

    A. The gonadal veins drain the testes in males and the ovaries in females.

    Q. What arteries play the leading roles in supplying blood to the brain?

    A. The internal carotid arteries and the vertebral arteries provide most of the brain’s blood supply.

    Glossary

    abdominal aorta
    portion of the aorta inferior to the aortic hiatus and superior to the common iliac arteries
    adrenal artery
    branch of the abdominal aorta; supplies blood to the adrenal (suprarenal) glands
    adrenal vein
    drains the adrenal or suprarenal glands that are immediately superior to the kidneys; the right adrenal vein enters the inferior vena cava directly and the left adrenal vein enters the left renal vein
    anterior cerebral artery
    arises from the internal carotid artery; supplies the frontal lobe of the cerebrum
    anterior communicating artery
    anastomosis of the right and left internal carotid arteries; supplies blood to the brain
    anterior tibial artery
    branches from the popliteal artery; supplies blood to the anterior tibial region; becomes the dorsalis pedis artery
    anterior tibial vein
    forms from the dorsal venous arch; drains the area near the tibialis anterior muscle and leads to the popliteal vein
    aorta
    largest artery in the body, originating from the left ventricle and descending to the abdominal region where it bifurcates into the common iliac arteries at the level of the fourth lumbar vertebra; arteries originating from the aorta distribute blood to virtually all tissues of the body
    aortic arch
    arc that connects the ascending aorta to the descending aorta; ends at the intervertebral disk between the fourth and fifth thoracic vertebrae
    aortic hiatus
    opening in the diaphragm that allows passage of the thoracic aorta into the abdominal region where it becomes the abdominal aorta
    arterial circle
    (also, circle of Willis) anastomosis located at the base of the brain that ensures continual blood supply; formed from branches of the internal carotid and vertebral arteries; supplies blood to the brain
    ascending aorta
    initial portion of the aorta, rising from the left ventricle for a distance of approximately 5 cm
    axillary artery
    continuation of the subclavian artery as it penetrates the body wall and enters the axillary region; supplies blood to the region near the head of the humerus (humeral circumflex arteries); the majority of the vessel continues into the brachium and becomes the brachial artery
    axillary vein
    major vein in the axillary region; drains the upper limb and becomes the subclavian vein
    azygos vein
    originates in the lumbar region and passes through the diaphragm into the thoracic cavity on the right side of the vertebral column; drains blood from the intercostal veins, esophageal veins, bronchial veins, and other veins draining the mediastinal region; leads to the superior vena cava
    basilar artery
    formed from the fusion of the two vertebral arteries; sends branches to the cerebellum, brain stem, and the posterior cerebral arteries; the main blood supply to the brain stem
    basilic vein
    superficial vein of the arm that arises from the palmar venous arches, intersects with the median cubital vein, parallels the ulnar vein, and continues into the upper arm; along with the brachial vein, it leads to the axillary vein
    brachial artery
    continuation of the axillary artery in the brachium; supplies blood to much of the brachial region; gives off several smaller branches that provide blood to the posterior surface of the arm in the region of the elbow; bifurcates into the radial and ulnar arteries at the coronoid fossa
    brachial vein
    deeper vein of the arm that forms from the radial and ulnar veins in the lower arm; leads to the axillary vein
    brachiocephalic artery
    single vessel located on the right side of the body; the first vessel branching from the aortic arch; gives rise to the right subclavian artery and the right common carotid artery; supplies blood to the head, neck, upper limb, and wall of the thoracic region
    brachiocephalic vein
    one of a pair of veins that form from a fusion of the external and internal jugular veins and the subclavian vein; subclavian, external and internal jugulars, vertebral, and internal thoracic veins lead to it; drains the upper thoracic region and flows into the superior vena cava
    bronchial artery
    systemic branch from the aorta that provides oxygenated blood to the lungs in addition to the pulmonary circuit
    bronchial vein
    drains the systemic circulation from the lungs and leads to the azygos vein
    cavernous sinus
    enlarged vein that receives blood from most of the other cerebral veins and the eye socket, and leads to the petrosal sinus
    celiac trunk
    (also, celiac artery) major branch of the abdominal aorta; gives rise to the left gastric artery, the splenic artery, and the common hepatic artery that forms the hepatic artery to the liver, the right gastric artery to the stomach, and the cystic artery to the gall bladder
    cephalic vein
    superficial vessel in the upper arm; leads to the axillary vein
    cerebrovascular accident (CVA)
    blockage of blood flow to the brain; also called a stroke
    circle of Willis
    (also, arterial circle) anastomosis located at the base of the brain that ensures continual blood supply; formed from branches of the internal carotid and vertebral arteries; supplies blood to the brain
    common carotid artery
