Prac 2 IMMS - Epithelia Flashcards
What cells are found in the epithelia of the intestines
goblet cells
Which intestine’s epithelia has more goblet cells?
Large intestine
what does the basement mem form
a permeabilty barrier between the epithelium and underlying connective tissue
What are and what do goblet cells do ?
- Single cell glands
2. Produce protective mucus that spreads over the entire surface of the epithelium when secreted
absorbative epithelial cells of intestine called ?
enterocytes
why do enterocytes have microvilli
1 increase SA for absorbtion
2 serve as attatchment sites of exo-enzymes that help digest incoming nutrients
Where in the body are the microvilli especially developed
Gut and kidney tubules
Which stain is the brush border much more visible in with light microscopy
PAS
How many cilia per epithelial cell
300
What do cilia do
- Help to transport mucus which contains inhaled particles towards the throat
- Help to transport the ovum towards the uterus in the uterine tube
Where does simple cuboidal epithelia occur?
Ducts of glands
e.g. Sweat
Saliva
Pancreas
Also in kidney where they form much of the nephron
Where is simple columnar microvillied epithelium found
gut enterocytes
Where is simple columnar ciliated epithelium found
Respiratory tract
Serosa ?
Single layer of squamous epithelial cells
pleural cavities?
thoracic
Peritoneal cavities ?
Abdominal
What are the outer layers of most thoracic and abdominal organs surrounded by?
Single layer of squamous epithelia
How come lungs and intestines can move freely without sticking to each other?
Epithelial layers are kept moist by a watery (SEROUS) exudate
Where is simple squamous epithelia found?
Thoracic cavities
Abdominal Cavities
Alveoli
Lining all blood and lymphatic vessels
Thinnest type of epithelium?
Simple Squamous Epithelium
Describe Simples Squamous Epithelium
single flattened layer of cells with cylindrical or elliptical nuclei whose long axes lie parallel to the bases of the cells.
What does non- keratinising stratified squamous epithelium line?
Mouth Throat oesophagus Anus Vagina
keritinised stratified squamous epithelium forms?
epidermal layer of skin
What is pseudo- stratified epithelium
appears stratified but its closer to simple epithelium
how does non- keratinising stratified squamous epithelium remain moist
secretion of glands
and by a fluid that exudes the layers of cells
Two main layers of skin
Outer epidermis and deeper dermis
what is keratin
a dense protein which fills the cytoplasm of the cells rendering them tough and waterproof.
What happens Once cells are filled with keratin
The cells die and eventaully become detached from the underlying layers and are sloughed off.
How does skin produce keratin
upper layers synthesize a unique collection of proteins that interact with the cytoskeleton of the cells to produce keratin
Example where pseudo-stratified epithelia is found
Trachea
Bronchi
How can you tell that trachea epithelium is pseudo stratified ?
In the contracted state the epithelium appears multi-layered (pseudostratified) but when stretched it is often reduced to single layer of cells.
What are two features of pseudostratified epithelia that distinguish them from stratified epithelia.
- All cells have direct contact with the basement membrane
- The cells are replaced by lateral migration rather than by vertical migration as is the case with stratified epithelia.
Three types of cell junctions
- Desmosomes
- Tight (adherent)
- Gap
What are Exocrine glands
Remain in contact with the surface from which they are derived by means of ducts
What do Exocrine glands do?
secrete fluids, lubricants or digestive enzymes on to the epithelial surface.
3 examples of glands?
- Sweat glands of the skin,
- The salivary glands that produce lubricants and enzymes to digest food
- The glands of the respiratory tract that produce a protective layer of mucus.
what do the serous components in mouth do
Produce enzymes that help to digest food or are concerned with oral hygiene.
What do the mucous elements do?
produce salivary mucus that helps to lubricate the bolus of food enabling it to be swallowed more easily.
mucous staining?
Pale
serous staining?
dark
How are mucus secreting cells organised
mucus-secreting cells are contained in separate acini (clusters) from the serous-secreting cells but occassionally mixed acini are encountered.
