Test Three GI Tract Flashcards
What are the four layers of the GI tract
Mucosa and submucosa, muscularis externa and adventitial layer
The mucosa layer is the inner or outer layer
Inner
The mucosa is made up of
Epithelium, lamina propria, and muscularis mucosa
What is the lamina propria
Layer of loose CT where there are blood vessels, lymphoid tissue and glands
What is in the muscularis mucosa
Thin circular layer and thin longitudinal layer of smooth muscle
What is the submucosa
Dense CT made up of collagen, elastic, and reticular fibers and may contain glands and lymphoid nodules
What is the muscularis externa
Inner circular and outer longitudinal layer of smooth muscle
The muscularis externa allows for what type of movement
Parastolic
AKA of adventitial layer
Serosa
What is the adventitial layer
Loose CT with blood vessels, lymph vessels or adipose
Function of adventitial layer
Separate organ from surrounding structures
What are the two different nerve plexus in the GI
Myenteric and submucosal
AKA of myenteric nerve plexus
Auerbach’s
Aka of submucosal nerve plexus
Meissners
Where is the myenteric nerve plexus found
Between the layers of the muscularis externa
Where is the submucosal nerve plexus found
In the submucosa
What is the epithelium in the esophagus
Non keratinized stratified squamous with a few keratohyalin granules
What is the lamina propria like in the esophagus
Loose CT with collagen and elastic fibers and numerous lymphocytes
Are there glands in the lamina propria of the esophagus
Yes and they are mucous secreting glands
What is the muscularis mucosa like in the esophagus
Longitudinal smooth muscle with elastic fibers
What is the submucosa like in the esophagus
Dense CT with collagen and elastic fibers which holds the esophagus in a stellate pattern
What is present in the submucosa of the esophagus
Meissners plexus and mucous secreting glands are present
The upper 1/3 of the muscularis externa in the esophagus is what type of muscle
Skeletal
The lower 1/3 of the muscularis externa in the esophagus is what type of muscle
Smooth
The middle 1/3 of the muscularis externa in the esophagus is what type of muscle
Smooth and skeletal
The adventitia of the esophagus is made up of
Loose CT that connects the esophagus to surrounding structures, covered by serosa
What are the two sphincters in the esophagus
Pharyngeoesophageal and gastroesophageal
What are the type of sphincters in the esophagus
Physiological
What are the four regions in the stomach
Fundus, body, cardia and pylorus
What two parts of the stomach looks the same histologically
Fundus and body
What are the folds called in the stomach
Rugae
Function of rugae
Allows for stomach to stretch
The fundus is normally filled with
Gas
What is the largest part of the stomach
Body
What creates the boundary of the body and the pylorus
Incisive notch
What are the two different sphincters in the stomach
Cardiac/ esophageal and pyloric sphincter
What sphincter in the pylorus is physiological
Cardiac and pyloric
What sphincter in the stomach is anatomical
Pyloric
Function of the stomach
Storage of food, some digestion and absorption
The mucosa of the stomach is made up of
Surface epithelium that invaginates into the lamina propria making gastric pits
Function of gastric pit in the stomach
Increase surface area and increases number of cells
What empties into the gastric pits of the stomach
Branched tubular glands
The lamina propria of the stomach is made up of
Loose CT with lymphoid cells, mast cells and macrophages
The muscularis mucosa in the stomach is made up of
Smooth muscle of inner circular and outer longitudinal
The surface epithelium of the stomach is made up of
Simple columnar
The surface epithelium of the stomach is held together by
Tight junctions
What is also found on the surface epithelium of the stomach
Microvilli to help with absorption
What is scattered amongst the surface epithelium of the stomach
Goblet cells that secrete mucous
Since stomach has an acidic pH what happens to epithelial cells
Live only 2 to 3 days
The mucous granules in the stomach epithelial lining are what in shape
Round to Ovoid, nucleus near basal portion and contain golgi complex and RER
What are the four types of cells found underneath the goblet cells in the fundus of the stomach
Chief cell, parietal cell, mucus neck cell, and APUD cell
Chief cell looks like
Simple cuboidal
Function of chief cell
Secrete pepsinogen through their granules that are near the lumen
What is the inactive form of the enzyme pepsin
Pepsinogen
Function of pepsin
Breakdown protein into amino acids
Where are chief cells found
Lower 1/3 of the gland
Function of parietal cell
Make hydrochloric acid and gastric intrinsic factor
Function of hydrochloric acid
Causes transformation of pepsinogen into pepsin and causes acidity in stomach
Look of parietal cells
Spherical cell wedged between chief cells
Where are mucous neck cells found in the glands of the fundus
Neck of the gland interspersed amongst the parietal cells
Function of mucus neck cells
Secrete mucus to help the stomach be in the acidic environment
Look of mucous neck cell
Flattened basal nuclei and large spherical granules in cytoplasm
Function of chief cell
Tell chief cells we need pepsinogen and tell parietal cells need more HCl
What does APUD mean
Amine precursor uptake and decarboxylation
What is in APUD cells
Basal secretory granules, supranuclear golgi complex and narrow apical region that reaches lumen with microvilli
What is found in cardia of stomach
Shallow gastric pits, lymphoid tissue, mucous cells and few APUD
What transition do you see in cardia
From stratified squamous of esophagus to simple columnar of stomach
