ICSE Class 8 Biology
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Circulatory System in Humans — Question 5
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Question Question 5
List the functions of the lymph.
Following are the functions of lymph:
- Transportation — The lymph helps in transporting nutrients and hormones to the body cells. It also removes waste materials from the body cells to the tissues and finally pours them into veins. Lymph carries lymphocytes and antibodies from the lymph nodes to the blood. The lymph also absorbs and transports fats (fatty acids and glycerol) from the small intestine to the blood.
- Defence — Lymph carries lymphocytes and antibodies, which destroy the harmful microorganisms and foreign particles in the lymph nodes. Lymph takes the bacteria entering the body to the lymph nodes for destroying them. This prevents the infection from spreading to other tissues.
- Drainage — The lymph drains excess tissue fluid from the intercellular spaces back into the blood.
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Biology | Chapter 8: Circulatory SystemWeb Content
Circulatory System – Interactive Study Guide
Quick Overview
The circulatory system transports blood, oxygen, nutrients, and hormones throughout the body. It consists of the heart (pump), blood (transport medium), and blood vessels (pipelines).
Blood Components
| Component | Function | Key Fact |
|---|---|---|
| Plasma (55%) | Transports dissolved substances | 90% water, carries nutrients, hormones, waste |
| RBC | Carry oxygen | Biconcave disc, no nucleus, contain haemoglobin |
| WBC | Fight infections | Have nucleus, larger than RBC, immune defence |
| Platelets | Blood clotting | Cell fragments, no nucleus |
Blood Group Quick Reference
ABO System
O = Universal Donor (no antigens) | AB = Universal Recipient (no antibodies)
| Group | Antigen | Antibody |
|---|---|---|
| A | A | anti-B |
| B | B | anti-A |
| AB | A & B | None |
| O | None | anti-A & anti-B |
Heart – Quick Facts
- 4 chambers: RA, RV, LA, LV
- 4 valves: Tricuspid (R), Bicuspid (L), 2 Semilunar
- Septum divides right (deoxy) from left (oxy)
- Left ventricle = thickest wall
Double Circulation
Two Circuits
Pulmonary: RV → Pulmonary artery → Lungs → Pulmonary veins → LA
Systemic: LV → Aorta → Body → Vena cava → RA
Blood Vessels Comparison
| Arteries | Veins | Capillaries | |
|---|---|---|---|
| Direction | Away from heart | To heart | Connect A to V |
| Walls | Thick | Thin | 1 cell thick |
| Valves | No | Yes | No |
Self-Test Questions
Test Yourself
- Why is the left ventricle wall thicker than the right?
- Draw and label the human heart.
- What is double circulation? Describe both circuits.
- Why is blood group O called universal donor?
- What is the function of valves in veins?