lecture 7 - connective tissue

• Types of Connective Tissue

  • Tendon
  • ligament
  • Capsule
  • Lamina propria
  • Bone
  • Cartilage
  • Fat
  • Blood
• tissue definition

  • a coherent grouping of cells bounded together by intercellular junctions or extracellular matrix (ECM)
  • epithelial: intercellular junctions
  • connective: ECM
• ECM

  • the regions around the cells
  • coloured green

  
• COMPOSITION OF extracellular matrix (ECM)

  • fibres
• COMPOSITION OF extracellular matrix (ECM)

  • fibres
  • Ground substance (amorphous gel, sol-gel matrix)

  A) ground substance

  B) fibres

  C) cell

  
• ground substance

  • the white stuff outside of the cells
• ECM - fibres

  • function: strength; Resistance to deformation/stretch
  • collagen fibres: most common type, has high tensile strength
  • elastin
  • reticular
• ECM - ground substance

  • function: Passage and exchange of molecules and metabolites, lubricant, barrier to invaders
  • Proteoglycans (proteins) attract and retain water (gel)
  • Glycoproteins: e.g. laminin, fibronectin
  • Glycosaminoglycan's
  • Water, electrolytes, hormones, gases
• Collagen fibre

  • Strong and inelastic – straightened but NOT stretched
  • Produced by fibroblasts

  examples
• Collagen fibre

  • Strong and inelastic – straightened but NOT stretched
  • Produced by fibroblasts

  examples

  • Tendons & ligaments: >80% collagen, resistance & tensile strength
  • Capsules: multiple layers. found in gonads, spleen. has resistance to tearing

  
• collagen fibre (2)

  • Type I: bone
  • Type II: cartilage
  • Type III: skin, glands, large blood vessels
• Tendons

  • carries forces from muscle to bone

  A) ground substance

  B) fibroblast

  C) collagen

  
• ligaments

  • connects bone to bone
  • like tendons, also made of fibroblast cells
  • more ground substance = less collagen fibre dense

  
• ligaments

  • connects bone to bone
  • like tendons, also made of fibroblast cells
  • more ground substance = less collagen fibre dense

  A) ligament

  B) flexibility

  
• collagen - capsule

  • fibroblast cells: coloured in dark purple
  • collagen fibres: coloured in light purple
  • ground substance: coloured in white
  • blood vessels: bigger round shaped ovals (simple squamous endothelial cell surrounding it)

  
• dermis of skin

  • mostly layers of collagen fibres
  • note: 5% elastic fibres

  A) collagen

  
• ECM -> fibres -> elastic

  • composition: fibrillin and elastin
  • fibres become elastic with water (more flexible than collagen fibres)
  • made of: fibroblast, smooth muscle cells, chondrocytes
  • FOUND IN: bloody vessels, dermis of skin, LUNG (ie. expansion of alveoli during gas exchange)
• ECM -> fibres -> elastic tissue -> blood vessel

  • purple lines = several layers of elastic tissue in this artery (called elastin)
  • light pink area = smooth muscle
  • blue = collagen

  
• ECM -> fibres -> elastic tissue -> dermis of the skin

  A) elastic

  B) collagen

  
• ECM -> fibres -> reticular

  • type III collagen
  • delicate fibres - needs cells in particular arrangement
  • found in: BONE MARROW, lymphoid organs, glands, around smooth muscle, blood vessels
• ECM -> fibres -> reticular fibres -> LIVER and LYMPH NODES

  • liver: dark purple lines are reticular fibres, holding together numerous cells
  • lymph nodes: dark brown lines are reticular fibres

  
• fibroblast

  • the MAIN CELL of connective tissue
  • it makes the fibres (collagen, elastic, reticular) of connective tissue

  A) collagen

  
• connective tissue cells -> types

  • MAIN: fibroblast cells
  • adipose tissue: adipose cell (fat cell)
  • bone: osteoblasts, osteocytes, osteoclasts
  • cartilage: chondroblast, chondrocyte
  • blood: neutrophils, eosinophils
• connective tissue cells -> adipose tissue -> adipose cells

  • nucleus is pushed to the periphery (outer edge) of adipose cell
  • ECM: not many fibres, mostly ground substance

  A) blood vessel

  B) nucleus

  
• connective tissue cells -> cartilage -> chondroblast & chondrocyte

  • main cell in cartilage: chondrocytes
  • ECM: lots of collagen fibres & proteoglycan gel, even though not that visible
  • 3 types of cartilage: hyaline cartilage, elastic cartilage, fibrocartilage
  • features: No nerves, lymph, blood vessels.

