GI Tract Flashcards
What is the life span of a chief cell?
about a year (long lifespan!)
Where is the primary site for absorption and digestion in the GI tract?
small intestine
Where would you find the parasympathetic motor nerve synapse in regards to the organ?
the ganglia are located very near the effector organ
Why is lipid digestion so drawn out?
it stages the amount of lipid released into the blood at one time to prevent issues from mass amounts of fat being introduced into the bloodstream
The production and secretion of urease ___ gastric pH and ___ acid production.
increases; increases
What are the 5 different classes of gastric glands?
- mucus secreting cells
- acid secreting cells
- pepsin secreting cells
- enteroendocrine cells
- undifferentiated stem cells
Food undergoes mechanical breakdown via muscle activity and chemical breakdown via gastric secretions to form ___.
chyme
The ____ is a small, blind-ended sac that is distal to the ileocecal junction.
appendix
Where would you find undifferentiated stem cells in gastric glands?
in the neck of the gland
Which structure of the rectum contains longitudinal folds called anal columns?
anal canal
How do you distinguish villi from plica circulares in section?
villi - core of lamina propria
plica - core of submucosa
Are anal glands branched, straight, tubular glands?
YES - which secrete mucus
What are the 5 phases of food breakdown?
ingestion fragmentation digestion absorption elimination
The stomach completes ___ and initiates ___ during the first phases of digestion.
fragmentation; digestion
What are APUD cells?
“amine precursor uptake and decarboxylation” cells
____ stimulates the contraction of the gallbladder and the release of bile acids.
CCK
__ cells secrete GIP, or gastric inhibitory peptide.
K
____ are extracellular droplets for transport; ____ are intracellular droplets for transport.
Micelles; chylomicrons
Epithelium of the villi is supported by the connective tissue ____ and contains capillaries and lymphatics for absorption of nutrients.
lamina propria
Where would you find parasympathetic ganglia in the GI tract?
ganglia are located within the walls of the gut organ, within the submucosa and muscularis externa
How often are enterocytes replaced?
every 3-5 days
Peyer’s patches contain both __ and __ cells.
B; T
How can someone decrease their risk of colon cancer?
- increasing fiber in diet
- decreases colon cancer
- by reducing transit time
- and increasing GI motility
What are the pancreatic proteolytic enzymes secreted as?
inactive precursors (zymogens); so, trypsinogen and chymotrypsinogen to prevent autolysis
What is the more technical term for swallowing?
degluttination
___ and ___ promote the secretion of the exocrine pancreas.
Secretin; CCK
What is secreted by G cells?
gastrin
Where are actively dividing stem cells of the small intestine located at the base of?
crypts
What is the inner, third layer of muscle in the muscularis externa of the stomach?
inner oblique
APUD cells are sometimes referred to as ___ cells since they target cells in the local vicinity.
paracrine
What are M-cells responsible for in MALT tissues?
antigen sampling
uptake of macromolecules
____ helps to produce and maintain an optimal pH for the very sensitive enzymes present in the small intestine.
Bicarbonate
___ and ___ amylases hydrolyze starch to disaccharides (sucrose, lactose, maltose, and isomaltose).
Salivary; pancreatic
What is the exit of the GI tract?
anus
Both the fundus and corpus of the stomach are ____ and almost non-discernible histologically.
glandular
What do the mucus secreting cells cover?
luminal surface and upper third of pit
In which mucosal layer might you find large numbers of lymphocytes and plasma cells?
within the lamina propria of the gut mucosa
What is one of the most common problems associated with the stomach?
peptic/gastric ulcers
Enterocytes produce various ____ for absorption of carbohydrates and amino acids.
carrier proteins
A cells secrete ___, which raises blood sugar.
glucagon
What are interspersed among the enterocytes and secrete mucus?
goblet cells
Where are plica circulares especially prominent?
in the jejunum
What are the clusters of parasympathetic ganglia within the submucosa called?
Meissner’s plexus (submucosal plexus)
How would glucose, galactose, or fructose be absorbed in the small intestine?
through facilitated diffusion since these are all monosaccharides
What are the two primary types of actions performed by the muscularis externa?
segmentation and peristalsis
____ is secreted by S cells and inhibits gastric secretions and stimulates smooth muscle contractions.
Secretin
Where are surface mucus cells located?
at the surface of gastric glands
What is the result of ingestion accompanied by fragmentation of food?
a bolus
___ actions in the gut are local contractions only that mix food. They can occur both proximally and distally (both directions).