    right common carotid artery arises from the brachiocephalic artery, and the left common carotid arises from the aortic arch; gives rise to the external and internal carotid arteries; supplies the respective sides of the head and neck
    common hepatic artery
    branch of the celiac trunk that forms the hepatic artery, the right gastric artery, and the cystic artery
    common iliac artery
    branch of the aorta that leads to the internal and external iliac arteries
    common iliac vein
    one of a pair of veins that flows into the inferior vena cava at the level of L5; the left common iliac vein drains the sacral region; divides into external and internal iliac veins near the inferior portion of the sacroiliac joint
    cystic artery
    branch of the common hepatic artery; supplies blood to the gall bladder
    deep femoral artery
    branch of the femoral artery; gives rise to the lateral circumflex arteries
    deep femoral vein
    drains blood from the deeper portions of the thigh and leads to the femoral vein
    descending aorta
    portion of the aorta that continues downward past the end of the aortic arch; subdivided into the thoracic aorta and the abdominal aorta
    digital arteries
    formed from the superficial and deep palmar arches; supply blood to the digits
    digital veins
    drain the digits and feed into the palmar arches of the hand and dorsal venous arch of the foot
    dorsal arch
    (also, arcuate arch) formed from the anastomosis of the dorsalis pedis artery and medial and plantar arteries; branches supply the distal portions of the foot and digits
    dorsal venous arch
    drains blood from digital veins and vessels on the superior surface of the foot
    dorsalis pedis artery
    forms from the anterior tibial artery; branches repeatedly to supply blood to the tarsal and dorsal regions of the foot
    esophageal artery
    branch of the thoracic aorta; supplies blood to the esophagus
    esophageal vein
    drains the inferior portions of the esophagus and leads to the azygos vein
    external carotid artery
    arises from the common carotid artery; supplies blood to numerous structures within the face, lower jaw, neck, esophagus, and larynx
    external iliac artery
    branch of the common iliac artery that leaves the body cavity and becomes a femoral artery; supplies blood to the lower limbs
    external iliac vein
    formed when the femoral vein passes into the body cavity; drains the legs and leads to the common iliac vein
    external jugular vein
    one of a pair of major veins located in the superficial neck region that drains blood from the more superficial portions of the head, scalp, and cranial regions, and leads to the subclavian vein
    femoral artery
    continuation of the external iliac artery after it passes through the body cavity; divides into several smaller branches, the lateral deep femoral artery, and the genicular artery; becomes the popliteal artery as it passes posterior to the knee
    femoral circumflex vein
    forms a loop around the femur just inferior to the trochanters; drains blood from the areas around the head and neck of the femur; leads to the femoral vein
    femoral vein
    drains the upper leg; receives blood from the great saphenous vein, the deep femoral vein, and the femoral circumflex vein; becomes the external iliac vein when it crosses the body wall
    fibular vein
    drains the muscles and integument near the fibula and leads to the popliteal vein
    genicular artery
    branch of the femoral artery; supplies blood to the region of the knee
    gonadal artery
    branch of the abdominal aorta; supplies blood to the gonads or reproductive organs; also described as ovarian arteries or testicular arteries, depending upon the sex of the individual
    gonadal vein
    generic term for a vein draining a reproductive organ; may be either an ovarian vein or a testicular vein, depending on the sex of the individual
    great cerebral vein
    receives most of the smaller vessels from the inferior cerebral veins and leads to the straight sinus
    great saphenous vein
    prominent surface vessel located on the medial surface of the leg and thigh; drains the superficial portions of these areas and leads to the femoral vein
    hemiazygos vein
    smaller vein complementary to the azygos vein; drains the esophageal veins from the esophagus and the left intercostal veins, and leads to the brachiocephalic vein via the superior intercostal vein
    hepatic artery proper
    branch of the common hepatic artery; supplies systemic blood to the liver
    hepatic portal system
    specialized circulatory pathway that carries blood from digestive organs to the liver for processing before being sent to the systemic circulation
    hepatic vein
    drains systemic blood from the liver and flows into the inferior vena cava
    inferior mesenteric artery
    branch of the abdominal aorta; supplies blood to the distal segment of the large intestine and rectum
    inferior phrenic artery
    branch of the abdominal aorta; supplies blood to the inferior surface of the diaphragm
    inferior vena cava
    large systemic vein that drains blood from areas largely inferior to the diaphragm; empties into the right atrium
    intercostal artery
    branch of the thoracic aorta; supplies blood to the muscles of the thoracic cavity and vertebral column
    intercostal vein
    drains the muscles of the thoracic wall and leads to the azygos vein
    internal carotid artery
    arises from the common carotid artery and begins with the carotid sinus; goes through the carotid canal of the temporal bone to the base of the brain; combines with branches of the vertebral artery forming the arterial circle; supplies blood to the brain
