Connective Tissue

• Define connective tissue:


  Less specialised tissue that supports a more specialised tissue type

  (Support cells & their associated extracellular matrix)
• What are the types of connective tissue?

  • Connective tissue proper
  • Specialised connective tissues
• What are the 2 types of connective tissue proper?

  • Loose irregular connective tissue (cells spaced out)
  • Dense irregular connective tissue

  (Irregular= fibres run in different directions)
• What are the 5 main cells responsible for forming connective tissues?

  • Fibroblasts
  • Chondrocytes
  • Osteoblasts
  • Myofibroblasts
  • Adipocytes
• What do chondrocytes do?

  Secrete the extracellular matrix components of cartilage
• What do osteoblasts do?

  Secrete the extracellular matrix components of bone
• What is the extracellular matrix (ECM)?

  • The bioscaffold of tissues
  • Composed mainly of fibrillar proteins & ground substance
• Examples of fibrillar proteins:

  • Collagen (including reticulin)
  • Elastin
• What is ground substance?

  Transparent, colourless jellylike substance

  Fills spaces between fibres & cells

  Contains GAGs (e.g, hyaluronic acid & glyceoproteins such as aggregan)

  These are good at binding to water
• What does the suffix -blast mean?

  Build
• What does the suffix -cyte mean?

  Maintenance
• What does the suffix -clast mean?


  Remove
• LOs:

  
• Cells that form tissues can be divided into 2 types:

  • Parenchymal cells- provide main function of tissue (e.g, brain, muscle, nervous tissue)
  • Support cells- provide structural scaffolding of tissue (e.g, bone)
• Types of specialised connective tissues:

  • Dense regular connective tissue (found in tendons & ligaments)-max strength as all fibres run in same direction
  • Cartilage-elastic, fibro & hyaline
  • Adipose tissue
  • Blood
  • Bone
  • Haemopoietic tissue
• Where is elastic cartilage found?

  Ears & epiglottis
• Where is fibrocartilage found?

  Intervertebral discs
• Where is hyaline cartilage found?

  Joints spaces
• What do fibroblasts do?

  Secrete the extracellular matrix components in most tissues- usually collagen & elastin

  Creates areolar tissue (loose connective) & dense (regular or irregular) connective tissue
• What does the prefix 'chondro-' mean?

  Cartilage
• What does the prefix 'Osteo-' mean?

  Bone
• What is endochondral ossification?

  Process of bone formation where a cartilage model is gradually replaced by bone tissue
• What are myofibroblasts?

  Secrete extracellular matrix components & have a contractile function
• What are adipocytes?

  • Lipid-storing support cells- act as energy store
  • Have an endocrine function & act as physical cushioning/padding in some anatomic regions
• Common features of connective tissue cells:

  • Embryological derivation from mesenchyme
  • Production of variety of extracellular matrix materials
  • When mature, cells become less active as they've already made ECM
  • Cell adhesion mechanisms interact with ECM rather than with other cells
• Connective tissue histological photo:

  
• ECM histological photo:

  (loose connective tissue)

  • nuclei spaced out
  • long lines = collagens
  • thinner fibrils = elastin

  
• Dense irregular tissue photo:

  A) fibroblast nuclei

  
• What is reticulin?

  Collagen type 3

  • Used when meshwork being formed e.g, in spleen & lymphatic system
  • Meshwork helps filter broken down parts in blood

  
• Another connective tissue photo:

  
• What are the main types of fibres?

  • Collagen
  • Elastic
  • Reticular
• Properties of collagen:

  • Most abundant
  • Flexible
  • Tensile strength
  • Wavy appearance
  • Collagen fibrils

  
• What are the 2 main types of collagen?

  • Type 1- tendons, ligaments, skin & bone
  • Type 2- cartilage (better at binding to water)
• Where do you find type 4 collagen mainly?

  Basement membrane
• Where do you find type 6 collagen mainly?

  Secreted by adipocytes
• Properties of elastic fibres:

  • Thinner than collagen
  • Arranged in branching pattern
  • Allow tissues to stretch & distend
  • Interwoven with collagen
  • Found in aorta & large arteries to accommodate high pressure

  
• Properties of reticular fibres:

  • Thin & short
  • (Type 3 collagen)
  • Form fine meshwork

  
• What is the purpose of the fine reticular meshwork in the spleen?

  Spleen filters out old red blood cells (hard & can't fit through tiny spaces)

  Meshwork blocks RBC & immune cells destroy them
• Why do fibroblasts get smaller?

  ECM made

  Reduce cytoplasm size

  Become a fibrocyte
• What do osteoclasts do?

  • Secrete acids to degrade old bone