Segmentation
Is pancreatic lipase water soluble?
YES
What is the brush border coated with?
protective glycocalyx of disaccharides
What are the large numbers of commensal bacteria found in the large intestine called?
coliforms
What are the glands associated with the GI tract?
liver
pancreas
intestinal glands
What type of connective tissue does the submucosa contain? What is its role?
loose to dense connective tissue; supports mucosa and contains larger blood vessels, nerves, and lymphatics
____ project into the lumen of the small intestine and are dome-shaped.
Peyer’s patches
What is the outer layer of the gut, containing a loose connective tissue layer and major nerves, vessels, and adipose tissue?
adventitia (serosa)
Can stem cells of the villi migrate up to replace any type of cell like stomach undifferentiated stem cells?
YES
Why is the term “peptic ulcer” preferred over “gastric ulcer?”
because the majority of these ulcers actually occur in the very first part of the duodenum
What is the most common sign of polyps?
rectal bleeding
How often are mucus secreting cells renewed?
every 3-5 or 4-7 days
How long is the small intestine in humans?
4-6 meters long
What would you find in the duodenum that is not present in the large intestine?
Brunner’s glands
The smooth muscle of the gut is controlled by the ____ nervous system.
autonomic
Where are parietal cells most numerous?
in the middle third of the gastric gland
___ action propels food distally in one direction ONLY with rhythmic contractions.
Peristalsis
____ stimulation is excitatory to the gut; ____ stimulation is inhibitory to the gut.
Parasympathetic; sympathetic
What step is ESSENTIAL to maximize the actions of pancreatic lipase?
emulsification of fat
Are carbohydrates starches?
YES
Does absorption occur in the stomach?
NO - except for water, alcohol, and some drugs
What are the prominent longitudinal folds in the stomach called?
rugae
In the lower third of the esophagus, what type of muscle is the muscularis externa composed of?
smooth muscle only
What do goblet cells synthesize? What is its function?
mucinogen (»mucus); lubricates and protects the epithelium
What secreted product helps delay gastric emptying?
GIP (gastric inhibitory peptide)
The liver, pancreas, and intestinal glands are all ____ of the GI tract.
embryological outgrowths
Where is mucinogen stored in goblet cells?
in membrane bound granules
____ coagulates milk proteins.
Rennin
What do surface mucus cells secrete?
thick insoluble mucus and bicarbonate ions
Enteroendocrine cells are what kind of cell? What do they do?
APUD cells; amine precursor uptake and decarboxylation
What are the 3 layers of mucosa?
epithelium
lamina propria
muscularis mucosae
What is the mesothelium?
the lining of the adventitia (simple squamous epithelium)
What bacteria are peptic ulcers associated with in chronic infections of the stomach?
Helicobacter pylori
What make up the epithelium of the villi?
enterocytes
Are the digested components of proteins and carbohydrates handled similarly in transport by the body?
YES - both transported to portal vein
Is the appendix active in adults?
NO - only in children
Panrcreatic secretions are highly ___. Why?
alkaline; high pH is due to high levels of bicarbonate
How do mucus secreting cells look on H+E staining?
clear
What is one of the cardinal features of Celiac disease?
malabsorption
What inhibits the secretion of gastrin?
somatostatin
What cells would you find in the mucosal epithelium of the small intestine but not in the epithelium of the large intestine?
paneth cells
The ___ of the stomach is surrounded by the smooth muscle cardiac sphnicter (GES) and contains predominantly mucus-secreting glands.
cardia
___ act as emulsifying agents for digestion of lipids, forming micelles.
Bile acids
What are the 3 overall functions of GI mucosa?
protection (barrier)
secretion
absorption
What is the purpose of microvilli? What are they the site of?
increase surface area for absorption; site of membrane digestion (at glycocalyx)
What is the basic process of carbohydrate breakdown?
primary starches»_space; disaccharides (sucrose, lactose, maltose, isomaltose)»_space; monosaccharides (glucose, galactose, fructose)
Where does the lymph eventually carry the chylomicrons to?
to the thoracic duct and eventually into general circulation
What are the two steps to digestion in the duodenum?
