Blood and cells
Blood Composition
- Fluid connective tissue; maintains uniform temperature and pressure.
- Total blood volume: 5β6 litres.
- pH: 7.35β7.45.
- Viscous fluid (thicker than water).
- 45% cells (RBCs, WBCs, platelets), ~55% plasma.
- Temperature: ~37Β°C (98.6Β°F).
Plasma
- ~55% of blood; 90β92% water; contains water, proteins, salts.
- Proteins:
- Albumin β maintains osmotic pressure.
- Globulins β immune function.
- Fibrinogen β 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 (βgraveyard of RBCsβ).
- Function: Carry oxygen from lungs β tissues; return COβ β 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 β most abundant, destroy bacteria.
- Eosinophils β anti-allergy.
- Basophils.
- Agranulocytes:
- Lymphocytes β form antibodies (T/B cells).
- Monocytes β phagocytosis.
- Granulocytes:
- Count: 4,000β11,000/Β΅L; 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: 7β10 days.
- Removed by spleen/liver.
- Count: 150,000β450,000/Β΅L.
- 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 β thrombosis or bleeding.
- Vitamin K β 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 Γ O = O
- O Γ A = O, A
- O Γ B = O, B
- O Γ AB = A, B
- A Γ A = A, O
- B Γ B = B, O
- A Γ AB = A, B, AB
- B Γ AB = A, B, AB
- AB Γ AB = A, B, AB
- A Γ B = A, B, AB, OβΊ
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) β oxygen transport
- White Blood Cells (WBCs) β defense/immunity
- Platelets β blood clotting
π PYQ (BPSC): What is the fluid part of blood? β 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)
π Expected MCQ: Which blood function is related to homeostasis? β Regulation of pH and water balance
Blood Groups
- Types: A, B, AB, O
- Determined by antigens on RBCs
- Rh Factor: + or β
- Example: A+, Bβ, AB+, Oβ
- Oβ β Universal Donor
- AB+ β Universal Recipient
π PYQ: Universal recipient blood group? β AB+
π Expected MCQ: Blood group that can be given to all? β Oβ
Hemoglobin
- Red pigment in RBCs
- Contains iron
- Binds and transports oxygen
- Normal levels:
- Men: ~13β17 g/dL
- Women: ~12β15 g/dL
π PYQ (CDPO): Deficiency of hemoglobin causes? β Anemia
π Expected MCQ: Hemoglobin carries...? β Oxygen
Blood Clotting
- Prevents excessive blood loss
- Involves: Platelets + Clotting proteins (like fibrin)
- Begins when blood vessels are injured
π PYQ (BPSC): Which component is responsible for clotting? β Platelets
π Expected MCQ: Which protein helps in clot formation? β Fibrin
Blood Volume
- Average adult has ~5 liters of blood
- Plasma makes up ~3 liters
- Loss of more than 40% blood β shock or death if untreated
π Expected MCQ: Average volume of blood in adults? β 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)
π Expected MCQ: Which disease is linked with abnormal hemoglobin genes? β 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
π Expected MCQ: Government scheme in Bihar for anemia control? β Anemia Mukt Bharat
Blood is a fluid connective tissue that performs vital functions like:
- Transport of gases (Oβ, COβ)
- Transport of nutrients and waste
- Regulation of temperature and pH
- Protection through clotting and immunity
π§ͺ Components of Blood
1. Plasma
- Makes up about 55% of blood volume
- Contains water, proteins, salts, hormones, and waste products
- Carries nutrients, COβ, hormones, urea
2. Blood Cells (Formed Elements)
a. Red Blood Cells (RBCs) / Erythrocytes
- Contain hemoglobin β carries oxygen
- Lifespan: ~120 days
- Formed in: Bone marrow
- Destroyed in: Liver and Spleen
π PYQ (BPSC): Which pigment is present in RBC? β Hemoglobin
b. White Blood Cells (WBCs) / Leucocytes
- Provide immunity against infections
- Larger but fewer than RBCs
- Types: Lymphocytes, Neutrophils, etc.
π PYQ (DPSC): Function of WBCs? β Immunity
c. Platelets / Thrombocytes
- Help in blood clotting
- Lifespan: 7β10 days
- Deficiency leads to excessive bleeding
π PYQ (Bihar Teacher): Which blood component helps in clotting? β Platelets
𧬠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
π PYQ (BPSC): Who can donate to everyone? β O negative
π 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
π PYQ (BPSC): Which blood vessel carries impure blood? β Vein
π§ Quick Facts for Revision
- Blood is a connective tissue
- RBCs β oxygen; WBCs β immunity; Platelets β 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
π Sources Used
- NCERT Science Class 7β10
- Lucent GK β Biology Section
- Drishti General Science Quick Book
- BPSC & DPSC PYQs β Ghatna Chakra, EduTeria
PYQs + Expected MCQs
π PYQ: Component of blood that forms clot? β Platelets
π PYQ: Universal blood recipient group? β AB+
π Expected MCQ: What is the color of plasma? β Straw-yellow
π Expected MCQ: Major function of RBC? β Transport of oxygen
π Expected MCQ: Disorder with low hemoglobin? β Anemia
Quick Revision Points
- Blood = Plasma + Cells (RBC, WBC, Platelets)
- Plasma β fluid, 55% of blood
- RBC β oxygen transport via hemoglobin
- WBC β fights infection
- Platelets β help in clotting
- Blood groups: A, B, AB, O (+/β Rh)
- Universal donor: Oβ; Universal recipient: AB+
- Disorders: Anemia, Hemophilia, Thalassemia, Leukemia
Sources Used
- NCERT Class 10 Science β Life Processes
- Lucent GK β Biology Section
- Drishti Science Quick Book
- EduTeria & Ghatna Chakra PYQs β BPSC, CDPO
- Bihar Health Department β Anemia Dashboard
- Ministry of Health β Anemia Mukt Bharat Data Portal