Epithelium- Histology

Question 1

define epithelial tissues?

Answer 1

Epithelia are tissues that serve as protective layers and/or secretory components of body organs and systems

Question 2

Whats the function of epithelial tissues?

Answer 2

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.

Question 3

What are the 5 common attributes?

Answer 3

Limited intercellular space
Single or multiple layers of cells
Free apical surfaces
Basement membrane
Epithelia

Question 4

Define Limited intercellular space?

Answer 4

Specialised intercellular junctions hold cell membranes close together – effective barrier – blocks infiltration of fluids between cells.

Question 5

Define Single or multiple layers of cells?

Answer 5

Form linings or coverings. Where diffusion/filtration is important, epithelia is a single layer – where protection e.g. abrasion is needed – multiple layers.

Question 6

Define Free apical surfaces?

Answer 6

All epithelia possess a free apical surface during development or at maturity. The apical surface is where cells of an epithelium face internal lumens.

Question 7

Define Basement membrane?

Answer 7

Basal surface attaches to underlying tissues via basement membrane derived from underlying connective tissue.

Question 8

Define Epithelia?

Answer 8

covering or lining tissues are constantly subjected to wear and tear. Mitotic capability enables repair and regeneration.

Question 9

What are 2 structural characteristics of epithelial tissues?

Answer 9

Cell Layer

• Simple
• Pseudo-stratified
• Striated

Cell Shape

• Squamous
• Cuboidal
• Transitional

Question 10

Define simple epithelial

Answer 10

1 cell thick

Question 11

Define stratified epithelial

Answer 11

Many cells thick but only bottom layer in contact with basement membrane

Question 12

Define pseudo- stratified epithelia

Answer 12

Appear more than 1 cell thick but all ells rest on the basement membrane.

Question 13

Dedine squamous cells?

Answer 13

Flattened cells

Question 14

Define columnar cells?

Answer 14

cells made taller than wide

Question 15

Define cuboidal cells?

Answer 15

Cells similar height width and depth

Question 16

Define transitional cells?

Answer 16

Cells in layers which can change shape when they’re stretched.

Question 17

Give an example of the location of simple squamous?

Answer 17

alveoli and capillaries of lungs

Question 18

Give an example of the location of simple cuboidal?

Answer 18

Kidney tubule

Question 19

Give an example of the location of simple columnar?

Answer 19

Small intestine

Question 20

Give an example of the location of transitional cells?

Answer 20

Urinary tract

Question 21

Give an example of the location of stratified squamous?

Answer 21

Oesophagus

Question 22

Give an example of the location of kertanized stratified squamous?

Answer 22

Skin

Question 23

Give an example of the location of pseudo-stratifed cells?

Answer 23

Trachea, nasal muscosa

Question 24

Give an example of the location of stratified cuboidal?

Answer 24

Sweat glands duct

Question 25

Give an example of the location of stratified columnar ?

Answer 25

Salivary gland duct

Question 26

What is the cutaneous membrane

Answer 26

The skin covering the outer surface of the body

Question 27

Define and explain the 2 serous membranes

Answer 27

Parietal layer- Attaches to the body

Visceral Layer- Attaches to organs.

Question 28

What is the cavity known as that covers in between the pleura|?

Answer 28

Pleural space

Question 29

What 2 structures cover the basal surface of the epithelia and explain them?

Answer 29

•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

Question 30

What 2 structures cover the apical surface of the epithelia and explain them?

Answer 30

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).

Question 31

What 3 structures cover the lateral surface of the epithelia and explain them?

Answer 31

•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)

Question 32

What structures cover the glandular epithelia and explain them?

Answer 32

Secrete wide range of products:
Hormones
Enzymes
Milk
Sweat
Mucousoil

Aggregates of epithelial cells clustered together to perform specific secretory or excretory function.

Question 33

Define the differences between exocrine and endocrine glands?

Answer 33

•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

Question 34

Define and explain the 3 secretory mechanisms?

Answer 34

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

Question 35

Describe the epithelial membrane?

Answer 35

Thin sheets of flexible tissue that line or cover parts of the body – membranes

Question 36

What components do epithelial membranes contain?

Answer 36

Epithelial membranes contain epithelium and an underlying connective tissue:

Mucous membranes – digestive system
Serous membranes – body cavities
Cutaneous membrane - skin
Synovial membrane - joints

Question 37

What does synovial joints contain?

Answer 37

Synovial membranes contain only connective tissues and line the cavities of synovial joints.

Question 38

Define the differences between serous and mucosa epithelial membranes?

Answer 38

•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.