Practical Histology Lab 3: Connective tissue
Connective tissues Connective tissue provides structural support for the body by binding cells and tissues together to form organs. It also provides metabolic support by creating a hydrophilic environment that mediates the exchange of substances between the blood and tissue.
Cells of connective tissues Fixed cells: cells differentiate from mesenchymal cells, such as adipocytes and fibroblasts; these cells are formed and reside in the connective tissue. Wandering cells: cells arise from hematopoietic stem cells, differentiate in the bone marrow and migrate from the blood circulation into connective tissue. such as: mast cells, macrophages, plasma cells, and leukocytes.
Connective tissue fibres 1. Collagenous fibers: composed of collagen 2. Reticular fibers: Very thin collagenous fibers 3. Elastic fibers: composed mainly of the protein elastin
Ground substance Colorless, transparent and homogenous Fills the space between cells and fibers of the CT. Formed mainly by two classes of components: I. Glycosaminoglycans II. Structural glycoproteins
Classification of connective tissues I. Connective Tissue Proper Loose connective Tissue Areolar Dense connective tissue regular & irregular II. Specialiazed CT Blood Adipose Recticular III. Supporting Connective Tissue Cartilage Bone
Proper connective tissue 1- loose (Areolar) connective tissue Gel-like matrix with all three connective tissue fibers Cells: Fibroblasts, macrophages, mast cells, and some white blood cells Highly cellular, numerous cell types present. provides padding between and around organs and tissues.
Dense connective tissue 1- Regular Dense CT: Parallel collagen fibers with a few elastic fibers Major cell type is fibroblasts Found in tendons, and ligaments
2- Irregular dense CT: Irregularly arranged collagen fibers with some elastic fibers Major cell type is fibroblasts Found in the dermis, submucosa of the digestive tract.
Supportive CT: Cartilage 1- Hyaline cartilage Amorphous, firm matrix with imperceptible network of collagen fibers Chondrocytes lie in lacunae
2- Elastic cartilage Similar to hyaline cartilage but with more elastic fibers Maintains shape and structure while allowing flexibility
3- Fibrocartilage Matrix similar to hyaline cartilage but less firm with thick collagen fibers Cells arranged singly or in long rows
Location of cartilages
Supportive CT: Bone 1. Compact Bone 2. Spongy Bone Histology of bone tissue Cells are surrounded by matrix. - 25% water - 25% protein - 50% mineral salts 4 cell types make up osseous tissue Osteoprogenitor cells Osteoblasts Osteocytes Osteoclasts
Compact bone - Osteon (groups of elongated tubules called lamella). osteocytes occupy lacunae which are between the lamella. - radiating from the lacunea are channels called canaliculi (finger like processes of osteocytes). - Blood vessels and nerves penetrate through horizontal openings called perforating (Volkmann s) canals and Central (Haversian) canals.
Spongy bone it is a trabecular bone tissue (filled with red bone marrow) The matrix is loose, spongy and with many spaces. short, flat and irregular bone is made up of mostly spongy bone.
Specialized connective tissue 1- Blood The main components of blood include is made up of plasma which is a highly viscous liquid and blood cells that are floating around in it.
Erythrocyte (RBC) Biconcave disc shape No nucleus Contain hemoglobin Main function is gases transport
Leucocyte WBC 1. Granulocyte Neutrophil They are the most numerous type of white blood cell and Have a segmented nucleus (3-5 lobes) having fine granules which are purple or violet in color. Eosinophil Have bilobed nucleus with spherical, darkly staining acidophilic granules. Basophil Lobulated nucleus often obscured by granules basophilic cytoplasmic granules (dark blue)
2. Agranulocyte Lymphocytes Smallest, with rounded nucleus, which occupies most of the cytoplasm Monocytes Largest, they have a kidney-shaped nucleus and are considered as the phagocytes of the blood
Platelets Biconvex discs which contain no nucleus but have cellular organelles. Their main function is to prevent bleeding (hemorrhage). 22
2- Adipose connective tissue Matrix similar to areolar connective tissue with closely packed adipocytes Found under skin, around kidneys, within abdomen, and in breasts.
3- Reticular connective tissue Loose ground substance with reticular fibers Cells: white blood cell, mast cell, and macrophage Found in lymph nodes, bone marrow, and the spleen