Functions of the blood
• Respiration: oxygen and carbon dioxide are transported
• Trophic: the nutrient materials are delivered to the tissues
• Excretive: the metabolites are delivered from tissues to excretory organs
• Regulative: the hormones and BAS are transported
• Homeostatic maintenance of water content and acid-base balance
• Protective immunity and non-specific resistance; blood coagulation
• Maintenance of body temperature: a result of a redistribution of blood volume between skin and the internal organs at high and low temperature of external environment.
Blood composition
• Blood consists of
liquid plasma (volume-55-60%)
formed elements (cells or corpuscles) (volume-40-45%)
• Formed elements include
Erythrocytes (red blood cells);
Leukocytes (white blood cells);
Thrombocytes (platelets)
The hematocrit - erythrocyte volume fraction (EVF), is the volume percentage (%) of red blood cells in the blood. It is normally about 40-48% for men and 36-42% for women
Blood plasma
• Composition: 90-92% of water 8-10% of dry substance mainly consisting from proteins (6-8%) Dry substance includes: inorganic (mineral) organic components
• The organic components of plasma include: proteins, lipids, carbohydrates waste.
Plasma proteins and their role
• Albumin - Transportation (65-85 g/l), regulation of oncotic pressure Regulation of pH
• Globulin - (28 g/l) - Transportation, Defense
• Fibrinogen - Blood clotting (haemostasis) (3 g/l)
The major plasma carbohydrate is glucose (3.3-5.5 mmol/L).
Plasma normally contains varying amounts of hormones, enzymes, pigments, and vitamins.
The composition of plasma varies with the body’s activity and different physiological states.
When fibrinogen is removed from plasma as a result of coagulation, such plasma without fibrinogen is called serum.
Physico-chemical constants of blood
• Osmotic pressure
• Oncotic pressure
• Blood pH
• Viscosity
• Specific gravity
• Erythrocyte sedimentation rate(ESR)
Osmosis - movement of water from lower concentration to higher concentration solution acrosssemi-permeability membrane. Osmotic pressure (7.6 atm)
Dissolved particles maintain the osmotic pressure.
Among them, the most active is
-NaCl (0.9 % isotonic) and also glucose (5 % isotonic)
In hypotonic solution - swelling and bursting occurs.
In hypertonic solution - shrinkage occurs.
Osmotic resistance of RBCs
Concentration at which complete hemolysis of erythrocytes occurs. Normal 0.35 - 0.45%
Maintenance of osmotic pressure
Osmotic pressure is a strict constant. The main organ that maintains osmotic pressure - the kidneys (with a salt load decreases diuresis, with water – increases). The sweat concentration changes. The amount of water vapor varies with breathing
Oncotic pressure, or colloid osmotic pressure, is a form of osmotic pressure exerted by blood plasma proteins. It usually tends to pull water (fluid) into the circulatory system (capillaries). It is the opposing force to hydrostatic pressure. Its normal value is: 0.03-0.04 atm (or) 20-25 mm Hg
pH is a strict constant. pH is a measure of the asidity and basicity of an aqueous solution. Normal pH of blood is: (arterial blood) 7.45 – 7.35 (venous blood), If pH is less than 7.3, it is acidosis, If pH is more than 7.5, it is alkalosis
Three primary systems that regulate the H+ concentration in the body fluids to prevent acidosis or alkalosis
(1) the chemical acid-base buffer systems of the body fluids, which immediately combine with acid or base to prevent excessive changes in H+ concentration; they react within a fraction of a second to minimize these changes. Buffer systems do not eliminate H+ from or add them to the body but only keep them tied up until balance can be reestablished.
(2) the respiratory system, which regulates the removal of CO2 (and, therefore, H2CO3) from the extracellular fluid; The second line of defense, also acts within a few minutes.
(3) the kidneys, which can excrete either acid or alkaline urine, there by readjusting the extracellular fluid H+ concentration toward normal during acidosis or alkalosis. The kidneys, can eliminate the excess acid or base from the body.
Functional system for maintaining pH
CORTECS behavior
АNC Lungs
LRC control apparatus Kidney рН (7.36-7.40)
glands of internal sweat glands chemoreceptors.
Secretion Liver
Blood buffer systems
Plasma Erythrocytes
Carbonate Haemoglobin
H2CO3/ NaHCO3 NaHCO3 + HCl = NaCl + H2CO3 HbO2/ Hhb
H2O + CO2 (lungs)
Phosphate
NaH2PO4/ Na2HPO4 NaH2PO4+ NaOH= Na2HPO4 +H2O (kidneys)
Protein
Erythrocyte Sedimentation Rate (ESR). The erythrocyte sedimentation rate (ESR), is the rate at which red blood cells sediment in a period of one hour. It is a common hematology test. Normal values: Men - 2-10 mm/hr; Women - 2-15 mm/hr