Sources : Sembulingam (Textbook of physiology)

Clotting mechanism – Enzyme cascade theory

Clotting – It is defined as the process in which blood looses it’s fluidity and becomes a jelly like substance few minutes after it is shed out.

Sequence of clotting mechanism – Enzyme cascade theory:

Cascade is a process that occurs through a series of steps , each step initiating the next until the final step is reached.

Stages of blood clotting :

  • Formation of prothrombin activator
  • Conversion of prothrombin into thrombin
  • Conversion of fibrinogen into fibrin

Sources – Sembulingam (Textbook of physiology)

Image source – Google images

Composition and Functions of Blood

By Dr Musaddika Shaikh Dentowesome @drmusaddikashaikh

Blood :- It is body fluid in body that delivers necessary substance like oxygen,nutrients to cell and transports metabolic waste away from cell.

  • Total blood volume :- 5-6litres 80ml/kg body weight
  • Viscosity :- 4-5 litres
  • Ph :- 7.4
  • Specific gravity :- 1.040-1.060

Composition :-

Anti coagulated sample of blood allow to stand in a tube,it settles cells and plasma.

A) Cells :- Cellular element is 45% of total blood volume called packed cell volume. 1. RBC/Erythrocytes :- Normal count 5million 2. WBC/Leucocytes :- Normal count 4000-11000 3. Platelets/Thrombosis :- Normal count 1.4-4 lakh

B) Plasma :- It is clear,straw colored with 55% of total volume. It contains 91% water+9% organic+1%inorganic substances. a) Inorganic substance:- 1. Na+,Ca+,HCO3(extracellular) 2. k+,Mg,Po4 (intracellular). 3. Ferrous and ferric oxide. b) Organic substance :- 1. Plasma protein. 2. Sugar. 3. Fat 4. Hormone

Non protein nitrogenous substance :- 1. Urea :- 20-40% mg% 2. Uric acid :- 2-4% mg% 3. Creatine :- 1-2% mg% Other substance are fat, phospholipids, glucose.

Functions :-

  1. Respiratory :- blood transprt oxygen from lungs to tissues and CO2 from tissues to lungs.
  2. Nutritive :- absorb food material,glucose,amino-acid,fatty acid and vitamins.
  3. Excreatory :- blood transport metabolic waste.
  4. Heamostatic function :- to regulate normal cell function by heamostasis
  5. Regulate body temperature :- regulate body temperature by buffer system.
  6. Chemical :- regulate negative feedback machanism and defence system for inflammation.

Reference :- Books Human physiology for bds A.K Jain. Google website , ,


By Dr Musaddika Shaikh Dentowesome @drmusaddikashaikh

Haemoglobin :- It is protein found in red blood cells that carries oxygen in blood and gives blood red colour

Structure :-

  • Heame is porphin called iron protoporphyrine 9th
  • Iron is ferrous form which combine with oxygen
  • Globin :- It is protein 4 polypeptide chain of alpha and beta which contains Mb amino acid each polypeptide attach are heam group
  • Hemoglobin react with oxygen in 0.01 sec
  • Molecular weight of hemoglobin 64,458 g/mol
  • Oxyheamoglobin :- hemoglobin affinity for oxygen by Ph, temperature, concentration
  • Carbaamino-heamoglobin :- carbon dioxide react with heamoglobin to form carbaamino-heamoglobin
  • De-oxegenated heamoglobin :- oxygen removed from heamoglobin
  • Carboxy-heamoglobin :- carba+monooxide reacts with heamoglobin
  • Metheamoglobin :- reduced or oxygenated heamoglobin exposed to drugs is oxidised ferrous to ferric acid metheamoglobin

Normal values of heamoglobin :-

Types :-

Synthesis :-

  • Role of protein :- Low protein reduces heamoglobin
  • Role of minerals :- It helps in formation of heame
  • Role of Cu :- It promotes absorption, mobilization and utilisation of iron
  • Role of cobalt :- It enhances absorption in GI tract
  • Role of vitamin :- Vit C,Vit B12,folic acid helps in synthesis of nucleic acid

Functions :-

  1. Transport of oxygen from lungs to tissues
  2. Transport of carbon dioxide from tissues to lungs
  3. Act as acid balance buffer
  4. It gives red colour to blood
  5. Genetic resistance to malaria etc
  6. Source of physiological active catabolites

Reference :- Book Human physiology for bds A.K Jain Google website,,