Connective Tissue PDF

Connective tissue general properties and composition functions exchange of maetrials - highly vascularized, thru blood vessels support and binding of other tissues tgt - epithelia, blood vessels and nerves protection - against infection, inflammation and immune respon...

Connective tissue general properties and composition functions exchange of maetrials - highly vascularized, thru blood vessels support and binding of other tissues tgt - epithelia, blood vessels and nerves protection - against infection, inflammation and immune response wound healing - fibroblasts will release collagen I and III cause tissue remodeling regulating behaviour of cells - migration, proliferation and differentiation embryonic origin - mesenchyme (mesoderm) ground substances extracellular substances exclu collagen and elastic fibers amorphous gelatinous material, fills space bwteen fibres n cells cont hyaluronic acid type of non sulphate glycosaminoglycan (GAG) viscous, slippery, good lubricant linear molecule most abundant where friction must be reduced proteoglycan binding of core protein + GAG traps water macromolecule like bottlebrush sidechain varied (keratin sulfate, chonddroitin sulfate)  proteoglycan attached to long hyaluronan molecule by linker protein forming aggregate aggregate has high density of -ve charge attracting cations (Na+) - > osmotically active, large amount of water trapped in matrix glycoprotein adhesion proteins links components of ground substance to surface of cells (fibronectin, laminin, osteopontin) fibronectin -> most abundant, laminate found in basal lamina all have multiple binding domains for extracellular components (binding to collagen or proteoglycans to stabilize extracellular matrix) anchor cells to ext matrix through binding of integrins of cell surface receptors cell migration within connective tissues fibrous components collagen fibres (type I collagen most abundant) -> resist tension - provide flexibility and high tensile strength - appear as wavy fibres w variable width - at least 29 are classified - synthesized from RER and processed in golgi - proteins then secreted into ext matrix n assemble into large fibers -> stable polymers wound healing - collg I and III - fibroblasts activated to prod coll III -> reticular fibre - coll III form mesh near injured site act as scaffold for tissue recovery - in recovery coll III replaced by coll I (stronger) reticular fibres (type III collagen) reticular fibre (coll III) found in base of epithelial tissue -> meshwork (not bundle) short and branched collagen fivres house cell for better cell-cell interactions (structural support) too thin to be seen under H&E (less bundling) -> silver stain used mesh framwork for soft organs (spleen, red bone marrow, liver, lymph node) elastic fibres -> resilient to deformations by stretching less distributed than collagen do not form bundles but form branches contains elastin -> stretch n recoil found in aortic wall, larynx, ligamentum flavum in vertebral column branching fibres w wavy appearance when relaxed fresh fibres appear yellow unstained part -> collagen marfan syndrome  autosomal dominant defect in prod of protein fibrillin-1 (used to form elastic fibres - > key contribution to elastic func of tissues) fibres loosely arranged bc increase in proteoglycans so lose stretch n recoil ability symptoms - long arms, long legs, long fingers n toes n tall dilation of roots of aorta, presnec of mitral valve prolapse and ascending aorta r cardio manifestions among patients hheart related complications proportions diff cellular components in connective tissues two categories extracellular matrix cellular components resident cells reside in region w/o moving around/low motility react based on surrounding env of connective tissue nearby transient cells - mobile cells that are temporary visitors - do not stay perm - fibroblasts - most common in connective tissue - produce all components of ext matrix - inactive form - fibrocytes - functions - synthesizes collagen, elastic and reticular fibres and ground substance of ext matrix - response to tissue damage and synthesize new matrix - firboblast is spindle shaped branching cell w deeply basophilic cytoplasm w prominent nucleolus and larger euchromatic nucleus - adipocyte - connective cell tissue specialized to store neutral fat and produces variety of hormones - 2 types - unilocular adipose tissue (white) - single large lipid droplet; nuclei squeezed to periphery - multilocular adiposse tissue (brown) - numerous distinct lipid droplets - brown adipose tissue found in newborns in neck region n back - brown has mitochondria which can help generate endogenous heat (thermogenesis) - white - found in humans around internal organs n deposit in abdomen, gluteal, and femoral as subcutanous fat pads - macrophages - phagocytic cells derived from monocytes in blood - either fixed or transient - phagocytosis of pathogens, dead cells and RBC, defence and immune response (nonspecific) - contains lysosomes to digest - macrophages in blood r not mature yet - cannot be identified - macrophages can be APC - antigen stored in phagocytic vesicle fuses w lysosome - antigen browkn down into smaller peptide fragments - binds to MHC - fuses with plasma membrane and antigen presented to lymphocyte (T-cell) - mast cells - large n oval - derived from immature mast cells n migrated to connective tissue from blood - innate immune system  - contain numerous secretory granules (v dense n obscure nucleus) - cellular granules contain vasocative and immunoreactive substances (histamine and heparin) - mediates inflammation and allergic reactions - has IgE antibodies expressed on cell surface - when antigen/allergen binds - exocytosis of granules occur - release of vasoactive and immunoactive substances - histamin - incerase permeability of blood vessels - heparin - anti coagulative effect - chemotactic factors to attract lymphocytes (neutrophils, eosinophils) - plasma cells - develop from B-cell - strong basophilia bc of RER and golgi - nucleus usually spherical - exhibit large clump of peripheral heterochromatin alternating w euchromatin - clock face nucleus - produces large amount of specific antibody classification of connective tissues mature connective tissue connective tissue proper specialized connective tissues - e.g bones, cartilage, adipose and hematopoietic tissues types of connective tissue (composition) loose (areolar) connective tissue more cells than fibres e.g lamina propria, mesentery  fine network of collagen/elastic/reticular fibres w ground substance filled space location - under epithelium of organ and dermis of skin initial site where pathogenic agents (bacteria) that breached epithelial surface r challenged n destroyed by cells of the immune system transient wandering cells that migrate from local blood vessels in response to specific stimulus site for undergoing inflammatory and immune reactions - conective tissue will swell mesentery of intestine is another example red fibres r collagen threadlike fibres r elastic fibres spaces r filled w ground substances abundant of fibroblasts for secreting ext matrix component dense connective tissue more fibres than cells regular vs irregular irregular large amount of collagen fibres  fibres arranged in random directions located in superficial connective tissue sheaths of muscle and nerves, adventitia of large blood vessels, capsules of glands n organs regular dense parallel orientation of collagen fibres withstand tensile force in one direction poorly vascularized attach muscles to bones; bone to bones, e.g tendons n ligaments mammary gland