Difference in appearance in mucus secreting cells
The nuclei of the serous cells appear round while those of the mucous cells appear flattened and lie at the outside edges of the acini (towards the bases of the cells)
Epithelia structure
A cohesive sheet of cells, with one or more layers resting gone a basement membrane
Three purposes of epithelia & examples
Protection e.g. Skin
Absorption e.g. Gut
Secretion e.g Pancreas
What does simples squamous epithelium line and what is this called?
- inside of blood vessels - endothelium
- outside of lungs - mesothelium
- abdominal organs - peritoneum
Describe simple cuboidal epithelium
Single layer of cells w similar height and width on a basement membrane
central spherical nucleus
Simple cuboidal epithelium lines?
Tubules of kidneys
small ducts e.g. in salivary glands
describe simple columnar epithelium
Singler layer of cells taller than they are wide on a basement membrane
- May or may not have cilia or microvilli
simple columnar epithelium lines?
surface of stomach and SM and uterus
What are microvilli
Microscopic projections on luminal surface of absorptive cells
Function of microvilli
- increase SA = absrobtion of h20 and substances can take place
- intestinal brush border
What are cilia
microscopic motile projections on luminal surface of cells
Fine hair projections - longer than microvilli
How do cilia work
Contain contractile proteins which allows them to rhythmically beat
Example of cilia working
In Respiratory tract - eg trachea
cilia beats to waft the mucus away from lungs towards the larynx
Example of cilia working
In reproductive tract e.g- Fallopian tube
waft fluid and fertilised ovum from ovary towards UTERINE CAVITY- where implantation and pregnancy can occur
Where is stratified epithelial found?
In parts of body that are exposed to frequent frictional (abrasive ) force eg skin mouth oesophagus vagina and cervix
Function of Stratified epithelia
Protective - many layers of cells continually being worn down, worn away cells can be replaced from below
2 types of stratified squamous epithelia
keritinising and non-keritinising
Purpose of non-kerinising squamous epithelia
wet sites where no need for waterproofing - oesophagus
Why does the cytoplasm of non-keritinising squamous epithelia sometime look paler ?
Bc the epithelial cells accumulate glycogen at certian points in the menstrual cycle
Purpose of Stratified squamous keritinised epithelia
Waterproofs skin prevents water moving in and out in wet or dry environments
describe Stratified squamous keritinised epithelia
Same as normal:
Multiple layers of cells on a basement mem
As mature become squamous bc move from basement membrane towards the surface
BUT ALSO
As mature accumulate keratin protein into the cytoplasm - therefore die = dead flat plates of keratin
Describe pseudo-stratified epithelium
Single layer of cells of variable height mimicking multiple layers on a basement mem
All cells in contact with basement mem
Nuclei at different heights = appears as layers even tho not
where is CILIATED PSEUDOSTRATIFIED COLUMNAR EPITHELIUM FOUND
conducting airways- RESPIRATORY EPITHELIUM
Whats the epithelium in bladder called?
UROTHELIUM
Describe urothelium
Looks stratified - but more than one layer in contact with basement mem
but surface layer cells (umbrella cells) are not
urothelium lines?
collecting part of urinary tract
What is basement mem composed of?
several extracellular proteins eg
COLLAGEN IV
FIBRONECTIN
Stain for basement mem
PAS - magenta
“Contact inhibition” of epithelial cells
They grow if not surrounded by neighbours But when in contact stop growing
3 TYPES of epithelial junctions
- Occluding (tight)
- Desmosomes ( Anchoring/ Adherent)
- Gap
Describe occluding junctions
- Band like fusions between cells that are impervious to most molecules
Purpose of occluding junctions
Prevent diffusion between cells
describe desmosomes
Plaques that form physical joins between cells and connect the cytoskeletons of adjacent cells
Purpose of desmosomes
Spread forces across several cells to increase likelyhood of single cells surviving
Describe purpose of gap junctions
Electrical junctions that permit the transfer of small molecules and ions between adjacent epithelial cells = ELECTRICALLY COUPLED