Connective Tissue.pdf

CONNECTIVE TISSUE STRUCTURE AND FUNCTION Connective tissue contributes to numerous body functions, including supporting organs and cells, transporting nutrients and wastes, defending against pathogens, storing fat, and repairing damaged tissues. Connective tissue is composed primarily of an extrac...

CONNECTIVE TISSUE STRUCTURE AND FUNCTION Connective tissue contributes to numerous body functions, including supporting organs and cells, transporting nutrients and wastes, defending against pathogens, storing fat, and repairing damaged tissues. Connective tissue is composed primarily of an extracellular matrix and a limited number of cells. Most connective tissues are composed of ground substance, fibers, and cells, although blood and lymph are specialized fluid connective tissues without fiber. Connective tissue is largely organized into subcategories based on its nonliving components. Placement of Connective Tissues Connective tissue is found in between other tissues everywhere in the body, including the nervous system. Components of connective tissue All forms of connective tissue are composed of (1) extracellular fibres, (2) an amorphous matrix called ground substance, and (3) stationary and migrating cells. The proportions of these components vary from one part of the body to another depending on the local structural requirements. In some areas, the connective tissue is loosely organized and highly cellular; in others, its fibrous components predominate; and in still others, the ground substance may be its most conspicuous feature. The anatomical classification of the various types of connective tissue is based largely upon the relative abundance and arrangement of these components. Extracellular fibres The fibrous components are of three kinds: collagenous, elastic, and reticular. Most abundant are the fibres composed of the protein collagen. The fibrous components of loose areolar connective tissue, when viewed with the light microscope, appear as colourless strands of varying diameter running in all directions, and, if not under tension, these have a slightly undulant course. At high magnification, the larger strands are seen to be made up of bundles of smaller fibres. Ground substance The amorphous ground substance of connective tissue is a transparent material with the properties of a viscous solution or a highly hydrated thin gel. Its principal constituents are large carbohydrate molecules or complexes of protein and carbohydrate, called glycosaminoglycans (formerly known as mucopolysaccharides). Stationary cells The ubiquitous fibroblasts are the principal active cells of connective tissue, occurring as long spindle- shaped cells stretched along bundles of collagen fibrils. Their function is to secrete tropocollagen and constituents of the ground substance and to maintain these extracellular tissue components. MIGRATING CELLS Migration is crucial in tissue morphogenesis, regeneration, or inflammation. Alterations of the migratory patterns of specific cell types, for example, leukocytes, underlie disease, for example, autoimmune disease. Migration is also an important component of the pathogenesis of cancer during invasion and metastasis. Conversely, lack of migration is a major cause of failure of potential regenerative therapies, for example, using stem cells. TYPES OF CONNECTIVE TISSUE BLOOD LOCATION: Closed circulatory system STRUCTURE: Erythrocytes, leucocytes and platelets in a liquid plasma FUNCTION: Transport of oxygen nutrients, hormones and waste LYMPH LOCATION: All around the cells in the body. STRUCTURE: Fluid oozed out of blood capillaries, contains leucocytes and liquid ground substance. FUNCTION: Protection of body from infections. AREOLAR TISSUE LOCATION: Between the skin and muscles, around blood vessels STRUCTURE: Different types of cells loosely arran- ged and supported. by a jelly-like ground substance and elastic fibres FUNCTION: Supports internal organs ADIPOSE TISSUE LOCATION: Below the skin and around internal organs STRUCTURE: Cells filled with. fat droplets, jelly-like ground substance FUNCTION: Insulation, supply of energy, storage of fats CARTILAGE LOCATION: Nose, ear, larynx, trachea STRUCTURE: Cells supported by fibrous, flexible Jelly-like ground substance FUNCTION: Lubricates the surfaces of bones, gives support and shape to organs BONES LOCATION: Skeleton (A specific structure extending throughout the body STRUCTURE: Osteocytes embedded in solid ground substance made up of calcium phosphate FUNCTION: Supports and protects different organs, helps in movement TENDONS AND LIGAMENTS LOCATION: At the joints STRUCTURE: Tendons, fibrous, strong, less elastic Ligaments, strong and highly flexible FUNCTION: Tendons: join muscles to bones Ligaments: join two bones to each other