Class 11 biology ch 18 Body fluid and circulation notes


Class 11 biology ch 18 Body fluid and circulation notes

Body fluid are the medium of transport of nutrients, oxygen and other important substances in the body.


Body fluids:-

  1. Intracellular fluid (fluid of each cell)
  2. Extracellular fluid (Blood, lymph etc.)

Blood is the most commonly used body fluid in most of the higher organisms. Lymph also transports certain substances like protein and fats.

कोरोना से बचाव कैसे हो -KORONA SAFTY


आईटीआई ट्रेड-I.T.I Trade


Blood is a fluid connective tissue composed of a fluid matrix, plasma and the blood corpuscles. It forms about 30-35% of the extracellular fluid. It is slightly alkaline fluid having pH 7.4.


Blood contain:

Formed elements- 1. Erythrocytes 2. Leucocytes 3. Thrombocytes

Plasma- water, protein, minerals, ions.


Plasma is a straw colored, viscous fluid constituting nearly 55per cent of the blood. Fibrinogen, globulins and albumins are the major proteins of plasma

Fibrinogen are needed for clotting or coagulation of blood, globulins are involved in defense mechanism of the body and the albumins help in osmotic balance. Plasma contains small amounts of minerals like sodium, calcium, glucose, amino acids etc.

Factors for coagulation of blood are present in the plasma in an inactive form. Plasma without the clotting factors is called serum.


Formed element:-

Erythrocytes, leucocytes and platelets are collectively called formed elements.


RBCs- 4.5 to 5.5 million per cubic millimeter of blood. Yellow color circular, biconcave denucleated, elastic, lack of cell organelles like ER, ribosomes, mitocondria etc.

Formed from birth onwards by bone marrow like 120 days. Transport of oxygen and some amount of co2 is held by them.


(WBCs) 5000-8000 per cubic mm of blood. Colorless rounded or irregular, nucleated 12 to 20mm wide. Formed in bone marrow, lymph nodes, spleen and thymus. Acts as soldiers scavengers and some help in healing.


(a) Lymphocytes- 20-45% in number. Large rounded nucleus. Lymph nodes spleen, thymus, bone marrow, life few days to months or even years. Non phagocytic.

(b) Monocytes- 2-10% in number. Largest of all bean shaped nucleus. bone marrow, life 10-20 hours. Phagocytic, engulf germs.


(a) Eosinophils- 1-6% in numbers, bilobed nucleus, granules in cytoplasm. Bone marrow, life 4 to 8 hours in blood. Play role in immunity non-phagocytic.

(b) Basophils- 0-1% in numbers. Three lobed nucleus. Bone marrow, life 4 to 8 hours in blood. Release heparin and histamin.

(c) Neutrophils- 40-75% in numbers. Many lobed nucleus fine granules. Bone marrow, life 4 to 8 hours. Phagocytic, engulf germ and dead cells.

Class 11 biology ch 18 Body fluid and circulation notes
Class 11 biology ch 18 Body fluid and circulation notes

Platelets thrombocytes:-

1,50,000-3,50,000 mm cube of blood. Colorless, rounded or oval, nonnucleated fragments of cells. Bone marrow about a week. Help in blood clotting.

Blood groups:-

Two blood grouping are done ABO and Rh.

ABO grouping-

ABO grouping is based on the presence or absence of two surface antigen on the RBCs namely A and B. The plasma of different individuals contain two natural antibodies. The distribution of antigens and antibodies in the four groups of blood, AB, AB and O.

The blood of a donor has to be carefully matched with the blood of a recipient before any blood transfusion to avoid severe problems of clumping, which leads to destruction of RBC.

Grouping O blood can be donated to persons with any other blood groups and hence O group individuals are called universal donors. Persons with AB group can accept blood from person with AB as well as the other groups of blood, and such persons are called universal recipients.

Class 11 biology ch 18 notes

Rh grouping:-

The Rh antigen similar to the one present in rhesus monkeys is also observed on the surface of RBCs of majority of humans, hence the antigen is known as Rh antigen.

