Lecture 2

• Tissues : collections of single type of differentiated cells

  • Individual cells are covered in extra cellular fluid and suspedned in an extra cellular matrix 
  • ECF contains blood plasma , interstitial fluid and transcellular fluid 
  • ECM contains basement membrane (thin layer of protein) and interstitial matrix (fibrous protein and allows for movement) 
  • Organs are made of a plethora of different types of cells 
• Principal tissues

  1. muscle tissue
  2. epithelial tissue
  3. connective tissue
  4. nervous tissue
• Connective tissue


  supportive - cartilage , bone

  fluid - blood , lymph

  connective tissue - dense , loose
• Protein fibers : collagen

  • Collagen fibrils lie in parallel to form bundles called fibres 
  • Strong and can resist pulling forces 
  • Relatively flexible 
  • Common in bone , cartilage, ligaments and tendons 
  • Found in repair sites eg scars 
  • When heart tissue dies it is replaced by collagen to fill the void to avoid infection extra the heart however will never function the same 
• Protein fibers : elastic 

  • Made of elastin molecules surrounded by fibrillin 
  • Smaller than collagen 
  • Forms networks within tissue 
  • Strong but elastic  
  • Found in skin, blood vessels and lung tissue 
•  Protein fibers : reticulin 

  • Type 3 collagen (has a glycoprotein coating) 
  • Smaller than collagen 
  • Forms branching networks around fat cells, nerve fibers and skeletal and smooth muscles 
  • Used as scaffolding in soft organs : liver , spleen , lymph nodes 
• Cells : fibroblasts and fibrocytes 

  • Secrete collagen, elastin and reticulin fibers (type three collagen) 
  • Secrete ground substance  
  • Fibroblast -> nucleus shrinks -> now known as fibrocytes 
  • Survey the area they are in  
• Cells : adipocytes  

  • Stores triglycerides 
  • Adipose (fat tissue) is a major reserve of energy 
  • Found under the skin and surrounding organs 
  • Brown smaller globs of fat easier to break down found more in babies 
  • White large glob of fat harder to break down found in adults  
• Allergies : Mast cells

  • Produced in the bone marrow 
  • Found in blood vessels  
  • Contain granules which have heparin and histamine 
• Allergies : Mechanism of action in hay fever

  • Initial exposure to allergen leads to the production of IgE antibodies which bind to mast cells 
  • Allergens bind to the IgE on the mast cells activating them 
  • The process of degranulation occurs 
  • Histamine is released causing the symptoms of hay fever  
  • Vessels dilate causing fluid to flow out  
• Loose connective tissue : 

  • Areola (pink) 
  • Adipose (white , chicken wire appearance) 
  • Reticular (black in colour) 
• Dense connective tissue : 

  • Irregular : layers of cells are irregular, more flexible but less strong 
  • Regular : regular structure of cells in layers, very strong and less flexible