Describe look of pylorus of stomach
Very deep pits, simple branched tubular mucus glands in lamina propria that contain mucous neck cells
Function of mucous neck cells in pylorus
Protect the pylorus from autodigestion
What is in submucosa of stomach
Irregular CT with no lymphoid elements, rich in mast cells, lymphocytes, and eosinophils
Muscularis externa of the stomach
Outer longitudinal, middle circular and inner oblique layer of smooth muscle, these all helps with stomach churning
What does adding third oblique muscle layer of the stomach do
Allow the stomach to move more
What are the functions of the small intestine
Digestion, selective absorption, and endocrine function
Where do you see most enzymes released in small intestine
Duodenum
Where does most absorption occur in the small intestine
Jejunum and ileum
What controls the endocrine system in the small intestine
APUD cells
Histologically what parts of small intestine look similar
Jejunum and ileum
What is used to create more surface area of small intestine
Plicae semilunaris, villi, and microvilli
Describe plicae semilunaris in small intestine
Mucosa and submucosa is folded which increases the surface area
Describe microvilli in small intestine
Cytoplasmic extension of cell
Describe villi of small intestine
Projections of mucosa, taking epithelial cells and folding them in order to get more of them per unit space
Where do crypts of lieberkuhn are found
In the small intestine a the base of the villi
What cells are found in crypts of lieberkuhn
Absorptive cells, paneth cells, goblet cells, M cells
What do the absorptive cells look like in crypts of lieberkuhn
Simple columnar cells with basal ovoid nuclei, mitochondria, supranuclear golgi, SER and microvillus brunch border with actin protein core
What holds the absorptive cells together in crypts of lieberkuhn
Tight junctions and desmosomes
Life span of absorptive cells in crypts of lieberkuhn
1 to 2 days
Where are paneth cells located
Base of the crypts of lieberkuhn
Describe paneth cells
Pyramidal in shape, round basal nuclei, eosinophilic granules, RER, golgi, and zinc granules in apical portion
What is in the granules in the paneth cells
IgA and IgG for the regulation of the intestinal flora and lysozyme for the breakdown of bacterial walls
M cells stand for
Microfold cells
Where are M cells found
In the lymphoid nodules of peyer’s patches in the crypts of lieberkuhn
Function of M cells
Pick up foreign material through endocytosis in lumen and transport to lymphoid nodules
What do M cells look like
Numerous invaginations that form pits for lymphocytes and macrophages, no villi, rough nucleus
Describe villi in the small intestine
Simple columnar epithelium, absorptive cells present and APUD cells on surface, brush border
The lamina propria of the villi in the small intestine contain
Blood vessels to absorb carbs and proteins, central lacteal to absorb lipids, and smooth muscle for rymthmic movement
Describe duodenum histologically
Simple columnar epithelium found in crypts and villi
What is found in the submucose of duodenum
Brunners glands -mucous glands
Function of brunners glands
Secrete mucous that has alkaline pH
Is adventicia present in duodenum
Test
Is there a typical muscularis in duodenum
Yes
What is different between duodenum and jejunoileum
Increase number of goblet cells and lymphoid tissue, no brunners glands
Describe lamina propria in jejunoileum
Loose CT with lymphoid tissue that form core of villi
Describe muscularis mucosa in jejunoileum
Inner circular and outer longitudinal layer of smooth muscle
Describe submucosa of jejunoileum
Dense CT with elastic fibers, lymphoid nodules make up peyer’s patches
What are peyer’s patches
GALT and are covered with M cells , contains primary B cells
Describe muscularis externa of jejunoileum
Inner circular and outer longitudinal smooth muscle
What is the appendix
Blind evagination of cecum with mucosal crypts containing lymphoid tissue
Describe epithelium of appendix
Absorptive with few goblet cells, paneth cells, and APUD cells at base of crypts, GALT present
The mucosa of the appendix looks like
Large intestine but no villi
Describe submucosa of appendix
Lymphoid nodules present with germinal centers and adipose tissue
Describe muscularis externa of appendix
Similar to small intestine with inner circular layer and outer longitudinal layer
Function of large intestine
Water reabsorption and mucous production
How is water reabsorbed in the large intestine
Moves sodium out inside large intestine and water will be reabsorbed, directly absorb Na+ and indirectly absorb water
Describe mucosa of large intestine
Smooth with no folds and lacks villi
Describe lamina propria of large intestine
Lymphoid cells, crypts are densely packed with a lot of goblet cells to move fecal matter
Describe muscularis mucosa of large intestine
Inner circular and outer longitudinal smooth muscle
Describe submucosa of large intestine
Loosely arranged with fat and no glands
Describe muscularis externa of large intestine
Completer inner circular muscular layer, longitudinal layer of smooth muscle is incomplete to create tenia coli
What is the tenia coli
One in front of large intestine and two in back and is the layer of the longitudinal muscle
Describe serosa of large intestine
Contains adipose tissue
The anal canal represents the transition zone bc
End of simple columnar and beginning of stratified squamous, non keratinized
Describe mucosa of anal canal
Forms longitudinal folds, which are the rectal columns
What is in the lamina propria of the anal canal
Large veins, hemorrhoidal veins
Describe muscularis mucosa of anal canal
Incomplete
