The Vasscular Tissue -Blood

 These comprise the Blood and lymph only . They are liquid tissues and flow in vessels . they are nearest to the connective tissues in structure

I-The Blood

Is afluid connective tissue that circulates through the cardiovascular system,consisting of cells and an extracellular matrix.The cells include :-

 (a)-Red blood cells

 are also called the Erythrocytes they constitute the largest   number of cells in the blood and these round  and  enucleated (non-nucleated),and they biconcave discs.

 (b)-White blood cells

also called the Leucocytes are colourless, nucleated , there are two types of leucocytes:

I – Granulocytes

 whose cytoplasm contains granules . According to the affinity of these granules towards stains, three different categories of granulocytes are recognized:

Neutrophils: Are the most numerous of the WBCs as well as the most common of the granulocytes , they larger than erythrocytes ,have granules stain well with most dyes . The nucleus of a neutrophil divided into a number of segments (3 – 5) connected with one another.

Acidophils (or eosinophils), whose granules stain with the acid dyes, their nucleus bilobed .

Basophils. Have the same size of neutrophils,their granules stain with the basic dyes and the nucleus is S shaped.

2- Agranulocytes

 whose cytoplasm is free of granules. Two categories are recognized:

Lymphocytes , are small, with a large nucleus and little cytoplasm.

Monocytes, are the largest leukocytes.  They possess a horse – shoe- shaped nucleus.

( c)- Platelets

 they are small in their size and have a biconvex shape, appear in the peripheral blood smear either singly or in clusters.