Histology of the GI Glands Flashcards
In general, what are the digestive glands good for?
lubricating, protecting, digestive, absorptive stuff mediated by their secretory products
what are the three main digestive glands?
major salivary glands –> associated with the oral cavity through independent excretory ducts (parotid, submandibular, sublingual)
exocrine pancreas –> secretes alkaline aqueous and enzymatic product to the duodenum
liver - endocrine and exocrine gland with extensive access to blood circulation
Exocrine glands have two parts, what are they and what do they do?
what’s the umbrella term that combines both of these together?
an acinus and a duct
acinus = circular organized sac of secretory cells that synthesize and release product (mucous or serous based, or even mixed)
Duct - conducting passageway for product to be released.
Salivon –> which also include the intercalated duct + Striated Duct + excretory duct
Salivary glands, what are they controlled by and what do they produce?
how are these salivary glands divided and what is important about these besides simply dividing?
what goes in between these lobules through the connective tissue septa?
ANS to produce saliva
the gland as a whole is surrounded by a connective tissue capsule.
the capsule extends into the gland dividing into lobes by Septa (interloper septa) and even smaller lobules (interlobular septa)
they are a route for neurovasculature
Saliva functions? (4)
lubricates oral mucosa for speech and digestive purposes
has enzymes that assist with antimicrobial function.
mineralize the teeth after tooth eruption.
also aids in digestion of food via enzymes.
What are the different types of acinus glands in the oral cavity?
Mucous Acini –> very pale pink to white staining
Serous Acini –> exact opposite, intensely hot pink/dark pink/red
Mucoserous Acini (mixed) –> components where you see mucous acini surrounded by a serous demilune (yellow) (hat or bonnet of serous cells that sit on the boundary)
myoepithelial cells?
located between epithelial cells and basal lamina; assist in moving secretory products towards the excretory duct
pathway of saliva flow? include the cell type of each.
what is most commonly seen in the excretory duct?
Acinus –> Intercalated duct –> Striated duct –> Excretory Duct
goes from Acinus –> low simple cuboidal epithelium –> simple cuboidal to columnar epithelium –> simple cuboidal to pseudo stratified columnar or stratified cuboidal
Excretory duct is most commonly stratified cuboidal but other options are seen
Which cell has the largest length of excretory duct?
largest length of striated duct?
largest intercalated duct?
Sublingual
Submandibular
Parotid
What are the parotid glands?
3 hallmarks?
largest salivary gland, that are serous only! (HM)
You’ll see a variable amount of adipose tissue! (HM)
CN VII (facial nerve) passes through! (HM) –> damage this and you’ll have facial paralysis.
intensely pink to reddish because of serous acini present.
What kind of cell shapes are in the parotid glands?
what is seen at their basal region?
they have pyramidal cells with a basally located nucleus
super prominent RER at their basal region.
What is the sublingual gland?
predominantly mucous, but mixed! so you’ll see a large majority of mucous. (HM)
they are separate from the serous acini.. they’re not mixed like the mucoserous.. so won’t see demilunes!
here in the sublingual gland, you won’t see a good capsule but still see the CT dividing it into lobes and lobules.
Submandibular gland?
what specific cell type do you also see in this section?
SEROUS cells are predominant (HM) but mucous also present
also you have serous demilunes (bonnet) (HM)! Its a centralized core with a little hat of the serous demilune sitting on top.
myoepithelial cells to control serous secretions to squeeze and mix stuff.
The pancreas?
what exocrine function does it have?
Which do we care about?
what divides it and surrounds it?
large glands with endocrine and exocrine functions, but bulk of glands is exocrine.
exocrine –> secrete zymogens that are needed to aide digestion
there’s a thin layer of loose CT that forms the capsule, and it divides gland into lobules, and just like the septa, neurovasculature travels within it too.
What is the functional unit of the exocrine pancreas?
What does this make up?
what is the other cell type of the pancreas to know?
serous acinus –> contains PANCREATIC ACINAR CELLS (which secrete zymogens) –> stain intensely
the serous acinus cells surround the acinus, and then you have the intercalated duct that projects out into the duodenum, but there are cells that extend down into the core of the acinus which is unique… these are called centroacinar cells
centroacinar are the boundary from the true acinus to the intercalated duct.
centroacinar cells are responsible for secreting HCO3, Na+, H20 to neutralize secretions
What do Pancreatic Acinar Cells do?
fact about dietary intake?
package up zymogen granules needed to digest the four macromolecules.
if you eat a high protein diet, your amount of synthesis of proteases goes up compared to someone who has high carb diet.
if you transition your diet, the enzymes transition accordingly
Trypsinogen?
Amylolytic enzymes (a-amylase)?
Lipases?
Deoxyribonuclease?
digest proteins
digests carbs
digests lipids
digests nucleic acids
Hallmark for a pancreas histo slide?
pancreas as a whole is usually very hot pink. and you see these little pockets where the islands are less staining and faintly staining (which are endocrine). that’s how you identify the pancreas
How do you distinguish parotid glands with pancreas?