- luminal digestion
2. membrane digestion
What constitutes erosion of the stomach?
when there is partial loss of the epithelial lining
What is the purpose of valves of Kerkring?
to increase surface area, slow down speed of food, and contain the submucosal core
When is the adventitia referred to as “serosa?”
when referring to it in regards to the abdominal cavity since the serosa = visceral peritoneum
What shape are gastric glands?
straight, tubular glands
____ cells secrete soluble mucus and are located at the upper third of the gastric pit.
Mucus neck
____ cells secrete a variety of peptide hormones in responses to local factors and control GI motility and gastric secretion.
Enteroendocrine
What are the 3 regions of the stomach?
cardia
fundus
pylorus
The small intestine is ___ in carnivores and ___ in herbivores.
shorter; longer
Can the adventitia merge with retroperitoneal tissue?
YES - this is why it may not be visible as a discreet layer
What is the junction called that separates the esophagus and the opening of the stomach?
gastroesophageal sphincter (at the gastroesophageal junction)
How much of our feces is our own sloughed epithelial cells?
a third
___ cells (epithelium) and ___ glands (submucosa) are found within the large intestine.
Goblet; colonic
The adventitia is continuous with the supporting ___ in the abdominal cavity.
mesentery
Which is grossly visible on the surfaces of mucosa? MALT or Peyer’s patches?
Peyer’s patches
How are proteins initially handled in the digestive tract?
they are initially denatured by HCl from parietal cells, then hydrolyzed by pepsin into polypeptide fragments
Rank the ileum, jejunum, and duodenum from shortest to longest.
duodenum»_space; jejunum»_space; ileum
Why do pepsin secreting cells stain purple?
they have large numbers of ribosomes
As ____ cells mature, they migrate up and down the gastric gland and differentiate into whatever cell type is needed.
undifferentiated stem
What are the larger clusters of ganglia called that are located between the circular and longitudinal muscle layers of the muscularis externa called?
Auerbach’s plexus (myenteric plexus)
Is swallowing voluntary? Why or why not?
YES; it is voluntary because the upper third of the esophagus contains voluntary skeletal muscle
____ is located in the lamina propria ad submucosa of the small intestine, contains plasma cells, and secretes IgA.
MALT
What is the brush border (striated border)?
it is a highly folded structure modified into microvilli
What is the appendix?
it is a vestigial cecum
What does pepsin do?
hydrolyzes protein
What are the parts of the large intestine?
cecum appendix ascending colon transverse colon descending colon rectum
In the duodenum, what do the pancreatic and biliary secretions do to fat?
emulsify it
What is the mucosa covered by?
a thick layer of mucus
Why are these proteolytic enzymes released as inactive precursors?
so the pancreas doesn’t start digesting itself
Which gastric cells secrete insoluble mucus? Which secrete soluble mucus?
surface mucus cells; mucus neck cells
What happens after amino acids and monosaccharides are absorbed by enterocytes lining the villi?
they are transported across the epithelium, enter capillaries within the lamina propria and enter the portal vein to be stored in the liver
The ____ layer consists of inner circular muscle layers and outer longitudinal smooth muscle layers, with the fibers oriented at right angles from each other.
muscularis externa
What does H. pylori produce that raises gastric pH and acid production?
urease
Where are Brunner’s glands located?
in the submucosa of the duodenum
I cells secrete ____, which stimulates pancreatic secretion and contraction of the ___.
cholecystekinin (CCK); gallbladder
How are lipids digested?
emulsified by actions of bile acids
What is secreted by D cells?
somatostatin
Where are chylomicrons transported to?
lacteals
What are intestinal villi lined by?
simple columnar epithelium
At what point of protein digestion can these components be absorbed by enterocytes via active transport by carrier proteins?
when they are digested into small peptides and amino acids
Which cells of the small intestine produce antibacterial proteins called defensins, as well as enzymes such as lysozyme?
paneth cells
Which anal sphincter is voluntary?
external anal sphincter
What are the intrinsic factors of the acid secreting cells necessary for?
this glycoprotein is necessary for the absorption of vitamin B12 from the ileum
Which cells of the gut do not require continuous replacement?
chief cells/peptic cells
What are the spaces called between villi?
crypts of Lieberkuhn
What is the diffuse lymphoid tissue scattered throughout the GI tract?
