What is blood?

Blood is the red coloured fluid flowing through heart and blood vessels. As per its composition blood is considered as a liquid connective tissue. It consists of some cellular elements suspended in a fluid matrix called plasma. As per its function blood is a transport tissue of the body because it acts as a medium for transport of various materials from one part of the body to another part. So the definition of blood may be written as a liquid connective tissue which circulates through heart and blood vessels to serve as a connecting link and a medium for transport of materials between different organs of the body.

Common physical properties of blood: –

i) Nature of blood: Blood is the softest issue of the body. It is viscous and colloidal in nature due to the presence of cellular elements and plasma proteins. It has a viscosity five times that of water.
ii) Colour of blood: It is red in colour due to the presence of an iron containing red pigment called the haemoglobin in it. If blood present in artery is bright red whereas blood present in vain is dark red. This difference is due to presence of oxygenated haemoglobin arterial blood and deoxygenated or reduced haemoglobin present in the venous blood.
iii) Taste of blood: Blood has a salty taste because of the presence of various inorganic salts in it.
iv) Reaction of blood: Blood is slightly alkaline in reaction and its pH value is 7.4.
v) Specific gravity of blood: The average specific gravity of blood is 1.057 in males and 1.053 in females at 15°C of temperature.
vi) Coagulation of blood: The blood remains in a fluid state within the blood vessels but Wayne each shed out of the vessels, it convert into a jellylike semisolid mass which is called the clot. The clot formation processes is called clotting or coagulation.

Composition of blood:

Blood Composition

Blood Composition

Blood is composed of two main constituents. Those are the cellular elements and the fluid portion named plasma. The cellular elements are called blood cells or blood corpuscles that remain suspended in the plasma. There are three types of blood corpuscles, those are great blood corpuscles or RBC, the white blood corpuscles or WBC and platelets.

The plasma is a complex extracellular fluid consisting of water in which various organic and inorganic materials remain in dissolved or mixed condition. Plasma contains most of the materials found in different tissues of the body because the tissues take up dorm materials for their metabolism from the plasma and release out most of their products to the plasma. The plasma proteins, nutrients, excretory products, hormones, antibodies, enzymes etc. are the chief organic constituents of plasma. The main inorganic constituents of plasma are chloride, bicarbonate, phosphate, sulphate and iodide salts metals like sodium, calcium, magnesia, potassium, iron, copper etc. and some gases like N2, O2, Co2.

The red blood cells constitute the majority of the cell volume of blood. The plasma is composter of about more than 90% of water and 8 to 9% of solids. Traces of gases like oxygen, nitrogen and carbon dioxide remain dissolved in it. Proteins such as albumin, globulin, fibrinogen and prothrombin are the major part of the solids present in the plasma. All of the proteins present in plasma are called plasma proteins collectively.