The Cardiovascular System and Heart Anatomy

Study Notes

The cardiovascular system (CVS) consists of the heart and blood vessels.
Arteries carry blood away from the heart, while veins carry blood toward the heart.
Capillaries connect arterioles to venules, facilitating gas exchange.
The heart functions as two pumps: the right heart for pulmonary circulation and the left heart for systemic circulation.
The right heart pumps deoxygenated blood to the lungs for oxygenation.
The left heart pumps oxygenated blood to the rest of the body.
The lymphatic system helps return interstitial fluid and proteins to the blood circulation.

The heart is enclosed in a protective sac called the pericardium.
The fibrous pericardium is a tough outer layer that anchors the heart and prevents overfilling.
The serous pericardium is a thin, slippery membrane with two layers: the parietal layer lining the fibrous pericardium and the visceral layer (epicardium) covering the heart.
Serous fluid between the layers allows for frictionless heart movement.

The heart wall has three layers:
- Epicardium (superficial): the outermost layer that is part of the visceral pericardium.
- Myocardium (middle): the thick muscular layer responsible for the heart's pumping action.
- Endocardium (innermost): the smooth lining of the heart chambers and valves.

The heart has four chambers: two atria and two ventricles.
Each atrium empties into the corresponding ventricle through an atrioventricular (AV) valve.
- The left AV valve is the bicuspid or mitral valve.
- The right AV valve is the tricuspid valve.
Semilunar valves control blood flow out of the ventricles:
- The aortic valve controls blood flow from the left ventricle to the aorta.
- The pulmonary valve controls blood flow from the right ventricle to the pulmonary artery.
The left ventricle wall is thicker than the right ventricle wall due to the higher pressure required for systemic circulation.
The atria and ventricles are separated by muscular septa.
The atrioventricular valves are anchored to the atrioventricular fibro-tendinous ring.

Cardiac muscle cells are striated, short, branched, and interconnected.
Intercalated discs connect cardiac muscle cells, allowing for efficient communication and coordinated contraction.
Cardiac muscle acts as a functional syncytium due to the interconnected nature of its cells.

The heart receives both parasympathetic (vagus nerve) and sympathetic innervation.
The vagus nerve primarily innervates the atria.
- The right vagus nerve supplies the SA node.
- The left vagus nerve supplies the AV node.
Vagal stimulation slows the heart rate.
Sympathetic nerves supply motor and sensory fibers to both atria and ventricles.
Sympathetic stimulation increases the heart rate and force of contraction and dilates coronary arteries.

Cardiac muscle cells have the intrinsic ability to depolarize and contract, independent of the nervous system.
The cardiac conduction system facilitates the generation and spread of electrical impulses for heart contraction.