10: Cardiovascular System
- Page ID
- 100113
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 10.1: Overview of the Cardiovascular System
- The cardiovascular system consists of the heart and blood vessels. They work together to circulate blood through the pulmonary and systemic circuits, delivering oxygen and nutrients while removing carbon dioxide and other wastes. In this unit, you will learn how these two circuits function, how blood flows through the heart and lungs, and how the system supports homeostasis by regulating temperature, pH, fluid balance, and rapid communication throughout the body.
- 10.2: Heart Anatomy — Overview
- The heart is a four-chambered muscular organ located in the mediastinum of the thoracic cavity and enclosed by the protective pericardium. Its chambers, valves, and septum allow it to function as a double pump that separates pulmonary and systemic circulation, while its intrinsic conduction system coordinates each heartbeat and the coronary arteries supply the cardiac muscle itself.
- 10.3: Pericardium and the Heart Wall
- The pericardium is a double-layered protective sac that anchors the heart within the mediastinum, reduces friction through serous fluid, and limits excessive expansion. The heart wall consists of three layers — epicardium, myocardium, and endocardium — with the thick, spiraled myocardium generating the forceful, twisting contractions that pump blood. Greater resistance in the systemic circuit explains why the left ventricle has a significantly thicker wall than the right.
- 10.4: Heart Anatomy - Details
- Detailed heart anatomy includes the external features, great vessels, coronary circulation, and the internal chambers, septa, and valves that coordinate efficient blood flow. Blood is traced step by step through the atria, ventricles, pulmonary and systemic circuits, while structures such as the chordae tendineae and papillary muscles ensure one-way movement and prevent backflow.
- 10.5: Generation and Transmission of Cardiac Impulses
- Specialized cardiac conducting cells generate and transmit electrical impulses that coordinate each heartbeat, beginning at the sinoatrial (SA) node and passing through the atrioventricular (AV) node, bundle branches, and Purkinje fibers to produce a precise sequence of atrial and ventricular contraction. The nervous system and hormones adjust how fast and how forcefully the heart pumps to match the body’s needs.
- 10.6: Electrocardiogram (ECG)
- An electrocardiogram (ECG) records the heart’s electrical activity using surface electrodes. A 12-lead ECG provides multiple electrical viewpoints for a detailed assessment of cardiac function. The P wave, QRS complex, T wave, and key intervals reflect specific electrical and mechanical events in the atria and ventricles. Interpreting ECG patterns allows recognition of conduction problems and arrhythmias.
- 10.7: Cardiac Cycle
- The cardiac cycle describes the repeating phases of atrial and ventricular systole and diastole that move blood through the heart and into the pulmonary and systemic circuits. Pressure changes within the chambers control when valves open and close, producing heart sounds and directing one-way blood flow. The P wave, QRS complex, and T wave on the ECG correspond to the electrical events that trigger these coordinated mechanical contractions and relaxations.
- 10.8: Heart Sounds
- Heart sounds are produced by the closing of the heart valves, with S₁ (“lub”) resulting from closure of the atrioventricular valves and S₂ (“dub”) from closure of the semilunar valves. Auscultation helps assess whether valves are functioning properly and whether blood flow is smooth or turbulent. Abnormal sounds, such as murmurs, can indicate valve defects, altered ventricular function, or other cardiac disorders.
- 10.9: Blood Vessel Structure and Function
- Blood vessels form a closed network of arteries, veins, and capillaries that transport blood between the heart, lungs, and body tissues. Their structural differences — thick, muscular arteries; thinner, valve-containing veins; and single-cell-layer capillaries — reflect their specific roles. Together, these vessels regulate blood flow within the systemic and pulmonary circuits, as well as gas, nutrient, and waste exchange, blood pressure, temperature, and overall homeostasis.
- 10.10: Circulatory Pathways
- 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.
- 10.11: Portal Systems
- Portal systems are specialized circulatory pathways in which blood passes through two capillary beds in sequence, connected by a portal vein, before returning to the heart. The hepatic portal system directs nutrient-rich blood from the digestive organs to the liver for processing and detoxification, while the hypophyseal portal system delivers hypothalamic hormones directly to the anterior pituitary for precise endocrine regulation.
- 10.12: Vital Signs and Pulse
- Vital signs are basic measurements — temperature, pulse, blood pressure, and respiratory rate — that provide immediate insight into how well the body’s major systems are functioning. Normal adult ranges help identify when values are elevated or decreased, allowing early detection of illness or distress. Monitoring these signs supports clinical decision-making and assessment of overall health status.
- 10.13: Understanding and Measuring Blood Pressure
- Systemic blood pressure refers to the force of blood pushing against arterial walls, measured as systolic pressure during ventricular contraction and diastolic pressure during relaxation. Pressure is highest and most pulsatile in the large arteries and steadily decreases through arterioles, capillaries, and veins. Accurate measurement and interpretation of blood pressure helps assess cardiovascular health and detects risk factors such as hypertension or arterial stiffness.
- 10.14: Hypertension
- Hypertension is a chronic elevation of systemic arterial pressure that strains the heart and blood vessels and increases the risk of heart attack, stroke, and kidney disease. Primary hypertension has no single identifiable cause and accounts for most cases, while secondary hypertension results from underlying conditions such as kidney or endocrine disorders. In contrast, hypotension is abnormally low blood pressure that can reduce organ perfusion and cause dizziness or fainting.
- 10.15: Atherosclerosis
- Arteriosclerosis refers broadly to stiffening and hardening of the arteries, while atherosclerosis is a specific type caused by plaque buildup that narrows the vessel lumen and restricts blood flow. Plaque formation can progress silently for years and may lead to heart attack, stroke, or peripheral artery disease when vessels become critically narrowed or blocked.
- 10.16: Capillary Exchange
- Capillary exchange is the movement of gases, nutrients, wastes, and fluids between the blood and tissues through diffusion, transcytosis, and bulk flow. Hydrostatic pressure pushes fluid out of capillaries while osmotic pressure pulls fluid back in, determining whether filtration or reabsorption occurs. Excess fluid is returned to the bloodstream by the lymphatic system, and failure of this drainage leads to edema.