1. Blood physiology
Lecture One
Dr. Majid Hameed

2. Blood:
It is a moving tissue circulates in a closed system of blood vessels. It consists of cellular elements {erythrocytes, leukocytes, and platelets} suspended in a liquid medium (plasma).

3. Functions of blood:
Transportation of O2, CO2, nutrients, heat, wastes, and hormones, enzymes & vitamins.
Regulation of pH, body temperature, arterial BP.
Prevention of blood loss; clotting factors
Protection against pathogens via WBCs.

4. Blood volume:
In Adult male ≈ 5 liters (equal to 8% of the total body weight)
In newborn baby ≈ 300 ml blood
It reaches the adult range at the time of puberty.

5. Mechanisms of regulation of blood volume
Capillary fluid shift mechanism.
 blood volume   capillary pressure   leakage of fluid from capillary to interstitial fluid   blood volume back to normal, and vise versa.
2. Reflex mechanisms (Baroreceptor reflex).
 blood volume  stretching and stimulation of baroreceptors  reflex inhibition of sympathetic nervous system  dilatation of renal arteries allowing excess urinary output.

6. 3. Hormonal mechanism
a) Atrial natriuretic factor (ANF).
 blood volume  release of ANF (from atria of heart)   sodium and water excretion through kidneys   blood volume back to normal
b) Aldosterone.
 blood volume  stimulates aldosterone secretion from adrenal cortex   absorption of sodium and water from kidney tubules   blood volume
c) Angiotensin.
It is released when blood volume is decreased. It causes retention of water and salt.
d) ADH (Anti-diuretic hormone).
 blood volume   release of ADH and allows water loss through kidneys and vice versa.

7. 4. Thirst mechanism:
it is stimulated when blood volume decreases.
5. Renal mechanism.
When blood volume falls below normal, exactly reverse events occur.

8. Conditions leading to increased blood volume: Physiological conditions
Age:
infants > adults when compared to body weight
infants < adults compared to surface area.
80 ml/kg in infants and 70 ml/kg in adults.
Sex:
males > females because of more erythropoietin activity, more body weight and greater surface area (cyclical loss of blood during menstruation).
Exposure to warm environment:  the blood volume.
Physiological conditions
Age: infants > adults when compared to body weight
and infants < adults compared to surface area.
It is 80 ml/kg in infants and 70 ml/kg in adults.
Sex: males > females because of more erythropoietin activity, more body weight and greater surface area.
Exposure to warm environment  the blood volume.
Pregnancy:  blood volume 20 to 30%.
Exercise: due to contraction of spleen and release of stored blood in circulation.
High altitude: Due to hypoxia there is increased erythropoietin secretion at high altitude. This in turn increases the production of RBC   blood volume.
Emotional disturbance: Sympathetic stimulation causes contraction of spleen which releases stored blood in circulation.

9. Conditions leading to increased blood volume:
Physiological conditions (cont.)
Pregnancy:  blood volume 20 to 30%.
Exercise: due to contraction of spleen and release of stored blood in circulation.
High altitude: Due to hypoxia there is increased erythropoietin secretion at high altitude. This in turn increases the production of RBC   blood volume.
Emotional disturbance: Sympathetic stimulation causes contraction of spleen which releases stored blood in circulation.
Physiological conditions
Age: infants > adults when compared to body weight
and infants < adults compared to surface area.
It is 80 ml/kg in infants and 70 ml/kg in adults.
Sex: males > females because of more erythropoietin activity, more body weight and greater surface area.
Exposure to warm environment  the blood volume.
Pregnancy:  blood volume 20 to 30%.
Exercise: due to contraction of spleen and release of stored blood in circulation.
High altitude: Due to hypoxia there is increased erythropoietin secretion at high altitude. This in turn increases the production of RBC   blood volume.
Emotional disturbance: Sympathetic stimulation causes contraction of spleen which releases stored blood in circulation.

10. Pathological conditions with high blood volume
Congestive cardiac failure:
Hyperthyroidism:
Hyperaldosteronism.
Cirrhosis of liver.
Polycythaemia vera.
Congestive cardiac failure: due to retention of sodium and water.
Hyperthyroidism:  thyroxine   RBC production rate.
Hyperaldosteronism.  aldosterone causes greater absorption of sodium and therefore water by the kidneys   ECF and blood volume.
Cirrhosis of liver. This condition is associated with secondary aldosteronism because the damaged liver cannot metabolize the hormone. Excess aldosterone causes greater
absorption of sodium and water by kidneys.
Polycythaemia vera. Mainly red blood cells increase.

