Blood

BLOOD

Blood is a special type of Connective Tissue that is composed of several types of cells suspended in a fluid matrix called Plasma

What is Plasma:

Plasma is a yellowish homogeneous fluid, a major component of plasma is water which constitutes about 90% of the volume and the remaining 10% dissolve solutes that dissolve in water components of plasma

About 80% dissolve solutes consist of Proteins (Albulins, Globulins, Fibrinogens)

The remaining 20% dissolve solutes consist of Nutrients (Glucose, Amino-acids, and Lipids)

The rest of the Plasma contains:

² Inorganic Salts, 

² Electrolytes, 

² Nitrogenous Compounds(Urea and Creatinine) ,

² Hormones, Enzymes, and Dissolve 

² Gases (Oxygen, carbon dioxide, and Nitrogen)

Elements Of Blood:

Erythrocytes (RBCs)

Leukocytes (WBCs)

Platelets ( Cytoplasmic Fragments derived from Megakaryocytes)

What are Megakaryocytes:

Megakaryocytes present in Bone-marrow

Erythrocytes/ RBCs:

Erythrocyte has pale yellow or tan color due to their content of hemoglobin, in dense masses erythrocytes gives red color characteristics of blood

Under normal conditions, RBCs do not leave the circulatory system, Erythrocytes have a lifespan of 120 days 

A mature Erythrocyte is shaped like a biconcave disc. It doesn’t contain a nucleus and is also devoid of typical cell organelles. In a living state erythrocyte measure about 7-8 micrometers in diameter,2.6 micrometers thick at the periphery(rim), and about 0.8 micrometers thick at the center

Erythrocyte enhances the surface area of the cell which facilitate gaseous exchange

What is anemia?

Disease in which reduction in oxygen carrying capacity of blood

² Decrease in the number of erythrocytes or reduction in the content of hemoglobin

Leukocytes:

Leukocytes possess a nucleus capable of ameboid movement and contain no hemoglobin

In adults normal total leukocytes count from 5000 to 10,000 cells per microlitre of blood

The count is higher in children

The number of leukocytes in blood may increase or decrease under certain diseased conditions

Leukocytosis:

A temporary increase in the number of leukocytes is called leukocytosis

Leukopenia:

Reduction in the number of leukocytes below the lowest normal range called leukopenia

Leukocytes classified into two main groups

Granulocytes (Presence of Specific Granules)

AGranulocytes (Absence of Granules)

Granulocytes: 

² Neutrophils (40-75% of total WBCs, average diameter 7-9 micrometers in fresh blood)

² Eosinophils(2-4% of circulating leukocytes, same size as neutrophils,

    constitute specific granules and azurophilic granules/lysosomes)

² Basophils(0.5-1% , measuring 7-9 micrometer in fresh blood and 10-12 micrometer in dried smears)

AGranulocytes:

Lymphocytes (T-lymphocyte/Cytotoxic T-cells, B-lymphocyte, Null cells)

Lymphocytes constitute 20-40% of total leukocytes in adult

In Children, lymphocytes constitute 30-70% of peripheral blood

² T- lymphocytes (70%) 

² B-lymphocytes (25%)

² Null Cells (5%)

T-Lymphocytes are classified into three main types:

About 200 markers have been identified on the surface of T-Lymphocytes

CD3, CD4, CD8, CD28, CD40

² Effector T-cells (CD8)

² Regulatory T-cells (CD4) (TH1 cells , TH2 cells)

² Memory T-cells (Quiescent)

B-Lymphocyte are classified into two types:

B cells also express CD markers on their surface which are CD9, CD19, CD20, and CD24

² Effector B-cells

² Memory B-cells

Platelets:

Platelets range from 200,000 to 400,000 per microlitre of blood

The average life span of platelets is about 10 days

Platelets show 2 regions

² Granulomere (darkly staining central region)

² Hyalomere (lighter staining homogeneous peripheral zone, 15-20 nm glycocalyx coat)

Functions:

Platelets play an important role in hemostasis(stoppage of blood leakage from injured blood vessels)

thrombosis, and 

wound recuperating

Hemopoiesis

The ability to self-renew, a divisional event that results in two HSCs, and the ability to multipotent differentiate into all mature blood lineages, that is, erythrocytes, platelets, lymphocytes, monocyte/macrophages, and granulocytes, are fundamental characteristics of hemopoiesis

The spongy substance inside your bones called bone marrow is the most prevalent location of blood cell formation. Medullary hematopoiesis refers to hematopoiesis that happens in your bone marrow. Blood cells are produced in the bone marrow and discharged into the circulation.

Other regions of your body, such as your liver and spleen, experience hematopoiesis less often. Extramedullary hematopoiesis refers to hematopoiesis that occurs outside of your bone marrow.

Hematopoiesis occurs in diverse parts of the body before and after birth