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Rahul DevashishCourseBiology Blood

2 Jul 2025·7 min read·

Blood and cells

Blood Composition

Fluid connective tissue; maintains uniform temperature and pressure.
Total blood volume: 5–6 litres.
pH: 7.35–7.45.
Viscous fluid (thicker than water).
45% cells (RBCs, WBCs, platelets), ~55% plasma.
Temperature: ~37°C (98.6°F).

Plasma

~55% of blood; 90–92% water; contains water, proteins, salts.
Proteins:
- Albumin → maintains osmotic pressure.
- Globulins → immune function.
- Fibrinogen → clotting.
Liquid component of blood; yellowish fluid matrix.
Salts: sodium chloride, sodium carbonate.

RBCs (Erythrocytes)

90% of blood cells, no nucleus in mammals (except camels).
Life span: ~120 days.
Structure: Biconcave; contain haemoglobin (iron-protein).
Formed in bone marrow, destroyed in spleen (“graveyard of RBCs”).
Function: Carry oxygen from lungs → tissues; return CO₂ → lungs.
Vitamin B12 and folic acid help in stimulation and maturation.
Higher requirement at high altitude.

WBCs (Leukocytes)

Defend against infections, regulate immunity.
Structure: Nucleated; no haemoglobin.
Types:
- Granulocytes:
  - Neutrophils → most abundant, destroy bacteria.
  - Eosinophils → anti-allergy.
  - Basophils.
- Agranulocytes:
  - Lymphocytes → form antibodies (T/B cells).
  - Monocytes → phagocytosis.
Count: 4,000–11,000/µL; produced in bone marrow; increase during disease.
Formation: bone marrow, lymph node, liver, spleen.
Destroyed in blood.
Function: destroy pathogens, produce antibodies, clear debris.
Lifespan: hours to years (e.g., memory lymphocytes).
Phagocytes engulf invading microbes.

Platelets (Thrombocytes)

Lifespan: 7–10 days.
Removed by spleen/liver.
Count: 150,000–450,000/µL.
Fibrinogen and prothrombin help in blood clotting.
Sodium and potassium oxalate speed up blood clotting.
Significance:
- Clotting of blood.
- Prevent blood loss.
- Aid wound healing.
- Dysfunction → thrombosis or bleeding.
- Vitamin K → essential for clotting.
Serum: residual yellowish substance.
Heparin: natural anticoagulant.

Blood Groups

Discovered by Carl Landsteiner.
Antigen present in RBC, antibody in plasma.
Rh factor: discovered by Landsteiner & Weiner (from Rhesus monkey).
Erythroblastosis foetalis: RBC destruction if Rh-negative woman carries Rh-positive baby (from 2nd pregnancy onward; cure available now).

Inheritance Patterns

O × O = O
O × A = O, A
O × B = O, B
O × AB = A, B
A × A = A, O
B × B = B, O
A × AB = A, B, AB
B × AB = A, B, AB
AB × AB = A, B, AB
A × B = A, B, AB, O⁺

Blood is a fluid connective tissue that transports essential substances like oxygen, nutrients, hormones, and waste products throughout the body.
It plays a critical role in immunity, regulation, and survival.
In Bihar, issues like anemia, malnutrition, and low blood donation rates make blood-related awareness essential for public health policies.

Composition of Blood

Plasma (55%):
- Yellowish fluid
- Contains water, proteins, hormones, waste products, minerals, etc.
Formed Elements (45%):
- Red Blood Cells (RBCs) → oxygen transport
- White Blood Cells (WBCs) → defense/immunity
- Platelets → blood clotting

📝 PYQ (BPSC): What is the fluid part of blood? → Plasma

Functions of Blood

Transport:
- Oxygen from lungs to body
- Carbon dioxide from tissues to lungs
- Nutrients from digestive tract to tissues
- Waste products to kidneys
- Hormones from glands to target organs
Protection:
- WBCs fight infections
- Platelets prevent blood loss via clotting
Regulation:
- Body temperature
- pH balance
- Water-salt balance (homeostasis)

📝 Expected MCQ: Which blood function is related to homeostasis? → Regulation of pH and water balance

Blood Groups

Types: A, B, AB, O
Determined by antigens on RBCs
Rh Factor: + or −
- Example: A+, B−, AB+, O−
O− → Universal Donor
AB+ → Universal Recipient

📝 PYQ: Universal recipient blood group? → AB+
📝 Expected MCQ: Blood group that can be given to all? → O−

Hemoglobin

Red pigment in RBCs
Contains iron
Binds and transports oxygen
Normal levels:
- Men: ~13–17 g/dL
- Women: ~12–15 g/dL

📝 PYQ (CDPO): Deficiency of hemoglobin causes? → Anemia
📝 Expected MCQ: Hemoglobin carries...? → Oxygen

