9/24 Histology of digestive system Flashcards
what is the general type of epithelium in the oral cavity?
stratified squamous: both deratinized (ortho and para) and non-keratininzed
what is the embriological origin of the oral cavity
derived from ectoderm, like skin, not endoderm like the rest of the gut
what is the average turn over of the stratified squamous of the oral cavity
1-2 weeks
the underlying connective tissue
lamina propria
How and why is there a large immune pressence in the oral cavity
many lymphocytes and the tonsils, 3X10^9 PMNs enter lamina propria everyday, and small mixeed sero/mucous salivary glands. all to take care of small immune responses to the large number of pathogens in the mouth
what covers the back of the toungue
lymphatic tissue, and the palatine tonsil
the structure near the back of the tounge wear most taste happens
circumvallate papilla
the structures on the majority of the dorsal surface of the toungue that taste
fungiform papilla
the structures of the dorsal of the tounge that cover most of the surface
filiform papilla
The layers of the tounge in the microscope
stratisfied epithelium; loose or dense connective tissue (lamina prpria) then striated skeletal muscle and adipose tissue
why do you have skeletal muscle tissue in the tounge
moves food back, and requeired for normal speech. arranged in all kinds of orientations
The most common form of cell on the dorsal surface of the tounge
filiform papillae
the moat that surrounds the circumvallate papillae
crypt
why does the circumvallate papillae have crypt
has glandular structures to wash material out to allow constant tasting of new things
the glands that wash out the crypt
Von Ebner’s gland: serous glands, they appear as globular structure in the connective tissue with ducts associated with the crypt
what is the purpose of saliva
lubricate the mouth w/mucous secretion. amylase in serous secretion (digest carbs). Helps prevent infection!
purpose of the salivary glands
Make saliva; get infected (mumps, and impacted ducts); growth factors; make haptocorrin.
how does salive act as defensive agent?
secrete lactoferrin (iron binding protien against bacteria), lysozyme (desolve bacteria cell walls), and defensins (anti-biotic protiens) and transport IgA (binds to pathogens)
what is haptocorrin?
a vitamin B12 binding protein
why would the saliva produce growth factors?
maybe to promote wound healing in the mouth and in other parts of the body when you lick wounds
cells that secrete in a serous fashion and are a spherical gland
Serous acinus
Glands that produce mucous
mucous tubule
combinded serous and mucous cells in a singe duct
mucous tubule and serous demilune
the course of mucous and serous once produced form serous acinus/demilune and mucous tubule
glands connected to intercalated ducts, striated ducts, and interlobular ducts
what ducts are found in the parenchyma of the secretory units
the glands and the intercalated ducts and striated ducts are in the parenchyma of the glands
the section of the duct that is in the stroma
the interlobular ducts
ducts in the stroma or connective tissue
interlobular ducts
what do the smooth muscle aorudn the interlobular duct do
Myoepithelial cells contract to push out saliva
what type of cells are the intercalated ducts
cuboidal cells
type of cells in striated duct
colomnar
describe the histological appearence of the serous secreting cells (serous demilune)
they are in a semi-circle of dark staining cells with prominate nucleus connected to a light stained area of duct
describe the histological appearance of the mucous secreting cells
they are light staining cells along the ducts with no clear nucleus
need special staining of anti-myosin to see well
the myoepithelial cells that squeez out the spit
describe the intercalated duct
cuboidal
describe the striated ducts
colomnar cells
how does striated duct cells control hemiostasis
recover sodium and chloride from the saliva, but don’t really recover much water, use a Na,K-ATPase to pump
histology of the interlobular ducts
may even be stratified columnar, surrounded by dense irregular connective tissue.
what is the general plan of the gut?
4 layers!
what are the 4 layers of the general plan of the gut?
Mucosa; Submucosa; Muscularis externa; Serosa (adventitia)
what are the layers of the mucosa?
the epithelium, lamina propria, musclaris mucosae
what are the sublayers of the muscularis externa?
circular muscle, myenteric plexus (nerves); longitudinal muscle
how does the mucosa change from the stomach to the intestine to the colon?
stomach has no villus, but has pits, intestine has villus, colon has no villi and no pits.
describe the mucosa layer of the gut
epithelium, lamina propria is hard to see, lined with muscularis mucosa at the bottom of the epithelium
describe the submucosa layer of the gut
dense irregular CT, large vessels; sumbucosal enteric nerve plexus (hard to see)
describe the muscularis externa layer of the gut
smooth muscle of 2 layers (inner circular, outher longitudinal); enteric plexus beween muscle layers (control motility)
describe the serosa or adventitia layer of the gut
connective tissue, when covered with mesothelium its a serosa, retroperitoneal organs can have both.
Unique Esophagus component in the submucosa
Esophageal glands
what is the purpose of esophageal glands?
add secretions that help food slide down the tube, and make the esophagus look different from the vagina tissue!
why is the fourth layer in the esophagus adventitia and not serosa
it doesn’t have a layer of mesothelium
what is the muscle in the esophagus?
at the top it is striated skeletal muscle and then it blends into smooth muscle and at the bottom it is just smooth muscle in the lower third
how do we know that the muscle in the upper 1/3 of esophagus is striated skeletal
large cells of muscle with nucleus on the outside
what are the functional muscles that contract or relax to alow food to pass?
the upper and lower esophageal sphincters.
how is the lower esophageal sphincter controlled?
it is a smooth muscle sphincter, that is tonically contracted and must be relaxes for material to enter the stomach
what are the characteristic structure seen in the epithelium of the stomach
Pits, necks (start of glands), glands, base (end of glands)
describe the junction of the esophagus/stomach
very sudden switch form stratisfied to simple colomnar
what causes heartburn?
lower esophageal sphincter fails to keep stomach acid out of the esophagus, causing pain.
what happens if common heart burn damages the epithelium
esophagitis
when chronic esophagitis
Gastro-Esophageal Reflux Disease or GERD
increased risk of dysplasia and esophageal cancer
chronic GERD, and barrett esophagus!
how is the barratt epithelium different?
it is red due to a lack of the stratisfied layers (now simple!)
replacement of stratified squamous non-keratinized epithelium by mostly simple colomnar epithelium with lots of goblet cells (looks like colon)
what is the general path to esophageal cancer?
