Chapter 15: Body Fluids and Circulation
15.1 Blood
Blood is a special connective tissue that transports nutrients, oxygen, and removes waste. It’s made of:
- 💧 Plasma (fluid matrix)
- 🔴 Formed elements (cells and fragments)
15.1.1 Plasma
Straw-colored, sticky fluid making up 55% of blood:
- 🔹 90–92% water
- 🔹 6–8% proteins:
- Fibrinogen: Helps blood clot 🩸
- Globulins: Fight infections 🛡️
- Albumins: Maintain fluid balance ⚖️
- 🔹 Also contains minerals like \(\mathrm{Na}^+\), \(\mathrm{Ca}^{++}\), \(\mathrm{Cl}^-\), glucose, amino acids, and lipids.
- 🔹 Serum = Plasma minus clotting factors.
15.1.2 Formed Elements
Make up 45% of blood:
1. Red Blood Cells (RBCs) 🩸
- 🔴 Most abundant blood cells
- 🔴 5–5.5 million per mm\(^3\) blood
- 🔴 Made in bone marrow
- 🔴 No nucleus (in mammals), biconcave shape
- 🔴 Contain hemoglobin (12–16 g/100 ml blood) for oxygen transport 💨
- 🔴 Live ~120 days → destroyed in spleen
2. White Blood Cells (WBCs) ⚪
- ⚪ 6,000–8,000 per mm\(^3\) blood
- ⚪ Have nucleus, no hemoglobin
- ⚪ Two types:
| Type | Function | % of WBCs |
|---|---|---|
| Granulocytes | ||
| – Neutrophils | Eat germs 🦠 (phagocytic) | 60–65% |
| – Eosinophils | Fight parasites/allergies 🤧 | 2–3% |
| – Basophils | Release histamine (inflammation) | 0.5–1% |
| Agranulocytes | ||
| – Lymphocytes (B & T cells) | Immune response 🛡️ | 20–25% |
| – Monocytes | Eat germs 🦠 (phagocytic) | 6–8% |
3. Platelets (Thrombocytes) 🧩
- 🧩 150,000–350,000 per mm\(^3\) blood
- 🧩 Cell fragments from bone marrow
- 🧩 Help blood clot 🩸
- 🧩 Low count → excessive bleeding
15.1.3 Blood Groups
Based on antigens (on RBCs) and antibodies (in plasma):
ABO Grouping
| Blood Group | Antigens on RBCs | Antibodies in Plasma | Can Donate To |
|---|---|---|---|
| A | A | anti-B | A, AB |
| B | B | anti-A | B, AB |
| AB | A & B | None | AB only |
| O | None | anti-A & anti-B | All groups |
🌟 Universal donor: Group O
🌟 Universal recipient: Group AB
Rh Grouping
- 🔸 Rh+: Rh antigen present (80% people)
- 🔸 Rh-: Rh antigen absent
- ⚠️ Problem in pregnancy: If Rh- mom has Rh+ baby:
- 1st pregnancy: Usually safe 🤰
- Mom makes anti-Rh antibodies after delivery
- Next Rh+ baby: Antibodies attack baby’s RBCs → Erythroblastosis fetalis (severe anemia/jaundice)
- 💉 Prevention: Give anti-Rh antibodies to mom after 1st delivery.
15.1.4 Blood Clotting 🩸
Stops bleeding after injury:
- Injury → Platelets release clotting factors
- Prothrombin \(\xrightarrow{\text{Thrombokinase + Ca}^{++}}\) Thrombin
- Fibrinogen \(\xrightarrow{\text{Thrombin}}\) Fibrin (sticky threads)
- Fibrin traps blood cells → forms clot
🔑 Key player: Calcium ions (\(\mathrm{Ca}^{++}\))
Key NEET Concepts 💡
- Hemoglobin & RBCs: Normal range (12–16 g/dL), function (O2/CO2 transport), lifespan (120 days).
- WBC Types & Functions: Neutrophils (phagocytosis), lymphocytes (immunity), eosinophils (allergies).
- Blood Groups: ABO compatibility (universal donor/recipient), Rh incompatibility in pregnancy.
- Clotting Process: Role of platelets, thrombin, fibrinogen → fibrin, and Ca++.
