Cardiovascular System: Key Structures, Functions, and Heart Cycle

Cardiovascular System

Composed of the heart, blood vessels, and blood.

Function of Cardiovascular System

Delivers oxygen/nutrients and removes waste from body tissues.

Arteries

Carry blood away from the heart.

Veins

Carry blood toward the heart.

Heart

Muscular organ that pumps blood throughout the body.

Apex

Pointed tip of the heart directed downward and to the left.

Base

Broad upper portion of the heart where major vessels attach.

Coronary arteries

Supply oxygen-rich blood to the heart muscle.

Pericardium

Double-layered membrane around the heart.

Parietal pericardium

Outer, tough sac of the pericardium.

Visceral pericardium

Inner layer on the heart surface.

Pericardial fluid

Reduces friction during each heartbeat.

Epicardium

Outer layer of the heart wall (same as visceral pericardium).

Myocardium

Thick, muscular middle layer of the heart wall; does the pumping.

Endocardium

Smooth inner lining of chambers and valves of the heart.

Heart Chambers

Right atrium → Tricuspid valve → Right ventricle; Left atrium → Mitral (bicuspid) valve → Left ventricle.

Pulmonary valve

Leads from right ventricle to pulmonary artery (to lungs).

Aortic valve

Leads from left ventricle to aorta (to body).

Pulmonary circulation

Right ventricle → lungs → left atrium.

Systemic circulation

Left ventricle → body → right atrium.

Systole

Contraction phase of the cardiac cycle (blood pumped out).

Diastole

Relaxation phase of the cardiac cycle (heart refills).

S1

Heart sound ("Lub") - closing of atrioventricular valves (tricuspid and mitral).

S2

Heart sound ("Dub") - closing of semilunar valves (pulmonary and aortic).