Composition and Functions of Blood

Composition and Functions of Blood - Vital River Ride

• General Functions: 📌 T-R-P (Transport, Regulation, Protection).
• Physical Characteristics:
  • Volume: 5-6 L (male), 4-5 L (female).
  • pH: $7.35-7.45$.
  • Viscosity: 3-5 times that of water.
  • Specific Gravity: Whole blood 1.052-1.061.
• Components Overview:
  • Plasma: ~55% (water, proteins, solutes).
  • Formed Elements: ~45% (RBCs, WBCs, Platelets).

⭐ Blood is a specialized fluid connective tissue.

Composition and Functions of Blood - Protein Punch Plasma

Plasma: The fluid matrix of blood.

• Composition:
  • Water: ~90-92%
  • Proteins: 6-8 g/dL 📌 Mnemonic: All Good Fighters (Albumin, Globulins, Fibrinogen)
  • Other solutes: Electrolytes (e.g., $Na^+$, $K^+$, $Ca^{2+}$, $Cl^-$), nutrients (glucose, amino acids), gases ($O_2$, $CO_2$), waste products (urea), hormones.

Plasma Proteins:

Composition and Functions of Blood - Oxygen's Express RBCs

Red Blood Cells (Erythrocytes):

• Structure: Biconcave disc (↑ surface area for O2 exchange), anucleate, flexible for capillary passage. Diameter: ~7.2 µm.
• Count: 4.5-5.5 million/µL. Lifespan: ~120 days.
• Hemoglobin (Hb): Carries O2 & CO2. Levels: 13-17 g/dL (M), 12-15 g/dL (F).
• Fate: Phagocytosed (spleen/liver). Hb: Iron recycled, Heme → Bilirubin (excreted in bile).

Erythropoiesis (RBC Formation):

• Site: Red bone marrow (adults).
• Stages: Proerythroblast → Reticulocyte → Erythrocyte (details in flowchart).
• Regulation: Erythropoietin (EPO) from kidneys (stimulus: hypoxia).
• Requirements: Iron, Vitamin B12, Folic acid. 📌 Mnemonic: "Iron Brew For Energy".

⭐ Reticulocyte count (normal: 0.5-2.5% of RBCs) is a key indicator of bone marrow erythropoietic activity.

Composition and Functions of Blood - Bodyguard Brigade WBCs & Platelets

• White Blood Cells (WBCs / Leukocytes): Body's defense. Normal Total Leukocyte Count (TLC): 4,000-11,000/µL.

  • 📌 Mnemonic for abundance: Never Let Monkeys Eat Bananas (Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils).
  • Types & Key Functions:

    WBC Type	% of TLC	Key Function(s)
    Granulocytes
    Neutrophils	40-70%	Phagocytosis, acute inflammation (first responders)
    Eosinophils	1-4%	Allergic reactions, parasitic infections (helminths)
    Basophils	0.5-1%	Release histamine & heparin; mediate hypersensitivity reactions
    Agranulocytes
    Lymphocytes	20-40%	Specific immunity: T cells (cell-mediated), B cells (antibodies), NK cells (cytotoxic)
    Monocytes	2-8%	Differentiate into macrophages; phagocytosis, antigen presentation (chronic inflammation)

  ⭐ A 'left shift' in Differential Leukocyte Count (DLC) refers to an ↑ in immature neutrophils (band forms), often indicating acute bacterial infection.

• Platelets (Thrombocytes):

  • Origin: Megakaryocytes in bone marrow.
  • Structure: Small, anucleate cell fragments.
  • Function: Hemostasis (blood clotting) - form platelet plug.
  • Normal count: 1.5-4.5 lakhs/µL.

High‑Yield Points - ⚡ Biggest Takeaways

• Blood volume is 7-8% body weight; plasma is 55%, formed elements 45%.
• Albumin: main plasma protein, maintains oncotic pressure; globulins for immunity.
• RBCs: O2 transport (Hb), anucleated, 120-day lifespan.
• Neutrophils: most numerous WBCs, key in acute inflammation & phagocytosis.
• Platelets (thrombocytes): crucial for primary hemostasis & clotting.
• Serum = Plasma - Fibrinogen & clotting factors.
• Key blood functions: Transport (gases, nutrients), Regulation (pH, temp), Protection (immunity, clotting).