  A) chondrocytes

  B) collagen

  
• connective tissue cells -> cartilage cells -> Hyaline cartilage

  • the most common type of cartilage cell
  • looks like little GLASS beads
  • location: surfaces of joints (so bones don't rub), costal & respiratory cartilages, epiphyseal growth plates

  A) cartilage

  B) chondrocytes

  
• reminder

  • ECM is made by the cells in the tissue
  • eg. ECM of cartilage is made by chondrocytes, it contains collagen fibres and proteoglycan "gel" (not visible)
• connective tissue cells-> cartilage -> elastic cartilage

  • a variant of hyaline cartilage
  • Yellowish
  • Matrix criss-crossed by elastic fibres
  • More chondrocytes
  • Flexible and elastic
  • location: ear, epiglottis, auditory tube
• connective tissue cells-> cartilage -> fibrocartilage

  • a variant of hyaline cartilage
  • colour: kind of white
  • more collagen
  • tensile strength and resistance to compression
  • location: Intervertebral disc, Link between tendon and bone
• connective tissue cells -> bones

  • cells within bones: osteoprogenitor, osteblasts, osteocytes, osteoclasts
  • function of bone: 1) skeletal support 2) Protects organs 3) Harbour bone marrow 4)Stores calcium and phosphate & ions
  • ECM: fibres, ground substance
  • Organic matrix: mostly type I collagen
  • Inorganic matrix: 65% of bone weight, mineral=calcium phosphate
• connective tissue cells -> bones -> compact & spongy bone

  • compact bone: dense and solid, with a tightly packed arrangement of OSTEONS, in outer layer
  • spongy bone: less dense, made of thin trabeculae plates which hold bone marrow, in inner layer.

  A) compact

  B) spongy

  C) osteon

  
• connective tissue cells -> bones -> Compact bone

  • very strong and dense, indicating lots of collagen fibres
  • the central (haversian) canal supplies all the tissue for compact bone
• connective tissue cells -> bones -> Compact bone

  • very strong and dense, indicating lots of collagen fibres
  • osteocytes -> this MAKES the bone tissue
  • Haversion canal function: brings nutrients to compact bone

  A) osteocyte

  B) collagen

  
• connective tissue cells -> bones -> compact bone -> osteocytes

  • osteocyte cells sit in lamellae (layers of bone tissue)
  • these osteocytes communicate with other osteocytes in sharing nutrients from central canal through "cytoplasmic processes / extensions"

  
• connective tissue cells -> bones -> spongy bone

  • composition: made of a lattice of trabeculae surrounded by bone marrow
  • location: found in epiphysis of long bones and core of short bones

  A) trabeculae

  B) osteoblasts

  
• connective tissue cells -> bones -> bone remodelling

  • bone is constantly remodelling (eg. from lifting weights..)
  • Osteoclasts: Resorption of bone (dissolve bone mineral and degrade collagen and proteoglycans)
  • Osteoblasts: MAKING new bone
  • Osteoid: is PREBONE, will later form lamellae then osteon

  A) bone marrow

  B) osteoid

  
• connective tissue cells -> bones -> bone development

  • Endochondral ossification: a process where cartilage replaced by bone (eg. femur, tibia)
  • Intramembranous ossification: process where mesenchymal tissue turns into bone (eg. skull)
  • in the image: blue stain = hyaline cartilage = prebone

  
• connective tissue cells -> blood -> cell types

  • erythrocytes (red blood cells)
  • leukocytes (white blood cells)
  • neutrophils
  • eosinophils
  • Macrophage
• connective tissue cells -> blood -> fluid connective tissue

  • ECM: plasma (fluid ground substance)
  • cells: erythrocytes (red blood cells), leukocytes (white blood cells), platelets
• connective tissue -> classification -> loose connective tissue

  • more open arrangement of fibres (eg. collagen & elastic), more flexible
  • function: packing material between cells/other tissues (eg. underneath epithelium of trachea & small intestine)
  • eg. adipose tissue, due to lack of fibres