Lecture 23: Traffic Across Cells: Properties Of Epithelial Cells Flashcards
What is the general form of epithelial tissue?
Cells arranged in continuous sheets in either single or multiple layers
What does epithelial tissue sit on?
A basement membrane
Where does epithelial tissue form?
The boundary between the body’s organs or between the body and the external environment (eg pathway through body is in contact with external environment
Describe the renewal of epithelial tissue?
Epithelial tissue is subject to physical breakdown and injury so it undergoes constant and rapid renewal processes (so transports molecules but is also a barrier)
What 6 key things are epithelial tissue important for?
- Protection
- Filtration
- Secretion
- Absorption
- Excretion
- Neuroendocrine functions
Discuss protection function
Barrier on the skin etc
Discuss filtration function
Epithelial tissue lines blood vessels, capillaries, has a filtration function in the kidneys
Discuss secretion function
Such as saliva, sweat, gastric juices in stomach: requires movement of ions in water
Discuss the absorption process
Get all dietary nutrients from gut, cells absorb carbohydrates (eg glucose) and amino acids and lipids. (Depends on the position in the gut)
Discuss excretion
Epithelial tissue forms urine
Discuss neuroendocrine functions
Epithelial cells can secrete a lot of hormones which regulate other epithelial tissues (example is the secretion of insulin by the beta cells in the pancreas) (are probably more neurotransmitters in the gut than in the brain)
What are the two types of epithelium?
- Covering and lining epithelium
2. Glandular epithelium
Examples of covering and lining epithelium?
Epidermis of skin
Lining of blood vessels and ducts
Lining respiratory, reproductive, urinary and GI tract
(So is a layer you need to move molecules across)
Examples of glandular epithelium?
Secreting portion of glands
Thyroid, adrenal and sweat glands
What is the histological classification of epithelium mean?
Basically the two types of distinctions (which are by arrangement or shapes)
What are the classifications by arrangement of cells into layers?
Simple
Stratified
Pseudostratified
What is a simple arrangement?
One cell layer thick
What is stratified arrangement?
Many cell layers thick
What is Pseudostratified arrangement?
Single layer where all cells don’t reach the apical surface
What are the classifications by shape of surface cells?
Squamous
Cuboidal
Columnar
Transitional
What is the squamous shape?
Flat
What is cuboidal shape?
Cube-shaped
What is columnar shaped?
Tall column
What is a transitional shape?
Shape that varies with tissue stretching
What are the two types of glandular epithelium?
- Exocrine glands
2. Endocrine glands
Where are glandular derived from?
The epithelial cells that sink below the epithelium surface during development
What are exocrine glands?
Cells that secrete substances (sweat, ear wax, saliva, digestive enzymes) onto free surface of epithelial layer
How are exocrine glands connected to the surface?
By tubes (ducts)
Are exocrine glands unicellular or multicellular?
They can be both
What are endocrine glands?
They secrete hormones into the bloodstream (and don’t have ducts)