BLOOD VOLUME
It is the total volume of blood in the circulatory system an average man with 60 kg of body weight has 5 litres (approx ) of blood in his body
Methods of measuring blood volume :
1.Direct method : in this method the animal is bleed to death the vessels are washed with water to draw out residual blood and the added water is subtracted to assess animal.s blood volume experimentally
2. Indirect Method: In this method : In this method a known volume of dye stuff like Evans blue congo red or radio active substance is being injected their dilutions are measured and total volume is then calculated these methods have some limitations
Physiological variations::
Blood volume undergoes proportional increase according to (1) body weight (2) surface area and (3) age however infants have proportionally more blood volume other factors that influence blood volume are (4) sex males have more blood volume than females (5) Pregnancy status increases blood volume in women (6) blood pressure : an increase in blood pressure lowers the blood volume and vice versa this is because more blood is squeezed out into the tissue spaces with an increase in filtration force (7) a noxia i.e state of decreased oxygen in blood increases the blood volume as a compensatory phenomenon (8) increase in altitube (e.g) climbing the himalaya ) also increases blood volume for the same reason as in anoxia or hypoxia (9) muscular exercise increases blood volume by splenic contraction (10) posture: while standing blood volume falls by 1/10th.(11) adrenaline injection increases blood volume by splenic contraction:
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