    internal iliac artery
    branch from the common iliac arteries; supplies blood to the urinary bladder, walls of the pelvis, external genitalia, and the medial portion of the femoral region; in females, also provide blood to the uterus and vagina
    internal iliac vein
    drains the pelvic organs and integument; formed from several smaller veins in the region; leads to the common iliac vein
    internal jugular vein
    one of a pair of major veins located in the neck region that passes through the jugular foramen and canal, flows parallel to the common carotid artery that is more or less its counterpart; primarily drains blood from the brain, receives the superficial facial vein, and empties into the subclavian vein
    internal thoracic artery
    (also, mammary artery) arises from the subclavian artery; supplies blood to the thymus, pericardium of the heart, and the anterior chest wall
    internal thoracic vein
    (also, internal mammary vein) drains the anterior surface of the chest wall and leads to the brachiocephalic vein
    lateral circumflex artery
    branch of the deep femoral artery; supplies blood to the deep muscles of the thigh and the ventral and lateral regions of the integument
    lateral plantar artery
    arises from the bifurcation of the posterior tibial arteries; supplies blood to the lateral plantar surfaces of the foot
    left gastric artery
    branch of the celiac trunk; supplies blood to the stomach
    lumbar arteries
    branches of the abdominal aorta; supply blood to the lumbar region, the abdominal wall, and spinal cord
    lumbar veins
    drain the lumbar portion of the abdominal wall and spinal cord; the superior lumbar veins drain into the azygos vein on the right or the hemiazygos vein on the left; blood from these vessels is returned to the superior vena cava rather than the inferior vena cava
    maxillary vein
    drains blood from the maxillary region and leads to the external jugular vein
    medial plantar artery
    arises from the bifurcation of the posterior tibial arteries; supplies blood to the medial plantar surfaces of the foot
    median antebrachial vein
    vein that parallels the ulnar vein but is more medial in location; intertwines with the palmar venous arches
    median cubital vein
    superficial vessel located in the antecubital region that links the cephalic vein to the basilic vein in the form of a v; a frequent site for a blood draw
    median sacral artery
    continuation of the aorta into the sacrum
    mediastinal artery
    branch of the thoracic aorta; supplies blood to the mediastinum
    middle cerebral artery
    another branch of the internal carotid artery; supplies blood to the temporal and parietal lobes of the cerebrum
    middle sacral vein
    drains the sacral region and leads to the left common iliac vein
    occipital sinus
    enlarged vein that drains the occipital region near the falx cerebelli and flows into the left and right transverse sinuses, and also into the vertebral veins
    ophthalmic artery
    branch of the internal carotid artery; supplies blood to the eyes
    ovarian artery
    branch of the abdominal aorta; supplies blood to the ovary, uterine (Fallopian) tube, and uterus
    ovarian vein
    drains the ovary; the right ovarian vein leads to the inferior vena cava and the left ovarian vein leads to the left renal vein
    palmar arches
    superficial and deep arches formed from anastomoses of the radial and ulnar arteries; supply blood to the hand and digital arteries
    palmar venous arches
    drain the hand and digits, and feed into the radial and ulnar veins
    parietal branches
    (also, somatic branches) group of arterial branches of the thoracic aorta; includes those that supply blood to the thoracic cavity, vertebral column, and the superior surface of the diaphragm
    pericardial artery
    branch of the thoracic aorta; supplies blood to the pericardium
    petrosal sinus
    enlarged vein that receives blood from the cavernous sinus and flows into the internal jugular vein
    phrenic vein
    drains the diaphragm; the right phrenic vein flows into the inferior vena cava and the left phrenic vein leads to the left renal vein
    plantar arch
    formed from the anastomosis of the dorsalis pedis artery and medial and plantar arteries; branches supply the distal portions of the foot and digits
    plantar veins
    drain the foot and lead to the plantar venous arch
    plantar venous arch
    formed from the plantar veins; leads to the anterior and posterior tibial veins through anastomoses
    popliteal artery
    continuation of the femoral artery posterior to the knee; branches into the anterior and posterior tibial arteries
    popliteal vein
    continuation of the femoral vein behind the knee; drains the region behind the knee and forms from the fusion of the fibular and anterior and posterior tibial veins
    posterior cerebral artery
    branch of the basilar artery that forms a portion of the posterior segment of the arterial circle; supplies blood to the posterior portion of the cerebrum and brain stem
    posterior communicating artery
    branch of the posterior cerebral artery that forms part of the posterior portion of the arterial circle; supplies blood to the brain
    posterior tibial artery
    branch from the popliteal artery that gives rise to the fibular or peroneal artery; supplies blood to the posterior tibial region
    posterior tibial vein
