Cardiovascular System

What is the primary physiological function of veins?

Veins collect blood from venules and return low-pressure blood back toward the heart.

What are the three structural layers (tunicae) of an arterial wall?

1. Innermost layer: Endothelium of simple squamous epithelial cells

2. Middle layer: Smooth muscle tissue

3. Outer layer: Connective tissue layer

How do the mechanical roles of the endothelium and smooth muscle layers differ in arterial blood circulation?

The endothelium forms a slick surface that minimizes fluid friction during blood flow. The smooth muscle layer actively contracts (vasoconstriction) or relaxes (vasodilatation) to regulate vessel lumen diameter and blood distribution under high pressure.

What structural and protective function does the outer connective tissue layer of an artery serve?

It provides mechanical strength, structural support, and anchoring protection against rupture under high systolic blood pressure.

What is an arterial aneurism?

A localized defect or weakening in an arterial wall causing the vessel to balloon outward or bulge inward, potentially obstructing flow or rupturing.

What clinical features and risks are associated with aortic aneurisms?

Aortic aneurisms often develop slowly over time and remain completely symptomless until rupture. Rupture of an aortic aneurism causes massive internal hemorrhage and can be rapidly fatal without immediate surgical intervention.

What structural feature defines arterioles within the vascular tree?

Arterioles are the smallest arterial branches that lead directly into capillary networks.

What is the physiological role of precapillary sphincters in microcirculation?

Precapillary sphincters are rings of smooth muscle located at arteriole-capillary junctions that open or close to regulate localized blood volume entering capillary beds.

How do vasodilation and vasoconstriction of arterioles impact capillary blood flow?

Vasodilation (relaxation of vascular smooth muscle) increases localized blood flow into capillaries. Vasoconstriction (contraction of vascular smooth muscle) decreases localized blood flow into capillaries.

What structural adaptations enable capillaries to serve as the exclusive sites of substance exchange?

Capillaries are microscopic, porous, and thin-walled, consisting of only a single layer of squamous endothelial cells.

Which components filter across capillary walls into tissue fluid, and which remain trapped inside the vessel?

Water, O2​, glucose, amino acids, and nutrients exit into interstitial fluid, while CO2​ and metabolic wastes enter the blood. Red blood cells (RBCs) and most plasma proteins are too large and remain inside the capillary.

What three anatomical mechanisms facilitate venous return to the heart against gravity?

1. Skeletal muscle contractions ("milking action" compressing thin-walled veins)

2. One-way venous valves preventing backward flow

3. Thoracic pressure changes associated with breathing

What is the structural composition and function of the pericardium?

The pericardium is a protective fibrous sac surrounding the heart that anchors it within the mediastinum and prevents overfilling.

Name the three structural layers composing the heart wall.

1. Epicardium (outer thin epithelial and connective tissue layer)

2. Myocardium (thick cardiac muscle layer)

3. Endocardium (inner thin endothelial lining)

Which heart wall layer is directly responsible for heart contractions, and how do electrical signals spread through it?

The myocardium. Electrical signals flow directly from cardiac muscle cell to cell, triggering synchronized muscular contraction during beats.

What anatomical boundary separates the right and left heart chambers?

The septum, a muscular partition that prevents mixing of deoxygenated and oxygenated blood.

Why is the muscular wall of the left ventricle significantly thicker than that of the right ventricle?

The left ventricle must contract with sufficient force to propel blood through high-resistance systemic circulation across the entire body, whereas the right ventricle only pumps blood through the low-resistance pulmonary circuit to the lungs.

Contrast the structural cusp counts and anatomical locations of the two atrioventricular (AV) valves.

Right AV Valve (Tricuspid valve): Has 3 cusps; located between the right atrium and right ventricle. • Left AV Valve (Bicuspid / Mitral valve): Has 2 cusps; located between the left atrium and left ventricle.

What is the functional relationship between chordae tendineae and papillary muscles during ventricular contraction?

Chordae tendineae are tough fibrous cords that anchor the AV valve leaflets to papillary muscles located on the ventricle floor. Papillary muscle contraction pulls on the cords to prevent valve cusps from everting back into the atria during high-pressure ventricular systole.

Identify the destination and ventricular origin for each semilunar valve.

Pulmonary Semilunar Valve: Controls blood flow from the right ventricle into the pulmonary trunk. • Aortic Semilunar Valve: Controls blood flow from the left ventricle into the aorta.

What fundamental functional distinction exists between the pulmonary and systemic circulatory circuits?

Pulmonary Circuit: Transports deoxygenated blood to the lungs to pick up O2​ and release CO2​. • Systemic Circuit: Transports oxygenated blood throughout the rest of the body where tissue cells consume O2​ and deposit CO2​ waste.

Trace the step-by-step route of deoxygenated blood through the pulmonary circuit starting from systemic venous return up to arrival in the left atrium.

1. Venae cavae → Right atrium

2. Right AV (tricuspid) valve → Right ventricle

3. Pulmonary semilunar valve → Pulmonary trunk → Right and left pulmonary arteries

4. Pulmonary capillaries (blood picks up O2​ and releases CO2​)

5. Pulmonary veins → Left atrium

Trace the sequential systemic blood flow route starting from the left atrium to systemic veins and return to the heart.

