Test 4 - Digestive Flashcards
Generally, what tissue types can be found in the main layers?
- mucosa: stratified squamous epithelium with goblet cells, lamina propria (loose and dense irr. CT), muscularis mucosa (smooth muscle)
- submucosa: dense irregular CT
- muscularis externa: smooth muscle (2 layers: circular muscle and longitudinal muscle)
- adventitia: serous membrane + CT (more adipose/touches organ)
- serosa: serous membrane + CT (touches body cavity/thinner)
What is a specialization located in the tonsils?
lymph nodules
What is the function of the tonsils?
initial response to protect against pathogens
What is parakeratinized epithelium?
cells filled with keratin but don’t lose nucleus and are incompletely keratinized (doesn’t stain as intensely with eosin)
Where is parakeratinized epithelium found?
in the masticatory mucosa lining of the oral cavity
How is the lining of the oral cavity different than integument when it comes to histology?
- it has parakeratinized epithelium
- only has 3 layers (stratum basale/stratum spinosum/stratum superficial)
How would you describe the lips on the facial region versus inside the mouth?
the lips closer to the facial region have more keratinization, which decreases as it goes further inside the mouth
from outside:
keratinized -> parakeratinized -> no keratinization
What is specialized about the mucosal layer of the tongue?
specializations are only on the dorsal surface and has papillae in different area of the tongue
What are the 4 types of papillae?
- circumvallate (back)
- foliate (side)
- fungiform (middle)
- filiform (texture & friction)
Do all papillae on the tongue have taste buds?
No, only the foliate and circumvallate have taste buds
Is taste perception specific to certain regions of the tongue?
No, taste perception is not just for specific regions of the tongue. Papillae have taste buds which contain multiple TRCs that are specific to a certain taste. In other words, taste perception is specific to gustatory cells/TRCs of taste buds and not regions of the tongue
Describe histological and/or physiological features of the tongue, mouth, etc. that assist with taste perception.
The papillae (circumvallate and foliate) have taste buds, which contain taste receptor cells. Moats around circumvallate papillae help trap in tastants from saliva where they enter into the taste bud via microvilli at the taste pore. There are 2 different types of gustatory cells: GPCRS (bitter, sweet, umami) and ion channels (sour, salty).
Which cell secretes enamel?
ameloblasts
What is enamel made up of?
hydroxyapatite (hardest substance in the body)(ectodermal epithelium)
What is the function of enamel?
protect tooth from wear and tear
Which cell secretes cementum?
cementocytes
What is cementum made up of?
bone-like, but avascular (has lacunae and canaliculi)
What is the function of cementum?
helps root tooth into jawbone
Which cell secretes dentin?
odontoblasts
What is dentin made up of?
calcified & hydroxyapatite (mesodermal epithelium)
What is the function of dentin?
hard bulk of tooth
What is gingiva?
masticatory mucosa surrounding neck of tooth (gums)
What is the periodontium?
all tissues attaching tooth to jaw bone
What is the function of the periodontium (4)
- tooth attachment
- tooth support
- bone remodeling
- nutrition of adjacent structures
What issues might arise if someone did not secrete much saliva?
- trouble swallowing
- dental caries
- trouble breaking down carbohydrates
Compare and contrast the secretions of the 3 major salivary glands?
- parotid (all serous)
- submandibular - mixed (mostly serous)
- sublingual - mixed (mostly mucous)
In a mixed gland, describe the setup of the serous and mucous cells.
The mucous doesn’t stain well since it is made up of sugars, but serous secretion will stain darker.
Describe the flow of saliva from the secreting cells to the mouth cavity with changes in epithelium
acinus (simple cuboidal) -> intercalated duct (tall simple cuboidal) -> striated duct (simple columnar) -> excretory duct (stratified cuboidal)
Describe a sphincter
specialization of the muscularis externa that close lumen so things don’t go backwards in the alimentary canal
What type of tissue makes up a sphincter?
smooth muscle tissue
What are the 4 sphincters and their functions?