    forms from the dorsal venous arch; drains the area near the posterior surface of the tibia and leads to the popliteal vein
    pulmonary artery
    one of two branches, left and right, that divides off from the pulmonary trunk and leads to smaller arterioles and eventually to the pulmonary capillaries
    pulmonary circuit
    system of blood vessels that provide gas exchange via a network of arteries, veins, and capillaries that run from the heart, through the body, and back to the lungs
    pulmonary trunk
    single large vessel exiting the right ventricle that divides to form the right and left pulmonary arteries
    pulmonary veins
    two sets of paired vessels, one pair on each side, that are formed from the small venules leading away from the pulmonary capillaries that flow into the left atrium
    radial artery
    formed at the bifurcation of the brachial artery; parallels the radius; gives off smaller branches until it reaches the carpal region where it fuses with the ulnar artery to form the superficial and deep palmar arches; supplies blood to the lower arm and carpal region
    radial vein
    parallels the radius and radial artery; arises from the palmar venous arches and leads to the brachial vein
    renal artery
    branch of the abdominal aorta; supplies each kidney
    renal vein
    largest vein entering the inferior vena cava; drains the kidneys and leads to the inferior vena cava
    right gastric artery
    branch of the common hepatic artery; supplies blood to the stomach
    sigmoid sinuses
    enlarged veins that receive blood from the transverse sinuses; flow through the jugular foramen and into the internal jugular vein
    small saphenous vein
    located on the lateral surface of the leg; drains blood from the superficial regions of the lower leg and foot, and leads to the popliteal vein
    splenic artery
    branch of the celiac trunk; supplies blood to the spleen
    straight sinus
    enlarged vein that drains blood from the brain; receives most of the blood from the great cerebral vein and flows into the left or right transverse sinus
    subclavian artery
    right subclavian arises from the brachiocephalic artery, whereas the left subclavian artery arises from the aortic arch; gives rise to the internal thoracic, vertebral, and thyrocervical arteries; supplies blood to the arms, chest, shoulders, back, and central nervous system
    subclavian vein
    located deep in the thoracic cavity; becomes the axillary vein as it enters the axillary region; drains the axillary and smaller local veins near the scapular region; leads to the brachiocephalic vein
    subscapular vein
    drains blood from the subscapular region and leads to the axillary vein
    superior mesenteric artery
    branch of the abdominal aorta; supplies blood to the small intestine (duodenum, jejunum, and ileum), the pancreas, and a majority of the large intestine
    superior phrenic artery
    branch of the thoracic aorta; supplies blood to the superior surface of the diaphragm
    superior sagittal sinus
    enlarged vein located midsagittally between the meningeal and periosteal layers of the dura mater within the falx cerebri; receives most of the blood drained from the superior surface of the cerebrum and leads to the inferior jugular vein and the vertebral vein
    superior vena cava
    large systemic vein; drains blood from most areas superior to the diaphragm; empties into the right atrium
    temporal vein
    drains blood from the temporal region and leads to the external jugular vein
    testicular artery
    branch of the abdominal aorta; will ultimately travel outside the body cavity to the testes and form one component of the spermatic cord
    testicular vein
    drains the testes and forms part of the spermatic cord; the right testicular vein empties directly into the inferior vena cava and the left testicular vein empties into the left renal vein
    thoracic aorta
    portion of the descending aorta superior to the aortic hiatus
    thyrocervical artery
    arises from the subclavian artery; supplies blood to the thyroid, the cervical region, the upper back, and shoulder
    transient ischemic attack (TIA)
    temporary loss of neurological function caused by a brief interruption in blood flow; also known as a mini-stroke
    transverse sinuses
    pair of enlarged veins near the lambdoid suture that drain the occipital, sagittal, and straight sinuses, and leads to the sigmoid sinuses
    trunk
    large vessel that gives rise to smaller vessels
    ulnar artery
    formed at the bifurcation of the brachial artery; parallels the ulna; gives off smaller branches until it reaches the carpal region where it fuses with the radial artery to form the superficial and deep palmar arches; supplies blood to the lower arm and carpal region
    ulnar vein
    parallels the ulna and ulnar artery; arises from the palmar venous arches and leads to the brachial vein
    vertebral artery
    arises from the subclavian artery and passes through the vertebral foramen through the foramen magnum to the brain; joins with the internal carotid artery to form the arterial circle; supplies blood to the brain and spinal cord
    vertebral vein
    arises from the base of the brain and the cervical region of the spinal cord; passes through the intervertebral foramina in the cervical vertebrae; drains smaller veins from the cranium, spinal cord, and vertebrae, and leads to the brachiocephalic vein; counterpart of the vertebral artery
    visceral branches
    branches of the descending aorta that supply blood to the viscera

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