Introduction
The circulatory system is vital for transporting nutrients, gases, hormones, and waste products throughout the body. Human body fluids, including blood and lymph, play a crucial role in maintaining homeostasis. In this post, we’ll explore the components of body fluids, the structure and function of the heart, blood vessels, and the mechanism of circulation.
1. Body Fluids
Human body fluids are mainly of two types:
a) Blood
- Blood is a connective tissue that circulates through the cardiovascular system.
- Components of blood:
- Plasma (55%) – Contains water, proteins (albumin, globulin, fibrinogen), salts, nutrients, hormones, and waste products.
- Formed elements (45%) – Includes:
- Red Blood Cells (RBCs / Erythrocytes): Transport oxygen using hemoglobin.
- White Blood Cells (WBCs / Leukocytes): Defend the body against pathogens.
- Platelets (Thrombocytes): Help in blood clotting.
b) Lymph
- Lymph is a clear fluid that circulates in the lymphatic system.
- It carries proteins, fats, and immune cells, helping in defense and fluid balance.
2. Circulatory System
The human circulatory system is a closed system, consisting of the heart, blood vessels, and blood. It is divided into systemic and pulmonary circulation.
a) Heart
- The heart is a muscular organ located in the thoracic cavity.
- Structure:
- Four chambers: Right atrium, Right ventricle, Left atrium, Left ventricle.
- Valves: Ensure unidirectional blood flow – Tricuspid, Bicuspid (Mitral), Pulmonary, Aortic.
- Function: Pumps blood through pulmonary and systemic circulation.
b) Blood Vessels
- Arteries: Carry oxygenated blood away from the heart (except pulmonary artery). Thick walls.
- Veins: Carry deoxygenated blood to the heart (except pulmonary vein). Contain valves.
- Capillaries: Microscopic vessels where exchange of gases, nutrients, and wastes occurs.
c) Circulation Types
- Pulmonary Circulation: Heart → Lungs → Heart.
- Systemic Circulation: Heart → Body → Heart.
3. Mechanism of Circulation
- Cardiac Cycle: Sequence of atrial and ventricular contraction (systole) and relaxation (diastole).
- Heart Rate and Cardiac Output:
- Heart rate: Number of beats per minute.
- Cardiac output: Volume of blood pumped per minute (Heart Rate × Stroke Volume).
- Blood Pressure: Force exerted by blood on vessel walls. Measured in mmHg.
4. Disorders of Circulatory System
- Hypertension: High blood pressure.
- Atherosclerosis: Narrowing of arteries due to plaque buildup.
- Coronary Artery Disease: Reduced blood supply to the heart muscles.
- Anemia: Low hemoglobin or RBC count.
MCQs for Exam Preparation
- Which component of blood is responsible for oxygen transport?
- A) WBC
- B) Platelets
- C) RBC
- D) Plasma
- Answer: C) RBC
- Which plasma protein helps in blood clotting?
- A) Albumin
- B) Fibrinogen
- C) Globulin
- D) Hemoglobin
- Answer: B) Fibrinogen
- Which type of blood vessel carries blood away from the heart?
- A) Veins
- B) Capillaries
- C) Arteries
- D) Lymph vessels
- Answer: C) Arteries
- The valve between the left atrium and left ventricle is called:
- A) Tricuspid
- B) Bicuspid (Mitral)
- C) Pulmonary
- D) Aortic
- Answer: B) Bicuspid (Mitral)
- Which fluid circulates in the lymphatic system?
- A) Plasma
- B) RBCs
- C) Lymph
- D) Platelets
- Answer: C) Lymph
- Pulmonary circulation carries blood:
- A) Heart → Body → Heart
- B) Heart → Lungs → Heart
- C) Body → Heart → Lungs
- D) Lungs → Body → Heart
- Answer: B) Heart → Lungs → Heart
- Which blood vessels are the site of exchange of gases and nutrients?
- A) Veins
- B) Arteries
- C) Capillaries
- D) Lymph vessels
- Answer: C) Capillaries
- Which organ controls the heartbeat?
- A) Lungs
- B) Brainstem
- C) Heart
- D) Kidneys
- Answer: B) Brainstem
- What is the function of platelets in blood?
- A) Carry oxygen
- B) Fight infections
- C) Blood clotting
- D) Transport nutrients
- Answer: C) Blood clotting
- Anemia is caused due to:
- A) Low WBC count
- B) Low hemoglobin or RBC count
- C) High platelet count
- D) High plasma volume
- Answer: B) Low hemoglobin or RBC count