Histology Lecture 10: Connective Tissue PDF

Histology lecture (10) Connective tissue (2) Histology 1. Undifferentiated Mesenchymal Cells 1. Mast cells 2. Fibroblasts. 2. Free macrophages 3. Adipose cells. 3. Plasma cells 4. Reticular Ce...

Histology lecture (10) Connective tissue (2) Histology 1. Undifferentiated Mesenchymal Cells 1. Mast cells 2. Fibroblasts. 2. Free macrophages 3. Adipose cells. 3. Plasma cells 4. Reticular Cells. 4. Pigment cells. 5. Macrophages cells. 5. Blood leucocytes  UMC.  Cannot divide.  Fully differentiated.  arrange in groups around blood vessels in loose CT of the mucosa of respiratory and digestive tracts.  Average.  Oval or rounded with few and short processes.  Their number increase in allergy.  Central, single and rounded. Occupied by large granules: 1. Chemical nature → Sulfated type of glycosaminoglycans (precursor of heparin). Protein substance (the precursor of histamine). Other chemical mediators e.g. serotonin. 2. Staining: Due to sulfated glycosaminoglycans, its granules can be stained by:  Hx & E → basophilic.  Metachromatic stain with toluidine blue → reddish purple color. Histology 1- The cell border is irregular with short process. 2- The cytoplasm contains: Much membrane-bounded electron dense granules. Ribosomes, rER and mitochondria. 1. Secretion of Heparin: natural anticoagulant. 2. Synthesis, storage and secretion of Histamine: in cases of allergy and inflammation. 3. Secretion of Slow Reacting Substance of Anaphylaxis (SRS-A): it has similar action as histamine but with long duration. 4. Secretion of Eosinophil Chemotactic Factor (ECF): attract eosinophils Histology  Activation of B-lymphocytes (originating from UMCs) by specific antigen leads to formation of plasmablasts which mature into plasma cells.  Cannot divide.  Fully differentiated.  More in Lymphoid organs, pleura, peritoneum.  Average.  Oval or rounded.  increases at sites of chronic inflammation.  Rounded and eccentric.  Cart-wheel in shape (clock-face appearance) due to special arrangement of condensed chromatin. 1. Deep basophilic with negative Golgi image. 2. Russell bodies: are large acidophilic bodies seen in old cells. They may be accumulations of defective products of antibody synthesis. 1. Cell border is irregular. 2. The cytoplasm is rich in rER, ribosomes, prominent Golgi and mitochondria.  Secretion of antibodies (responsible for humoral immunity). Histology  Melanin-containing C.T. macrophage that engulfs melanin made by melanocytes.  Choroid of eye  Dermis of skin.  Branched with melanosomes in the cytoplasm. Blood leucocytes leave the blood stream and accumulate in the C.T. in certain conditions, e.g.: 1. Eosinophils: in allergy or parasitic infestation. 2. Neutrophils: in acute infections. 3. Monocytes & lymphocytes: in chronic infections. Types 1- Loose (areolar =ordinary) CT. 4- White fibrous C.T. 2- Adipose C.T. 5- Yellow elastic C.T 3- Mucoid C.T. 6- Reticular C.T. Histology  Loose=flexible:  Gelatinous  Areolar: false cavities appear.  Called ordinary as it is widely distributed all over the body  Fibers: collagenous and elastic fibers.  All types of cells specially fibroblasts, macrophages and fat cells.  The matrix is rich in hyaluronic acid.  It binds tissues and organs together.  It carries blood vessels, lymphatics and nerves.  Swells during inflammation (edema)  Tendons  Sclera of eye, capsule of organs  Cornea of eye.  Outer fibrous layer of the periosteum & perichondrium.  Parallel collagenous bundles.  Irregular collagenous bundles.  Fibroblasts (tendon cells, corneal  Fibroblasts or fibrocytes between corpuscles): the cells have thin the bundles. nuclei and the cytoplasm is not apparent. Histology Histology  Arteries.  Tracheo-bronchial tree and between lung alveoli.  Ligaments (Ligamentum flavum between vertebrae, Ligamentum nuchae in back of neck and Suspensory ligament of the penis).  Regular elastic fibers.  Fibroblasts or fibrocytes between the fibers.  Stroma of parenchymatous organs e.g. liver, spleen and lymph nodes.  Reticular lamina of the basement membranes.  Formed of reticular cells and fibers that form a network. Histology Brown due to: 1- Cytochromes in its much White due to natural color of fat. mitochondria 2- Blood color in its rich capillary supply.  The majority of adipose C.T. in  Adipose tissue in newborn infants. adults e.g. buccal pad of fat,  In adults, present in: subcutaneous tissue and Mediastinum. perinephric fat. ↑ Between the 2 scapulae.  In ♂ → more in the back of neck & upper shoulder.  In ♀ → more in hip region & upper thigh and breast region. 1. Lobules of White adipocytes 1. Lobules of Brown adipocytes (characters are mentioned before) (characters are mentioned before) separated by loose C.T. separated by loose C.T. 2. with less capillary supply than the 2. with more capillary supply than the brown type. white type. 1. Energy depot (Storage of fat). 1. Rapid heat production in newborn 2. Heat insulation. infants on exposure to cold. 3. Gives contour to the body. 2. Energy production in hibernating 4. Support organs e.g. kidney. animals. 5. Cushions during seating. Histology  Wharton's jelly of the umbilical cord.  Vitreous body of the eye.  Pulp of the teeth.  The matrix is soft as it is rich in mucin and hyaluronic acid.  UMCs or young fibroblasts (mucinous cells) with long processes which intercommunicate with those of the neighboring cells. funcTions of connecTive Tissues  Structural support is the major function of connective tissue.  Forms the framework upon which all other body tissues are assembled.  The viscosity of the extracellular matrix, due largely to hyaluronic acid, slows the progress of many bacteria and foreign particles  Antigen presenting cells  The connective tissue cells secrete growth factors.  Reserves of water and electrolytes, especially sodium, are stored in the extracellular matrix.  Except in CNS, most blood and lymphatic vessels are surrounded by loose connective tissue, which is thus a crossroads for transporting substances to and from other tissues.