Epithelia

Epithelia

Simple epithelia
1. Simple cuboidal epithelia
  1. single layer
  2. appear square
  3. Found on absorptive, secretory or lining surfaces
    1. e.g. thyroid gland, kidney tubules, ducts of other glands, and covering of ovary
2. Simple squamous epithelia
  1. appear flattened
  2. single layer
  3. Reduces friction between adjacent cells
    1. e.g. wall of Bowmans capsule, lining outside the heart, gut, peritoneum and pleural cavities
3. Simple columnar epithelia
  1. appear longer than they are wide
  2. single layer
  3. Nucleus often basally positioned
  4. tight junctions
    1. e.g. digestive tract, gall bladder, bile ducts and many different glands
  5. Villi may be present on intestinal cells and gobelt cells are interspersed
Pseudostratified epithelia
1. pseudostratified ciliated columnar epithelia
  1. nuclei are at different levels giving the false impression of several layers of cells
  2. single layer
  3. All cells are attached to basement membrane but not necessarily reach the surface
    1. e.g. upper respiratory tract, (nose, trachea, bronchi and bronchioles)
Stratified epithelia
1. Stratified squamous non-keratinized epithelia
  1. protective function, resistant to abrasion
    1. e.g. extremities of digestive tract (buccal cavity, oesophagus and anal canal), also vagina
  2. associated with moist surfaces
  3. many layers
2. Stratified squamous keratinized epithelia
  1. mechanically protective and moisture proof
    1. e.g. skin
  2. more than one layer
  3. dead cells at the surface
Transitional epithelia
1. present ONLY in urinary passage i.e ureter, bladder and urethra
2. Superficial cells are rounder and sometimes binucleate
  1. NOTE shape of cell changes when tissue is stretched
3. Similar to stratified sqaumous non-keratinized

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	Criado por lauren7king mais de 10 anos atrás