Islets are the way to distinguish. parotids DO NOT have any islets.. instead you’ll find adipose tissue in parotid glands
The liver classic organization?
what is the major cell type?
what are 3 functions of these?
the liver is organized into octaganal shaped lobules structures. the cell types that comprise the liver are hepatocytes.
the hepatocytes are organized into cellular “cords”.. so you will NOT see an acinar structure, it’ll be In cords.
they function in metabolism, storage, and bile production (exocrine)
What is the blood supply to the liver?
which is oxygenated, which isn’t?
portal vein (80%) –> transports deoxygenated blood from GI tract, spleen, and pancreas
Hepatic artery (20%) –> oxygenated from systemic circulation.
how does the classic definition of the liver work with blood supply? (octagonal structure)
there’s a central large structure (central vein) and on the outer periphery we have the delivery of the portal system via the branch of the hepatic portal vein and a branch of the hepatic artery.
these both mix and drain into sinusoids, which is exposed to the lining of the hepatocytes and drains back out the central vein –> sublobular veins –> IVC
so goes from outer to the inner.
what’s good to know about hepatocytes and bile?
hepatocytes in these cords have exocrine function which is to produce bile. this bile goes in the opposite direction that the blood does.
they drain away from the central vein (in a tube called the bile canaliculus) to go to right and left hepatic bile duct –> hepatic duct –> common bile duct –> gallbladder
hepatocytes.. what do they look like?
large, polygonal cells. Many are binucleate and some even tetraploid (have a lot of DNA then).
hallmark = have a ton of organelles dedicated to metabolism and breaking down of toxins (peroxisomes, lysosomes, extensive sER, large Golgi)
Secrete bile (which is a mix of water and bile salts). bile drains into a tube called the bile canaliculus
What should you know about the bile canaliculus?
what happens if you have less bile?
functions of bile?
it’s lined with cholangiocytes.
these join up to contribute to to the biliary tree
loose stools because more fat is in there not able to be absorbed
emulsification of fats, fat absorption, excretion of cholesterol, bilirubin, iron, copper
What is the general orientation the octagonal structure?
this is called the “classic lobule bounded by the portal triad”
we have hepatocytes arranged in cords (1 cell thick)… interspersed between are sinusoids.
blood comes in from the branches of hepatic portal vein and hepatic artery come in, it mixes, and when it flows through the sinusoids it’s exposed to the hepatocytes so they can absorb nutrients and toxins (from the diet) .
they metabolize it to break it down but also making lipoproteins, albumins, etc and bile and that bile is collected in the canaliculus (draining tube), and it drains into the bile duct.
What is the periportal space (space of Mall)?
space located at the edges of the canals between stromal CT and hepatocytes
so there’s an enwrapping of the portal triad and between the space of the hepatocyte and that connective tissue wrapping is the space of mall. that’s where LYMPH is collected, pulled into lymphatic vessels and drained out of the liver!
What is the perisinusoidal space of disse?
sinusoids have an endothelial lining and in this case it’s discontinuous.. but the hepatocytes still have a cell boundary and there’s a gap between there.
so its the site of exchange of material between blood and liver.
this is the site of the material exchange from stuff coming in to feed into the hepatocytes and releasing lipoproteins into the blood supply too.
it looks like there’s a whole lot of nothing in it, a bunch of junk.
What are hepatic sinusoids?
what cell type would you see here that is kind of a hallmark?
thin discontinuous epithelium with discontinuous basal lamina.
super large fenestra to allow exchange to occur
Kupffer cell = macrophage based cell and it functions like a macrophage but its specific. it monitors the age and composition of red blood cells.
they’re the hallmark to hepatic sinusoids
How do we categorize the functional liver (favoring exocrine)
through the portal lobule –> draw imaginary lines between 3 central veins and that’s it. it’s like a triangle.
Outlines bile drainage pathway from adjacent lobules into the same bile duct. the bile duct will be in the core. the hepatocytes within this triangle drain to that bile duct.
this is best if you only care about exocrine function
Clinically, which is the best acinus? (functional liver again, but best for the clinic)
Liver acinus –> draw a diamond from one central vein to another.
in the center of that diamond perpendicular to the central veins are 2 sets of the portal triads. (making the sides of the diamond)
as they move away from the portal triad is zone 1, 2, 3.
cells in zone 1 will be exposed to the highest amount of nutrients and oxygen, but also the highest amount of toxins.
zone 3 has the least toxins + least oxygen.
if someone cut off blood supply to the liver, which zone of the liver acinus would be most impaired first?
what if most sensitive to toxins?
3! because the blood supply is already super low and deoxygenated, so cutting off blood supply would be awful. (3 is most sensitive to ischemic events)
1! because the highest toxins is exposed to cells in zone 1.
Classic Hepatic vs. Portal vs. Hepatic Acinus, which one is for which?
Classic = structural
Portal = Exocrine function
Acinus = clinical (blood)
Gallbladder
what does it look like under the microscope?
what kind of epithelium?
does it have muscle?
does it have adventitia or serosa?
Sac like structure that concentrates bile
SUPER highly folded mucosa because it needs to expand when its full. (looks like villi)
lined with simple columnar epithelium.
lined with muscular to maintain tension and release components that have been stored.
gallbladder has BOTH AN ADVENTITIA AND SEROSA depending on where its exposed
adventitia is found where the gallbladder is against the liver. serosa where it’s exposed to the peritoneal cavity
What are Rokitansky-Aschoff Sinuses?
deep diverticula of mucosa that extend into the muscular external layer.
what happens if they increase your risk for chronic inflammation so increased risk for developing gallstones.
Acinar cells vs centroacinar cells, what kind of staining would you see?
acinar = intense staining centroacinar = stain lightly
Of the portal triad, histologically which is biggest and which is smallest
Portal vein –> Hepatic Artery –> Bile Duct
from largest to smallest
