Connective Tissue

Connective Tissue

1. mesoderm origin

2. binds cells and organs of the body together

3. 2 basic components

   • Cells
     • fibroblasts: secrete fibres + components of ground substance
     • mast cells: produce histamine
     • adipocytes: store triacylglycerides (fats)
     • WBC: immune response (neutrophils and eosinophils)
     • macrophages: phagocytose bacteria and cellular debris
     • plasma cells: secrete antibodies
   • Extracellular material
     • ground substance
       • complex combination of proteins and polysaccharides
       • found between cells and fibres
         • can be fluid, semifluid, gelatinous or calcified
       • functions to support and bind cells, store water and allow exchange between blood cells.
     • fibres
       • collagen
       • elastic
       • reticular

4. 2 types

   • connective tissue proper
     • loose - loose network of fibres with cells in between
       • AREOLAR connective tissue - most widely distributed in the body. Contains several types of cells and 3 fibres.
       • ADIPOSE connective tissue - contains adipocytes. Good for insulation and energy reserves.
         • white (common) and brown adipose tissue
       • RETICULAR connective tissue - fine interlacing reticular fibres and cells. Forms the stroma of liver, spleen, and lymph nodes
     • dense - dense network of fibres with cells in between
       • dense connective tissue - contains numerous, thicker and denser fibres. Packed closely with fewer cells than loose connective tissue.
       • dense REGULAR connective tissue - bundles of collagen fibres are regularly arranged in parallel patterns for strength. Tendons and most ligaments.
       • dense IRREGULAR connective tissue - collagen fibres are usually irregularly arranged. Found where pulling forces are exerted in many directions. Dermis of skin and heart.
       • dense ELASTIC connective tissue - contain branching elastic fibres. Strong and can recoil to original shape after stretching. Lung tissue and arteries.
   • specialised connective tissue
     • cartilage
       • specialised cells embedded in a matrix of extracellular fibres and other material
       • a dense network of collagen fibres and elastic fibres firmly embedded in chondrotin sulfate
       • chondrocytes - found in lacunae
       • perichondrium - covering of dense irregular connective tissue that surrounds the cartilage.
         • 2 layers - outer fibrous layer and inner cellular layer.
       • no blood vessels/ nerves except in the perichondrium
       • types of cartilage
         • fibrocartilage
           • chrondrocytes are scattered among bundles of collagen fibres with the extracellular matrix
           • lack perichondrium
           • strongest type of cartilage
           • found in intervertebral disc
         • elastic cartilage
           • chondrocytes are located within a threadlike network of elastic fibres.
           • perichondrium is present
           • provides strength and elasticity
         • hyaline cartilage
           • most abundant cartilage in body
           • surrounded by perichondrium (some exceptions like articular cartilage)
     • bone
       • composed of several different connective tissues - osseous, periosteum and endosteum
       • can be compact or spongey
         • compact bone is arranged in Haversian systems
         • spongey/ cancellous bone lack osteons
           • have trabeculae
       • osteoblasts become encased in a calcified cartilage matrix and become osteocytes
       • osteoclasts digest bone tissue and allow for growth and modification
     • blood