Connective Tissue Cells PDF

Connective Tissue Cells Dr Fatma Meligy CT Cells Fixed Cells - Mesenchymal cell - Fibroblast - Fat cell Free Cells - Plasma cell - Mast cell -Macrophage -Leucocytes A.) Fixed cells: These are stable long – lived cells and include fibroblasts, fat (Adipose) cells and mesenchymal cells. B.) Free (wand...

Connective Tissue Cells Dr Fatma Meligy CT Cells Fixed Cells - Mesenchymal cell - Fibroblast - Fat cell Free Cells - Plasma cell - Mast cell -Macrophage -Leucocytes A.) Fixed cells: These are stable long – lived cells and include fibroblasts, fat (Adipose) cells and mesenchymal cells. B.) Free (wandering) cells: These are short – lived cells that are changing population which include mast cells, plasma cells, macrophages, and leukocytes. Fixed cells Mesenchymal cells These are branched cell with pale basophilic cytoplasm. Function: give rise to any other types of C.T.cells. Fibroblast The most common cell in CT proper. Origin: from mesenchymal cells. LM: -Young cells appear as branched cells with abundant basophilic cytoplasm &oval pale nucleus with prominent nucleolus. -Old fibroblasts (fibrocytes) have flattened shape, little pale acidophilic cytoplasm, flat or oval nucleus &prominent nucleolus. Fibroblast EM: Since the fibroblast is a secretory cell it reveals the characters of these cells. It contains numerous RER, well developed Golgi apparatus, ribosomes, mitochondria and transfer &secretory vesicles. Functions: 1. Formation of both components of the intercellular substance. a) They secrete tropocollagen through secretory vesicles to the outside forming the collagenic fibers. b) Secretion of mucopolysacharide of the matrix 2. Secretion of elastin. 3. Repair of wounds. They are present singly or in groups. 3. Fat (adipose) cell or adipocyte: *Origin: Fat cells develop from fibroblasts at sites which accumulate fat, whereas in developing sites they are formed from mesenchymal cells. The mother cell (accumulates small fat droplets in its two poles then the small droplets of fat unite and form a single large droplet which pushes the nucleus to one side. *Structure: Using H&E stain, fat cells appear as empty spaces which have signet ring appearance due to the peripheral nucleus and thin rim of cytoplasm characteristic of fat cells. It can be stained black with Sudan black and Osmic acid. Free (wandering) cells Plasma Cell Origin: from B-lymphocyte. enter the loose C.T. from the blood stream. LM: -its shape is spherical or ovoid when present free &angular when compressed. -Nucleus is eccentric with clockface heterochromatin. -Cytoplasm is intensely basophilic with a pale area close to the nucleus (negative Golgi area). Plasma Cell EM: -numerous RER &free ribosomes. -well developed Golgi located beside the nucleus &a pair of centrioles. -mitochondria &secretory vesicles. -Russell bodies. Function: Secretion of antibodies. rounded acidophilic bodies, (Russell bodies). Russell bodies are larger than secretory vesicles and represent accumulations of secretion in rough surfaced vesicles. They signify the beginning of degeneration Mast Cell Origin: from bone marrow LM: -They are rounded or oval shaped, found in groups around blood vessels. -Have rounded central nucleus &basophilic granules in the cytoplasm. The granules stain metachromatic with basic dyes ( toluidine blue). EM: have granules variable in size &irregular in outline, mitochondria, RER &Golgi. Function: secrete histamine, heparin &chemical mediators Macrophage *Origin: From mesenchymal cells in prenatal life. From monocytes which come to loose C.T. from the blood in postnatal life. Macrophage It has oval shape when present free and elongated or angular when it is compressed by other tissues. Its surface is irregular. It has eccentric condensed nucleus which is indented. Macrophages can be identified with vital stains such as Trypan blue by the appearance of phagocytozed particles of the dye in their cytoplasm. By E/M: Macrophages are characterized by the numerous phagocytosed particles (Phagosomes), residual bodies, and multivesicular bodies together with numerous lysosomes. A few cisternae of RER and prominent Golgi complex are also present. *Function Phagocytosis of foreign materials. They are the big eaters. Choose The Correct Answer 1- …………… is one of the fixed C.T.cells: a. Macrophage. b. Mast cells. c. Fibroblasts. d. Leucocytes. 2- Because of their phagocytic activity, macrophages have many: a. Lysosomes. b. Secretory vesicles. c. Ribosomes. d. Microtubules. 3- Mast cell granules are: a. Acidophilic. b. Invisible by basic stains. c. metachromatic. d. Well stained with orcein. Thank you