- pharyngoesophageal: prevents entry of air into esophagus
- pyloric: controls release of chime
- ileocecal valve: prevents reflex of colon contents into small intestine
- internal anal: prevents passage of feces into anal canal
What type of epithelium is in the mucosa of the esophagus?
stratified squamous epithelium (has glands)
Does the esophagus have a muscularis mucosa?
yes it does it is thick at the top mixed with some skeletal muscle (swallowing)
Are there glands in the submucosa of the esophagus?
yes the submucosa as well as the mucosa has glands
Is the histology of the esophagus the same along its entirety?
Muscle at top is thick with skeletal for swallowing but decreases as you go down the esophagus and no skeletal muscle as you get closer to the stomach. Towards the top there are more esophageal glands proper that secrete watery acid and the bottom has more esophageal cardiac glands that make more mucous secretion.
Why does the esophagus not have keratinized epithelium?
In humans it is not keratinized (no exposure to the sun), other animals have a keratinized due to coarse food diet - we do have keratohyaline granules
What might be a good purpose for the esophagus to have the epithelium it has?
stratified squamous is beneficial because there is a lot of abrasion and stress from different foods so this area is thicker
What are the same histological specializations in the stomach regions?
- simple columnar epithelium
- submucosal glands
- 3rd oblique layer of smooth muscle
What are the 3 regions of the stomach?
- cardiac (cardiac glands)
- fundic (has rugae & gastric glands)
- pyloric (pyloric glands)
What are the cell secretion types of the stomach and what do they secrete?
- mucous neck cells: secrete mucus
- chief cells: secrete pepsinogen
- parietal cells: secrete HCL and intrinsic factor
- enteroendocrine (on other slide)
What are the 4 secretions of enteroendocrine cells in the STOMACH?
- somatostatin
- ghrelin (stimulates hormones and appetite sensation)
- VIP
- gastrin (promotes acid production by parietal cells)
What specializations exist in the small intestine mucosal layer and what is their function (5)?
- plicae circulares
- villi
- microvilli
- crypts of Lieberkuhn
- all above aid in absorption by increase in surface area - GALT (immune)
What type of epithelium is in the small intestine?
simple columnar
What are the 5 cell types and their functions in the small intestines?
- Enterocytes: absorption
- Goblet: mucin secreting
- Paneth: maintain mucosal innate immunity
- Enteroendocrine: secrete hormones (CCK, GIP, motilin)
- M cells: antigen transporting cells
What specializations exist in the small intestine submucosa with functions by region?
- Duodenum: has Brunner’s glands in submucosa (alkaline secretion = bicarbonate ions + basic glycoproteins)
- Jejunum: same as duodenum but w/o Brunner’s glands
- Ileum: has Peyer’s patches in mucosa (lymph nodules that protect from pathogens entering into colon), thick mucosa, crypts are hard to see
How does the mucosa of the large intestines differ from that of the small intestine?
- large is smooth lacking microvilli/villi/plicae
- same as s.i.: crypts are present and GALT (but not lymph vessels)/ has goblet cells and simple columnar
- diff as s.i.: has pericryptal fibroblast sheath
Describe submucosa of the large intestine
mainly CT
How does the muscularis externa of the large intestine differ from that of the small intestine?
- teniae coli (longitudinal outer layer that gives appearance of segments)
- haustra - inner circular layer of muscle
What do the enteroendocrine cells secrete in the small intestine?
in all 3 - CCK (fat breakdown0
duo & jej - motilin (increase motilin and increase mobility) - GIP (increase GIP and decrease gut emptying)
Are there any enteroendocrine secretions in the large intestine?
somatostatin & VIP
How would you describe the function of the veriform appendix? What feature does it have to accomplish this?
keep bacteria and pathogens out of large intestine - a lot of lymphatic nodules extending into submucosa
How does the epithelium differ between the 3 zones of the anus?
- colorectal zone: simple columnar
- anal transitional: stratified cuboidal
- squamous zone: stratified squamous (continuous with skin)
What are the functions of the liver (10)?
- exocrine (secrete bile)
- endocrine (secrete plasma proteins)
- storage of glycogen
- synthesis of urea & plasma proteins
- metabolism of cholesterol and fats
- detox
- cleansing of bacteria from blood
- processing steroid hormones, and vitamins A,D,K
- volume reservoir for blood
- catabolism of hemoglobin from recycled erythrocytes
What are the exocrine functions of the liber (2)?1.
