L29. Alimentary Canal Flashcards
Describe the tubular portion of the GI tract
mucosa muscularis mucosae submucosa muscularis externa adventitia
Describe the mucosa layer
- endodermally derived
- loose CT with lymphoid nodes
Describe the musclaris mucosae
contains smooth muscle
Describe the submucosa layer
dense irregular CT
Meissner nerve plexus (autonomic ganglia)
Describe the Muscularis Externa
- regulates peristalsis
- has an inner circular and outer longitudinal layer
- smooth muscle : has a thickening at the eosphogal/cardiac and duodenal/pyloric opening : sphinctors that control the flow of lumen
Describe the adventitia layer
- thinlayer of CT
- simple squamous epithelial covering
- may or may not attach to abdominal wall and contains blood vessels and nerves
Describe the esophagus
- conduit that links the pharynx with the stomach
- does not participate in absorption or secretion
Describe the different layers of the esophagus
Mucosal: stratified squamous epithelial (non-keratinized), protective
Lamina propria: loose CT
Submucosal: dense irregular CT, secrete seromucous (to lubricate and has anti-bacterial properties)
Adventitia:skeleal muscles needed for swallowing(top portion) lower portion: involuntary required for peristalsis
Describe the mucosal layer of the stomach
- apically secretes acids,enzymes and mucous
- basally secretes paracrine release factors
- simple columnar epithelium with depressions =gastric glands
- has rugae(transient gastric mucosal folds) that flatten when stomach is full
What is Barette’s Syndrome
when your cardiac sphincter muscles doesn’t work, loads of acid reflux causes the tissues in the esophagus to be changed to stomach tissue
Describe the gastro-esophageal junction
abrupt transition from stratified squamous to columnar epithelium
separated by cardiac sphinctor
name the different types of stomach cells
- stomach lining cells
- regenerative cells
- mucous neck cells
- oxyntic parietal cells
- zymogenic chief cells
- enteroendocrine cells (DNES/APUD)
What is the function of stomach lining cell
produce some protective mucus
What is the function of regenerative cell
contains stem cells has proliferative ability
What is the function of mucous neck cells
like goblet cells produce a lot of protective mucus
What is the function of oxyntic parietal cells
secretes acid /HCL (synthesis of acids similar to RBC)
What is the function of zymogenic chief cells
secretes pepsinogen apically
pepsinogen is inactive and will be activated by acid in the stomach
lots of RER
What is the function of enteroendocrine cells
secretes peptides basally acts as paracrine or endocrine factors (paracrine:gastrin and endocrine:VIP)
What is the function of VIP endocrine factor
VIP (vasoactive intestinal pepide) increases peristalsis of intestine
What is the function of the gastrin paracrine factor
increases parietal cell acid secretion and relaxes pyloric sphinctor muscle
release of chyme into the duodenum
Describe the gastro-duodenal junction
thickening of the smooth muscles of the muscularis externa =pyloric sphinctor
Describe the small intestine
- has digestive function: facilitated by enzymes secreted from the pancrease
- absorptive function: increased surface area for absorption through mucosal projections (villi) and depressions (crypts)
Describe the epithelium of the small intestine
- contains goblet cells that secrete mucous
- absorptive cells : enterocytes
- anti-bacterial cells: paneth cells
- simple columnar cells
Describe the lamina propria of the small intestine
- loose connective tissue
- prominent MALT
- many vascular capillaries and lacteals
Describe the Paneth cells
- eosinophilic secretory vesicles
- released apically, contains anti-bacterial lysosyme
- can become antigen presenting cells , founds deep within the crypts at their base
Describe the submucosa of the small intestine
- contains Brunner gland
- Brunner gland is an exocrine gland that secretes alkaline mucous that protects and neutralize acid entering small intestine
Describe the large intestine
- highly absorptive for water and ions
2. contains enterocytes and goblet cells
Describe the mucosa layer of the large intestine
- Absorptive
2. crypts and glands are present but have no vili
Describe the epithelium layer of the large intestine
simple columnar, has enterocytes with goblet cells
Describe the submucosa layer of the large intestine
dense irregular connective tissue no Brunner gland
Describe the m. externa of the large intestine
external - skeletal muscles
internal - smooth muscles
terminal thickening: anal sphincters
Describe the epithelial transition at the recto-anal junction
-metaplastic can change from simple columnar to stratified squamous at the divison
What is the pectinate line at the recto-anal junction
congenital malformations can occur: site where the epithelium from the endoderm and ectoderm fuse
Describe the 2 anal sphincters at the recto-anal junction
- superior internal sphincter: smooth muscle
- external sphincter: skeletal muscle : voluntary control
Describe hemorrhoidal veins in the recto-anal junction
-at the mucosal and submucosal CT there are large diameter hemorrhoidal veins
What happens to the hemorrhoidal veins when a person has hemorrhoids
veins are swollen and bulge in the recto-anal canal ( due to poor venous return to the hepatic portal vein; worsens due to hypertension)
