Connective Tissue

• Connective Tissue provide:

  • Structure
  • Physical Metabolic support for specialised tissues
  • Mechanical strength
  • Fill spaces in body
• 3 Key Properties of CT:

  1. Tensile strength = Collagen (fibrous protein)
  2. Elasticity = Elastin
  3. Volume = Ground substance - provide base & support
• 4 Types of CT:

  1. Connective Tissue proper
  2. Cartilage
  3. Bone
  4. Blood
• CT proper:

  1. Loose
  2. Dense
• Loose CT proper:

  1. Areolar - strong yet cushioning, underlies epithelium (forms lamina propia)
  2. Reticular - fibres supportive mesh, supports organs
  3. Adipose - adipocytes (lipids)
• Adipose - adipocytes (lipids)

  • White = stores energy (large amount of lipids)
  • Brown = thermoregulation (many mitochondria)
• Dense CT proper:

  1. Regular - parallel fibres (1 direction - eg ligaments & tendons)
  2. Irregular - non-parallel fibres (eg dermis)
• Cartilage:

  1. Hyaline - smooth, translucent, few collagen fibres, ends of bones & tracheal rings
  2. Fibrocartilage - many collagen fibres, eg cartilaginous joint & menisci of knee joint
  3. Elastic - elastin & collagen fibres, mush more elasticity, eg ear
• Hyaline Cartilage =

  • Smooth
  • Translucent
  • Few collagen fibres
  • eg ends of bones & tracheal rings
• Fibrocartilage =

  • Many collagen fibres
  • eg cartilaginous joint & menisci in knee joint
• Elastic Cartilage =

  • Elastin & collagen fibres
  • Much more elasticity
  • eg ear
• Bone:

  • Collagen containing ECM, but becomes calcified (by minerals produced from bone)
• Bone:

  1. Compact bone - hard bone on outside
  2. Cancellous bone - form trabeculae on inside
• Compact Bone:

  • Hard
  • On outside
• Cancellous Bone:

  • Form trabeculae
  • Within centre
  • Layout depends on - stress/weight bearing nature of bone
• Individual cells embedded within ECM
• The constituents of ECM determines the properties of the tissue
• Support cells =

  • Derived from embryological tissue called mesenchyme
  • Produce ECM components
  • Different support cells in different types of CT
• Support cells of each type of CT:

  • CT proper = fibroblasts --> fibrocytes
  • Cartilage = chondroblast --> chondrocyte
  • Bone/Osseous = osteoblast --> osteocyte
  • Adipose = adipocytes
• ECM characteristics crucial to function performed by tissue

  • Mature CT ECM has sparse cellular components
• CT proper ECM Components & Functions:

  • Gel-like ground substance
  • All 3 fibre types
  • Acts as binding tissue
  • Resists mechanical stress + partially tension
• Cartilage ECM Components & Functions:

  • Gel-like ground substance
  • Has smaller proteins within it
  • Collagen fibres
  • Elastin fibres in some
  • Resists compression
  • Cushions
  • Supports body structures
• Bone/Osseous ECM Components & Functions:

  • Gel-like ground substance harden by mineralisation with calcium salts
  • Collagen fibres
  • Rigid
  • Resist compression & tension
  • Support
• All ECM is the same for different tissues, True or False? False
• CT proper - Loose areolar CT ECM:

  • Fibrocytes = support cells
  • Collagen
  • Elastin - thin
  • Ground substance - space, cushioning & volume support
• CT proper - Dense Regular CT ECM:

  • Fibrocytes - squashed bw/ collagen
  • Collagen - tons more collagen, provide more strength in 1 direction (parallel)
• White Adipose Tissue ECM:

  • Very little ECM
  • Lots of support cells = adipocytes
  • Lots of lipids
  • Organelles pushed to top
  • Store lots of energy
• Cartilage ECM:

  • Glassy
  • Firm
  • Almost solid ECM
• Bone ECM:

  • Lots of collagen (calcified w/ ECM)
  • Hard
  • Rigid ECM
• Support cells secrete ECM
• Characteristics of ECM crucial to function of tissue
• Cells in CT adhere to EC materials rather than other cells
• ECM made up of:

  1. Ground substance - GAGs, Proteoglycans
  2. Fibrillar proteins - strength (collagen) or elasticity
  3. Adhesion proteins - link fibres, GS & cells together
• ECM - Ground Substance:

  • Glycosaminoglycans (GAGs) = very long unbranched polysaccharides (sugar molecules)
  • Proteoglycans - proteins that covalently bond to GAGs
• Ground substance binds to water, salts, collagen proteins, other molecules to make a massive matrix structure
• ECM - Fibrilar proteins:

  • Provide strength or elasticity
  • Collagen = strength
  • Elastin = elasticity
  • Are very long
• ECM - Adhesion proteins:

  • Connects all stuff together
  • Link fibres, ground substance & cells together
• Glycosaminoglycans (GAGs):

  • Long unbranched polysaccharide (sugar) chains
  • Hyaluronic acid (hyaluronate) = most common GAG -->Longest of all GAGs
  • Long linear molecules of 2 repeating sugar molecule
  • Other GAGs attach via core proteins forming proteoglycans
  • Negatively charged to stop from folding/binding onto on another = hydrophilic - can bind to water
• Proteoglycans & Glycosaminoglycans:

  • From the ground substance
  • Create volume & compression resistance
  • Interact with: each other, water & salts, collagen & other fibres/molecules
• Core protein binding with GAG = Hyaluronate & will have other GAGs that come off of it = proteoglycans