Blood Clotting

Prevents excessive blood loss
Involves: Platelets + Clotting proteins (like fibrin)
Begins when blood vessels are injured

📝 PYQ (BPSC): Which component is responsible for clotting? → Platelets
📝 Expected MCQ: Which protein helps in clot formation? → Fibrin

Blood Volume

Average adult has ~5 liters of blood
Plasma makes up ~3 liters
Loss of more than 40% blood → shock or death if untreated

📝 Expected MCQ: Average volume of blood in adults? → 5 liters

Blood Disorders

Anemia: Low hemoglobin/RBC
Leukemia: Blood cancer (excessive WBCs)
Thalassemia: Genetic disorder affecting hemoglobin
Hemophilia: Clotting disorder (platelet/protein deficiency)
Sickle Cell Disease: Abnormal RBC shape (found in some Bihar tribal areas)

📝 Expected MCQ: Which disease is linked with abnormal hemoglobin genes? → Thalassemia

Bihar-Specific Relevance

High Anemia Rates: Especially among women & adolescents
Govt schemes: Anemia Mukt Bharat, Poshan Abhiyaan
Low rural awareness of blood donation
Blood bank accessibility is low in backward districts
Screening of blood group and hemoglobin often absent in village-level PHCs

📝 Expected MCQ: Government scheme in Bihar for anemia control? → Anemia Mukt Bharat

Blood is a fluid connective tissue that performs vital functions like:

Transport of gases (O₂, CO₂)
Transport of nutrients and waste
Regulation of temperature and pH
Protection through clotting and immunity

🧪 Components of Blood

1. Plasma

Makes up about 55% of blood volume
Contains water, proteins, salts, hormones, and waste products
Carries nutrients, CO₂, hormones, urea

2. Blood Cells (Formed Elements)

a. Red Blood Cells (RBCs) / Erythrocytes

Contain hemoglobin – carries oxygen
Lifespan: ~120 days
Formed in: Bone marrow
Destroyed in: Liver and Spleen

📝 PYQ (BPSC): Which pigment is present in RBC? → Hemoglobin

b. White Blood Cells (WBCs) / Leucocytes

Provide immunity against infections
Larger but fewer than RBCs
Types: Lymphocytes, Neutrophils, etc.

📝 PYQ (DPSC): Function of WBCs? → Immunity

c. Platelets / Thrombocytes

Help in blood clotting
Lifespan: 7–10 days
Deficiency leads to excessive bleeding

📝 PYQ (Bihar Teacher): Which blood component helps in clotting? → Platelets

🧬 Blood Groups

Discovered by Karl Landsteiner
Main groups: A, B, AB, O
Based on presence/absence of antigens A and B
Also classified by Rh factor (positive or negative)

Important Facts

O negative: Universal donor
AB positive: Universal recipient

📝 PYQ (BPSC): Who can donate to everyone? → O negative

🔄 Blood Circulation

Blood flows through arteries, veins, and capillaries
Pumped by the heart to every organ
Arteries: Carry blood away from heart (oxygen-rich)
Veins: Carry blood to heart (oxygen-poor)
Pulmonary artery and pulmonary vein are exceptions

📝 PYQ (BPSC): Which blood vessel carries impure blood? → Vein

🧠 Quick Facts for Revision

Blood is a connective tissue
RBCs → oxygen; WBCs → immunity; Platelets → clotting
Hemoglobin: Iron-rich protein in RBCs
Blood volume in adult: ~5 liters
Spleen: Known as the "graveyard of RBCs"
Liver: Produces blood clotting proteins

📚 Sources Used

NCERT Science Class 7–10
Lucent GK – Biology Section
Drishti General Science Quick Book
BPSC & DPSC PYQs – Ghatna Chakra, EduTeria

PYQs + Expected MCQs

📝 PYQ: Component of blood that forms clot? → Platelets
📝 PYQ: Universal blood recipient group? → AB+
📝 Expected MCQ: What is the color of plasma? → Straw-yellow
📝 Expected MCQ: Major function of RBC? → Transport of oxygen
📝 Expected MCQ: Disorder with low hemoglobin? → Anemia

Quick Revision Points

Blood = Plasma + Cells (RBC, WBC, Platelets)
Plasma → fluid, 55% of blood
RBC → oxygen transport via hemoglobin
WBC → fights infection
Platelets → help in clotting
Blood groups: A, B, AB, O (+/− Rh)
Universal donor: O−; Universal recipient: AB+
Disorders: Anemia, Hemophilia, Thalassemia, Leukemia

Sources Used

NCERT Class 10 Science – Life Processes
Lucent GK – Biology Section
Drishti Science Quick Book
EduTeria & Ghatna Chakra PYQs – BPSC, CDPO
Bihar Health Department – Anemia Dashboard
Ministry of Health – Anemia Mukt Bharat Data Portal