Blood

Difinition of blood:

Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells.Blood is red fluid in the body that contains white and red blood cells, platelets, proteins, and other elements. The blood is transported throughout the body by the circulatory system. Blood functions in two directions: arterial and venous.In vertebrates, it is composed of blood cells suspended in a liquid called blood plasma. Plasma, which constitutes 55% of blood fluid, is mostly water (92% by volume) and contains dissipated proteins, glucose, mineral ions, hormones, carbon dioxide, platelets and blood cells themselves.

Content:

Blood accounts for 8% of the human body weight with an average density of approximately 1060 kg/m³, very close to pure water's density of 1000 kg/m^3. The average adult has a blood volume of roughly 5 liters (1.3 gal), composed of plasma and several kinds of cells (occasionally called corpuscles); these formed elements of the blood are erythrocytes (red blood cells, RBCs), leukocytes (white blood cells), and thrombocytes (platelets). By volume, the red blood cells constitute about 45% of whole blood, the plasma about 54.3%, and white cells about 0.7%.
Blood-  1.Erythrocytes                       2.Leucocytes                                        3.Thrombocytes
                (Red blood cell)                       a)Agranulocytes-    Monocytes
                                                                                                 Lymphocytes
                                                                 b)Granulocytes-     Neutrophils
                                                                                                 Eosinophils

Constitution of normal blood
Parameter	Value
Hematocrit	45 ± 7 (38–52%) for males 42 ± 5 (37–47%) for females
pH	7.35–7.45
base excess	−3 to +3
PO2	10–13 kPa (80–100 mm Hg)
PCO2	4.8–5.8 kPa (35–45 mm Hg)
HCO3−	21–27 mM
Oxygen saturation	Oxygenated: 98–99% Deoxygenated: 75%

                                                                                                  Basophils

                         

One microliter of blood contains:

Cell:

Erythrocytes : 4.7 to 6.1 million (male), 4.2 to 5.4 million (female)

Leukocytes : 4,000–11,000

Thrombocytes: 200,000–500,000

Plasma: (55% of whole blood)

plasma volume totals of 2.7–3.0 liters (2.8–3.2 quarts),water: 92%,Plasma protein: 8% and trace amount of other materials.

Circulating plasma contain : dissolved nutrients, such as glucose, amino acids, and fatty acids (dissolved in the blood or bound to plasma proteins), and removes waste products, such as carbon dioxide, urea, and lactic acid. Other important components include:

·         Serum albumin

·         Blood-clotting factors (to facilitate coagulation)

·         Immunoglobulins (antibodies)

·         lipoprotein particles

·         Various other proteins

·         Various electrolytes (mainly sodium and chloride)

Functions of Blood:

	1.Transports: Dissolved gases (e.g. oxygen, carbon dioxide); Waste products of metabolism (e.g. water, urea); Hormones; Enzymes; Nutrients (such as glucose, amino acids, micro-nutrients (vitamins & minerals), fatty acids, glycerol); Plasma proteins (associated with defence, such as blood-clotting and anti-bodies); Blood cells (incl. white blood cells 'leucocytes', and red blood cells 'erythrocytes').
	2.Maintains Body Temperature
	3.Controls pH    The pH of blood must remain in the range 6.8 to 7.4, otherwise it begins to damage cells.
		4.Removes toxins from the body The kidneys filter all of the blood in the body (approx. 8 pints), 36 times every 24 hours.       Toxins removed from the blood by the kidneys leave the body in the urine. (Toxins also leave the body in the form of sweat.)
	5.Regulation of Body Fluid Electrolytes    Excess salt is removed from the body in urine, which may contain around 10g salt per day    (such as in the cases of people on western diets containing more salt than the body requires).