Flashcards in Histology of Upper GI Tract: Esophagus and Stomach Deck (84):
3 functions in the GI Tract
swallowing, digestion, absorption
Where does swallowing occur
oral cavity and esophagus
Where does digestion occur
Where does absorption occur
What is the function of villi
increase surface area for absorption
4 Main digestive organs
esophagus, stomach, small intestine, large intestine
4 concentric layers
Where does chemical digestion start
in the stomach
3 features of mucosa
epithelium, lamina propria, muscularis mucosa
3 features of submucosa
connective tissue that contains glands, blood vessels, and nerves
Features of muscularis externa
2/3 layers of smooth muscle
Features of serosa
connective tissue that supports and binds organ to other
Where is the epithelium stratified squamous
oral cavity, esophagus, anal canal
Where is the epithelium simple columnar
stomach, small intestine, large intestine, and rectum
Function of epithelium
selective permeable barrier
transport, digestion, absorption
Function of lamina propria
where vascular supply comes in
lymphatic nodules present
Where is the lamina propria most relevant
small intestine and large intestine
What is the nickname for the lamina propria in small intestine and large intestine
Peyer's Patch and GALT
Function os muscularis mucosae
increases contact area with food
propel and mix food in GI tract
Characteristics of submucosa
dense irregular connective tissue with large blood vessels, lymphatics, and nerves
What organs have glands in their submucosa?
esophagus and duodenum
What are the folds of mucosa/submucosa in the stomach and called?
What are the folds of mucosa/submucosa in the small intestine called?
What is the function of mucosal glands?
increase secretory capacity
What is the function of mucosal villi?
increase the absorptive capacity of digestive tube
What would happen if the mucosa was to acidic?
could lose the function of the mucosa
What is the function of plicae and rugae?
to increase surface area and help with absorption
Where is Meissner's plexus located?
in the submucosa
Where is the Myenteric plexus located?
in the muscularis layer
T/F Only the jejunum and ileum have a meissner's and myenteric plexus?
F, all segments of the GI tract will have both plexi
What are the 2 layers of smooth muscle in the Muscularis Externa
Circular layer and longitudinal layer
What is the function of the circular layer?
contraction reduces the lumen and helps move food and propel food thru the organs
What is the function of the longitudinal layer?
to make the tube shorter and move food thru the tube
What innervation is the voluntary control of the GI tract
Extrinsic (ANS) via sympathetic (decrease motility) and via parasym (increase motility)
What nerve innervates the parasympathetic system
vagus via pelivc splanchnic nerves
What innervation does involuntary control of the GI tract
intrinsic/enteric system through Meissner's plexus and Myenteric plexus
Function of the intrinsic/enteric system
1. peristaltic contractions to move food bolus
2. secretory activity of mucosal/submucosal glands
What is the function of the esophagus
carry food down to stomach via peristaltic contractions
Function of Lower Esophageal Sphincter
when contracting: help prevent reflux and regurgitation of stomach contents
when relaxing: allow food passage and swallowing
Difference between the upper esophagus and lower esophagus
upper part inside the muscularis externa there is skeletal muscle
lower part inside the muscularis externa there is smooth muscle
What is the change in mucosa shape at the gastroesophageal junction?
from stratified squamous to simple columnar
What layer of the esophagus produces lubricant
mucosal and submucosal
What is the function of the upper esophageal sphincter
initiation of swallowing
What is the function of the lower esophageal sphincter
prevent gastric reflux
What occurs with a person has GERD?
change in epithelium to columnar, chronic esophagitis, dysphagia, fibrosis
when abnormal columnar epithelium replaces the stratified squamous epithelium that is normally in distal esophagus
involves esophagus and stomach
involves only stomach
Function of the stomach
chemically process swallowed semisolid fluid
What is orad motility?
area: cardia and upper fundus
function: relaxes the sphincter, holding changer where the food is going to go first
What is caudad motility?
function: contraction and emptying food and putting it into duodenum
secrete gastric juice
What are the 5 major cell types of gastric glands
1. Mucous neck
2. Chief cells
3. Parietal cells
4. Stem cells
5. Gastroenteroendocrine cells
What do mucous cells produce
What is the function of the mucin
- hold a lot of water and make a insoluble gel to make a protective layer
- traps bicarbonate
- neutralize microenvironment
What do chief cells secrete
Function of pepsinogen
proenzyme stored in zymogen and is converted to pepsin in acidic environment
When is pepsinogen stimulated
by feeding, after fasting
What do parietal cells produce
make HCl and Intrinsic Factor
What occurs if you don't make enough intrinsic factor?
wont be able to absorb B12
What occurs if something attacks parietal cells?
can't make HCl and can't absorb B12
destruction of parietal cells causing reduction in hydrochloric acid in gastric juice and less intrinsic factor resultingin B12 deficiency and pernicious anemia
What parasympathetic mediator and what peptide can help stimulate HCl
Acetylcholine and gastrin
Where are Ach and gastrin produced?
enteroendocrine cells of pyloric antrum
Function of Ach in stomach
help secrete HCl
Function of gastrin in stomach
send signal to other cells to upregulate their function to help digestion (upregulate parietal cells)
Where do Helicobactor Pylori thrive?
in the mucus epithelium of the stomach especially pyloric antrum
What are S/S of H. pylori?
peptic ulcers and adenocarcinoma
What is produced by gastoenteroendocrine cells?
What is the largest endocrine organ in the body and why
GI system- because so many gastroenteroendocrine cells that produce peptide hormones
What is secretin
a peptide hormone released by duodenal glands of Lieberkuhn
When is secretin released
when gastric contents enter the duodenum
Function of secretin
- stimulate pancreatic and duodenal bicarbonate and fluid release
- regulate pH of duodenal contents
What occurs when secretin and CCK work together
stimulate growth of exocrine pancreas
What cells does secretin stimualte
chief cells to secrete pepsinogen
What peptide hormones does secretin inhibit
gastrin- to reduce HCl secretion and reduce acidity
What cells produce gastrin
Main functions of gastrin
- stimulate production of HCl in parietal cells
- activate CCK to stimulate gallbladder contraction
What are the 4 peptide hormones
CCK, Glucose-dependent insulinotropic peptide, Motilin, Ghrelin
Function of CCK
in duodenum, stimulate gallbladder contraction and relaxation when protein and fat chyme come thru
Function of glucose dependent insulinotropic peptide
in duodenum, stimulates insulin release when glucose detected in small intestine
Function of Motilin
in upper small intestine, stimulate gastrointestinal motility
Function of Ghrelin
in stomach, stimulates secretion of growth hormone
*increased during fasting triggering hunger by acting in hypothalamic feeding centers