L1 histo.pdf

Lec 1 Histo Histology of blood cells Blood o Blood is regarded as a special type of connective tissue formed of cells: - red blood corpuscles (RBCs) - white blood cells (Leucocytes) - blood plate...

Lec 1 Histo Histology of blood cells Blood o Blood is regarded as a special type of connective tissue formed of cells: - red blood corpuscles (RBCs) - white blood cells (Leucocytes) - blood platelets or thrombocytes (45%) - intercellular fluid known as plasma(55%). o It arises from the mesenchyme, which arises from the mesoderm. o Blood Plasma is formed of: Water, organic substances, inorganic substances, gases, hormones and enzymes. RBCs o The number varies from 4.5 to 5.5 million per cubic millimeter. o Normal diameter is varies between 7- 9 µm (7.5 microns average) and the normal thickness is 1.9 microns at the periphery and 1.1 microns at the centre of RBCs. Histological Structure: o They are not true cells; they have neither nuclei nor organoids. o They are rounded, biconcave discs. o In slow blood stream and in blood films RBCs adhere together due to their surface tension showing a rouleaux appearance. o They are surrounded by cell membranes which are formed of lipoprotein. o The RBCs are filled with hemoglobin (Hb). Function: transfer of gases between alveolar air and tissues. Leucocytes (WBCs) o They are called also white blood cells (WBCs). o They are colorless, but when they are packed together,They appear white in color. o They contain all the cell organoids and the cell inclusions. o They have an amoeboid movement, so they can penetrate through the capillary walls doing their phagocytic function in the C.T. outside the blood vessels. o They vary in number from 4000 to 11.000 per cubic millimeter, and can be counted by hemocytometer. o There are 5 types of leucocytes: granular; Neutrophil, Eosinophil, Basophil and non- granular; Lymphocyte, Monocyte. 1|Page  Lec 1 Histo 1. Neutrophil or Polymorphonuclear Leucocytes (60 to 75%) o Their diameter varies from 10 to 12 microns. L/M: the nucleus is single but it is segmented, it is formed of 2 to 5 segments connected with each other by chromatin threads. The cytoplasm contains large azurophilic granules and small specific granules. E/M: the cytoplasm of neutrophils contains few mitochondria, endoplasmic reticulum, glycogen granules and the following two types of Granules: Azurophilic Granules: which are few in number and large in size. They are considered as lysosomes because they are very rich in hydrolytic enzymes. Specific Granules: which are numerous and small in size. They contain collagenase enzyme, alkaline phosphatase and bactericidal substance. Function: Phagocytosis and destruction of microorganisms by the specific & the azurophilic granules. 2. Eosinophil Leucocytes (2 to 5 %) o Their diameter: varies from 12-14 microns. L/M: the nucleus is bilobed or horse shoe shaped, the cytoplasm contains large, coarse, specific acidophilic granules which appear shiny red. E/M: the cytoplasm contains few mitochondria, small Golgi body and few endoplasmic reticulum. It is rich in granules which are considered as Lysosomes. They contain histaminase and sulphatase enzymes. Functions: they are attracted to the site of allergic reactions. 3. Basophils (0 - 1%) o Their diameter varies from 10-12 microns. L/M: their cytoplasm is filled with large basophilic granules similar to those of mast cells. These granules can be stained by Giemsa stain. Their nuclei are large and irregular (S shaped) in shape. E/M: the cytoplasmic electron dense granules are large, membrane bounded with highly ordered internal patterned structure. Functions: are related to production and carriage of histamine and heparin. They are slightly phagocytic cells. 2|Page  Lec 1 Histo 4. Lymphocytes: - According to the diameter, lymphocytes are classified into: A. Small Lymphocytes (15-20%): o Their diameter varies from 6-8 microns. L/M: their cytoplasm is scanty and contains few azurophil granules. The nuclei are small, darkly stained and filling the whole cytoplasm E/M: are covered by microvilli. Their cytoplasm shows many free ribosomes, few mitochondria, few endoplasmic reticulum and a pair of centrioles. B- Large lymphocytes (5-10%): o Their diameter varies from 10-15 microns. L/M: their cytoplasm is more abundant. The nuclei are less darkly stained. E/M: their cytoplasm contains many ribosomes, mitochondria and well developed Golgi complexes. The nucleus is slightly indented. Functions: concerned with immunity. 3|Page