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Key Terms Chapter 20: The Cardiovascular System: Blood Vessels and Circulation

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    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
    anaphylactic shock
    type of shock that follows a severe allergic reaction and results from massive vasodilation
    angioblasts
    stem cells that give rise to blood vessels
    angiogenesis
    development of new blood vessels from existing vessels
    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
    aortic sinuses
    small pockets in the ascending aorta near the aortic valve that are the locations of the baroreceptors (stretch receptors) and chemoreceptors that trigger a reflex that aids in the regulation of vascular homeostasis
    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
    arteriole
    (also, resistance vessel) very small artery that leads to a capillary
    arteriovenous anastomosis
    short vessel connecting an arteriole directly to a venule and bypassing the capillary beds
    artery
    blood vessel that conducts blood away from the heart; may be a conducting or distributing vessel
    ascending aorta
    initial portion of the aorta, rising from the left ventricle for a distance of approximately 5 cm
    atrial reflex
    mechanism for maintaining vascular homeostasis involving atrial baroreceptors: if blood is returning to the right atrium more rapidly than it is being ejected from the left ventricle, the atrial receptors will stimulate the cardiovascular centers to increase sympathetic firing and increase cardiac output until the situation is reversed; the opposite is also true
    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
    blood colloidal osmotic pressure (BCOP)
    pressure exerted by colloids suspended in blood within a vessel; a primary determinant is the presence of plasma proteins
    blood flow
    movement of blood through a vessel, tissue, or organ that is usually expressed in terms of volume per unit of time
    blood hydrostatic pressure
    force blood exerts against the walls of a blood vessel or heart chamber
    blood islands
    masses of developing blood vessels and formed elements from mesodermal cells scattered throughout the embryonic disc
    blood pressure
    force exerted by the blood against the wall of a vessel or heart chamber; can be described with the more generic term hydrostatic pressure
    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
    capacitance
    ability of a vein to distend and store blood
    capacitance vessels
    veins
    capillary
    smallest of blood vessels where physical exchange occurs between the blood and tissue cells surrounded by interstitial fluid
    capillary bed
    network of 10–100 capillaries connecting arterioles to venules
    capillary hydrostatic pressure (CHP)
    force blood exerts against a capillary
    cardiogenic shock
    type of shock that results from the inability of the heart to maintain cardiac output
    carotid sinuses
    small pockets near the base of the internal carotid arteries that are the locations of the baroreceptors and chemoreceptors that trigger a reflex that aids in the regulation of vascular homeostasis
    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
    circulatory shock
    also simply called shock; a life-threatening medical condition in which the circulatory system is unable to supply enough blood flow to provide adequate oxygen and other nutrients to the tissues to maintain cellular metabolism
    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
    compliance
    degree to which a blood vessel can stretch as opposed to being rigid
    continuous capillary
    most common type of capillary, found in virtually all tissues except epithelia and cartilage; contains very small gaps in the endothelial lining that permit exchange
    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
    diastolic pressure
    lower number recorded when measuring arterial blood pressure; represents the minimal value corresponding to the pressure that remains during ventricular relaxation
    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
    ductus arteriosus
    shunt in the fetal pulmonary trunk that diverts oxygenated blood back to the aorta
    ductus venosus
    shunt that causes oxygenated blood to bypass the fetal liver on its way to the inferior vena cava
    elastic artery
    (also, conducting artery) artery with abundant elastic fibers located closer to the heart, which maintains the pressure gradient and conducts blood to smaller branches
    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 elastic membrane
    membrane composed of elastic fibers that separates the tunica media from the tunica externa; seen in larger arteries
    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
    fenestrated capillary
    type of capillary with pores or fenestrations in the endothelium that allow for rapid passage of certain small materials
    fibular vein
    drains the muscles and integument near the fibula and leads to the popliteal vein
    filtration
    in the cardiovascular system, the movement of material from a capillary into the interstitial fluid, moving from an area of higher pressure to lower pressure
    foramen ovale
    shunt that directly connects the right and left atria and helps to divert oxygenated blood from the fetal pulmonary circuit
    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
    hemangioblasts
    embryonic stem cells that appear in the mesoderm and give rise to both angioblasts and pluripotent stem cells
    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
    hypertension
    chronic and persistent blood pressure measurements of 140/90 mm Hg or above
    hypervolemia
    abnormally high levels of fluid and blood within the body
    hypovolemia
    abnormally low levels of fluid and blood within the body
    hypovolemic shock
    type of circulatory shock caused by excessive loss of blood volume due to hemorrhage or possibly dehydration
    hypoxia
    lack of oxygen supply to the tissues
    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 elastic membrane
    membrane composed of elastic fibers that separates the tunica intima from the tunica media; seen in larger arteries
    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
    interstitial fluid colloidal osmotic pressure (IFCOP)
    pressure exerted by the colloids within the interstitial fluid
    interstitial fluid hydrostatic pressure (IFHP)
    force exerted by the fluid in the tissue spaces
    ischemia
    insufficient blood flow to the tissues