Bile:
1. conjugated, degraded waste products returned to intestine for disposal
2. substances that bind metabolites in intestines to aid absorption
What are the endocrine functions of the liver (5)?
- plasma proteins: albumin, globulins
- convert vitamin D to circulating form
- tyroxine (T4) -> T3
- modifies growth hormone
- degrades insulin, glucagon
Describe the histology of classic lobule in the liver.
- based on organization of parenchyma and blood flow
- hexagonal
- central veins at points and triad at center
Describe blood flow through a classic lobule in the liver.
portal vein (pancreas, spleen) + portal artery -> sinusoids -> central vein
Liver parenchyma.
plates of hepatocytes, organized into cords (no lumen that’s why)
Liver stroma.
CT continuous with capsule of Glisson plus everything else (vessels, lymphatics, nerves, bile ducts)
Kupffer cells
- specialized macrophage (MPS for liver and stores iron
- in sinusoids
Ito cells
- macrophage that’s stellate shaped
- in space of Disse
Describe portal lobule in liver.
triangular-shaped with central veins at points and portal triad at the center
Describe liver acinus lobule.
- 2 central veins and 2 portal triads in parallelogram shape
- the central veins are at the poles and triads at the equator
Why is the liver acinus lobule the most useful to pathologists?
because of the correlation between blood perfusion, metabolic activity, and liver pathology
What are some issues that can be detected by looking at the liver acinus lobe? Can severity be detected, and if so, how?
- zone 1 is a metabolic storage such as O2, nutrients, toxins - so it is the first zone to show evidence of metabolic disease or toxicity
- the severity can be detected by the level of necroses in zone 3, if the blood is not reaching zone 3 due to issues in zone 1 it will necrose and help indicate severity
What is the function of the gallbladder?
storage and concentration of bile
How can someone live without a gallbladder?
common hepatic duct directly into duodenum
Out of the typical regions of the digestive system, which one does the galbladder have or not have?
Has: mucosa, muscularis externa, adventita/serosa
No: muscularis mucosa & submucosa
How is the epithelium of the gallbladder different from small intestines?
- no goblet cells in epithelium
- microvilli don’t make brush border
- plicae not present
- bigger muscularis externa
- no submucosa or muscularis
- fingerlike projections aren’t as folded
Describe the pancreas histology in terms of exocrine and endocrine portions?
- exocrine stains darker and looks like parotid glands
- endocrine stains light with H&E
What are the exocrine secretions of the pancreas?
- secretin: stimulates release of bicarbonate
- CCK: stimulates proenzyme production
What are the endocrine secretions of the pancreas?
- glucagon: stimulates liver to breakdown glycogen (increase blood sugar)
- insulin: signals glucose transporters for glucose uptake into cells (decrease blood sugar)
- somatostatin: hematocrin inhibitor
Histologically, how do Type I and Type II diabetes differ in the pancreas?
Type I has evidence of apoptosis of islet cells - Type II has presence of amyloid deposits
Where are the only places you see striated muscle in the digestive system?
esophagus, oral cavity, tongue, anal canal
What is a plexus?
bundle of intersecting nerves (sensory & motor neurons connected by interneurons)
Are submucosal and myenteric plexus located in all organs of the digestive system?
Yes, the enteric plexus made of these two is a complex autonomic nerve that runs from esophagus to anus.
What do you notice about the fxs of simple columnar vs stratified squamous epithelium in the digestive system?
simple columnar - does more absorption and excretion (intestines)
stratified squamous - in areas with high stress and abrasion (esophagus, anus)
What pattern do you notice about secretions by enteroendocrine cells throughout the digestive system?
Hormone secretions that regulate digestion and are found from the esophagus through the colon generally along the base of the epithelium
Did you notice the presence of mucous-secretions along the alimentary canal?
Mucous secretions aid in protection from the acidic contents of the stomach chyme to prevent damage to the epithelium.
What is the purpose of the two opposing groups of the muscularis external?
contractions mix and propel GI tract contents= peristalsis
