BLOOD

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Blood is a body fluid that carries oxygen from the Lungs to all part of the body and carbon dioxide from all part of the body to the Lungs. It is also called the “Fluid of Life”, “Fluid of Growth”, “Fluid of Health etc. Blood is called the fluid of life because it carries oxygen from lungs to all parts of the body and carbon dioxide from all parts of the body to the lungs.
It is named the fluid of growth because it carries nutritive substances from the digestive and also carries hormones from endocrine glands to all the tissues in the body.
Blood is also called the fluid of health because it protects the body against diseases and get rid of the waste products and unwanted substances by transporting them to excretory organs such as the Kidney.

PROPERTIES OF BLOOD

Blood possesses the following.

Blood

|Color: Blood has only one color which is RED color. The blood is of two group which are the Arterial blood and the Venous blood, The arterial blood is scarlet red and this is because it has more oxygen while the venous blood is purple red in color this is also because the venous blood has more carbon dioxides.
Volume: The average blood volume in a health living adult should be 5L. In new born the total volume is 450ml, while the volume of blood is slightly less in females and it is about 4.5L.
Reaction: Blood is slightly alkaline in nature.
pH: The pH of a normal blood is 7.4

COMPOSITIONS OF BLOOD

Blood is composed of two elements namely;
a.Formed Elements: These are also called the blood cells and they are;

Red blood cells (RBCs)
White blood cells (WBCs)
Platelets (Thrombocytes)
b. Plasma: This is a straw-colored clear liquid part of blood; it contains 92% of water and 8% of solids. The solids are in two forms i.e. the organic and inorganic substances. Examples of the organic solids substances in the blood are the plasma proteins which are the Albumin, Globulin and fibrinogen and other substances. Examples of inorganic solid substances of the blood are sodium, calcium, chloride, iron, magnesium, potassium etc.
FORMED ELEMENTS

The Red Blood Cells (RBCs)

Red blood cells are the non-nucleated formed elements in the blood, RBCs are also called the erythrocytes (erythro means RED). Red blood cells are disk shape and biconcave with a thin central portion and a thick periphery, this blood cells is only present in mammals and camel is the only mammal with a nucleated Red blood cells, The average lifespan of the RBCs is 120 days. The main function of RBCs is that they carries the blood group antigen and also transport oxygen from the lungs to the tissues.

ERYTHROPIESIS

This is the process of development and maturation of red blood cells. The development and maturation of blood takes place in two stages

Fetal Life: In fetal life erythropoiesis takes place in the mesenchyme of yolk sac, spleen, lymphoid, bone marrow and liver.
New born babies, children and adult: In this stage erythropoiesis takes place in the bone, liver, spleen etc.

The White Blood Cells (WBCs)
These are colorless and nucleated formed elements of the blood, it is also known as the Leukocytes. The life span of WBCs is not constant as that of RBCs, Some WBCs have granules in the cytoplasm and based on the presence and absence of granules in the cytoplasm, the leukocytes are classified into two groups;
• Granulocytes (which have granules)
• A-granulocytes (which have no granules)
The Platelets
Platelets are also formed elements of blood which are small, colorless, non nucleated and moderately refractive bodies. Platelet is considered to be the fragment of cytoplasm. It is constituted by cell membrane, micro tubules and cytoplasm and the average lifespan of Platelets is 10 days.

FUNCTIONS OF BLOOD

Transportation of respiratory gases is done by the blood.
Removal of waste product formed in the tissue during metabolic activities
Transportation of nutrient from GIT to all part of the body for both energy and growth production
Blood plays an important role in defense of the body
Maintenance of thermoregulatory mechanism in the body
COAGULATION/CLOTTING OF BLOOD

This is define as the process in which blood loses its fluidity and becomes a jelly like mass few minutes after it is shed or collected in a container.
Stages of Blood Clotting
Formation of Prothrombin activator
Conversion of Prothrombin into Thrombin
Conversion of Fibrinogen into Fibrin