Connective Tissue Lecture 16 PDF

Connective Tissue Connective tissue is one of the four basic types of animal tissue. It develops from the mesoderm. Structurally, it composed from three classes of components: cells and extracellular matrix (fibers and ground substance). Different type of connective tissue are responsible for a...

Connective Tissue Connective tissue is one of the four basic types of animal tissue. It develops from the mesoderm. Structurally, it composed from three classes of components: cells and extracellular matrix (fibers and ground substance). Different type of connective tissue are responsible for a variety functions such as supporting, linking, storage, protection, transportation, insulation, defense and nourishment. Cells: Connective tissue has many types of cells such as: 1. Fibroblast: Is the principle and most common cell of connective tissue, it responsible for the synthesis of extracellular matrix components, it fusiform cell with oval or elongated nuclei. 2. Macrophage: It is phagocytosis cells derived from monocyte which migrates from bloodstream into connective tissue where they differentiate into macrophage, it irregularly shapes cells with kidney shape nuclei, and it engulfs dead cells and other foreign bodies, addition to their role in immunological reactions. 3. Mast cells: They come from bone marrow and go into all tissues of the body, it irregularly oval shape with spherical nuclei. Each mast cell contains secretory granules (histamine and heparin), these can be secreted when mast cells are triggered, leading to allergic and inflammatory disease. 4. Plasma cells: Are large, oval with spherical and eccentric nuclei, nucleus of plasma cell have a clock-face appearance, plasma cell produce antibody. 5. Pigment cells or Chromatophores: they are containing small granules called melanin pigment which primarily responsible for skin color. 6. Adipose cells or Fat cells: These cells contain thin cytoplasm due to presence of large droplet of oil with flattened nucleus, their function are fats storage. 7. Leukocytes (White blood cells, WBC): these cells are wander in connective tissue after migrate from blood vessels especially during inflammation, therefore, these cells are responsible for initiating immune responses. Fibers: Three types of fibers are found in connective tissue matrix in varying amount depending on the structural needs and function of the connective tissue, these fibers are produced by fibroblast cells. 1. Collagen (white) fibers: Are the most abundant structural components of the connective tissue, it composed from fibrous protein called collagen, they are flexible. 2. Elastic fibers: They are composed from elastin protein and typically thinner than collagen fibers, they are arranged in a branching pattern, it can stretch and recoil. 3. Reticular fibers: consist from collagen fibrils, it short and branching. They are produce by fibroblast in connective tissue and reticular cells in myeloid and lymphoid for give supporting network. There are three types of loose connective tissue: Areolar connective tissue: It most widely spread in the body such as lamina properia and surround capillaries Its functions include supporting and binding of other tissues (fibers), holding body fluids defending against infection (WBC & acrophages), storing nutrients fat cells( and when a body region is inflamed, the areolar tissue in the area soaks up excess fluid causing local swelling (edema).  Reticular connective tissue: It has a network of reticular fibers which are synthesized by special fibroblast called reticular cells Its supports the lymphoid organs which play role in filtration of blood and lymph It found around liver, kidney and lymphoid organs (lymph node, bone marrow, spleen, thymus gland and tonsils). Adipose C.T: In this type the adipocytes (adipose or fat cell) is 90% of tissue mass, it consider as excellent nutrient storage, supporting and protects organs, it usually accumulate in subcutaneous tissue for prevents heat loss from the body such as around the kidneys, within abdomen and under the skin. Dense connective tissue: This type contains relatively little ground substance, because of its high proportion of collagen fibers. It less flexible and more resistant to stress than loose connective tissue. Dependent on the arrangement of collagen fibers, dense connective tissue was classified to: Regular dense C.T: Parallel bundles of collagen fibers with a few elastic fibers running in the “pull” direction, the collagen fibers of this tissue are aligned with the linear orientation of fibroblasts in response to prolonged stress, like tendon (attach muscle to bone), ligament (join bone to bone) and cornea of the eye. Irregular dense C.T: This tissue is similar to the regular dense C.T but the dominant collagen fibers are arranged without definite orientation, major cell type is fibroblast, withstands tension in many directions providing structural strength, it found in the dermis of the skin, sub mucosa of the digestive tract, and fibrous organ capsules. Elastic dense C.T: It composed of bundles of thick, parallel elastic fibers which appear yellow color and great elasticity. The space between fibers is occupied by thin collagen fibers and flattened fibroblast. Elastic tissue is present in the ligaments of vertebral column.