what are the four layers of the digestive tract wall?
muscularis externa (smooth muscle)
Serosa or adventitia
what is the differences between the serosa and adventitia?
serosa is the visceral peritoneum where it covers some organs
adventita is the CT outer layer that surrounds portions of the organs that aren't surrounded by the serosa
inner most later
contains simple columnar epithelium
deep boundary is muscularis mucosae
What is the underlying loose CT of the mucosa called?
may contain glands
contains dense irregular CT
contains the Meissner nerve plexus
where are submuscosal glands found?
esophagus and duodenum
how can you tell which submucosal gland you are looking at between the duodenum and esophagus?
duodenum: simple columnar
esophagus: stratified squamous epithelium
Provides parasympathetic innervation to the muscularis mucosae and mucosa
Meissner nerve plexus ganglion
where is the muscularis externa found?
The muscularis external is what kind of tissue?
Where is the myenteric plexus located?
Between the circular smooth muscle of the muscularis external and the longitudinal smooth muscle of the muscularis extern
What outer layer contains:
visceral peritonenum mesothelium and connective tissue
structures within the peritoneal cavity
What structures within the peritoneal cavity do you have serosa?
most of the small intestine
portion of colon
What outer layer contains:
CT layer only
structures OUTSIDE the peritoneal cavity
what structures outside the peritoneal cavity do you have adventitia
duodenum (portion of)
ascending and descending colon
what is the esophagus lined with?
non-keratinized stratified squamous epithelium
What is the esophagus in the thoracic cavity lined with?
What is the esophagus in the abdominal cavity lined with?
What is characteristic about the mucosa in the esophagus?
found in the proximal and distal portions of the esophagus
What is characteristic about the submucosa in the esophagus
mucus secreting glands throughout the length of the esophagus
*called esophageal glands proper
what is unique about the muscularis externa of the esophagus
Upper third: Skeletal muscle
Middle third: Skeletal and smooth muscle
Lower third: Smooth muscle
where does the abrupt transition from stratified squamous epithelium to simple columnar epithelium with gastric pits occur?
at the gastroespohageal junctions
some absorption takes place in the stomach...what is it of?
Name two functions of the stomach
Secrete mucous to protect stomach lining
Secrete intrinsic factor for absorption of vitamin B12--Important for normal development of cells and RBCs (can cause anemia), also neruological conditions, and intraoral indications of B12 deficiency
four regions of the stomach
Cardia--narrow zone near GE junction
Fundus--upper aspect of the stomach
body--bulk of the stomach
Pylorus--distal region near the gastroduodenal junction
what is the stomach mucosa lined with?
simple columnar mucous secreting epithelium
what is a characteristic feature of the stomach?
the gastric pits
epithelium invaginate into the underlying lamina propria and there are simple branched gastric glands at the base
what is the submucosa in the stomach made of and what does it contain
dense irregular CT
Meissner nerve plexus
what is unique about the stomach muscularis externa
it has 3 layers!!
Inner oblique layer
Middle circular layer
Outer longitudinal layer
Does the stomach contain serosa or adventitia?
what shape are the gastric glands?
Simple tubular (with or without branching)
what are the 4 different cell types of the gastric glands?
1.Mucous neck cells
2.Parietal cells (produce HCl and intrinsic factor)—in top of the gland
3.Chief (zymogenic) cells—granular, paler, look like basophils—at the base of the gland—produce pepsinogen
what cells are pale staining, located mainly in the upper third of the gastric glands and secrete muscus?
mucous neck cells
what cells are Large, triangular-shaped, eosinophilic cells, Most conspicuous, Scattered, but most are in the upper half of gland and Secrete hydrochloric acid and intrinsic factor (IF)
what cells are more basophilic than parietal cells and are more abundant near the base of the gastric glands
chief (zymogenic) cells
what cells secrete pepsinogen
chief (zymogenic) cells
Cells Found at base of gastric glands and Secrete gastrin
gastric enteroendocrine cells (G cells)
located in the lamina propria, simple tubular mucous glands, glands are continuous with gastric pits
resembles the cardia but gastric pits are deeper
what do the gastric pits int eh pylorus contain
mucus-secreting simple branched or coiled tubular pyloric glands that are similar to the cardiac glands
plyoric glands secrete
where does the abrupt transition back to intestinal epithelium occur?
plyoric- duodenal junction
project from surface of the intestinal epithelium and cause velvety appearance on inside
___ ____ ____ cells found with microvilli in the intestinal epithelium
simple columnar absorptive
Crypts of Lieberkühn found throughout intestines have no what?
what does the intestinal epithelium contain?
submucosal glands (brunner glands)
functions of the small intestine (4)
Completion of digestion (Enzymes from pancreas and liver and Surface glycocalyx contains enzymes)
Absorption of nutrients
Transportation of chyme and waste
larger permanent folds of mucosa--accordian like folds in the small intestine that increase surface area
finger like projections covered by simple columnar epithelial cells
cores of lamina prepares with lacteals
give folds velvety like surface
Create a visible “brush border” (aka striated border) in the intestines
where are the crypts of luberkuhns found?
at the base of the villi
found throughout the small intestine
what three special cells do the crypts include?
Paneth cells (look like eosinphils and are always at the base of the crypts)
Stem cells (mitotic cells)
Enteroendocrine cells (APUD cells)
dark esoinophillic granules in the crypts of luberkuhn that contain antimicrobial substances
defining characteristics of the duodenum (3)
Numerous broad and tall villi
Fewer Goblet cells
First segment contains submucosal duodenal glands of Brunner (These glands are mucous-secreting, Buffer acidic chyme, Thought to produce hormone urogastrone)
True/False: muscularis mucosa sits directly beneath the crypts of luberkuhns in the duodenum
defining characteristics of the jejunum (3)
Villi are tall
Tall, columnar absorptive cells and interspersed Goblet cells
Does not contain submucosal glands of Brunner
TRUE/FALSE: the jejunum is similar to the duodenum no submucosal glands of Brunner and more Goblet (mucous) cells
Will see more as you go down the intestines
defining characteristics of the ileum (3)
Fewer and shorter villi
Lot of Goblet cells
Peyer patches are prominent (large aggregates of lymph nodules and part of the mucosa-associated lymphoid tissue (MALT) or gut-associated lymphoid tissue (GALT)
What are the defining characteristics of the colon? (4)
No plicae circulares or villi (flatter surface)
No Paneth cells
The outer longitudinal layer of the muscularis externa is arranged into 3 bands called taeniae coli
Haustra are pouch-like folds in the wall of the colon due to contraction of taeniae coli
What color do the goblet cells stains in the colon
where is the appendix located?
it is on the right side of the body and sits on the junctions of the small intestine and colon
in the anorectal junction the cells go from what to what?