connective tissue

• specialised tissues cell types:

  • permanent cell type
  • metastable cell type
  • labile cell type
• 4 tissue types:

  • connective - support and packing
  • epithelium - lining and barrier
  • muscular - contractile
  • nervous - action potential and transmission
• connective tissue is characterised by copious extracellular matrix which cells are dispersed within
• connective tissue is composed of different cell types within differing extracellular matrix
• two key functions of connective tissues:

  • binding tissues together
  • support
• types of connective tissues:

  • connective tissue proper
  • cartilage
  • bone
  • blood
• connective tossues derived from embryonic mesenchyme cells
• examples of cells in connective tissues:

  • adipocyte cells - fat cells
  • fibroblasts and fibrocytes - fibre cells
  • chondrocytes and chondroblasts - cartilage cells
  • osteoblasts and osteocytes - bone cells
  • blood cells
• the extracellular matrix for connective tissue varies with tissue and cell type
• different extracellular matrixs include:

  • fibres (fibro, hyaline and elastics)
  • chondroitin sulphate matrix (with and without fibres, cartilage)
  • bone matrix (calcium salt base)
  • fluid (plasma)
• connective tissue proper - classifications:

  • areolar (loose connective tissue)
  • adipose
  • fibrous
• areolar tissue is the most generalised of the connective tissue proper classifications that is used for packing and support
• areolar tissue is distributed:

  • under the skin
  • around blood vessels and nerves
  • between muscles
  • withon the digestive tract (submucosa)
• areolar tissue is mainly composed of gelatinous material (hyaluronic acid) and a few fibres
• areolar tissue mainly consists of:

  • mast cells - basophils in blood - that contain 5-HT and histamines
  • macrophages which are both fixed and mobile
  • some adipocytes and fibroblasts
• 5-HT = 5-hydroxytryptamine
• adipose tissue acts as an energy reservoir which helps with insulation and endocrine roles that are associated with hormones
• adipose tissue contains triglyceride droplets which coalesce to fill the cytoplasm
• coalesce - to come together to form one mass or unit
• this type of tissue is found under the skin as a subcutaneous layer and around the heart - epicardial - and arounf the kidneys - perinephric
• fibrous tissue are made of dense - fibre - connective tissues with the two main fibre types being collagen and elastic
• collagen = white
• elastic = yellow
• white fibres:

  • thinner
  • wavy
  • inelastic
  • arranged in bundles
• white collagen fibres are often found in tendons, ligaments and the capsule for many organs like the kidneys and liver
• yelllow fibres:

  • thicker
• yellow elastic fibres are found in the middle wall of the artery which is also known as the tunica media
• tendons connect muscle to bone
• ligaments connect bone to bone
• cartilage - protective covering at the end of bone to protect the bone from degeneration from constant friction due to movement
• cartilage is abundant in extracellular matrix
• cartilage made up of:

  • elastin fibres
  • collagen fibres
  • proteoglycan - jelly-like ground substance
  • 60-80% water
• specialised cell for cartilage is known as chrondrocytes
• types of cartilage:

  • hyaline
  • elastic
  • fibrocartilage
• hyaline - flexible and resilient
• elastic - highly bendable
• fibrocartilage - compression and tension resistant
• hylaine cartilage have a amorphous and form texture
• hyaline has collagen fibres which form and imperceptible network
• imperceptible - so slight that it cannot be percieved