Tissues (epithelia) Flashcards
Name the 4 main types of tissue
- Epithelia
- Connective
- Muscle
- Nerve
What is the PRIMARY role of epithelia?
To cover surfaces
Name the three features of epithelia that allow them to cover surfaces
- No contact inhibition
- Cell-cell junctions
- Cell- extracellular matrix junctions
What is meant by “no contact inhibition”
Contact inhibition is a process of arresting cell growth when cells come in contact with each other. As a result, normal cells stop proliferating when they form a monolayer in a culture dish.
Epithelial cells lack contact inhibition which allows them to cover surfaces
Name the 4 different types of cell-cell junction found in epithelial cells
- Tight junctions (a network of claudins and other proteins which seal adjacent epithelial cells and limit the passage of molecules and ions)
- Desmosomes (specialized adhesive protein complexes which adhere the epithelial cell to other cells)
- Gap junctions (channels between adjacent animal cells which enable intercellular communication)
- Intercalated disks (adhere heart muscle cells to one another)
Name the cell-extracellular matrix junctions which attach epithelial cells to the basement membrane
Hemidesmosome
Name 5 other roles of epithelia (other than covering surfaces)
- To form glands and separate compartments
- To withstand wear and tear (thick epithelium e.g. on palms of hands)
- To facilitate diffusion
- Movement (cilia)
- Absorption
What are cilia made from?
Cilia are made from a 9 + 2 arrangement of microtubules
What is epithelium?
The epithelia inside of structures (e.g. inside a blood vessel)
Name the type of epithelia
Simple squamous epithelia
Name the type of epithelia
Simple cuboidal epithelia
Name the type of epithelia
Simple columnar epithelia
Name the type of epithelia
Stratified squamous epithelia
Name the type of epithelia
Stratified cuboidal epithelia
Name the type of epithelia
Stratified columnar epithelia
Name the type of epithelia
Stratified transitional epithelia
Name the type of epithelia
Pseudostratified columnar epithelia
Where are transitional epithelia found?
Transitional epithelia are only found in the bladder. The top layer of cells can expand and become very flat when the bladder is full.
Provide three examples of where pseudostratified columnar epithelium would be found
Found in trachea and bronchi and fallopian tube
What are glands made of?
Secretory epithelial cells
Name a single celled gland
`Goblet cell
Where do exocrine glands secrete into?
Exocrine glands secrete into tubes/ducts
Where do endocrine glands secrete into?
Endocrine glands secrete into the blood
Where do exocrine glands originate from and how do they grow?
Exocrine glands originate from the epithelium and grow downwards
Name the two different types of exocrine gland
- Simple (tubular OR acinar)
- Compound (Tubuloacinar- both tubular and acinar)
Name the two types of exocrine secretion
Mucous and serous
What is a mucous secretion?
A secretion rich in proteoglycans (proteoglycan= a protein + a carbohydrate)
This secretion + water gives mucus
What is a serous solution?
Serous exocrine glands secrete a watery, protein rich secretion filled with enzymes
Name a serous exocrine gland
Exocrine pancreas
Name a mucous exocrine gland
Mucous glands of the trachea
Explain the three different methods of secretion
- Merocrine gland remains whole and small vehicles are secreted by exocytosis into the lumen.
- Apocrine gland- A small part of the gland containing the secretion is pinched off and secreted into the lumen
- Holocrine gland- the whole gland containing the secretion disintegrates and becomes the secretion and then the gland regenerates.
What is a myoepithelial cell? What is it’s function?
Muscular type cells that sit around the outside of the acini (round, multicellular gland) that help the secretion leave the lumen. They squeeze the acini (gland) and facilitate the release of the gland’s secretion.
List 5 ways in which epithelial glands can function abnormally
- over-proliferation
- under-proliferation
- over-secretion
- under-secretion
- loss of cilia / ciliary beat
