The two most significant human body fluids are blood and lymph. The circulatory system transports blood throughout the body. Let's learn about the composition and properties of blood and lymph (tissue fluid) and the mechanism of circulation of blood.
The most crucial human body fluids are blood and lymph. Plasma, white blood cells, red blood cells, and platelets make up blood. Lymph is a clear liquid that flows inside lymphatic veins.
Blood is the most commonly used body fluid by most of the higher organisms including humans. It is a special connective tissue consisting of a fluid matrix, plasma, and formed elements.
Plasma is a straw coloured, viscous fluid constituting nearly 55 per cent of the blood. Plasma consists of:
Erythrocytes, leucocytes and platelets are collectively called formed elements and they constitute nearly 45 per cent of the blood.
Erythrocytes - Also known as red blood cells (RBC), erythrocytes are devoid of nucleus in most of the mammals and are biconcave in shape. They have a red coloured, iron containing complex protein called haemoglobin, hence the colour and name of these cells. A healthy adult man has, on an average, 5 millions to 5.5 millions of RBCs mm–3 of blood. RBCs have an average life span of 120 days after which they are destroyed in the spleen (graveyard of RBCs).
Leucocytes - Also known as white blood cells (WBC), leucocytes are colourless due to the lack of haemoglobin. They are nucleated and are relatively lesser in number which averages 6000-8000 mm–3 of blood. The two main categories of WBCs are – granulocytes and agranulocytes. Lymphocytes (20-25 per cent) are of two major types – ‘B’ and ‘T’ forms, and both of these are responsible for immune responses of the body
Platelets - Also called thrombocytes, platelets are cell fragments produced from megakaryocytes. Blood normally contains 1,500,00-3,500,00 platelets mm–3. Platelets release a variety of substances most of which are involved in the coagulation or clotting of blood.
Two blood groupings – the ABO and Rh – are widely used all over the world.
Persons with ‘O’ blood group are called 'universal donors' as they can donate blood to persons with any other blood group and persons with ‘AB’ blood group are called 'universal recipients' as they can receive blood from any other group.
Coagulation of blood is a mechanism to prevent excessive loss of blood from the body. Blood exhibits coagulation or clotting in response to an injury or trauma. Calcium ions play a very important role in clotting.
Here's how blood coagulates:
BODY FLUIDS AND CIRCULATION. https://ncert.nic.in/textbook/pdf/kebo118.pdf Accessed 20 Dec, 2021.