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Tuesday, 26 February 2019

Blood cells and the function of the blood

function of the blood

Blood cells and the function of the blood

Definition of Blood:

 it is a vascular connective tissue in fluid form Containing dissolve substances and blood cells Circulating throughout the body.

It passes through the blood vessels.
Pumped by the heart.
It is known as the “river of life”.
Under the microscope, the color of blood is pale yellow.

Functions of Blood: 

It used to transport:

Oxygen from the lungs to the cells and Carbon dioxide from cells to the lungs.
Water and digested substances from the digestive tract to other organs.
Organic wastes to the excretory system.
Hormones from glands to places of use.
Also, it serves as a defense mechanism against foreign bodies and maintains water balance in the body.

Blood Composition:

Blood Plasma: generally makes up about 55% of blood 
Blood cells or corpuscles
Red Blood Cells(erythrocytes): typically made up about 44% of a blood sample.
White Blood Cells (Leukocytes).

Blood Plasma:

90% fluid
10% inorganic minerals and digested food substances
The clear, yellowish part is called serum.
It transports the blood cells and other substances such as dissolved nutrients, hormones, and waste products.
Digested food is in the simplest form.

Red Blood Cells(erythrocytes):

Mature erythrocytes lack nuclei.Transport oxygen and carbon dioxide to and from the tissues and the lungs. 
Lack of nuclei enables them to carry respiratory gases more efficiently. 
Every erythrocyte is filled with approximately 280 million molecules of a red-pigmented protein called hemoglobin. 
Transports oxygen and carbon dioxide, and is responsible for the characteristic bright red color of arterial blood.
The life span of about 120 days. 

Daily :

About 1% of the oldest RBCs are removed.
Are phagocytized by liver and spleen.
By macrophages. 
Some components saved, some discarded.

White Blood Cells(Leukocytes):

The five types of leukocytes are divided into two classes based upon the presence or absence of visible organelles called granules:

1- granulocytes:
Neutrophil: 60–70% of the total number of leukocytes. 

Eosinophils: have reddish, or pink-orange granules in their cytoplasm, constitute about 2 – 4% of the total number of leukocytes.

Basophils: 1.5 times larger than erythrocytes, least numerous of the granulocytes, constitute about 0.5–1% of the total number of leukocytes, always exhibit a bilobed nucleus and abundant blue-violet granules in the cytoplasm.

2- Agranulocytes:

Agranulocytes are leukocytes that have such small granules in their cytoplasm that they are frequently overlooked upon casual observation—hence the name agranulocyte and it include both lymphocytes and monocytes. 

T-lymphocytes (T-cells): manage and direct an immune response
some directly attack foreign cells and virus-infected cells.

B-lymphocytes (B-cells): stimulated to become plasma cells and produce antibodies.

Natural killer cells (NK cells): attack abnormal and infected tissue cells.


Irregular, membrane-enclosed cellular fragments about 2 micrometers in diameter.
In stained preparations, they exhibit a dark central region.
Sometimes called thrombocytes.
Continually produced in the red bone marrow by cells called megakaryocytes.

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