Property,composition and functions of blood:

Introduction to blood:

Blood is a connective tissue in the form of fluid ,and which help to transport substances from one part of the body to another part .

Blood is known as "fluid of life" because it carries oxygen from the lungs to all the part of the body and carbon dioxide from all the part of the body to the lungs.

Blood is also considered as the "fluid of growth" because transports nutritive substances from the digestive system and hormones from the endocrine gland to all the tissues present in the body.

The blood is also called the "fluid of health" because it protects the body from diseases and remove waste products from the body by transporting them to the excretory organs like kidney.

Describe the properties, composition and function of blood

Fig:Blood

Properties of the blood :

1.colour of the blood :

The colour of the blood is opaque red due to the presence of the pigment haemoglobin in the red blood cells. The colour of the arterial blood is scarlet red ,because the arterial blood contains more oxygen.

On the other hand the venous blood is purple red in colour, because this type of blood contains more carbon dioxide.

2.Volume of blood:

In a normal adult the average volume of the blood is about 5 L. The volume of blood in a new born baby is 450ml . It increases during growth and reaches 5L at the time of puberty. In females the volume blood is slightly less and is about 4.5 L .

It is about 80%of the body weight in a normal young healthy adult, weighing about 70kg . The volume of blood in female is slightly less ,because of loss of blood through menstruation ,more fats and less body surface area.

3.Viscosity of blood :

The viscosity of blood is five times more than that of water.

4.Specific gravity of blood :

Specific gravity of total blood is 1.052-1.061

Specific gravity of blood cells is 1.092-1.101

Specific gravity of plasma is 1.022-1.026.

5.pH of blood:

pH of blood is about 7.4(ranges from 7.38 to 7.42) i.e. it is alkaline in nature.

Composition of blood:

Blood is composed of two main components plasma (liquid portion) and blood cells ( these are the formed elements of blood)

Blood cells

There is present three types of blood cells:

1. Red blood cells or erythrocytes(5million/mm³)

2. White blood cells or leukocytes(4000-11000/mm³)

3. Platelets or thrombocytes(1.5-4lakh/mm³)

These blood cells constitutes about 45% of the total volume of blood .

Plasma :

Plasma is a clear straw-coloured liquid portion of the blood.

Plasma constitutes about 55% of the total volume of blood .

Plasma contains 91-92% of water and 8-9% solids.

Functions of blood:

1. Nutritive function

Blood carries the nutritive substances like glucose ,amino acids,lipids,and vitamins derived from digested food are absorbed from gastrointestinal tract and carried by blood to different parts of the body for growth and production of energy.

2. Respiratory functions:

Blood picks up oxygen from the alveoli of lungs and delivers it to the various tissues and also carries away CO2 from the tissues to the alveoli of the lungs.

3. Excretory function:

Blood transports various metabolic waste products such as urea ,uric acid and creatine formed in the tissues during various metabolic activities ,to the excretory organs like kidney ,skin , intestine,lungs.

4.Regulation of water balance:

Water content of the blood is freely interchangeable with intestinal fluid . This helps in the regulation of water content of the body.

5. Regulation of body temperature:

Because of the high specific heat of blood it is responsible for maintaining the thermoregulatory mechanism in the body that is the balance between heat loss and heat gain in the body.