Connective tissue

Connective tissue

1. general features of connective tissue

   • Functions
     • 1. provides a protective and supportive framework 2.combating and ingesting foreign proteins 3.secret various components: contribute to the matrix 4.storage of lipid ,water and electrolyte 5.repair scar tissue 6.transport:mediate exchange of metabolites via tissue fluid
   • structures
     • Cells
       • 1.fibroblasts 2.mast cells 3.macrophages 4.adipose substance
     • matrix
       • amorphous ground substance and various matrix
       • amorphous ground substance
         • -non living -consist of carbohydrates and protein-derived material
     • fibers
       • 1.collagenous 2.reticular 3.elastic fibers

2. Fibers

   • 2.collagenous
     • classification**
       • based on physical properties, morphology and amino acid composition
       • II
         • 1. found in hyaline and elastic cartilage 2.produced by chondroblast activity
         • 1. fibers are thin 2. composed of fibrils arranged in a meshwork with copious amount of proteoglycans
       • III
         • 1.found in tissue contains type I collagen 2.reticular fiber contains type III collagen 3.
       • IV
         • 1. usually found in basement membrane 2.neither fibers and fibrils are visible on light microscope 3.contain significant amount of carbohydrates:produce strong reaction of basement membrane to PAS
       • V
         • 1. prodeced by wide range of cells in small quantities
         • functions: 1.maintain tissue integrity 2. attachment of cells to adjacent structures
       • VI
         • disulfide rich -found in boundary zones where interstitial collagenous fibers(I & II) are linked to non collagenous elements
       • I
         • 1.form the thick collagen fiber 2.major structural protein in the lung3.other:liver,kidneys
     • features
       • -composed of protein collagen -stain with acid dye -birefringent,not elastic -have flexibility
     • staining reaction
       • type I collagen stains strongly with acid dyes: methods: a) Van Gieson(compound solution of acid dyes) b)Masson's trichrome(sequential demonstration)
   • 1.Reticular
     • features
       • 1. fine fibers connected to coarser and stronger collagenous fibers(type I )2. composed of protein collagen coated with glycoprotein3.weak/non birefringent 4.argyrophilia of reticular fibers is due to proteoglycan content
     • functions
       • 1.form a delicate supporting framework for soft organs 2.form a network around nerve fibers,fat cell, lymph nodes and smooth and skeletal muscle fibers
     • staining reaction
       • argentaffin metallic impregnation e.g. Gomori, Gordon & Sweets
   • 3.Elastic fibers
     • Features
       • -composed of the protein elastin and elastic fiber microfibrillar protein(EFMP)\ -located in skin and walls of blood vessels: provide greatest flexibility allow tissue to stretch -weakly birefringent -moderate yellow autoflourescence
     • structural content
       • 1. young fibers have a high content of EFMP 
       • 2.increaing age of elastic fibers: ratio of EFMP to elastin change --increase level of glutamic, aspartic acid  and calcium effect: a)wrinkle and loose fitting of skin b)loss of elasticity of elastic arteries
     • Demonstration
       • 1.Verhoeff Hx 2.Victoria blue 3.Taenzer orcein

3. Basement membrane

   • structural content
     • composed of : 1. collagen type IV 2. ground substances 3.reticulin fibers 4.mucopolysaccharides
   • Functions
     • present under epithelium, around muscles, nerves, capillaries and fat cells: -provide support to epithelial cells, muscle fibers and peripheral nerves
     • -act as diffusion barriers to rapid ion exchange -connect epithelium to underlying connective tissue
   • general structure
     • Three layers: 1. lamina rara:mainly of carbohydrates complexes 2.lamina densa:predominantly type IV collagene, associated with carbohydrates complexes 3.lamina reticularis :fibrous elements
     • e.g. GBM
       • glomerular basement membrane: 1.particular thick 2.central lamina densa is bordered on both side by lamina rara