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BIOL 241_Fall 2011_Tissues_Part I - Identification of cell types and epithelium

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BIOL 241_Fall 2011_Tissues_Part I - Identification of cell types and epithelium Powered By Docstoc
					        How to Identify the type of epithelium?

• Combination of shape and number of layers!




• In order to decide the type of epithelium, we must
  determine
            » How many layers there are
            » The shape of the epithelial cell




                                                       1
                 Classification of Epithelia

• Singular epithelium; plural epithelia
• Classes of Epithelia
   – Based on shape
      • Squamous epithelium : thin and flat
      • Cuboidal epithelium : square shaped
      • Columnar epithelium : tall, slender rectangles


   – Based on layers
      • Simple epithelium: single layer of cells
      • Stratified epithelium: several layers of cells
                                                         2
Classification of Epithelia - Based on shape




                                               3
 Classification of epithelia based on number of layers



• Simple epithelium
   – All cells in contact with the basement membrane
   – Filtration, absorption or secretion

• Stratified epithelium
   – Apical and basal layers
   – Abrasion

• Pseudostratified epithelium
   – All attached; not all reach apical region

                                                       4
5
Classification of epithelia types based on layers and shape




                                                        6
        Squamous epithelium – examples of

– Simple squamous epithelium
  • Absorption and diffusion


– Mesothelium
  • Lines body cavities


– Endothelium
  • Lines heart and blood vessels


                                            7
                       Simple squamous




Figure 4–3 Squamous Epithelia.




                                         8
9
                     Stratified squamous




Figure 4–3 Squamous Epithelia.




                                           10
              Stratified squamous epithelium
• Multiple layers of flattened cells




                                               11
   Simple cuboidal
Secretion and absorption




                           12
13
    Stratified cuboidal
Sweat ducts and mammary ducts




                                14
Transitional Epithelium




                          15
                  Columnar epithelium


• Simple columnar epithelium

   – Absorption and secretion



• Stratified columnar epithelium

   – Protection



• Pseudostratified columnar epithelium

   – Cilia movement
                                         16
                                 Simple columnar




Figure 4–5 Columnar Epithelia.




                                                   17
                           Stratified columnar




Figure 4–5 Columnar Epithelia.




                                                 18
Pseudostratified columnar




                            19
                    Four Types of Tissues

• Tissues are collections of cells and cell products that
  perform specific, limited functions


• Types of tissue
   – Epithelial tissue
      • Covers exposed surfaces
      • Lines internal passageways
      • Forms glands


                                                            20
– Connective tissue
   • Fills internal spaces
   • Supports other tissues
   • Transports materials
   • Stores energy


– Muscle tissue
   • Specialized for contraction
   • Skeletal muscle, heart muscle, and walls of hollow
     organs


– Neural tissue
   • Carries electrical signals from one part of the body
                                                       21
     to another
                      Epithelial Tissues


• Characteristics of Epithelia
   – Cell junctions
   – Apical and basal surfaces
   – Attachment (basal lamina)
   – Avascularity
   – Regeneration




                                           22
What name
would you give
this tissue?




                 23
                     Epithelial Tissues

• Functions of Epithelial Tissue
   – Provide physical protection
   – Control permeability
   – Provide sensation
   – Produce specialized secretions (glandular epithelium)




                                                         24
       Epithelial Tissues -Intercellular Connections


• Cell junctions

   – Form bonds with other cells or extracellular material:



      • Tight (occluding) junctions

      • Gap junctions

      • Desmosomes

      • Hemidesmosomes

                                                         25
26
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                     Epithelial Tissues

• Epithelial Maintenance and Repair

   – Epithelia are replaced by division of germinative cells
     (stem cells)

   – Near basal lamina




                                                          30
               Two major groups of glands

• Glandular Epithelia


   – Endocrine glands




   – Exocrine glands




                                            31
Gland: A group of cells combined to secrete a specific
hormone
Endocrine glands: they release hormones directly into the
blood circulatory system and modulate internal body
processes. Also known as ductless glands. Example:
Pituitary




                                                         32
                                                         32
Exocrine glands: they secrete fluids into the epithelial
surfaces of the body. They usually have ducts leading to
the body surfaces. Example: Sweat glands




                                                           33
                                                           33
         Modes of Secretion in Glandular Epithelia

• Merocrine secretion
  – Is released by vesicles (exocytosis)
  – For example, sweat glands

• Apocrine secretion
   – Is released by shedding cytoplasm
   – For example, mammary gland

• Holocrine secretion
  – Is released by cells bursting, killing gland cells
  – For example, sebaceous gland

                                                         34
Classification of Epithelia




                              35
                       Classification of Epithelia




Figure 4–6 Modes of Glandular Secretion.




                                                     36
                       Classification of Epithelia




Figure 4–6 Modes of Glandular Secretion.




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