The Heart: Structure, Function, and Circulation

Heart Size

Size of a fist, weighs 250-300 grams.

Heart Location

Located in mediastinum, two-thirds left of midline.

Heart Orientation

Base points to right shoulder, apex to left hip.

Pericardium

Double-walled sac enclosing the heart.

Fibrous Pericardium

Protects, anchors, prevents overfilling of heart.

Serous Pericardium

Has parietal and visceral layers surrounding heart.

Pericardial Cavity

Contains serous fluid, reduces friction.

Epicardium

Outer layer of the heart wall.

Myocardium

Cardiac muscle layer, supports heart valves.

Endocardium

Lines heart chambers, continuous with blood vessels.

Right Atrium

Receives blood from vena cavae and coronary sinus.

Left Atrium

Receives blood from four pulmonary veins.

Right Ventricle

Pumps blood into pulmonary trunk.

Left Ventricle

Pumps blood into the aorta.

Pulmonary Circuit

Transports oxygen-poor blood to lungs.

Systemic Circuit

Delivers oxygenated blood to body tissues.

Tricuspid Valve

Right AV valve, prevents backflow during contraction.

Mitral Valve

Left AV valve, prevents backflow during contraction.

Semilunar Valves

Prevent backflow into ventricles after ejection.

Coronary Circulation

Supplies blood to heart muscle via arteries.

Sinoatrial Node

Primary pacemaker of the heart.

Atrioventricular Node

Delays impulse for atrial contraction.

Cardiac Cycle

Includes phases of filling, contraction, and relaxation.

Stroke Volume Regulation

Influenced by preload, contractility, and afterload.

Heart Rate Regulation

Controlled by nervous system and hormones.

Congestive Heart Failure

Inefficient pumping leads to fluid buildup.