Cardiovascular System – Anatomy and Physiology of Heart
Introduction
The cardiovascular system, also known as the circulatory system, is responsible for transporting blood, nutrients, oxygen, and waste materials throughout the body. It consists of the heart, blood vessels, and blood.
The heart works as a pump that pushes blood through vessels to reach every cell in the body, maintaining life and energy balance.
Definition
The heart is a muscular organ that pumps blood through the circulatory system. It ensures that oxygen-rich blood reaches body tissues and carries away carbon dioxide and waste materials.
Original Notes:
Anatomy of the Heart:
Location and Size
The heart is located in the thoracic cavity, slightly to the left of the midline, between the lungs and behind the sternum. It weighs about 250–300 grams in adults and is roughly the size of a clenched fist.
Coverings of the Heart
The heart is enclosed in a protective covering called the pericardium, which has two layers:
- Fibrous Pericardium: The outer tough layer that protects and anchors the heart.
- Serous Pericardium: The inner double-layered membrane (parietal and visceral layers) that secretes pericardial fluid to reduce friction during heartbeats.
Structure of the Heart
The heart is divided into four chambers:
- Right Atrium: Receives deoxygenated blood from the body through the superior and inferior vena cava.
- Right Ventricle: Pumps deoxygenated blood to the lungs via the pulmonary artery.
- Left Atrium: Receives oxygenated blood from the lungs through the pulmonary veins.
- Left Ventricle: Pumps oxygenated blood to the body through the aorta, the largest artery.
The right side of the heart handles deoxygenated blood, and the left side handles oxygenated blood.
Heart Valves
Valves maintain a one-way flow of blood and prevent backflow:
- Tricuspid Valve: Between right atrium and right ventricle.
- Pulmonary Valve: Between right ventricle and pulmonary artery.
- Mitral (Bicuspid) Valve: Between left atrium and left ventricle.
- Aortic Valve: Between left ventricle and aorta.
Blood Supply to the Heart
The heart muscle (myocardium) receives oxygen and nutrients through the coronary arteries. Blood returns through coronary veins into the right atrium.
Physiology of the Heart
Circulation of Blood
The blood flow through the heart and body occurs in two circuits:
Pulmonary Circulation
- Carries deoxygenated blood from the right ventricle to the lungs.
- Blood gets oxygenated in the lungs and returns to the left atrium.
Systemic Circulation
- Carries oxygenated blood from the left ventricle to the whole body.
- Deoxygenated blood returns to the right atrium.
Cardiac Cycle
The cardiac cycle is one complete heartbeat consisting of contraction (systole) and relaxation (diastole) of the heart chambers.
Average duration: 0.8 seconds.
- Atrial Systole: Atria contract, pushing blood into ventricles.
- Ventricular Systole: Ventricles contract, pumping blood to lungs and body.
- Diastole: Heart muscles relax, and chambers fill with blood again.
Heartbeat and Heart Rate
The heart contracts rhythmically due to electrical signals generated by specialized tissues:
- SA Node (Sinoatrial Node): Natural pacemaker that initiates the heartbeat.
- AV Node (Atrioventricular Node): Receives impulse from SA node.
- Bundle of His and Purkinje Fibers: Spread impulses through ventricles for coordinated contraction.
Normal heart rate: 72 beats per minute in adults.
Heart Sounds
- “Lub” (S1): Closure of AV valves (tricuspid and mitral).
- “Dub” (S2): Closure of semilunar valves (aortic and pulmonary).
These sounds indicate proper valve opening and closing during the cardiac cycle.
Functions of the Heart
- Pumps oxygenated blood to body tissues and deoxygenated blood to lungs.
- Maintains continuous blood circulation throughout the body.
- Regulates blood pressure and ensures oxygen supply to vital organs.
- Maintains body temperature and homeostasis.
- Helps in the removal of carbon dioxide and metabolic wastes.
Common Disorders of the Heart
- Hypertension: High blood pressure due to increased workload on the heart.
- Myocardial Infarction (Heart Attack): Blockage in coronary arteries causing death of heart tissue.
- Arrhythmia: Irregular heartbeat due to electrical conduction disturbance.
- Heart Failure: Inability of the heart to pump enough blood.
- Valvular Disorders: Malfunction of heart valves leading to improper blood flow.
