Vet histology lecture 10 &11 (Epithelium)
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Group of closely apposing cells of similar morphology with very little intercellular space having a free apical surface and an attached basal surface
Differentiate between epithelium tissue and epitheloid tissue?
Free surface (apical) is missing
Epithelium sits ontop of what shape of connective tissue?
Nipple shaped connective tissue with capillary beds in them
What do you call a hole in the epithelium of the stomach?
A gastric ulcer
What are the 2 MAJOR subdivisions of epithelium?
- Surface epithelium
- Glandular epithelium
Which embryonic germ layers are epithelium derived from?
Epithelium often contacts a what membrane?
Does epithelial tissue have vascularizaqtion?
Nope it is avascular
While epithelium is avascular is it capable of divison?
It is capable of its own mitosis
What is meant by the polarity of epithelial tissue?
It has a free end and a basal end
5 functions of epithelial tissue?
- Covering and protection
- Secretion and excretion
- Selective permeability/barrier
What are the 3 laminas we SEE below the epithelium, describe each briefly
- Lamina lucida - light coloured lamina from the anchorming proteins and hemidesmosomes attaching to the basement membrane
- Lamina densa - The actual basement membrane
- Sub lamina densa - anchoring proteins below the basement membrane probably to connective tissue
3 ways to classify epithelia based on number of cell layers
- Simple - 1
- Stratified - 2 or more
- Psuedostratified - 1 layer but appears to have more than 1
3 ways to classify epithelia based on shape of SURFACE CELLS
Which shape of epithelia is most often stratified?
Where would we most likely find columnar cells?
Layers of keratinized stratified squamous epithelium reflect what kinds of changes in the cell as it gets closer to the skin
Functional changes as it changes functions as it slowly moves up
Why would we not want blood vessels in the epithelium?
Rubbing skin would cause bleeding
The skin comes from which embryonic layer? Digestive lining? Blood vessel lining?
The epithelium is avascular does it have any nerves? If so where?
Yes inbetween cells is where they hide
Differentiate between the epidermis and dermis?
Epidermis is the layer of epithelium sitting ontop of the dermis which is very dense connective tissue underneath that supports hair follicles etc
Who produces the proteins for the lamina lucida?
Can different epithelia fuse?
Yes if they come close enough together and lose their basement membrane it is possible
Can you see the basement membraqne with a light microscope? Why?
- Lots of carbs sticking out from it
Can all shapes of epithelium have surface decorations
An easy way to distinguish the type of cell the epithelium is, is by looking at the shape of the nucleus explain.
The shape of the nucleus follows the shape of the cell but is easier to see, for example columnar cells have long columny shaped nuclei and squamous have flattened ones
What is the name of the simple squamous epithelium lining all the blood vessels
Endothelium because it is special cause it covers all the blood vessels
What are the simple squamous cells lining the outside of an organ called?
Wher ein the body do we see pseudo stratified epithelium
Where we need multiple jobs done, such as cilia and secretion
Transitional epithelium is the what?
Stratified cuboidal epithelium in the bladder that stretches and goes from tall to multilayered flat cells as the bladder fills
Stratified squamous at the top of the skin layers are living or dead cells? What is the term of the process of gluing all the dieing cells together?
Other than skin where else would we see keratinized stratified squamous epithelium
In the esophagus of the cow
In keratinized stratified squamous epithelium what is the most basal bottom mitotic layer called?
starting from the stratum spinosum name the layers as we go up the skin.
- Stratum spinosum - mitotic
- Stratum spinosa - desmosomes (spiny layer)
- Granulosum - granules
- Keratoline - Producing keratin
- Stratum lucidum - dead cells light coloured
- St corneum - darkened dead cells ontop
What are 3 ways we classify glands?
- Morphological characterisistics
- nature of secretory product
- Mose of release of product
Differentiate between glandular epithelium and a gland
- Secretory cells of glands consitutue glandular epithelium
- A gland is glandular epithelium, duct system, and supportive connective tissue
What is the parenchyma? The stroma?
- Parenchymna is the combination of the functional portion of the gland, including glandular epithelium and duct system
- The stroma is only the supportive connective tissue
a lobe of a gland is further divided up into different tiers of?
Are glands always their own unique tissue?
No they can be imbedded into other tissues
What is smaller than a lobule of a gland?
What are myoepitheliel cells?
Epithelial cells that take the place of muscle cells andf contract to allow secretory units to secrete
Small ducts are often lined with what kind of epithelial cells? (shape) what about larger ducts?
- Squamous epithelial
- Cuboidal epithelial
The stroma contains not only supportive tissue such as collaghen fibers etc but what to bring life to the gland?
What are the 3 shapes of the secretory units that we can classify the glands by?
Which shape fo the secretory unit has a very small lumen?
What is the most common type of shape?
Tubulo acinar Combination shape
Mucus producing cells stain what colour?
Clear and light
Serous producing or protein producing cells stain wghat colour?
Dark under H&E
What is a cell that produces both serous and mucus secretions?
Describe the list and the order you should go in to classify a gland
- Presence/absence of branching patterns
- Shape of secretory units
- Number of cells
- Chemical nature of secretory product
- MOde of release fo secretory product
Differentiate between endocrine and exocrine glands?
Exocrine have a duct system where as endocrine and have no duirect way to secrete
What are 2 general shapes of the endocrine gland?
- Chords and clumps
- Follicle - band of cells on the outside of a completely locked lumen
Does the mucus cell actually produce a fully watery mucus?
No it produces a tough sticky carbohydrate substance that will later be added to water to create the mucus we know and love
Are simple glands often discernible with the naked eye?
Nope usually if you can see it it is compound
Describe the glands based on branching of duct system and secretory units
- Compund - branching of duct system and automatically implies branched
- Branched - branching of the secretory unit
- Simple - not compound
Note: if not branched and simple just omit the branched portion do not refer to as not branched
Ducts found within the lobule are reffered to as? Ducts found between lobules are reffered to as?
- Intralobular ducts
- Interlobular ducts
Which ducts are more likely to be simple epithelia, intra or interlobular ducts? Why?
Intra because within lobules and presumably smaller
Larger ducts tend to have what kind of epithelial lining?
Stratified and possibly cuboidal
LECTURE 11 IS A GOOD LECTURE TO READ OVER AGAIN JUST TO SEE PICTURES AND BE ABLE TO IDENTIFY, MANY OF THE MORPHOLOGIES ARE BETTER SEEN
goblet cells are shaped like what?
in a goblet cell is there a lot of cytoplasm and nucleus?
No the secretory areas grow and take over like 90% of the cell
What are the 2 ways a gland can be classified based on # of cells?
Unicellular or multicellular
2 ways to classify the gland based on what it is secreting? How do they look differently?
- Serous secretions and mucus secretions
- Mucus are clear, serous are very darkly stained
an interlobular duct will be found in what kinds of tissues? what about intralobular?
Connective tissues within the actual secretory tissues
In an interlobular duct how can you tell it apart from a blood vessel?
Blood vessel has simple squamous epithelium while a duct has cuboidal epithelium
2 ways to classify glands based on modes of release of products?
Diferentiate between merocrine and apocrine release
- apocrine will have blebs on the surface of the cells because it is often and more lipophilic molecule and needs to be surrounded by a container and is essentially pinched off with cytoplasm and cell membrane
- Merocrine is basically simple exocytosis
Why would cells ever practise holocrine release?
Because sticky dense materials don't just release well they cant really leave so cell sacrifices
Where do you find myoepithelial cells?
Sitting ontop of the secretory units like a octopus
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