The Heart: Anatomy and Function

The Heart

• The heart is a transport system pump that propels blood through a system of vessels, ensuring the delivery of oxygenated blood to the body's cells, tissues, and organs, and the return of deoxygenated blood to the lungs.
• The heart is composed of specialized muscle tissue (cardiac muscle) that can spontaneously and continuously depolarize to cause contractions.

Location of the Heart

• The heart is located in the mediastinum, slightly off-center, taking up more space on the left side of the thorax.
• The apex of the heart is pointed infero-laterally towards the left, while the great vessels attach at the superior surface of the heart, opening into the heart chambers.

Pericardium

• The heart is enclosed within a double-walled membranous sac called the pericardium, which arises from the tissue overlying the diaphragm and attaches to the heart around the great vessels.
• The pericardium has two main layers: fibrous pericardium (superficial layer of tough, dense fibrous connective tissue) and serous pericardium (deep layer of smooth, thin, slippery epithelium).
• The serous pericardium has two layers (parietal and visceral) and a space (pericardial cavity) filled with serous fluid, which lubricates and allows for smooth movement.

Layers of the Heart Wall

• The heart wall is composed of three tissue layers: epicardium (outermost layer, which is actually the visceral layer of the serous pericardium), myocardium (middle layer composed mostly of cardiac muscle tissue), and endocardium (innermost layer continuous with the lining of the blood vessels).

Heart Chambers

• The heart consists of four chambers: two atria (left and right, receiving chambers) and two ventricles (left and right, pumping chambers).

Heart Valves

• The heart has four valves that control the flow of blood into and out of the heart chambers: two atrioventricular valves (between atria and ventricles) and two semilunar valves (blood leaves heart).

Blood Flow Through the Heart

• Blood returning to the heart from the body tissues or lungs enters the atria, then passes through the AV valves to enter the ventricles, and is then pumped from the ventricles through the semilunar valves into blood vessels to the lungs or body tissues.

Great Vessels of the Heart

• The great vessels of the heart are those continuous with the heart chambers, including both arteries (deliver blood away from the heart) and veins (deliver blood to the heart).
• Arteries carry oxygenated blood (red) and veins carry deoxygenated blood (blue).

Circulatory Paths

• The heart is a dual pump that circulates blood through two circulatory paths, in series: the systemic circulation and the pulmonary circulation.

Learn about the heart's structure and role in the human body, including its function as a pump and delivery of oxygenated blood to cells and organs.