MALT or GALT
___ stimulates gastric secretions.
Gastrin
____ are large numbers of highly convoluted, branched, tubuloalveolar submucosal glands.
Brunner’s glands
____ digestion involves enzymes of the glycocalyx on the plasma membrane of enterocytes.
Membrane
What are the steps to lipid digestion?
- emulsification by bile acids
- broken down into monoglycerides and fatty acids by pancreatic lipase
- form extracellular micelles
- micelles absorbed by enterocytes
- micelles re-synthesized into triglycerides within cells
- form chylomicrons
- transported to lacteals
The mucosal ___ secretes and absorbs materials to have a variety of functions and is modified differently at each level of the GI tract.
epithelium
Does the large intestine have villi and plicae circulares?
NO
The mucosal ___ is the thin layer of smooth muscle that places a boundary between mucosa and submucosa.
muscularis mucosae
What is responsible for the formation of haustra (sacs) on the large intestine?
the outer longitudinal muscle layer in muscularis externa is reduced or incomplete and forms easily discernible longitudinal strips
What are the main functions of the duodenum?
neutralize gastric acid
neutralize pepsin
(do this with assistance of pancreas and gallbladder)
Contractions of smooth muscle is called ____, like what guides the bolus down the esophagus. Under what control is it under?
peristalsis; autonomic control
What does the secretion of gastrin stimulate?
the secretion of HCl and pepsin
Are there lacteals present in the lamina propria within the crypts of the large intestine?
NO
What are the proteolytic enzymes of pancreatic secretions?
trypsin
chymotrypsin
amylase
lipase
What are the 4 distinct layers of the GI tract?
mucosa
submucosa
muscularis externa
adventitia (serosa)
How many liters of watery gastric juice are secreted per day?
2 L
What constitutes a gastric ulcer?
when the damage extends BELOW the level of the basement membrane and there is associated bleeding
What portion of the stomach secretes acid, pepsin, and some mucus?
fundus
What prominent structures form the entrances to gastric glands in the stomach?
gastric pits OR foveolae
The mucosal ___ is the underlying connective tissue that contains lymphoid nodules, glands, blood vessels, and lymphatics.
lamina propria
____ digests lipids.
Lipase
What are the longitudinal strips on the large intestine called?
tenia coli
What does it mean when something is “pre-neoplastic?”
after repeated trauma, cells begin to become abnormal (can later develop into cancer if left unchecked)
When does the transition from mucosa to simple columnar epithelium to stratified squamous epithelium occur?
at the anal canal
What are some enzymes synthesized by enterocytes?
peptidases
peptide hydrolases
disaccharides
What does “aboral” mean?
to be moved away from the oral cavity
The external anal sphincter contains ___ muscle; the internal anal sphincter contains ___ muscle.
skeletal; smooth
What is the function of APUD cells (enteroendocrine cells) scattered throughout the small intestine?
regulate GI motility and secretion
In the middle third of the esophagus, what type of muscle is the muscularis externa composed of?
skeletal muscle and smooth muscle
In the ___, the resorption of water and elimination of waste occurs.
colon
Does the epithelium of the stomach/GI tract contain blood vessels?
NO
Where are chief cells located at in the gastric gland?
at the base of the gland in the bottom third
The ___ of the stomach contains primarily mucus- and gastrin-secreting glands and controls the outflow of the stomach.
pylorus
Colon cancers are called _____.
adenocarcinomas
What happens when the micelles are absorbed and re-synthesized within enterocytes?
they are coated with proteins and phospholipids to form intracellular chylomicrons
Are polyps generally asymptomatic?
YES
What tissue type does the appendix contain large amounts of?
MALT (active in children)
Anal columns are also called ___.
columns of Morgani
Which anal sphnicter is involuntary?
internal anal sphincter
Are Peyer’s patches and MALT histologically identical?