The individuals having Rh antigen are called Rh positive and those in whom this antigen is absent are called Rh negative. An Rh negative person, if exposed to Rh positive blood, will form specific antibodies against the Rh antigens, and hence Rh groups should also be matched before transfusion.

A special case of Rh incompatibility has been observed between the Rh negative blood of a pregnant mother with Rh positive blood of the foetus, which leads to a disease known as erythroblastosis foetal.

Rh antigens of the foetus do not get exposed to the Rh negative blood of the mother in the first pregnancy as the two bloods are well separated by the placenta, during the delivery of first children maternal blood may get exposed to small amounts of the Rh positive blood from the foetus and the mother starts preparing antibodies against Rh in her blood.

In case of subsequent pregnancies, the Rh antibodies from the mother Rh negative can leak into the blood of the foetus and destroy the foetal RBCs, which cause severe anemia and jaundice to the body leading to a condition known erythroblastosis foetal

Erythroblastosis foetal can be avoided by administering anti- Rh antibodies to the mother immediately after the delivery of the first child.

Coagulation of blood:-

You would have observed a dark reddish brown scum formed at the site of a cut or injury over a period of time. It is a clot or coagulam formed mainly of a network of threads called fibrins in which dead and damaged formed elements of a blood are trapped.

Fribrins are formed by the conversion of inactive fibrinogens in the plasma by the enzyme thrombin. Thrombins, in turn are formed from another inactive substance present in the plasma called prothrombin. An enzyme complex, thrombokinase, is required for the above reactions.

This complex is formed by a series of linked enzyme reactions involving a number of factor present in the plasma in an inactive state. An injury or a trauma stimulates the platelets in the blood to release certain factor which activate the mechanism of coagulation.

Certain factors released by the tissue at the site of injury also can initiate coagulation. calcium ions play a very important role in clotting.

Lymph (Tissue fluid)

As the blood passes through the capillaries in tissues, some water along with many small water soluble substances move out into the spaces between the cells of tissues leaving the larger proteins and most of the formed elements in the blood vessels.

This fluid released out is called the interstitial fluid or tissue fluid. It has the same mineral distribution as that in plasma. Exchange of nutrients, gases, etc.,

between the blood and the cells always occur through this fluid. An elaborate network of vessel called the lymphatic system collects this fluid and drains it back to the major veins. The fluid present in the lymphatic system is called the lymph.

Lymph is a colorless fluid containing specialized lymphocytes which are responsible for the immune responses of the body.

Lymph is also an important carrier for nutrients, hormones, etc. Fats are absorbed through lymph in the lacteals present in the intestinal villi.

Shramik Card List -Labour Card Suchi

Circulatory pathways-

The circulatory patterns are of two types-

  1. open circulatory system- present in arthropods and molluscs
  2. Closed circulatory system- present in annelids and chordates.

All vertebrates possess a muscular chambered heart. Fishes have a 2 chambered heart with an atrium and a ventricle. Amphibians and the reptiles ( except crocodile0 have a 3 chambered heart with the two atria and a single ventricle, whereas crocodiles, birds and mammals possess a 4 chambered heart with two atria and two ventricle.

In fishes the heart pumps out deoxygenated blood which is oxygenated by the gills and supplied to the body parts from where deoxygenated blood is returned to the heart ( single circulation).

In amphibians and reptiles, the left atrium recieves oxygenated blood from the gills/ lungs. skin and the right atrium gets the deoxygenated blood from the other body parts.

However, they get mixed up in the single ventricle which pumps out mixed blood ( incomplete double circulation). In birds and mammals, oxygenated and deoxygenated blood received by the left and right atria respectively passes on to the ventricles of the same sides.

The ventricles pump it out without any mixing up i.e., two separate circulatory pathways are present in these organisms. hence, these animals have double circulation.

Class 11 biology ch 18 Body fluid and circulation notes

Class 11 Biology ch 17 breathing and exchange of gases.


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