201 L3 Flashcards
Histology
What are the main functions of epithelia?
Protection
Barrier between external and internal surfaces
Maintain homeostasis
secretion and absorption
Are epithelia vascularised?
No
Epithelia are highly polerised. They have specialisations in the —– and —— surface of the cells. This polerisation can happen when there is ——— or ——— epithelia.
Epithelia are highly polerised. They have specialisations in the apical and basal surface of the cells. This polerisation can happen when there is simple or stratified epithelia.
For pseudostratified epithelia all the cells rest on the ——- ——-, but do not reach the ——-.
For pseudostratified epithelia all the cells rest on the basal lamina, but do not reach the surface.
Columnar cells have an —- nucleus that is usually near the —— end of the cell.
Columnar cells have an oval nucleus that is usually near the basal end of the cell.
What part of the cell are microvilli found?
Apical surface of epithelial cells
What is the function of microvilli?
Short finger-like projections of the cell membrane which increase the contact surface between the epithelial cell and the cavity they line.
Microvilli are primarily found in ———- epithelia that require high level of ——- of ——— between the ——- and the ——– of the cavity.
Microvilli are primarily found in absorptive epithelia that require high level of exchange of substances
between the cytoplasm and the lumen of the cavity
(e.g., intestinal mucosa and proximal tubules
of the kidney)
Microvilli are continuous with the —– ———-.
Cell membrane
What is at the centre of microvilli?
Actin filaments
The —— filaments go down into the —– and connect to the ————- through a specialised
structure called the ——– —.
The actin filaments go down into the cell and connect to the cytoskeleton through a specialised
structure called the terminal web
What interaction may allow the microvilli to produce movement?
Once the actin is in the cytoplasm it can interact with myosin molecules which may produce movement
in the microvilli.
What are stereocilia?
They are long microvilli
Stereocilia do —– have a motile ———– therefore can ——— produce ————. They are found in the ———- and —- ———– where they ——– the ———- ——– for fluid absorption
Stereocilia do not have a motile cytoskeleton therefore can not produce movement. They are found in the epididymis and vas deferens where they increase the surface area for fluid absorption
What is the difference between cilia and microviili?
Cilia have a cytoskeleton contractile apparatus that allows them to beat.
What does the beating motion of cilia function to do?
Beating of the cilia is used to move substances along the lumen of the cavity they line
(e.g., mucous in the respiratory tube, particles or cells).
Where is cilia found in the body?
Respiratory tracts and uterine tubes
What is the cytoskeleton of cilia made up of?
Microtubules
Each cilium has ———– arranged as a
ring of - ———– around a —– in the centre.
The arrangement at the ——– of the body of the ———- is slightly different which
allows the cilia to ——-.
Each cilium has microtubules arranged as a
ring of 9 doublets around a pair in the centre
The arrangement at the bottom of the body
of the microtubules is slightly different which
allows the cilia to beat
What is the difference between the cytoskeleton of microvilli and sterocilia
There is no difference
Microvilli are surrounded by a cell membrane that is ———.
continuous
Why does cilia have a different cytoskeleton to the other 2 specialisations.
Because the cytoskeleton is formed by different structures.
For stratified epithelium the apical specialisations are usually expressed —– the tissue.
The cells at the —– end are producing more cells.
For stratified epithelium the apical specialisations are usually expressed within the tissue.
The cells at the basal end are producing more cells.
Name in order the junctions involved in the apical junctional complex from apical to basal of the cell.
Tight junction - Zonula Occludens
Anchoring junction - Zonula adherens
Desmosome - Macula adherens
What does the Zonula occludens do?
These junctions make the epithelium leak proof - non paracellular transport.
What proteins and filaments are involved in the tight junction?
Occludins, claudins and ZO proteins.
Actin filaments