YES
The ___ contains transverse rectal folds and large numbers of mucus glands.
rectum
What enzymes break down proteins into smaller peptide fragments?
pancreatic enzymes (trypsin) (chymotrypsin) (elastase) (carboxypeptidase)
What do Brunner’s glands secrete, unique to the duodenum?
mucus and zymogens
Where do the pancreatic duct and bile duct empty into?
the duodenum at the major duodenal papilla
____ mucus cells secrete thick, insoluble mucus and bicarbonate ions.
Surface
HCl, pepsinogen (precursor to pepsin), gastrin, rennin, and lipase are all constituents of ____.
gastric juice
What type of epithelium is the esophagus lined by?
stratified squamous nonkeratinized epithelium
What are some alternative names for pepsin secreting cells?
chief cells
peptic cells
zymogenic cells
How are dead cells shed from the villi?
cells migrate up the villus, mature, and then are shed from the tips
Where are paneth cells found?
at the base of crypts of Lieberkuhn
What forms from the actions of pancreatic lipase to break down monoglycerides and fatty acids?
extracellular micelles
In the small intestine, what is the mucosal surface made up of?
villi that contain a core of lamina propria
Which portions of the small intestine accomplish primary absorption of nutrients?
jejunum and ileum
Is vomiting involuntary?
YES
What are some examples of secretory products in the GI tract? What portion of the mucosa secretes these products?
digestive enzymes hormones mucus antibodies; mucosal epithelium
What are the three stages of protein digestion?
- denatured by HCl
- hydrolyzed by pepsin
- further hydrolyzed by pancreatic enzymes
How is an H. pylori infection treated?
“triple therapy” consisting of 2 long-term antibiotics and a proton pump inhibitor
How are monosaccharides absorbed?
by facilitated diffusion
How is pepsinogen converted to pepsin?
by the action of HCl
Trypsin is activated by ____; trypsin then activates ___.
enterokinase; chymotrypsin
Within the anal canal, where do the anal glands extend into?
the submucosa and muscularis externa
What are the valve-like rings or folds called in the small intestine?
plica circulares (valves of Kerkring)
What results from the occasional enlargement and irritation of submucosal veins?
hemorrhoids
What are the primary starches?
polysaccharides
oligosaccharides
disaccharides
____ are benign adenomas/masses in the wall of the colon that protrude into the lumen.
Polyps
In the upper third of the esophagus, what type of muscle is the muscularis externa composed of?
voluntary skeletal muscle
S cells secrete ___, which stimulates release of ___ from the pancreas.
secretin; bicarbonate
What are chylomicrons?
drops of triglycerides coated with proteins and phospholipids
What are our primary sources of lipids to be digested?
triglycerides from diet
____ are blind-ended lymph vessels within the lamina propria of villi.
Lacteals
The epithelium of MALT tissues contains ___, which are squamoid enterocytes modified for antigen sampling and macromolecule uptake.
M-cells (microfold cells)
What does chyme from the stomach stimulate the release of?
stimulates the release of 2 hormones from APUD cells - secretin and CCK
Does MALT in the large intestine form grossly visible patches?
NO
What are two alternative names for acid secreting cells?
parietal cells
oxyntic cells
Which glands are unique to the duodenum?
Brunner’s glands
What are parietal and chief cells controlled by?
autonomic nervous system and hormones from endocrine cells in the region of the pylorus
What area of the stomach is the glandular portion?
fundus
What are the primary functions of the colon?
water and electrolyte resorption (also produces some mucus for waste elimination)
____ is the inactive precursor to pepsin.
Pepsinogen
The mucosal folds in the colon contain a core of ____. How is this different than the cores of plicae circulares?
lamina propria; plicae circulares contain cores of submucosa, NOT lamina propria
Repeated damage to the esophagus can lead to ____, which is a pre-neoplastic condition.
Barrett’s
Why does increasing fiber intake decrease the risk of colon cancer?
because fiber promotes GI motility, decreasing the time that carcinogens may rest against the walls of the colon and cause neoplastic cells to form
What cells secrete pepsin?
chief cells/peptic cells
How often is the entire epithelial lining of the small intestine replaced?
every 3-5 days
What is the technical term for heartburn, that results from the regurgitation of stomach acid into the distal portion of the esophagus from the cardia of the stomach?
pyrosis
What do chief cells secrete?
pepsinogen
Starch is broken down into what?
disaccharides
Which disease causes villus blunting and atrophy, leading to malabsorption and weight loss due to gluten intolerance?
Celiac disease (gluten enteropathy)
What do parietal cells secrete?
HCl and intrinsic factor
Where are foveolae located?
in the body of the stomach
What would we refer to our single-chambered stomach as, especially in the veterinary world?
monogastric
____ digestion involves the mixing of chyme with pancreatic enzymes for molecular breakdown.
Luminal