11. Conditions which reduce blood volume Physiological conditions
Acute exposure to cold.
Posture. erect < recumbent state
Obesity. Blood volume per kilogram of body weight in an obese person is lower
Conditions which reduce blood volume
Physiological conditions
Acute exposure to cold.
Posture. erect < recumbent state, because
the pooling of blood in lower limbs during erect posture increases the hydrostatic pressure and passage of fluid from blood vessels into the tissue spaces.
Obesity. Blood volume per kilogram of body weight in an obese person is lower but
it is normal when considered in relation to the body surface.

12. Conditions which reduce blood volume Pathological conditions
Haemorrhage or blood loss.
Fluid loss.
Reduction in red blood cells.
Hypothyroidsim.
Conditions which reduce blood volume
Pathological conditions
Haemorrhage or blood loss. Acute external or internal haemorrhage occurs in accidents. It occurs in females from uterus during menstruation or various abnormalities. It occurs from bleeding peptic ulcer.
Fluid loss: It occurs in burns, vomiting, diarrhoea, excessive sweating, polyuria in diabetes mellitus or diabetes insipidus.
Reduction in red blood cells. In anaemia or excessive destruction of red cells by various haemolytic agents causes reduction in blood volume. But sometimes in anaemia blood volume may be maintained by entry of fluid into the blood vessels causing haemodilution.
Myxoedema.

13. Blood components:

14. Properties of Blood
Heavier, thicker, and 3-4 X more viscous than water
temperature: 38 °C
pH :
pH < 7.38 ….. Acidosis
pH > 7.42 ….. Alkalosis

15. Plasma:
It is the straw-colored fluid portion of the blood (intravascular fluid) in which the cells are suspended.
Its quantity = 3,500 ml = 5% of the total body weight.
It consists of
91.5% water
8.5% solutes (70% plasma proteins, % low-molecular-weight substances, 10% electrolytes).

16. Proteins (7 – 7.5 g/dl). Albumins: 4.5 g/dl, synthesized in liver.
Globulins: 2.7 g/dl, synthesized in liver, lymphoid tissue, (α, β, γ)
Fibrinogen: 0.3 g/dl, synthesized in liver
Normal albumin-globulin ratio is about 2:1.
Change of this ratio occur mainly in liver diseases because only albumin synthesis is reduced.

17. Functions of plasma proteins
Colloid osmotic pressure.
plays important role in exchange of water between tissue fluid and blood.
It is normally 25 to 30 mmHg.
Albumin contributes 70 to 80% of osmotic pr.
2. Viscosity.
Fibrinogen and globulins due to their asymmetrical shape.
It provides resistance to flow of blood in blood vessels, & to maintain blood pr. in the normal range.
3. Buffering action. Plasma proteins can combine with acids and bases. They are responsible for about 15% of buffering capacity of blood.
3. Buffering action. Serum proteins like other proteins are amphoteric and thus can combine with acids and bases. In acidic pH, NH2 group acts as base and can accept
proton and is converted to NH4. In alkaline pH, COOH group acts as acid and can donate a proton and thus become COO−. At normal pH of blood, proteins act as acids and combine with cations (mainly sodium).

18. Functions of plasma proteins
4. Binding and transport function.
CO2 (carbamino compound), hormones (thyroxine binding protein (TBP) Cortisol (transcortin); drugs, electrolyte (calcium), iron (transferrin), Cu (Ceruloplasmin); lipids and fat soluble vitamins (A, D and E) (HDL and LDL).
5. Immunity. Gamma globulins in plasma are antibodies and they protect body against bacterial infections.
6. Clotting of blood. Whenever there is injury to the blood vessel fibrinogen is converted to fibrin which forms blood clot. This clot seals the hole in the vessel and therefore prevents blood loss.
Binding and transport function. CO2 is transported by plasma proteins in the
form of carbamino compound.
Several hormones are transported in blood in association with plasma proteins, e.g.
thyroxin is transported in association with an alpha-globulin called thyroxine binding
protein (TBP). Cortisol is transported by a mucoprotein called transcortin.
Many drugs and dyes are transported in plasma in combination with albumin. Half
of calcium of plasma is bound to protein for transport. Beta one globulin transports
iron in plasma (transferrin).
Lipids and fat soluble vitamins (A, D and E) are transported by high and low density
lipoproteins (HDL and LDL).
Bilirubin is associated with albumin and also with fractions of the alpha globulins.
Ceruloplasmin (alpha2 globulin) binds with copper. Transcobalamine binds with
vitamin B12. Haptoglobin binds with free haemoglobin in the vessels and carries it to
reticuloendothelial system.
5. Immunity. Gamma globulins in plasma are antibodies and they protect body
against bacterial infections.
6. Clotting of blood. Whenever there is injury to the blood vessel fi brinogen is
converted to fi brin which forms blood clot. Th is clot seals the hole in the vessel and
therefore prevents blood loss.