1. Left atrium → Left AV (bicuspid) valve → Left ventricle

2. Aortic semilunar valve → Aorta

3. Branching systemic arteries → Arterioles

4. Systemic capillaries (delivers O2​/nutrients, picks up wastes)

5. Venules → Systemic veins → Venae cavae → Right atrium

What is the primary physiological function of the coronary arteries?

Coronary arteries branch directly off the aorta to supply oxygen-rich blood directly to the heart muscle (myocardium) itself.

What is the primary physiological function of the coronary veins?

Coronary veins collect deoxygenated blood from myocardial capillary beds and channel it back directly into the right atrium.

What is the average duration of one complete cardiac cycle in a resting heart beating 72 times per minute?

Approximately 0.8 seconds.

Contrast ventricular systole and diastole phases regarding heart valve status and blood movement.

Ventricular Systole (~0.3 s): Ventricles contract; AV valves close (producing S1 "lubb") and semilunar valves open to eject blood into great arteries. • Ventricular Diastole (~0.4 s): Ventricles relax; semilunar valves snap shut (producing S2 "dupp") and AV valves open to allow passive ventricular filling.

What mechanical event occurring during atrial systole completes ventricular filling?

Both atria contract (~0.1 s) while AV valves are open and semilunar valves are closed, forcing the remaining atrial blood volume into the ventricles.

What clinical technique is used to listen to internal heart sounds?

Auscultation (listening to bodily sounds, typically using a stethoscope).

What specific mechanical event generates the first heart sound (S1, "lubb")?

The forced closure of the atrioventricular (AV) valves at the onset of ventricular systole, producing a louder and longer sound.

What specific mechanical event generates the second heart sound (S2, "dupp")?

The closure of the semilunar valves (aortic and pulmonary) at the beginning of ventricular diastole, producing a softer and sharper sound.

What are heart murmurs?

Abnormal heart sounds caused by turbulent blood flow, frequently resulting from damaged or leaky heart valves.

Where are arterial baroreceptors located, and what is their primary function?

Baroreceptors are pressure-sensitive sensory receptors located in the walls of the aorta and carotid arteries that monitor arterial blood pressure.

How does the autonomic cardiovascular control loop respond when baroreceptors detect elevated arterial blood pressure?

1. Vessel stretching increases baroreceptor nerve firing rates to the cardiovascular center.

2. Cardiovascular signals lower heart rate and force of contraction (decreasing cardiac output).

3. Blood vessels are signaled to dilate, reducing vascular resistance to lower blood pressure back to normal homeostasis.

How high can cardiac output (CO) increase during strenuous exercise in non-athletes versus trained athletes?

Non-athletes: Up to 20–25 liters/min • Trained athletes: Up to 35 liters/min

What clinical condition is characterized by angina, and what primary pathology causes it?

Angina is chest pain and tightness caused by temporary narrowing of coronary arteries (atherosclerosis) leading to diminished blood flow (ischemia) to the myocardium.

What diagnostic imaging procedure visualizes narrowed coronary arteries in angina patients?

Angiography (coronary angiogram).

What medical and surgical treatment options exist for managing angina?

Medications (e.g., vasodilators) • Balloon angioplasty (stent placement) • Coronary artery bypass graft (CABG) surgery

What is a myocardial infarction (heart attack)?

Permanent tissue damage or cell death in the myocardium resulting from severe or complete blockage of coronary blood flow.

What classic symptoms accompany a acute myocardial infarction?

Intense chest pain, tightness or pressure, radiating pain down the left arm, jaw and back pain, shortness of breath, and nausea.

Which clinical diagnostic tools confirm a suspected myocardial infarction?

1. Electrocardiogram (ECG/EKG)

2. Blood tests detecting cardiac intracellular enzymes released by damaged muscle cells

What is congestive heart failure?

A condition where weakened heart muscle pumps inefficiently, causing blood backing up and fluid accumulation (edema) in tissue interstitial spaces.

What physical signs indicate fluid accumulation in congestive heart failure?

Shortness of breath, swollen ankles and legs, and distended neck veins.

What defines a vascular embolism?

Sudden blockage of a blood vessel caused by a traveling mass (embolus) floating in the bloodstream.

List five potential materials that can form an embolus.

1. Dislodged blood clots

2. Cholesterol deposits

3. Tissue fragments or cancer cell clumps

4. Clumps of bacteria

5. Air bubbles

Differentiate between the clinical outcomes of a cerebral embolism versus a cardiac embolism.

Cerebral Embolism: Blocks brain vasculature, causing an ischemic stroke. • Cardiac Embolism: Blocks coronary arteries, causing a myocardial infarction (heart attack).

What is a stroke (cerebrovascular accident)?

Brain tissue damage caused by an interruption of blood supply to a specific region of the brain.

What are the two most common underlying vascular causes of stroke?

1. Embolism blocking a cerebral blood vessel (ischemic stroke)

2. Rupture of a cerebral artery (hemorrhagic stroke)

How do emergency medical interventions differ for ischemic versus hemorrhagic strokes?

Ischemic Stroke (embolism): Patient receives clot-dissolving (thrombolytic) medications. • Hemorrhagic Stroke (rupture): Surgical repair or clip placement to control bleeding.

What is a cardiac xenotransplant?

Surgical transplantation of a heart harvested from another animal species (e.g., pig) into a human patient.