Connective tissue Histology lab 6 Notes by Omar Sami

Transcription

1 Connective tissue Histology lab 6 Notes by Omar Sami The connective tissue is composed of: 1- Cells. 2- Extra Cellular Matrix; fibers & ground substance. Ground substance is where you find both Cells & Fibers; we can find them in different percentages which will result in different categorization. Cells are either fixed (always found in the connective tissue) OR transient(they come to the connective tissue on demand) However, some cells like macrophages is considered both fixed and transient. Medical situation: Once an individual in injured, the antigen like bacteria, will enter the underlying CT; so cells within the CT will fight this antigen and recruit more cells to fight the antigen, once the antigen is degenerated, the cells who fought the antigen will die in the connective tissue in a process called apoptosis. The most common type of cells within the CT is the fibroblasts and fibrocytes. Fibroblasts are involved in synthesizing the ground substance and both proteoglycans & glycoproteins. Fixed cells within the CT:

2 1- Mast cells 2- Fibroblasts 3- Adipocytes Transient cells within the CT; 1- Plasma cells 2- White blood cells Remember: Macrophages are both transient & fixed Plasma cells produce antibodies; which when attached to the antigen it will result in DE- Activation of the antigen. Adipocytes are found in the CT with a number; and if that number numerously increased then it shall be called adipose tissue. Don t forget that White Blood Cells (WBC s) include both Lymphocytes and Monocytes. Lymphocytes produce plasma cells. Monocytes produce Macrophages. Fat Cells: Features: 1- Its cytoplasm is white because it accumulates lipids in the cytoplasm. 2- The lipids push the cytoplasm and the nucleus towards the peripheral side of the cell. 3- Ring appearance. 4- Large cells. 5- The difference between a fat individual and a thin one is the size of the fat cells not the number of them; as their number is always fixed.

3 Macrophage - Kidney shaped nucleus, like doughnut, we call this appearance ---- Indented Appearance. - Irregular borders; due to frequent phagocytic activity using pseudopodia. - Aggregation of foreign material in its cytoplasm; this foreign material is either: a- Residual Bodies. b- Exogenous pigment; as ink in tattoo. - We can t discriminate these cells under the LM; its special features are not always prominent. - However, we can still find some methods to be able to distinguish these cells, like: A- If we, exogenously, injected a foreign material as ink. B- If these cells are so active in phagocytosis; due to their location which is exposed to many foreign bodies like: 1- lungs of smoker; mottled with black color, which are toxins within the macrophages in the connective tissue. 2- Also, they can be found in the liver; as liver is exposed to many different types of toxins. Mast cell (alarm cells) ** we can easily notice the aggregation of the secretory vesicles in these cells; so we can t see the cytoplasm. ** Mast cells are seen using special stain called: Toluidine Blue

4 Notice: it is supposed that the whole cell is stained with blue. However, we can easily notice that the granules are pigmented with violet color; so we call them Metachromatic Granules OR we can call the phenomenon as Metachromatesia; which is the ability of the structure to change the color from blue to violet. The granules Contain Certain inflammatory mediators; heparin & histamine. Let s have a closer look at what do we mean by Mucosa: First of all, there is a mucous membrane that covers all body openings in the body; these mucous membranes are composed of: A. epithelium. B. thin layer of CT. The connective tissue which is under the epithelium in mucous membrane of body openings is called: Lamina Propria. We can find the mucosa in: Oral Cavity stomach respiratory tract. So, the location of Mast Cells is: 1- Around blood vessels of the skin. 2- CT of the mucosa. In conclusion, the Mast cells can be found in the Lamina Propria of the mucous membrane. ** when mast cells are exposed to an allergen they DE-Granulate; which means they undergo exocytosis to expel their product ( heparin & histamine ).

5 Medical situation: When someone is exposed to an allergic material; we can notice these symptoms: a- Swelling: because of the increasing in the permeability of the blood vessels; which means that more fluids will leave the blood and go to the CT. b- Redness: because of the increasing in the blood flow towards the specified area. c- Itchy: because of having many mediators are compressing the nerve endings. The treatment: Anti-Histamines; to stop the action of histamines. Asthma patients suffer from Hyper-Sensitivity of these cells. Remember: that granules are either ---- Metachromatic(VIOLET) OR Blue. Question: how to differentiate between macrophages and mast cells under the LM: 1- Granules in mast cells are so dense that you can t even see the cytoplasm, while in macrophages you can distinguish the cytoplasm. 2- Granules ( or we can call them metachromatic granules ) in mast cells are uniformed, unlike the ingested material in the macrophage; which is not uniformed. 3- Granules of mast cells are either blue or violet, while the ingested material in macrophage isn t blue ( unless you ingested the macrophage with blue substance; then you must consider the rest of the differences)

6 حاسس انو منها سؤال: cell Plasma - Easily recognized because of its many features. - They produce antibodies; which are proteins. - At the supranuclear side of the plasma cell, we can easily notice an unstained or lightly stained area; indication for Golgi apparatus, which we call negative Golgi stain. - Prominent Golgi and RER; for antibodies(protein) synthesis. - Here the cytoplasm is basophilic; unlike the normal cells because of the RER. Fibers: 1- Collagen. 2- Elastic. 3- Reticular. ** Only collagen can be seen using H&E, the most common type of collagen is Type1, which is the only type of collagen we can see using H&E. Remember: that both the cytoplasm & the ECM are acidophilic; so, both of them will look pinkish in color; that s why we can t discriminate the plasma membrane of fibrocytes and thus we can only see naked nuclei.

7 Remember: 1- That fibroblasts are the most common cells within the CT. 2- The white spaces within the CT; are the ground substance; which is Amorphous { has no shape }. 3- All of the CT s have ALL of the fibers, but in different percentages. Reticular fibers are collagen type 3. Reticular fibers are stained with PAS. Rich in carbohydrate; which is highly negatively charged. اكييد عليه سؤال الحكي الجاي Reticular fibers: Are stained with both PAS & Silver method; the reticular fibers reduce silver which will result in deposition of silver and then they look like black threads. Elastic fibers are stained with: Elastin stain Collagen is synthesized by fibrocytes. The only kind of collagen that has a bundle shape is Collagen Type 1. سنكون يوم ا ما نريد.. ال الرحلة ابتدأت وال الدرب انتهى!!