mesenchymal tissue

mesenchymal tissue

1. provides:

   • general structure / mechanical strength
   • space filling
   • physical support
   • metabolic support - adipose and bone
   • protection - bone and cartillage
   • immunoligical protection
   • blood vessels/lymphatics

2. general properties

   • tensile strength
   • elasticity
   • volume / padding
   • supports epithelial tissues

3. support cells

   • inflammatory cells (resident)
     • macrophages
     • mast cells
     • plasma cells
   • fibroblasts
   • myofibroblasts

4. extracellular matrix

   • ground substance
     • glucasoaminoglycans
       • long, unbranched polysaccharides e.g. hyaluronate
     • tissue fluid
     • proteoglycans (GAGs + proteins)
       • binds with hyaluronic acid to produce massive hydrophillic molecules - attracts tissue fluid which is resistant to compression e.g. umbilical cord
       • binds with remodelling factors, growth enzymes cell surface receptors
   • protein fibres
     • collagen
       • I = main type found in skin, tendond, ligaments etc.
       • II = cartillage
       • III = forms reticular network of organs / lymph nodes aka reiticulin
       • IV = basement membranes
     • elastin
       • secreted by fibroblasts as tropoelastin
         • tropoelastin + fibrillin and fibrillin-1 = elastive fibres --> aggregate
       • blood vessels, lungs, bladder etc.

5. adult

   • loose (areolar)
     • cells > collagen/elastic fibres
     • mucosa and submucosa of various organs + blood vessels, nerves and muscles
   • dense
     • regular
       • collagen > cells
       • regular arrangement of collagen, forms tendons + ligaments + cornea
     • irregular
       • fibres > cells
       • irregular arrangement of collagen, found in dermis

6. embryonic

   • cells of all connective tissues are derived from precursor cells called mesenchyme
   • "wharton's jelly" in the umbilical cord is embryonic CT, a source of mesnchymal stem cells

7. specialised

   • adipose
     • white
     • brown
   • cartillage
     • chondroblasts
       • chondrocytes
     • hyaline cartilage
     • fibrocartilage
     • elastic cartillage
   • bone
     • osteoblast
       • osteocyte
         • osteclast
     • woven
     • lamellar
   • bone marrow