Epithelium- Histology Flashcards
define epithelial tissues?
Epithelia are tissues that serve as protective layers and/or secretory components of body organs and systems
Whats the function of epithelial tissues?
Most epithelia possess common characteristics that contribute to their functional capabilities.
Formed into tightly cohesive cellular sheets.
Function is to cover/line body surfaces e.g. alimentary canal, exocrine ducts.
Form functional units of secretory glands e.g. salivary, mammary, sweat.
What are the 5 common attributes?
Limited intercellular space Single or multiple layers of cells Free apical surfaces Basement membrane Epithelia
Define Limited intercellular space?
Specialised intercellular junctions hold cell membranes close together – effective barrier – blocks infiltration of fluids between cells.
Define Single or multiple layers of cells?
Form linings or coverings. Where diffusion/filtration is important, epithelia is a single layer – where protection e.g. abrasion is needed – multiple layers.
Define Free apical surfaces?
All epithelia possess a free apical surface during development or at maturity. The apical surface is where cells of an epithelium face internal lumens.
Define Basement membrane?
Basal surface attaches to underlying tissues via basement membrane derived from underlying connective tissue.
Define Epithelia?
covering or lining tissues are constantly subjected to wear and tear. Mitotic capability enables repair and regeneration.
What are 2 structural characteristics of epithelial tissues?
Cell Layer
- Simple
- Pseudo-stratified
- Striated
Cell Shape
- Squamous
- Cuboidal
- Transitional
Define simple epithelial
1 cell thick
Define stratified epithelial
Many cells thick but only bottom layer in contact with basement membrane
Define pseudo- stratified epithelia
Appear more than 1 cell thick but all ells rest on the basement membrane.
Dedine squamous cells?
Flattened cells
Define columnar cells?
cells made taller than wide
Define cuboidal cells?
Cells similar height width and depth
Define transitional cells?
Cells in layers which can change shape when they’re stretched.
Give an example of the location of simple squamous?
alveoli and capillaries of lungs
Give an example of the location of simple cuboidal?
Kidney tubule
Give an example of the location of simple columnar?
Small intestine
Give an example of the location of transitional cells?
Urinary tract
Give an example of the location of stratified squamous?
Oesophagus
Give an example of the location of kertanized stratified squamous?
Skin
Give an example of the location of pseudo-stratifed cells?
Trachea, nasal muscosa
Give an example of the location of stratified cuboidal?
Sweat glands duct
Give an example of the location of stratified columnar ?
Salivary gland duct
What is the cutaneous membrane
The skin covering the outer surface of the body
Define and explain the 2 serous membranes
Parietal layer- Attaches to the body
Visceral Layer- Attaches to organs.
What is the cavity known as that covers in between the pleura|?
Pleural space
What 2 structures cover the basal surface of the epithelia and explain them?
•Basement membrane:
Separation from the underlying connective tissue – acts to support epithelia a selectively permeable filter between epithelium and connective tissue.Anchors epithelium to connective tissue via cell-matrix adhesions.
Basal lamina:
Supportive sheet between epithelium and underlying connective tissue
What 2 structures cover the apical surface of the epithelia and explain them?
Microvilli:
Finger like extensions of the plasma membrane of apical epithelial cellIncrease surface area for absorption (small intestine).
Cilia:
Whip like, motile extensions
Moves mucus, etc, over epithelial surface, in once direction. (trachea and respiratory bronchus).
What 3 structures cover the lateral surface of the epithelia and explain them?
•Desmosomes:
Adhesive spots on lateral sidesInvolves proteins called cadherins
•Tight junctions:
Plasma membrane of adjacent cells fuseNothing passes(GI tract doesn’t let enzymes from gut into blood stream)
•Gap junction:
Present in many locationsLets small molecules pass(cardiac muscle tissue)
What structures cover the glandular epithelia and explain them?
Secrete wide range of products: Hormones Enzymes Milk Sweat Mucousoil
Aggregates of epithelial cells clustered together to perform specific secretory or excretory function.
Define the differences between exocrine and endocrine glands?
•Exocrine
Pour products into ducts that open into lumen of organ or onto the skin
•Endocrine
Have no duct system – ductless glands – secrete into empty tissues spaces – eventually enter blood stream
Define and explain the 3 secretory mechanisms?
Merocrine
e.g. salivary gland – secretion passes from cells without damage to plasma membrane – exocytosisMost glands secrete this way
Holocrine
e.g. sebaceous gland – cellular debris part of secretion (sebum)Involves death of the cell
Apocrine
e.g. mammary gland
Apical end pinched off
Describe the epithelial membrane?
Thin sheets of flexible tissue that line or cover parts of the body – membranes
What components do epithelial membranes contain?
Epithelial membranes contain epithelium and an underlying connective tissue:
Mucous membranes – digestive system
Serous membranes – body cavities
Cutaneous membrane - skin
Synovial membrane - joints
What does synovial joints contain?
Synovial membranes contain only connective tissues and line the cavities of synovial joints.
Define the differences between serous and mucosa epithelial membranes?
•Serous (serosa) Simple squamous (usually) Resting on thin layer of loose connective tissue Found in body cavities Serous fluid – lubrication
•Mucous (mucosa)
Lines cavities open to outside
Mucus cells/glands lumen of digestive (microvilli), reproductive, respiratory systems (ciliated)
Epithelial cells vary in morphology and function.
