<aside> 💡 Primary Tissue 1: Epithelia Structure and Function

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1. Outline the characteristics of structure and function of the “epithelia” class of tissues.

   1. Epithelium function
      1. Form barriers and layers
      2. Glands
   2. Epithelium characteristics

      1. Avascular

         1. Nourished by blood from underlying CT (no blood/lymph vessels)
         2. Isolation from vascular system prevents damage from wear/tear, protects vascular system

      2. Anchored

         1. Lined by basal lamina
         2. Provides support/integrate epithelia; selectively permeable; influence epithelia organisation and survival

      3. Adhesion

         1. Tight junctions and desmosomes bind epithelial cells to each other and underlying (basal) tissue

      4. Polarity

         1. Specific orientation as outer (apical/luminal) side has different specialization from inner (basal) side

         2. Ex. microvilli on luminal/apical side, desmosomes on basal side

            

      5. Proliferation

         1. Epithelia need to be continually replaced as especially susceptible to damage and shearing
         2. Progenitor cells present to replenish epithelium cells

2. Describe the structural specializations within epithelia’s and account for how this leads to diversity within the functions of this tissue type.

   1. Epithelium structure

      

      1. Shape:
         1. Squamous
            1. Thin/flattened
            2. Thin/indistinct amount of cytoplasm
            3. Rapid filtration/exchange of substances
            4. Narrow/flattened nucleus
         2. Cuboidal
            1. Square cells as wide as they are tall
            2. Secretion and absorption
            3. Spherical/circular central nucleus, large proportional to cell volume
         3. Columnar
            1. Tall thin cells
            2. Secretion/absorption
            3. Apical specialisations ex. Microvilli
            4. Basal Nuclei, ovular
      2. Organization:

         1. Simple

            1. Single layer of cells
            2. Easy diffusion/transport

         2. Stratified

            1. Multiple layers of cells

         3. Pseudostratified

            1. Seeming to consist of multiple layers

            2. Nuclei at different heights based on cell age

            3. Newer cells lower nuclei, older cells higher nuclei

            4. Cells of differing height for multiple complex functions

               

         4. Transitional

            1. Dome like stratified squamous (apical) and cuboidal/columnar (basal) cells

            2. Epithelia stretches to permit rapid, repetitive distention of urinary bladder, ureters and part of the urethra

               

3. Identify and recall the locations of the major different types of epithelia’s within the body.

   1. Simple squamous

      1. Endothelium

         1. reduces friction of blood

         2. prevents turbulence which leads to coagulation

            

            

      2. Serosae

         1. thin serous membranes which slide over each other smoothly

      3. Alveoli

         1. small diffusion distance

   2. Simple cuboidal

      1. Pancreas

      

      

      1. Nephrons

         1. tubular reabsorption, secretion

            

   3. Simple columnar

      1. Non-Ciliated

         1. Goblet cells

            

            

      2. Ciliated:

         1. Bronchi
         2. Fallopian tubes

      3. Function in absorption and secretion

         

         

   4. Stratified squamous

   5. Pseudostratified columnar

   6. Transitional

4. Outline the characteristics of structure and function of the epithelial gland cells

5. Describe the structural specializations/classifications of glands and discuss different modes of secretion.

6. Identify and recall the locations of the mucous and serous membranes (specialized epithelia) within the body.