Histology 2

• Tissue level of Organization

  Microscopically identify the different tissue types and discuss the relationship between structure and function with special reference to regeneration and cancer
• Epithelium


  Relationship between structure and function
• Glandular epithelia


  • Contain gland cells
  • Produce fluid secretions

  
• Types of glands


  • Endocrine glands
  • Exocrine glands

  
• Endocrine glands


  Release hormones into interstitial fluid
• Exocrine glands


  Produce secretions onto epithelial surfaces/passageways through ducts

  
• Exocrine gland classification


  • Structure of the glands
  • How they secrete their products
  • What those products are

  
• Types of exocrine glands

  • Unicellular
  • Multicellular

  
• Types of multicellular exocrine glands

  • Structure of the duct
  • Shape of the secretory portion of the gland
  • Relationship between ducts and glandular areas

  
• Merocrine secretion


  Watery perspiration from sweat glands
• Apocrine secretion


  Secretion from mammary glands

  
• Holocrine secretion


  Secretion from sebaceous glands

  
• Types of exocrine secretions

  • Serous glands (watery solution containing enzymes)
  • Mucous glands (mucins that hydrate to form mucus)
  • Mixed exocrine glands (more than one type of gland cell – produce two different exocrine secretions)

  
• Connective tissue


  • Specialized cells
  • Solid extracellular - protein fibers
  • Fluid extracellular - ground substance
• The matrix of connective tissue (extracellular fibers & ground substance) makes up the majority of the tissue volume, never exposed to external environment occurring throughout the body
• Connective tissue is highly vascular & contain sensory receptors
• Functions of connective tissue

  • Establishing a structural framework for the body
  • Transporting fluids and dissolved materials
  • Protecting delicate organs
  • Supporting, surrounding, & interconnecting other types of tissue
  • Storing energy reserves, especially in the form of triglycerides
  • Defending the body from invading microorganisms
• Classification of connective tissue by physical properties


  • Connective tissue proper
  • Fluid connective tissues
  • Supporting connective tissues
• Connective tissue proper


  Connect and protect
• Types of connective tissue proper

  • Loose connective tissue
  • Dense connective tissue
• Loose connective tissue


  More ground substance, fewer fibers
• Dense connective tissue


  More fibers, less ground substance
• Fluid connective tissues


  Transport (i.e., blood and lymph)
• Supporting connective tissues


  Structural strength & protection (less diverse cell population and densely packed fibers)
• Cell types in connective tissue proper

  • Fibroblasts
  • Fibrocytes
  • Adipocytes
  • Mesenchymal cells
  • Macrophages
  • Mast cells
  • Lymphocytes
  • Microphages
  • Melanocytes
• Fibroblasts


  The most abundant cell type, found in all connective tissue proper, secrete proteins and hyaluronan
• Fibrocytes


  The second most abundant cell type, differentiate from fibroblasts, maintain the fibers of connective tissue proper
• Adipocytes


  Fat cells, each cell stores a single, large lipid droplet
• Mesenchymal cells


  Stem cells that respond to injury or infection, daughter cells differentiate into fibroblasts, macrophages, etc.
• Mast cells


  Stimulate inflammation after injury or infection, release histamine and heparin
• Macrophages


  Large phagocytic cells, engulf damaged cells or pathogens, fixed or free-moving
• Lymphocytes


  Numbers increase during tissue damage, develop into plasma cells that produce antibodies
• Melanocytes


  Synthesize and store the brown pigment melanin, determine skin color
• Microphages


  Phagocytic blood cells, respond to signals from macrophages and mast cells

  
• Types of connective tissue fibers

  • Collagen fibers
  • Reticular fibers
  • Elastic fibers
• Collagen fibers


  Most common fibers in connective tissue proper, long, straight, and unbranched, bundle of fibrous protein, strong and flexible
• Reticular fibers


  Network of interwoven fibers, strong and flexible, stabilize functional cells and structures
• Elastic fibers


  Contain elastin protein, branched and wavy, return to original length after stretching
• Ground substance


  Clear, colorless and viscous, fills spaces between cells and slows pathogen movement
• Types of loose connective tissue

  • Mucous connective tissue in embryos
  • Adipose tissue
  • Areolar tissue
  • Reticular tissue