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Circulation of blood in Human Body (Circulatory System)


 All animals and plants have specialized Systems for the exchange of food, gas, and emissions.  especially in animals, these systems are more developed. William Harvey was first discovered in The circulatory system. The Blood circulatory system exists in almost all animals in the world. In some animals, there is variation in the circulatory system, From this, there are two main types of the circulatory system in animals

Important Types of the circulatory system 

  1. Open Blood Circulatory System
  2. Closed Blood Circulatory System

Difference between Open Blood Circulatory System and Closed Blood Circulatory System

Open Blood Circulatory System Closed Blood Circulatory System
1. the blood flows through channels called & lacunae large open spaces and also from sinuses among the tissues.  1. In closed circulatory system blood flows through a closed system of chambers called the heart and blood vessels. 
2. In the Open circulatory system  Tissues are in direct contact with the blood. 2. Blood does not come in direct contact with tissue.
3. Blood flow is very slow, and blood has very low pressure. 3. blood has a high pressure & the Blood flow is quite rapid n a closed circulatory system.
4. the Exchange of nutrients & gases takes place directly between blood and tissues. 4. Nutrients and gases pass through the capillary wall to the tissue fluid from where they are passed. 
5. Less efficient as the volume of blood flowing through the tissue cannot be controlled as blood flows out in open space.   5. More efficient as the volume of blood can be regulated by the contraction and relaxation of the smooth muscles of the blood vessels. 
6. Open circulatory system is found in higher invertebrates like most arthropods such as prawns, insects, etc., and some mollusks. 6. Closed circulatory system is found in echinoderms, some mollusks, annelids, and all vertebrates. 
7. Respiratory pigment, if present, is dissolved in plasma; RBCs are not present.  7. Respiratory pigment is present and may be dissolved in plasma but is usually held in RBCs.
Difference between Open Blood Circulatory System and Closed Blood Circulatory System

William Harvey

William Harvey: 

  • William Harvey first discovered the circulatory system.
  • He is also known as the Father of Technical Circuits.
  • He first studied blood vessels on a snake.
  • His mentor Fabricius discovered valves in the long veins

Blood Cells/ Corpuscles

Types Blood Cells

  1. RBC – Red Blood Cell / Corpusclesn
  2. WBC – White Blood Cell / Corpusclesn
  3. Platelets
  1. RBC – Red Blood Cell / Corpusclesn : 
  • Red blood cells are Circular, Biconcave, and non-nucleated cells These cells are called Erythrocycytes. Erythro means red & cycles mean cells.
  • RBCs are very small in size, i.e.their Diameteris 7 micrometers and their Thickness is 2.5 micrometers.
  • Due to Haemoglobin RBC get red color.
  • RBC is usually lower in women.
  • RBCs usually live for 127 days and then die in the spleen. (Spleen is also called a graveyard of RBC).
  • Hemoglobin:
  • An important component in RBC
  • One RBC contains millions of hemoglobin
  • In hemoglobin, Haeme is iron and globin is a protein.
  • Oxygen is carried by hemoglobin.
  • Hemoglobin deficiency causes a disease called Anaemia, while high hemoglobin causes a disease called polycythemia.
  • One hemoglobin can carry a maximum of four 
  • molecules of oxygen.
  1. WBC – White Blood Cell / Corpusclesn:
  • Large in size, colorless, and cells that have nuclei.
  • WBC is larger than RBC
  • their Diameteris is between 8 to 15 micrometers.
  • These cells are also Leukocytes.
  • typically live three to four days
  • There are five main types of WBC.
  • WBC was created in bone marrow as well as in Sleen.
  1. Platelets: 
  • They are convex in shape and colorless.
  • These blood cells are found only in Mamallian Animals.
  • Platelets are also called Thrombocytes.
  • These cells are very small (2.5 to 4.5 micrometers).
  • Can live five to ten days.
  • Helps in the process of Coagulation.

Major Properties of Blood:

  • Blood is about 8% of body weight.
  • Studying the blood is called Haematology.
  • Blood is a type of connective tissue.
  • The average human body contains five liters of blood.
  • Normal blood pH is 7.35 to 7.45 is alkali.

 Special For UPSC

1) Bicarbonate (HCO3 Ion) acts as a buffer for Blood and maintain the blood pH

2) Haemoglobin is also acted as a buffer. (Buffer means, the substance which maintains pH.)

3) Viscosity of Blood is mainly due to RBC & WBC.

4) WBC shows special property which is known as diapedesis i.e. squeezing of WBC from blood


5) Platelets are biconvex while RBC is biconcave.

6) Among WBCs, Lymphocytes have two types, B-Lymphocytes which are formed in bone marrow while

T-Lymphocytes are formed in the Thymus gland.

7) Normal cholesterol level in blood

blood = 50-180mg/dl.

👉 UPSC (Notes)
👉 Subject: Science
👉 Topic: Blood Circulatory System