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
What junction is described below:
—– parts of the cell membrane of two ———- cells come in very close contact, just below the —— surface.
The two membranes are held together by ———— ———.
This narrows the extracellular space forming a barrier of ——— between the ——- and
———– ends of the epithelium.
The —– proteins attach the two membranes of the adjacent cells and on the ———— side link to ——- which allows the interaction with the ———— and ———- —.
This allows the
Information to be transmitted to ——– columnar cells
Lipid parts of the cell membrane of two adjacent cells come in very close contact, just below the apical surface.
The two membranes are held together by membrane proteins.
This narrows the extracellular space forming a barrier of diffusion between the apical and basolateral ends of the epithelium.
The link proteins attach the two membranes of the adjacent cells and on the intracellular side link to actin which allows the interaction with the cytoskeleton and terminal web. This allows the
Information to be transmitted to adjacent columnar cells
Where in the body are tight junctions prominent?
Epithelia lining the intestine, bladder, seminiferous testis, liver and pancreas.
What proteins and filaments are involved in Adherens junction?
Cadherins and catenin
actin filaments
What is the function of the adherens junction?
They help the cells stick together and maintain the integrity of the epithelial sheet.
What junction is described below:
On the ———- side ———-hold the membranes
of the two adjacent cells together.
On the ——— side, there is a thin —– of ——— proteins
that go around the ———— of the cell, that provides attachment to contractile
———— filaments that are rich in ———.
They link the ——— of two adjacent epithelial cells.
The ability of ———- to bind to each other requires ———– so the process is highly ———-
The junctions are involved in cell to cell ————.
On the extracellular side cadherins hold the membranes of the two adjacent cells together.
On the intracellular side, there is a thin belt of anchoring proteins that go around the circumference of the cell, that provides attachment to contractile cytoskeleton filaments that are rich in actin.
They link the cytoskeleton of two adjacent epithelial cells.
The ability of cadherins to bind to each other requires calcium so the process is highly regulated.
The junctions are involved in cell to cell remodelling.
What proteins and filaments are involved in desmosomes?
Cadherins
Armadillo/Plakins
Intermediate filaments
What is the funciton of desmosomes?
Provide spots of high level attatchment between cells.
What junction is described below:
The membranes of the cells are not in ———– and are joined together on the ———- side by ———-.
On the ———– side there is an attachment plaque which is linked to the ———— ——- of the ———-.
The membranes of the cells are not in contact and are joined together on the extracellular side by cadherins.
On the intracellular side there is an attachment plaque which is linked to the intermediate filaments of the cytoplasm.
Where are demosomes often found in the body?
The skin epithelial cells and cardiac muscle to protect them from stress forces.
What is the main function of gap junctions?
Communication between adjacent cells.
What proteins are involved in gap junctions?
connexons and connexins
What junction is described below:
These junctions are formed by membrane proteins called ———– which are made up of ———– proteins.
——— are arranged in the cell ———- to form a —— at the centre of the —– junction.
Each cell contributes —– a — junction.
When two cells come together, a —— is formed that connects the ——— of the two cells.
The properties of the ———- proteins forming the ———– determine the function of
the —— junction.
These junctions are formed by membrane proteins called ———– which are made up of ———– proteins.
——— are arranged in the cell ———- to form a —— at the centre of the —– junction.
Each cell contributes —– a — junction.
When two cells come together, a —— is formed that connects the ——— of the two cells.
The properties of the ———- proteins forming the ———– determine the function of
the —— junction.
What junction forms a belt?
Adherens junction
What does the basal end of the epithelium lined with?
Basal lamina
What junctions help the cells attach to the basal lamina?
Hemidesmosomes
The basolateral side of the cell attaches to the ——- ——- through ——— which are able to bind molecules in the — like ——–, —– or —–.
The basolateral side of the cell attaches to the basal lamina through intigrins which are able to bind molecules in the ECM like fibronectin, laminin or collagen.
Sometimes, the basal lamina can be separated into the ——– ——– and the —— ——–.
Below the basal lamina there is another layer of —– that is rich in ——– fibres called the ——— ———-.
Sometimes, the basal lamina can be separated into
the lamina lucida (integrins are here), the lamina densa ( high levels of fibronectin which allows the attachment of basal lamina to the reticular lamina)
Below the basal lamina there is another layer of extracellular matrix that is rich in collagen fibres called the reticular lamina.
What makes up the basement membrane of epithelial cells?
Basal lamina and reticular lamina.
What is the function of the basement membrane?
The basement membrane attaches the epithelia to the underlying connective tissue
The folding in the —– part
of the epithelium ——- the ———- contact between
the ———- tissue and the ————- tissue to make sure that they are kept together
The folding in the basal part
of the epithelium increase the surface contact between
the connective tissue and the epithelium tissue to make sure that they are kept together
Epithelia often contain ——— cells that release their ———- to an ——— ——– or to the ———– body environment.
Epithelia often contain secretory cells that release their secretions to an external cavity or
Surface (exocrine) or to the internal body environment (endocrine).
Secretory specialisations can be either ——— or ———-
Unicellular or multicellular.
At what surface of the cell do the secretions happen?
Apical surface
———- glands are called ——– when they secrete watery solutions, ——— when they secrete mucin or ——– when they produce a mixture of both
Are called serous when they secrete watery solutions (e.g., saliva), mucous when they secrete mucin (a type of glycoprotein), or mixed when they produce a mixture of both
Endocrine glands release ———- into the ——- or ———- fluid.
Endocrine glands
Release hormones into the blood or extracellular fluid.
Unicellular exocrine glands are usually found scattered among other ————
cells and usually secrete ——-.
Unicellular exocrine glands are usually found scattered among other epithelial cells and usually secrete mucin.
What unicellular exocrine gland is found in columnar epithelium that lines the intestines?
Goblet cell
Where are mucus cells found?
In the pseudostratified ciliated columnar epithelium that lines the trachea.
Why is the nucleus of goblet cells found at the basal end?
So the secretions can be together.
What type of glands vary in complexity?
Multicellular exocrine glands
Each multicellular exocrin gland tends to have its own ———.
They originate from the ———–, where there is cell ——– causing the cells to ——– into the underlying ———- tissue and start forming a —— that the secretions are secreted in.
Each multicellular exocrine gland tends to have its own shape.
They originate from the epithelium, where there is cell division causing the cells to migrate into the underlying connective tissue and start forming a cavity that the secretions are secreted in.
What are the glands called when they lose their connection with the cavity and where do they secrete their secretions?
Docterant glands that secrete into the blood stream
If you see cells that are coloured the same as the
Epithelium but are in the connective tissue
That suggests that it is a ——-
Gland
Define the shape of sweat glands.
Simple coiled tubular
What mode of secretion is described below:
Contents are released into the lumen when secretory vesicles fuse with the apical
surface of the cell.
Merocrine secretion
What mode of secretion is described below:
Contents are released into the lumen as parts of the cytoplasm containing the secretory vesicles
Apocrine secretion
What mode of secretion is described below:
The entire secretory cell bursts apart to release the secretions.
Holocrine secretion
What mode of secretion do goblet cells perform?
Melocrine secretion
What mode of secretion do lactiferous glands perform?
Apocrine secretion
What mode of secretion do sebaceoues glands perform?
Holocrine secretion
