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THE
BLOOD
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Blood Whether life was born on earth or was seeded on it from extraterrestrial
sources is a matter for debate amongst the evolutionist . But amongst
them is unanimity on the opinion that life evolved from unicellular
organism to man & it migrated from oceans to the land . The unicellular
organisms surrounded by the oceans once , entrapped it within them
as they evolved in the multi-cellular form. The primitive marine water
underwent profound modifications to be transformed into what we now
call " The Blood". |
| COMPOSITION
OF THE BLOOD: |
The
blood can be regarded as a specialized connective tissue , consisting
of liquid intercellular substance, the plasma & the cellular elements
or the formed elements. The plasma constitutes about 55 % & the cells
about 45 % of the total blood volume. The composition of the whole can
be summarized as follows :-
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1.
The Cells or corpuscles
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The red blood corpuscles or the erythrocytes(R.B.C.)
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The white blood corpuscles or the leukocytes (W.B.C.)
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The platelets or the thrombocytes
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2.The
plasma
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- Water-
91 to 92 percent
- Solids-
8 to 9 percent
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i)
Inorganic Constituents 0.9 percent. |
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Sodium,Potassium,Phosphorus,iron,copper |
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ii)
Organic Constituents: |
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(a)
Proteins-7.5G percent-serum albumin,serum globulin,fibrinogen,prothrombin
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(b)
Non-protein-Nittrogenous Substances(NPN)25 to 35 mg percent Urea,uric
acid,xanthine,hypoxanthine,creatinine,creatine,ammonia, ammino acids
etc.
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(c)
Fats-Cholesterol-150-250 mg.percent Triglycerids-40-145mg percent.
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(d)
Carbohydrates-sugar Fasting(F) 80 to 120 mg percent Post prandial(PP)120
mg percent (2 hrs after food)
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(e)
Bile Pigments-Serumbilirubin
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(f)
Enzymes
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(a) Immunoglobulins
(b)
Hormones-of Pituotary, thyroid, thymus, suprarenal glands & sex hormones
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PROPERTIES
OF THE BLOOD: |
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The
blood is a opaque viscous,thick,sticky liquid,It is red in colour.It is
faintly alkalinein reaction (PH 7.4)Its specific gravity is 1.055.Biochemically
it is a colloidal solution in which are suspended the formed elements.When
collectedin a test tube & kept standing for a short while its clots.The
formed elements are entangled in the clot & yellow colored plasma separates
a top the clot. |
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The
Red Blood Corpuscles (Erythrocytes)-/Red Blood Cells (R.B.C.S .)- |
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As
the name suggests these cells are red in color.They are circular in shape.They
have no nucleus.Hence technically they are 'ghost cells.When viewed from
side they appear biconcave;but when viewed from front they are discoid.They
are thinner in the center & thick towards the periphery.They contain a Pigment
haemoglobin(hb) which is red in color.The haemoglobin imparts red color
not only to the R.B.C.S . but to the blood too. |
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The
White Blood Corpuscles (Leukocytes)-/White Blood Cells (W.B.C.s . )- |
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They
are not 'white' but are colorless.To view them,it is necessary to stain
them with a dye.They are nucleated cells.They exhibit movements like an
amoeba . They move on their own irrespective of the flow of the blood .There
are five types of W.B.C.s |
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1.
Neutrophils :- Also called as granulocytes because they contain
enzyme - filled granules . They are of two types:
a) in mature or band neutrophils
b)
mature or segmented neutrophils. Their nucleus has many lobes. The cytoplasm
takes neutral stain.
2.
Lymphocytes :- They do not contain granules. Some of them are large
& some small in size.They are of two types:
a) 'T ' lymphocytes
b) 'B' lymphocytes
3. Eosinophils :- They contain coarse granules . They are stained
with acid dyes like eosin. Their nucleus has two lobes.
4.
Basophils :- Their cytoplasm contains granules of various sizes. They
take deep basic stain.Their nucleus is lobed.
5. Monoccctes :-They have single lobe. They are not granulated.
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The
Platelets (Thrombocytes ) :- They resemble particles. They are smaller than
R.B.C. &W.B.C.s . They do not have definite form. They gather at the site
of bleeding or at rough surface in the blood vessles. In the main stream
they move freely but at roughened sites they become sticky. |
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FUNCTIONS
OF THE BLOOD |
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1.
Transportation of respiratory gases:-
The
R.B.C.s are filled with haemoglobin ( Hb) which enables them to carry
oxygen O2 from lungs and deliver it to all body tissues. The tissue
cells consume this oxygen to provide energy to them liberate carbon
dioxide (CO2 ) as a waste product. The Hb forms loose complex with CO2
, carries CO2 from the tissues and transports it back to the lungs.
The blood helps the lungs in their respiratory function.
2.
Body Defense :-
The
white blood cells (W. B. C. s) form the great defensive force of the
body.By their amoeboid movements (throwing pseudopodia , the false
limbs) the W. B. C. s engulf the bacteria ( phagocytosis). The W.
B. C. s also develop chemical substances known as antibodies to destroy
the bacteria and to combat certain toxic agents . In acute bacterial
and fungal infections the neutrophils bear the first brunt . They
devour the infecting agents and ingest the foreign debris. The "T"
lymphocytes come into action against viral infection . They also can
detect and destroy some cancer cells . The "B" lymphocytes develop
into special type of cells , the plasma cells which produce antibodies
. The monocytes ingest dead or damaged cells. They also provide the
immunologic defenses against many infective organisms. The eosinophils
come into action to combat allergies. They also try to kill certain
parasites and cancer cells . The basophils participate in allergic
responses and in lead poisoning .
3.
Arrest Hemorrhage ( Bleeding) :-
The
platelets or the thrombocytes protect the body against hemorrhage
. They gather at the site of bleeding, become sticky and seal the
small capillaries and the larger blood-vessels. At the same time they
release a substance that helps clotting.
4.
Transport of Nutrition :-
It
carries various nutrient materials to the tissues .
a) carries digested food material absorbed from the intestines to the
cells.
b) carries stored food materials from the storage depots to the cells
in conditions like starvation and emergency extra nutritional requirement.
5.
Acts as a Vehicle :-
The
blood acts as a vehicle through which the hormones and other essential
chemicals are transported to the places of their activity.
6.
Drainage of Waste-products :-
It
carries waste-products of cellular activity and reaches them to the
organs of excretion like the kidneys.
7.
It takes part in maintenance of water balance of the body.
8.
It plays an important role in the regulation of the body temperature.
9.
It plays an important role in the maintenance of the acid - base equilibrium
of the body.
10.
With the help of the reservoirs of the blood like the spleen , muscles
etc. it participates in the regulation the blood pressure.
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HEMOGLOBIN(Hb) |
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The
hemoglobin is the coloring substance of the R.B.C.s and hence indirectly
that of the blood . It is a colored protein ( chromoprotein). It is made
of two factions (a) hem- the coloring substance containing iron, and (b)
the globin-the protein part. The iron forms the central core which is surrounded
by four porphyrin rings . As the protein is attached to the metal, it is
known as metalloprotein .Almost 80% of the body iron is found in the hemoglobin
. It is a very molecule . On isolation it can be crystallized . It forms
loose chemical compounds with oxygen and carbon-di-oxide forming oxyhemoglobin
and carboxyhemoglobin respectively.This property enables the blood to carry
oxygen from the lungs to the body tissues and transport carbon-di-oxide
from the tissues to the lungs. |
