Circulatory System in Humans — Question 4
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What is lymph? How is it different from blood?
Lymph is a fluid that contains infection-fighting white blood cells. When blood reaches the capillaries, some of the water and dissolved solutes are filtered out from the plasma into tissue spaces to form a tissue fluid called lymph. Some of this lymph enters tiny channels called lymph vessels.
Difference between Blood and Lymph — Basically, lymph has all the elements of blood except RBCs and blood platelets. It is slightly yellowish in colour and contains special type of white blood cells called lymphocytes.
Circulatory System – Interactive Study Guide
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
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
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
- 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?