The fluid blood is composed of two roughly equal parts, corpuscles and plasma, which convey oxygen and nutritive
and other products of metabolic importance to the tissues of the body and simultaneously carry away carbon dioxide
and metabolic waste products to the Lungs. Kidneys, Liver and Spleen for disposal.
The body of an adult contains about five liters of blood, composed of (a) red cells (about 5 million per cubic mm. of blood),
containing a complex iron-protein pigment Hemoglobin whose function is to carry oxygen from the lungs,
and taking up in exchange carbon dioxide which it carries back to the lungs, whence
it is expelled ; (b) white cells (Leucocytes, about 7000 per cubic mm. of blood).
The leucocytes or white cells are of various types. Which one group (Phagocyte-Greek phagein, to eat ; Kytos, cell)
perform the vital function of combating infection by destroying bacteria and removing impurities and diseased tissue ;
another group (Lymphocytes-Latin lympha, water ; Kytos, cell) helps in the process of immunization.
The plasma is a yellowish fluid 90 percent water and 7 percent protein (mainly albumin) which maintains the osmotic pressure
( the pressure with which salts, sugar, etc. In solution draw water across the cell membrane),
together with globulins (concerned with immunity) and fibrinogen, (essential for blood coagulation by the formation
of a clot to seal bleeding vessels). Plasma also contains salts, glucose, hormones, antibodies
and enzymes with metabolic function.
Blood Group:-Every human has blood which belongs to one of the four major groups (A, B, AB, O)
differentiated by the presence or absence, in the corpuscles and serum, of certain substances
called agglutinogens and agglutinins. When blood from incompatible groups is mixed,
agglutination or sticking together of red corpuscles occurs, with possibly fatal results.
A compatible transfusion is ensured by using blood group or from group 0 which has no
antibodies or the specific substances produced in the blood as a reaction to an antigen.
The Rhesus factor must also be taken into account ; a blood factor also found in Rhesus monkeys
and in 85 percent of persons. A Rh-negative person transfused with Rh-positive blood suffers no
ill-effects at the time, but the Rhesus factor stimulates the recipient's tissue to produce
antibody which may agglutinate transfused red cells in any second transfusion with
Rhesus-positive blood, a dangerous possibility of great importance in obstetric of midwifery.
If Rhesus-negative women becomes pregnant by a Rhesus-positive man, she receive an antigen
stimulating Rhesus-antibodies, which may destroy the blood of any subsequent Rhesus-positive
foetus, causing the death of the newly born. But now you can get synthetic blood.
Blood Pressure:-When the heart is pumping the blood into the aorta, the pressure rises to
a maximum (systolic pressure) ; this is measured to give the 'blood pressure' , which in normal
case has the following range
Childhood 70 to 100
Young adults 90 to 125
Adults 130 to 150.
Blood pressure is highest (systolic pressure) as mentioned above at each heart beat
and goes down to a minimum (diastolic pressure) as the heart relaxes.
In young adults the blood pressure is usually about 120 /80
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