Epithelium Flashcards
What is the function of epithelial tissue?
- Protects underlying tissue from injury
- Prevents loss of fluid from underlying tissue
- prevents bacterial invasion
What is epithelium?
Group of tissues that cover body
What is epithelium made up of ?
And what can the be?
Packed cells
- single layer
- multi layer
What is epithelium specialised to do?
To from a lining / covering for ALL internal and external structures
Where can specialised epithelium he found?
Lining of cavities
Lining of tubes
In glands
What is the early layers of epithelium called?
Embryo germ layer
How many embryo germ layers does a human have? And what is this called?
3
Tribloblastic
What is the first layer of embryo germ layer?
Endoderm - outer
Describe the endoderm layer
- inner layer
- provides epithelial lining to 2 majors tubes; digestive and respiratory
What is the second layer of embryo germ layer?
Mesoderm
Describe the mesoderm layer
Middle layer Where body’s internal organs are found Gives rise too; - muscle - blood - connections tissue - dentine - cementum
What is the third layer of embryo germ layer?
Ectoderm - outer
Describe the ectoderm layer
Outer layer
Gives rise to;
- central nervous system
- skin
- enamel
What is the structure of epithelium ?
Cells closely packed together
Lie on basement membrane
Matrix is minimal
Receives nourishment from underlying connect tissue eg. Blood
What are the 2 types of epithelial tissue ?
Simple epithelium
Stratified epithelium
What are the 4 types of simple epithelium?
Squamous
Columnar
Cuboidal
Ciliated
Where are the types of simple epithelium found?
Usually In absorptive and secretory areas.
Not in areas subject to stress
Describe squamous epithelium
Single layer
Closely fit together / slot together = smooth inactive lining
Where is simple squamous epithelium found?
Blood vessels
Lining of body cavities
Alveoli of lungs
Describe simple cuboidal epithelium
Fit closely together on basement membrane
Cubed shaped
What is simple cuboidal epithelium involved in?
Absorption
Secretory
Excretion
What does simple cuboidal epithelium from?
Some glands (eg. Salivary) Kidney tubules
Describe simple columnar epithelium
Single layer
Elongated in shape
Height greater than width
What does simple columnar epithelium line?
Line organs
Alimentary tract
Ducts of glands (salivary glands)
Why is simple columnar epithelium specialised?
Had modified cells - releases goblet cells
What does a goblet cell do and where is it found
Secretes mucous
In simple columnar epithelium
Describe ciliated columnar epithelium
Has fine like hair processes called Cilla only seen on edge of the cells / free surface of cells.
Where is cilia found?
On the edge of cells of free surface of cells
In columnar epithelium
What does cilia do?
Fine hair like processes
Has beating action (one direction only)
Propels contents of tube - respiratory epithelium.
What is ciliated epithelium covered In? And what does it do?
Mucous - traps minute dust particles, propels towards opening of cavity - action done by cilia
What is a hemidesmosomes and what do they do
Specialised juncting complexes
Enables cells to adhere to eachother
What are hemi-demosomes called when they join
Demosomes
Where are hemi-demosomes found?
Cell membrane of epithelial cells OR
Between epithelial and connective tissue
What do heno-desmosomes have?
Tonifibrils
What do tonofibrils do?
Cause thickening of cell wall
Radiate into cytoplasm
Describe stratified / compound epithelium & it’s function
Several layers
Superficial layers grow up from below
Basement membrane usually absent
Protects underlying structures