Here we are providing the short notes on Biology which will be help to crack science part in may examinations like SSC, Railway and other competitive exams


The Lymphatic System

  • The spleen serves as a reservoir for blood, and filters or purifies the blood and lymph fluid that flows through it.
  • If the spleen is damaged or removed, the individual is more susceptible to infections.


  • Antibodies: Antibodies are a type of protein molecule known as immunoglobulins.


  • Blood is a fluid connective tissue.
  • The quantity of blood in the human’s body is 7% of the total weight.
  • pH value of blood is 7.4.
  • There is an average of 5-6 litres of blood in human body.
  • Female contains half litre of blood less in comparison to male.
  • It also fights infection and regulates temperature.


Blood cells are produced in BONE MARROW

The main functions of blood are to transport oxygen, carbon dioxide, water, nutrients, hormones and waste around the body. Blood also fights infection and regulates temperature.

Blood has four components:

  1. Plasma
  2. Red blood cells
  3. White blood cells
  4. Platelets

PLASMA -> Liquid portion of Blood

  • It constitutes for about 54% of our blood. 92% of it is water.
  • maintaining a satisfactory blood pressure
  • volume to supplying critical proteins for blood clotting and immunity.
  • medium for exchange of vital minerals such as sodium and potassium
  • helps to maintain a proper pH (acid-base) balance in the body, which is critical to cell function.

RED BLOOD CELLS -> Carry oxygen

  • Red blood cells are disc-shaped cells containing haemoglobin,
  • haemoglobin (haem=iron-containing)
  • Haemoglobin enables the cells to pick up and deliver oxygen to all parts of the body, then pick up carbon dioxide and remove it from tissues.
  • Its life span is from 20 days to 120 days and are then broken down into pigments called bilirubin and biliverdin in the liver.
  • Its destruction takes place in liver & spleen. Therefore, liver is called grave of RBC.
  • they are made in the bone marrow,
  • they have no nucleus,
  • B. oxyhaemoglobin =oxygen rich haemoglobin,
  • deoxyhaemoglobin=low oxygen haemoglobin

WHITE BLOOD CELLS -> Defend Body (Fighter)

  • White blood cells, also called leukocytes
  • White cells are the body’s primary defense against infection.
  • They can move out of the blood stream and reach tissues to fight infection.
  • They are essential for good health.
  • Its life span is from 1 to 2 days.
  • White blood cells have nuclei and are also made in the bone marrow.

PLATELETS-> Responsible for clotting

Platelets are the cells that circulate within our blood and bind together when they recognize damaged blood vessels.

Study of blood = HEMATOLOGY




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