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CONNECTIVE TISSUES Most abundant type of tissue Fills internal spaces, provides structural support for other tissues, and stores energy reserves Includes tissues such as fat, bone, and blood Most types are well vascularized All types have a common origin (mesenchyme) Includes 3 components:
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CONNECTIVE TISSUES • Most abundant type of tissue • Fills internal spaces, provides structural support for other tissues, and stores energy reserves • Includes tissues such as fat, bone, and blood • Most types are well vascularized • All types have a common origin (mesenchyme) • Includes 3 components: • specialized cells • extracellular protein fibers • ground substance • fluid or semi-solid which surrounds cells
3 Major Cell Types • Fibroblast • Most common fixed cell • Large, star shaped • Produces fibers by secreting protein into matrix
Macrophages • Wandering Cells that originate as WBC’s • Function as scavengers that clear foreign particles Phagocytosis • Also, play a role in immunity by allerting other WBC’s of foreign particles
Mast Cells • Large, widely distributed cells • Associated with inflammation • Releases heparin and histamine
3 CATEGORIES: Connective tissue proper tissue with many types of cells and extracellular fibers in a syrupy ground substance ex. Adipose tissue Fluid connective tissue cells suspended in a watery matrix that contains dissolved proteins ex. Blood Supporting connective tissue low diverse cell population and a matrix of closely packed fibers ex. Bone and cartilage CLASSIFICATION
CONNECTIVE TISSUE PROPER • Composed of many kinds of cells • Fibroblasts, Macrophages, Adipocytes • 3 types of fibers • Collagen - long, straight unbranched; flexible but strong ex: tendons, ligaments • Reticular – cells suspended in a watery matrix that contains dissolved proteins Bone & Cartilage: stabilizes cells & vessels • Elastic - contains the protein “elastin”. Branched, wavy, will contract after stretching ex: elastic ligaments • Ground Tissue - • high viscosity; slows the spread of pathogens to make them easier for phagocytes to catch
Connective Tissue Proper • Loose connective tissue (areolar) • characterized by white and yellow fibers between fibroblasts • packing material of the body, cushions, attaches skin to the body, supports blood vessels
Adipose tissue • dominated by adipocytes • energy storage, brown fat in infants (highly vascularized) • each cell consists of large vacuole filled with triglycerides
Reticular Connective Tissue • complex open framework of reticular fibers • supports walls of organs such as liver and spleen
Dense Connective Tissue • consists of many closely packed collagen fibers, elastin fibers, and few fibroblasts • regular - collagen fibers are parallel to each other • tendons, ligaments • irregular - collagen fibers are randomly arranged and interwoven : provides strength to resist forces applied from many directions; interwoven meshwork • dermis
Elastic Connective Tissue • - consists of mainly yellow elastic fibers • parallel or branching • walls of hollow organs, large arteries, heart etc.
FLUID CONNECTIVE TISSUES • Ground substance – plasma • Blood contains formed elements: Erythrocytes, leukocytes, Platelets • Arteries carry blood from heart to capillaries, water and solutes move into interstitial fluid, Veins return blood to heart
Erythrocytes: carry oxygen (confined to vessels) • Leukocytes: fight infection (wander) • Platelets: blood clotting
Supportive Connective TissueBone & Cartilage • I. Cartilage • Cells: Chondrocytes • Matrix: Firm gel of proteoglycans • Avascular: heals slowly • Covering: Perichondrium: Composed of 2 layers • Outer layer: dense irregular tissue • Inner layer: cells • Growth: Interstitial & Appositional • Appositional: undergoes extensive remodeling on a regular basis • Interstitial: • 3 main types
Hyaline - Tightly packed collagen fibers • Most Common Type • Looks like white glass • Functions: Reduces friction, important in growth and repair of bones • Locations: Between bone surfaces, nose, trachea, intercostal cartilage
Elastic - Numerous elastic fibers • flexible • Functions: Provides support but distorts without damage • Locations: Ears, nose, epiglottis • Fibrocartilage - matrix dominated by collagen fibers • Extremely durable • Functions: Resists compression, limits movement • Locations: Between vertebrae, pads within knee joints
II. Bone - Most rigid connective tissue • Cells - Osteocytes • Matrix - 1/3 collagen fibers & mixture of calcium salts • Vascularized - caniculi - extensive blood vessels in matrix for exchange of materials • Covering - Periosteum (2 layers) • fibrous outer layer • cellular inner layer • Growth - Appositional • undergoes extensive remodeling on a regular basis • responds to stresses: grow thicker & stronger = exercise