Connective Tissue

• Connective Tissue


  • Bind, support and protect body parts
  • Cells occupy less space than matrix
  • Most cells are not in direct contact with each other
  • Supports, connects and protects organs
  • Highly variable vascularity
• Connective Tissue Functions


  • Connecting organs: Tendons and ligaments
  • Support: Bone and cartilage
  • Physical protection: Cranium, ribs, sternum
  • Immune protection: White blood cells attack foreign invaders
  • Movement: bones provide lever system
  • Storage: fat, calcium, phosphorus
  • Heat production: metabolism of brown fats in infants
  • Transport: Blood
• Components of Connective Tissue

  • Cells
  • Extracellular Matrix
  • Protein fibres
  • Reticular fibres
  • Elastic fibres
  • Ground substances
• Fibroblasts


  Produce fibres and ground substance of matrix
• Macrophages


  Phagocytize foreign material and activate immune system when they sense foreign matter (antigens)
• Leukocytes or white blood cells


  • Neutrophils attack bacteria
  • Lymphocytes react against bacteria, toxins, and other foreign agents
• Plasma cells


  Synthesize antibodies (proteins)
• Mast cells


  • Often found alongside blood vessels
  • Secrete heparin to inhibit clotting
  • Secrete histamine to dilate blood vessels
• Adipocytes


  Store triglycerides (fat molecules)
• Collagenous fibres


  • Collagen is most abundant of the body's proteins 25%
  • Tough, flexible and stretch-resistant
  • Tendons, ligaments, and deep layer of the skin are mostly collagen
  • Less visible in matrix of cartilage and bone
• Reticular fibres


  • Thin collagen fibres coated with glycoprotein
  • Form framework of spleen and lymphnodes
• Elastic fibres


  • Thinner than collagenous fibres
  • Branch and rejoin each other
  • Made of protein called elastin
• Ground Substance


  • Usually has a gelatinous to rubbery consistency
  • Glycosaminoglycans (GAGs) regulate water and electrolyte balance of tissue
  • Chondroitin sulfate is most abundant GAG and responsible for stiffness of cartilage
  • Proteoglycans form gravy-like colloids that hold tissue together
  • Adhesive glycoproteins are protein-carbohydrate complexes
• Connective Tissue Classification

  • Connective tissue proper
  • Supporting connective tissue
  • Fluid connective tissue
• Loose Connective Tissue


  Much gel-like ground substance between cells
• Types of Loose Connective Tissue

  • Areolar
  • Adipose
  • Reticular
• Areolar Loose Connective Tissue

  • Loosely organised fibres, abundant blood vessels, and a lot of seemingly empty space
  • Possess all six cell types
  • Fibers run in random directions
  • Mostly collagenous, but elastic and reticular also present
  • Found in tissue sections from almost every part of the body
  • Surrounds blood vessels and nerves
  • Nearly every epithelium rests on a layer of Areolar tissue
  • Blood vessels provide nutrition to epithelium and waste removal
  • Ready supply of infection-fighting leukocytes that move about freely on Areolar tissue
• Areolar Loose Connective Tissue


  Underlies epithelia, in serous membranes, between muscles, passageways for nerves and blood vessels
• Functions of Areolar Loose Connective Tissue

  • Strength
  • Elasticity
  • Support
• Connective Tissue Proper

  • Loose Connective Tissue
  • Dense Connective Tissue
• Supporting Connective Tissue

  • Cartilage
  • Bone
• Fluid Connective Tissue

  • Blood
• Loose Connective Tissue - Adipose


  Adipose tissue (fat)
• Adipose tissue


  • Tissue in which adipocytes are the dominant cell type
  • Space between adipocytes is occupied by Areolar tissue, reticular tissue and blood capillaries
• Fat is the body's primary energy reservoir
• The quantity of stored triglyceride and the number of adipocytes are quite stable in a person
• Fat is recycled continuously - new triglyceride is synthesized while old molecules are hydrolyzed and released to blood
• Types of fat


  • White
  • Brown
• White fat

  • Main type (only fat in adults)
  • Specimens resemble chicken wire
  • Provides thermal insulation
  • Cushions organs such as eyeballs, kidneys
  • Contributes to body contours-female breasts and hips
• Brown fat


  • In foetuses, infants and children
  • Colour comes from blood vessels and mitochondrial enzymes
  • Functions as a heat-generating tissue
• Adipocytes


  Empty-looking cells with thin margins; nucleus pressed against cell membrane
• Adipocytes


  • Energy storage, insulation, cushioning
  • Subcutaneous fat and organ packing
  • Brown fat of juveniles produces heat
• Loose Connective Tissue - Reticular Tissue


  • Mesh of reticular fibres and fibroblasts
  • Forms supportive stroma (framework) for lymphatic organs
  • Found in lymphnodes, spleen, thymus and bone marrow
• Dense Connective Tissue


  • Fibres fill spaces between cells
  • Types vary in fibre orientation
• Dense Regular Connective Tissue


  • Densely packed, parallel collagen fibres
  • Compressed fibroblast nuclei
  • Elastic tissue forms wavy sheets in some locations
  • Tendons attach muscles to bones and ligaments hold bones together
• Dense Irregular Connective Tissue


  • Densely packed, randomly arranged, collagen fibres and few visible cells
  • Withstands unpredictable stresses e.g.joints
  • Locations: Deeper layer of skin, Capsules around organs, Submucosa of GI tract
• Cartilage


  • Stiff connective tissue with flexible matrix
  • Gives shape to ear, tip of nose and larynx
  • Chondroblasts: Cartilage cells that produce the matrix that will trap them
  • Chondrocytes: Cartilage cells that are trapped in lacunae (cavities)
  • Perichondrium: Sheath of dense irregular connective tissue that surrounds elastic and most hyaline cartilage (not articulated cartilage)
• Hyaline Cartilage


  • Clear, glassy appearance because of fineness of collagen fibres
  • Eases joint movement, holds airway open, moves vocal cords, growth of juvenile long bones
  • Locations: Articular cartilage, Costal cartilage, Trachea, Larynx, Fetal skeleton
• Fibrocartilage


  • Cartilage containing large, coarse bundles of collagen fibres
  • Resists compression and absorbs shock
  • Locations: Pubic symphysis, Menisci, Intervertebral discs
• Elastic Cartilage


  • Cartilage containing abundance of elastic fibres
  • Covered with perichondrium
  • Provides flexible, elastic support
  • Locations: External ear, Epiglottis