    Korotkoff sounds
    noises created by turbulent blood flow through the vessels
    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
    lumen
    interior of a tubular structure such as a blood vessel or a portion of the alimentary canal through which blood, chyme, or other substances travel
    maxillary vein
    drains blood from the maxillary region and leads to the external jugular vein
    mean arterial pressure (MAP)
    average driving force of blood to the tissues; approximated by taking diastolic pressure and adding 1/3 of pulse pressure
    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
    metarteriole
    short vessel arising from a terminal arteriole that branches to supply a capillary bed
    microcirculation
    blood flow through the capillaries
    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
    muscular artery
    (also, distributing artery) artery with abundant smooth muscle in the tunica media that branches to distribute blood to the arteriole network
    myogenic response
    constriction or dilation in the walls of arterioles in response to pressures related to blood flow; reduces high blood flow or increases low blood flow to help maintain consistent flow to the capillary network
    nervi vasorum
    small nerve fibers found in arteries and veins that trigger contraction of the smooth muscle in their walls
    net filtration pressure (NFP)
    force driving fluid out of the capillary and into the tissue spaces; equal to the difference of the capillary hydrostatic pressure and the blood colloidal osmotic pressure
    neurogenic shock
    type of shock that occurs with cranial or high spinal injuries that damage the cardiovascular centers in the medulla oblongata or the nervous fibers originating from this region
    obstructive shock
    type of shock that occurs when a significant portion of the vascular system is blocked
    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
    perfusion
    distribution of blood into the capillaries so the tissues can be supplied
    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
    precapillary sphincters
    circular rings of smooth muscle that surround the entrance to a capillary and regulate blood flow into that capillary
    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
    pulse
    alternating expansion and recoil of an artery as blood moves through the vessel; an indicator of heart rate
    pulse pressure
    difference between the systolic and diastolic pressures
    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
    reabsorption
    in the cardiovascular system, the movement of material from the interstitial fluid into the capillaries
    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
    resistance
    any condition or parameter that slows or counteracts the flow of blood
    respiratory pump
    increase in the volume of the thorax during inhalation that decreases air pressure, enabling venous blood to flow into the thoracic region, then exhalation increases pressure, moving blood into the atria
    right gastric artery
    branch of the common hepatic artery; supplies blood to the stomach
    sepsis
    (also, septicemia) organismal-level inflammatory response to a massive infection
    septic shock
    (also, blood poisoning) type of shock that follows a massive infection resulting in organism-wide inflammation
    sigmoid sinuses
    enlarged veins that receive blood from the transverse sinuses; flow through the jugular foramen and into the internal jugular vein
    sinusoid capillary
    rarest type of capillary, which has extremely large intercellular gaps in the basement membrane in addition to clefts and fenestrations; found in areas such as the bone marrow and liver where passage of large molecules occurs
    skeletal muscle pump
    effect on increasing blood pressure within veins by compression of the vessel caused by the contraction of nearby skeletal muscle
    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
    sphygmomanometer
    blood pressure cuff attached to a device that measures blood pressure
    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
    systolic pressure
    larger number recorded when measuring arterial blood pressure; represents the maximum value following ventricular contraction
    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
    thoroughfare channel
    continuation of the metarteriole that enables blood to bypass a capillary bed and flow directly into a venule, creating a vascular shunt
    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
    tunica externa
    (also, tunica adventitia) outermost layer or tunic of a vessel (except capillaries)
    tunica intima
    (also, tunica interna) innermost lining or tunic of a vessel
    tunica media
    middle layer or tunic of a vessel (except capillaries)
    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
    umbilical arteries
    pair of vessels that runs within the umbilical cord and carries fetal blood low in oxygen and high in waste to the placenta for exchange with maternal blood
    umbilical vein
    single vessel that originates in the placenta and runs within the umbilical cord, carrying oxygen- and nutrient-rich blood to the fetal heart
    vasa vasorum
    small blood vessels located within the walls or tunics of larger vessels that supply nourishment to and remove wastes from the cells of the vessels
    vascular shock
    type of shock that occurs when arterioles lose their normal muscular tone and dilate dramatically
    vascular shunt
    continuation of the metarteriole and thoroughfare channel that allows blood to bypass the capillary beds to flow directly from the arterial to the venous circulation
    vascular tone
    contractile state of smooth muscle in a blood vessel
    vascular tubes
    rudimentary blood vessels in a developing fetus
    vasoconstriction
    constriction of the smooth muscle of a blood vessel, resulting in a decreased vascular diameter
    vasodilation
    relaxation of the smooth muscle in the wall of a blood vessel, resulting in an increased vascular diameter
    vasomotion
    irregular, pulsating flow of blood through capillaries and related structures
    vein
    blood vessel that conducts blood toward the heart
    venous reserve
    volume of blood contained within systemic veins in the integument, bone marrow, and liver that can be returned to the heart for circulation, if needed
    venule
    small vessel leading from the capillaries to veins
    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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