Tissues: Epithelium

Nota:

• The others are Nervous, Muscle, and Connective Epi- above thele: teat -ium indicates biological structure

1. Simple Epithelium
   1. Filtration, Diffusion, secretion, and absorption
      1. Cuboidal
         1. glands
         2. tubules of the kidney
         3. terminal bronchioles of the lungs
         4. ducts of reproductive tracts
      2. Columnar
         1. line the gastroins\testinal tract
            1. secretion
            2. absorption
               1. Absorption: Certain epithelial cells lining the small intestine absorb nutrients from the digestion of food.
         2. may have micriovilli
            1. enhance the surface are of the cell and increase the rate of diffusion of materials into the cell
         3. Uterus (womb)
      3. pseudostratified columnar
         1. often have cilia
            1. Cilia are used to move the cell or to move objects over the surface of the cell with power strokes
               1. Cleaning: Ciliated epithelium assists in removing dust particles and foreign bodies which have entered the air passages.
         2. ducts of reproductive tracts
         3. air condition pathways of the respiratory tract
      4. Diffusion: Simple epithelium promotes the diffusion of gases, liquids and nutrients. Because they form such a thin lining, they are ideal for the diffusion of gases (eg. walls of capillaries and lungs).
   2. fast absorption
      1. Squamous
         1. Heart cavaties
         2. Internal surfaces of all blood and lymph vessels
            1. Reduces Friction: The smooth, tightly-interlocking, epithelial cells that line the entire circulatory system reduce friction between the blood and the walls of the blood vessels.
         3. air cells of lung
         4. filtration capsules and thin tubules in the kidney
            1. Excretion: Epithelial tissues in the kidney excrete waste products from the body and reabsorb needed materials from the urine.
               1. Sweat is also excreted from the body by epithelial cells in the sweat glands.
         5. major body cavaties
   3. Sensation: Specialised epithelial tissue containing sensory nerve endings is found in the skin, eyes, ears, nose and on the tongue.
2. Stratified Epithelium
   1. resistant to wear and tear because of ready replacement of cells
      1. Squamous
         1. skin
            1. keratin

               Nota:

               • scleroprotein
               1. protects epithelial cells from damage or stress that has potential to kill the cell
               2. Keratin is a type of filament protein, called an intermediate filament. The filaments anchor the cells to each other, which prevents the cells from pulling apart
            2. protection: protect underlying tissue from mechanical injury, harmful chemicals, invading bacteria and from excessive loss of water
            3. Epidermis
         2. oral cavity
         3. vocal folds
         4. esophagus

            Nota:

            • pherein "to carry" (see infer) + -phagos, from phagein "to eat" (see -phagous).
         5. vagina
         6. anus
         7. basal layers can be squamous, cuboidal or columna
      2. Transitional
         1. contracted, bumpy surface allows urinary organs to bend and stretch
            1. bladder
            2. ureters
            3. prostate
      3. Cuboidal
         1. Protects glands
3. Glandular Epithelium
   1. Secretion: In glands, epithelial tissue is specialised to secrete specific chemical substances such as enzymes, hormones and lubricating fluids.
      1. Exocrine (out)
         1. retain a duct to the free surface fo the cavity or skin
      2. Endocrine (in)
         1. dense capillary networks
4. Basal side: Holds to connective tissue
5. Apical side
6. Functions
   1. Protection: skin
   2. Sensation: sensory
   3. Secretion: glands
   4. Absorption: digestive system
   5. Excretion: kidneys, sweat glands
   6. Diffusion: gases, liquids, nutrients.
   7. Cleaning: celia
   8. Reduce friction: circulatory system