What is blood|composition|functions

Definition:

Blood is a living connective tissue in a fluid state. When compared to water, blood is denser and more viscous than water and clots outside the body. It is present in the heart and blood vessels.

Color of the blood

Blood is red in color due to presence of haemoglobin in red blood cells. The blood is bright red when haemoglobin is oxygenated and dark red when haemoglobin is deoxygenated.

Crculation of blood

The heart pumps oxygenated blood in the arterial system, blood vessels and circulates throughout the body and deoxygenated blood returns to the right side of the heart via the venous system.The deoxygenated blood is oxygenated in the lungs ,then to the left side of the heart which pumps blood in the blood vessels, and in this way blood circulates in the body.

Table of contents

1.	Definition
2.	Colour
3.	Volume
4.	Composition
6.	Functions

Total blood volume

Total blood volume is 80 milliliter per kg of bodyweight. Usually, 5 – 6 liters (average 5 liters).

Composition of blood

A. Fluid portion: This is known as plasma, and constitutes 55% of the total blood volume. It is a clear straw-colored portion of the blood and has 91% water and the rest 9% solids in it. The solid substances are:

Inorganic -1% sodium, potassium, calcium, magnesium, phosphate, iron, etc., in ionic form and

Organic substances -7% plasma protein and 1% non-protein nitrogenous substances like sugar, fat, enzymes, etc. 

 B. Formed elements of blood constitute 45% and are of three types :

1. Erythrocyte: Red blood corpuscle – Red blood cell.
2. Leucocyte: White blood cell.
3. Thrombocyte: Platelet.

Formed elements of blood can be divided into two types:

1. Nucleated: White blood cells
2. Non-Nucleated: Red blood cells and Platelets.

The differences in Plasma and Serum

Plasma is blood minus formed elements of blood, i.e., cells of the blood.

Serum = Plasma – fibrinogen, prothrombin, liable factor or proaccelerin and anti-hemophilic factor (AHF).

The serum is Plasma minus fibrinogen and some clotting factors-factor II, V, and VIII. Other clotting factors VII, X, XI, and XII, are present in the serum.

Functions of blood:

A.Transportation:

1. Oxygen from lungs to the cells and

2. Carbon dioxide from cells to the lungs.

3. Absorbed nutritive materials from the GIT to the tissues for utilization and storage.

4. Metabolite waste from the tissues to the excretory systems.

B. Homeostasis -controls the internal environment of the cells.

C. Regulate body temperature

D. Exerts osmotic pressure.

E. Haemostasis.