Structure of the human heart, blood vessels, blood composition, circulation process

1. Introduction to the Circulatory System

1. The circulatory system is responsible for the transport of oxygen, nutrients, hormones, and waste materials throughout the body.
2. It consists of the heart, blood vessels, and blood.
3. It plays a crucial role in maintaining homeostasis.

2. Structure of the Human Heart

1. The human heart is a four-chambered, muscular organ located in the chest cavity.
2. It is enclosed in a protective membrane called the pericardium.
3. The four chambers of the heart:
   • Right Atrium: Receives deoxygenated blood from the body.
   • Right Ventricle: Pumps deoxygenated blood to the lungs.
   • Left Atrium: Receives oxygenated blood from the lungs.
   • Left Ventricle: Pumps oxygenated blood to the body.
4. The heart has valves that prevent the backflow of blood:
   • Tricuspid Valve: Between right atrium and right ventricle.
   • Bicuspid (Mitral) Valve: Between left atrium and left ventricle.
   • Pulmonary Valve: Between right ventricle and pulmonary artery.
   • Aortic Valve: Between left ventricle and aorta.

3. Blood Vessels

1. Arteries: Carry oxygenated blood away from the heart (except the pulmonary artery).
2. Veins: Carry deoxygenated blood back to the heart (except the pulmonary vein).
3. Capillaries: Tiny blood vessels where exchange of gases and nutrients occurs.

4. Blood Composition

1. Blood is composed of plasma and blood cells.
2. Plasma: The liquid part of blood containing water, proteins, nutrients, hormones, and waste products.
3. Red Blood Cells (RBCs): Contain hemoglobin and transport oxygen.
4. White Blood Cells (WBCs): Help in immunity and fight infections.
5. Platelets: Assist in blood clotting.

5. Circulation Process

(a) Pulmonary Circulation

1. Transports deoxygenated blood from the right ventricle to the lungs.
2. Gas exchange occurs in the alveoli, where blood gets oxygenated.
3. Oxygenated blood returns to the left atrium.

(b) Systemic Circulation

1. Oxygenated blood is pumped from the left ventricle to the body via the aorta.
2. Nutrients and oxygen are delivered to body cells, and waste products are collected.
3. Deoxygenated blood returns to the right atrium via the vena cava.

(c) Coronary Circulation

1. Supplies oxygen and nutrients to the heart muscle.
2. Blockage in coronary arteries can lead to heart attacks.

6. Cardiac Cycle

1. The sequence of events in one complete heartbeat.
2. Includes atrial systole (contraction of atria), ventricular systole (contraction of ventricles), and diastole (relaxation phase).
3. The heart beats at an average rate of 72 beats per minute.

7. Blood Pressure

1. It is the force exerted by blood against the walls of blood vessels.
2. Measured as systolic pressure (when ventricles contract) and diastolic pressure (when ventricles relax).
3. Normal blood pressure is around 120/80 mmHg.

8. Regulation of Heart Function

1. Controlled by the medulla oblongata in the brain.
2. SA Node (Sinoatrial Node): The natural pacemaker of the heart.
3. AV Node (Atrioventricular Node): Transmits electrical impulses to the ventricles.

9. Common Circulatory Disorders

1. Hypertension: High blood pressure increases the risk of heart disease.
2. Coronary Artery Disease: Blocked arteries reduce blood supply to the heart.
3. Heart Attack: Occurs when blood flow to a part of the heart is blocked.
4. Anemia: Low red blood cell count leading to reduced oxygen supply.
5. Stroke: Blocked or burst blood vessels in the brain.

10. Summary of the Circulatory System

11. Conclusion

1. The circulatory system is essential for the transport of oxygen, nutrients, and waste.
2. Proper functioning of the heart and blood vessels ensures a healthy body.
3. Maintaining a healthy lifestyle reduces the risk of heart diseases.