Flashcards in Esophagus and Stomach Deck (44)
What are the four layers of the digestive tract from inward to outward?
3. Muscularis externa
4. Serosa / Adventitia (Fibrosa)
What are the layers of the mucosa and their properties?
1. Epithelium - SSNK or simple columnar
2. Lamina propria. LCT + diffuse or nodular lymphatic tissue called GALT, maybe containing mucosl glands
3. Muscularis mucosae - Thin layer of smooth muscle, with inner circular and outer longitudinal components.
What is the submucosa of the digestive tract? Where does it contain glands?
Dense irregular connective tissue with blood vessels, lymphatics, and nerves. Contains ganglion cells of the submucosal or Meissner's plexus.
It contains glands in the esophagus and duodenum only.
What is the muscularis externa? What type and arrangement of muscles is it?
Two muscle layers normally: inner circular and outer longitudinal. Smooth muscle except in beginning of esophagus and end of anal canal
3 layers in stomach - inner oblique added
Contains Ganglia of myenteric (Auerbach's) plexus
What is the myenteric / Auerbach's plexus?
Plexus found between layers of muscularis externa. The ganglia are found here and are a component of the intrinsic enteric autonomic nervous system
- Regulate peristalsis and secretory functions of mucosa and submucosal glands
What is the serosa / adventitia layer of the digestive tract?
Serosa (peritoneal) - outer layer of CT covered by a simple squamous mesothelium
Adventitia (fibrosa) (retroperitoneal) - no mesothelial covering when retroperitoneal, just CT
What is definitive about the lining of the oropharynx?
1. SSNK epithelium
2. Prominent elastic layer in lamina propria that sends fibers to anchor mucosa into muscle layer
3. Submucosa typically not present
4. Has an adventitia (not peritoneal)
What is definitive about the mucosa of the esophagus?
1. SSNK epithelium
2. Mucosal or cardiac glands near ends of esophagus in lamina propria
3. Muscularis mucosae is a single, well-developed layer of longitudinally oriented smooth msucle
What is distinctive about the submucosa of the esophagus?
Has esophageal glands proper - submucosal glands.
They are compound tubuloalveolar glands, which are mostly mucous, but are some serous cells that produce LYSOZYME
How does the muscularis externa of the esophagus change travelling downward?
Upper third is skeleton, transitions to smooth muscle by lower third. (Voluntary to involuntary swallowing)
What happens at the esophagogastric junction in terms of the epithelium?
There is an abrupt change from stratified squamous nonkeratinized to simple columnar
What are the three histological regions of the stomach?
1. Cardiac stomach - contains cardiac glands
2. Fundic stomach - gastric or funduic glands
3. Pyloric stomach - pyloric glands
What are rugae?
TEMPORARY longitudinal folds of the SUBMUCOSA present in stomach, for expansion / filling
What are mammillated or gastric areas of the stomach?
Small, bulging areas of the stomach which represent thickened mucosa, for increased surface area for secretion.
What are gastric pits?
Indentations or holes in mucosa which mucosal glands of the stomach empty into.
What characterizes the surface epithelium of the stomach and what is its function?
Simple columnar epithelium which covers surface and gastric pits with surface mucous cells. They produce a thick, cloudy mucus which has a high bicarbonate content to protect the epithelium from acidic damage
Where do the mucosal glands of the stomach lie?
In the lamina propria of the mucous layer. includes cardiac, gastric, and pyloric.
What characterizes the muscularis mucosae of the esophagus / stomach?
It is deep to the glands, but has smooth muscle projections between the glands to contract and empty the glands
What are the layers of the muscularis externa of the stomach and its general function? Where is the myenteric plexus found here?
Inner oblique, middle circular, outer longitudinal. They function to contract and homogenize food as the gastric secretions are added, creating chyme.
Myenteric plexus: between circle and longitudinal layers
What are the two staining areas of gastric glands and what accounts for this?
Upper portion: eosinophilic - parietal cells
Lower portion: basophilic - chief cells
What cells are found primary in the neck area of gastric glands + their function?
Mucous neck cells - produce a soluble mucinogen which is different than surface mucous cells
Parietal cells - Acidophilic cells which secrete HCl and produce gastric intrinsic factor
What is the appearance of parietal cells and why?
They contain intracellular canaliculi which are deep plasma membrane invaginations. Increases SA for secretion of HCL. They also have abundant mitochondria to make them look eosinophilic.
How do parietal cells produce HCl? This is convoluted
Through carbonic anhydrase, which converts water and CO2 into H+ and HCO3-. Active cells have tubulovesicular membranes which contain H+,K+ ATPase that fuse with plasma membrane to increase intracellular canaliculi.
Anion exchanger pumps out bicarbonate and brings in Cl-. Cl- is channeled out by passive transport.
K+ is brought into the cell by Na+ / K+ ATPase, allowed to diffuse into lumen to be used in H+ / K+ ATPase exchanger, to bring K+ back in and pump out H+.
The H+ and Cl- are ultimately released into the gland, while NaHCO3 is in the lamina propria.
What happens to inactive parietal cells?
An increase in cytoplasmic tubulovesicular membrane system, with canaliculi retracted back into the cytoplasm
What stimulates HCl secretion by parietal cells?
Gastrin, acetylcholine, and histamine
What is gastric intrinsic factor?
Glycoprotein produced by parietal cells which complexes with vitamin B12, which is necessary for small intestinal absoprtion
How is heartburn treated?
Histamine receptor antagonists, which competitively inhibit histamine receptors which stimulate parietal cells
What would happen if gastric intrinsic factor was not produced?
Lack of B12 uptake and subsequent anemia
Why are chief cells basophilic?
Because they have lots of rough ER and prominent golgi complexes for the production of pepsinogen granules