BLOOD - LEUCOCYTES AND WHITE BLOOD CELLS (W.B.C.)

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LEUCOCYTES AND WHITE BLOOD CELLS

Ques. 1 What are is Leucocytes?
Ans. The Leucocyte or white blood corpuscles are one of the cellular elements of blood which are nucleated and serve mainly the defensive function of the body.

Ques. 2 What are the varieties of leucocytes?
Ans. Leucocytes are of two types broadly known as granulocytes and agranulocytes.
a) Agranulocytes, i.e. which not contain any granules in their cytoplasm, they are – (i) Lymphocyte, and (ii) Monocyte.
b) Granulocytes, i.e. the presence of granules in the cytoplasm, they are – (i) Neutrophil, (ii) Eosinophil, and (iii) Basophil.

Ques. 3 What are eosinophils?
Ans. Eosinophil cells : It is a granular leucocyte having a nucleus with 2 lobes connected by a thread of chromatin and cytoplasm containing, round granules of uniform size, reddish in colour. Size 10 to 12 in diameter. Normal percentage 1 to 4% Absolute No. 150 to 400 per cu. mm.

Ques. 4 What are Basophil cells?
Ans. Basophil cells or Mast cells : It is a granular leucocyte with an irregularly shaped, relatively pale-staining nucleus that is partially constricted into 2 lobes, and with cytoplasm containing course (bluish black granules of variable size). Size 8 to 10 Normal percentage within 1% Absolute number 0 to 100 per cu. mm.

Ques. 5 What are neutrophils?
Ans. Neutrophil cells or Polymorphonuclear Leucocytes : Their granules are maximum in number, smallest in size, neutral in colour (violet), lobes of nuclear 2 - 7, size 10 – 12 in diameter. Normal percentage is 60 to 70% Absolute No. 3,000 to 6,000 per cu. mm.

Ques. 6 What are lymphocytes?
Ans. Lymphocytes : They are of two types viz. large and small with round nucleus and basophilic cytoplasm. Small lymphocytes are deeply stained (nucleus). Almost covering whole cell leaving a very thick bank of cytoplasm which is clear. Size – large about 12 & small 7.5 in diameter. Normal percentage 25 to 30% of which large 4 to 8% and small 20 to 25% Absolute No. 1500 to 2700 per cu. mm.

Ques. 7 What are monocytes?
Ans. Monocyte Notched or kidney shaped nucleus with 1/3rd portion of cytoplasm which is ground glass like appearance. Sometimes we may get few vacuoles or fine thin red staining rods. Size – 16 to 18 in diameter. Normal percentage is 5 to 10%.

Ques. 8 Describe the functions of leucocytes.
Ans. Functions of Leucocytes :
a) The neutrophil manufactures trypsin like enzyme and help in the digestion of bacteria in dead tissue.
b) Lymphocytes and monocytes elaborate pepsin like enzyme, which liquefy solid dead tissue.
c) The leucocytes are supposed to form a growth- promoting substance called Trephone which is used by damaged tissues to repair themselves.
d) The basophil secretes heparin which prevents intra-vascular clotting.
e) Anti histaminic function – The eosinophils are very rich in histamine content which prevents all short of allergic functions that occur in daily life.
f) Formation of Platelets- These are formed from the fragments of the disintegrated white blood cells.
g) Formation of plasma protein: The cytoplasmic remnants of the dead leucocytes form albumin and globulin part of plasma protein.
h) They are supposed to form fibroblastic cells for tissue regenerations and repair.
i) Phagocytosis – The leucocytes engulf foreign particles and bacteria and generally digest them. By this process it serves the great defensive functions.
j) Antibody formation – They manufacture anti body and helps in defensive action against any foreign bacteria.
Total number of W.B.C. : In healthy adults, number of leucocytes, called the total count of W.B.C., is between 4000 to 11000/cu. mm of blood. (Infants – 6000 to 20000 and Children – 5000 to 15000).

Ques. 9 What is the life & fate of leucocytes?
Ans. Life & fate of leucocytes : All the white blood corpuscles remain in the blood stream for 1 to 5 days after their formation, them they are disintegrated and disappeared in the blood stream. Some W.B.C. are killed during fight against bacteria. These disintegrated W.B.C. are ingested by reticulo-endothelial cells.

Ques. 10 Describe briefly where & how Leucopoiesis occur? (or state the development or origin of Leucocytes) –
Ans. White Corpuscles develop extra-vascularly and pass by amoeboid movement throught the lining walls of capillaries into the circulation.
I. In early foetal life – White corpuscles are formed in the liver and somewhat later, in the spleen.
II. When bone-marrow has developed – All the granular leucocytes and to a slight extent monocytes & lymphocytes take origin from the red-marrow. The main sources of origin of monocytes and lymphocytes are the spleen and lymphatic glands in general respectively.
According to Sabin, granular leucocytes, lymphocytes & monocytes are all derived from a common-stem cell called reticular cell. This is a fixed mesenchymal cell found in red marrow, spleen & lymphatic glands. It is believed that some products of cellular disintegration such as nucleic acid & its derivatives stimulate the red-marrow for the formation of new white corpuscles.

Ques. 11 What is the Character of W.B.C.?
Ans. Character of W.B.C. : (1) The size of W.B.C. is bigger than R.B.C. and they do not contain haemoglobin. (2) They are nucleated and their life span is shorter by about 5 days. (3) Amoeboid movement is present. (4) Several varieties of leucocytes are present.

Ques. 12 What are the variations of R.B.C. Count under physiological conditions?
Ans. Diurnal variation : maximum in the evening and lowest during sleep. (ii) Count rises: during the muscular exercise, at higher altitude, due to high external temperature, when O2 tension is low, when CO2 tension is high, when adrenal is ejected etc. (iii) Count falls : at lower altitude.

Ques. 13 What are the average ratio of total W.B.C. count with the total R.B.C. count?
Ans. It is about 1 : 700, i.e. for 1 WBC there are 700 RBC.

Ques. 14 What is Red Blood Corpuscle?
Ans. It is a red, non-nucleated and perfectly elastic, biconcave disc. It envelope consists of proteins & lipoids (cephalin, lecithin and cholesterol), and is responsible for its characteristic permeability. The envelope encloses a solution of haemoglobin and various electrolytes, e.g. K, Mg, Ca, and P.

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