Chronic inflammation; Mataplasia; balance of tumor suppressors and promoters
newer model of the development of barret’s esophagus…
residual embryonic cells invade and migrate up the esophagus after acid reflux lead to metaplasia of colon like cells.
what are the four anatomical regions of the stomach
cardia; fundus; body; pylorus
what are the three histological divisions of the stomach
the cardia; the body/fundus; and the pylorus cells
how do we tell the difference between cardia/body/pylorus cells in the stomach
cardia: pit and glands have about the same length;
Body: pit is a bit shorter than the glands
Pylorus: pit is much longer than the glands
what do you often see where there is a transition between different epithelial layers
lymphatic agrigates (blobs of dark staining cells)
what does the light staining fo the cardia glands tell us
they are producing mostly mucus
what are the light and dark colored cells in the body and fundus of the stomach located just below the glands in the epithelium
the parietal and chief cells!
how is the stem cell unusual in the stomach?
the stem cells are found in the top of the glands! maybe to replace the very short lived pit cells above them?
what are the three regions of the gland in the stomach epithelium?
the isthmus, the neck, the base.
what is the life span of a pit cell?
about 3 days to a week
what is the life span of a gland cell?
week to a month
the body cells are also called:
Gastric epithelium
the cells that line the pits:
Suface mucus cells
the cells in the glands that are large, pale cytoplasm with central nucleaus (fried eggs!)
the Parietal cells
the cells that make mucus in the glands, stuck between the parietal and chief cells
the neck mucous cells;
the cells that are dark staining in the glandular region of the epithelium of the body of the stomach (like dark fried eggs)
Chief cells
hormone producing cells in the stomach
Enteroendocrine cells
Amine precursor uptake and decarboxylation
APUD enteroendocrine cells
what is the DNES?
the diffuse Neuroendocrine system
Enteroendocrine cells in the stomach produce what?
gastrin (yellow cells!), glucagon, histamine, somatostatin, serotonin and gherlin
stimulates hunger if not enough food in stomach
gherlin
stimulate parietal cells to secrete HCl
gastrin
Cells that produce acid
Parietal cells
how do parietal cells secrete acid?
through H+,K+ - ATPase
what stimulates the release of parietal cell acid
several agents including gastrin and histamine
how do the parietal cells control release of acid
they have membrane bound tubules with the proton pump that fuse with the plasma membrane to allow the release of the HCl acid
the only critical function of the stomach, a function of the parietal cells
gastric intrinsic factor for vitamin B12 absorption
what if lose GIF producing parietal cells
lose the absorption of B12 and then get pernicious anemia
describe the movement of acid out of parietal cells
On Lumen: ATP pump moves protons out and Cl- pore facilitate diffusion to give HCl;
On Blood vessel side: pump HCO- out and Cl- into the cell.
where does the H+ and the Cl- come from in the gastric parietal cell?
the Cl- is pumped in from the blood using HCO-/Cl- pump. The H+ is from CO2 and H2O forming H2CO3 using carbonic anydrase, that is carbonic acid and releases the H+
Control of parietal cell acid secretion
from vegus nerve, enteroendocrine cells, etc. a veriety of different controls
cephalic phase
when just think about or anticipate food the vegus nerve stimulates the release of acid.
stiumuli to produce acid include?
smell, taste, cinditioning, distension, amino acids, small peptides etc.
Phases of acid secretory control
Cephalic phase (see or think aobut food) Gastric phase (distension etc). Intestinal phase (inhibits when digesting food)
Chief cells!!
found in the bottom of the glands, secrete pepsinogen and gastric lipase
the other names of chief cells
peptic cells or incorrectly zymogenic cells
the mucus that is produced by the mucus cells is critical, why is that?
it traps bicarbonate, and provides a barrier to acid coming into the cells, provides physical barrier for the pepsin attacking the cells.
why would stress H. pylore, or smoking/alcohol or pharmaceuticals lead to damage of the cells in the stomach
breaks down the mucus and leads to pepsin and acid damage
How can we discriminate the Plexis in the muscularis externa and serosa
the nerves can be detected due to the light staining in the middle of the dark staining of the muscle
the enteric plexi and the vegas nerve seem to influence what kind of movement in the stomach?
Gastric movements that churn the stomach contents and then spurt out 10ml of contents or so into the duodenum
what are the 2 basic patterns of GI motility?
paristalisis or contraction of smooth muscle waves to activly move material down the length of the intestine;;; or segmental contractions that squich and release the contents and mix it up and down the intestine – you get a balance of these two movements
what does the muscosal barrier protect the epithelium from
acid and proteases like pepsin both a diffusion and a chemical barrier
what if the mucus in broken down
ulcer
what if the mucus is broken and break down the muscular mucosa into the submucosal, what do you have?
peptic ulcer
treatment with antiacids is not as effective as other ulcer treatment such as:
antibiotic against H. pilore and anti-histimines etc.
gastric adenocarcinoma is dangerous, but why?
it is very asymptomatic and very difficult to detect until it has progressed.
Am I going to get gastric adenocarcinoma?
probably not, rare in N. America and probably because of diet and environement
what is the histology of adenocarcinoma
you can’t decipher the different gland and epithelial cells of the pits and and mucosal layers…all the epithelial cells look the same!
