Tubular Gut Flashcards
(85 cards)
Describe the embryonic germ layer from which the epithelium, glands, CT and muscle are derived.
epithelum + BM - endoderm
lamina propria (LCT) - mesoderm
glands - endoderm (open to lumen)
muscularis mucosa - mesoderm
submucosa - mesoderm
muscularis externa - mesoderm
serosa/adventitia - mesoderm
cell bodies of Meissner’s and Auerbach’s - neural crest
What is the intrinsic nervous system of GI tract and what is the extrinsic nervous system –how are they related.
Intrinsic NS - enteric nervous system (ENS)
Extrinsic NS - ANS
What are the names of the two ganglionic plexuses and what structures (neurons/fiber types) are found within each ganglionic plexuses.
Where is each plexus located within the wall and what is the function of each plexus.
Meissner’s plexus - submucosa; control fluid, gland secretion, muscularis mucosa movement
Auerbach’s plexus - muscularis externa; control smooth muscles for peristalsis, mixing, segmentation
both have ENS and ANS (parasympathetic postgangionic (vagus), sympathetic nerve (splanchnic), and visceral afferent fibers)
How will the function of the GI tract be impacted if Neural crest cells fail to migrate (hint: think about the structure in the GI tract to which
they give rise to)
The GI tract wouldn’t be able to function as the cell bodies in the ganglia of Meissner’s and Auerbach’s are derived from neural crest cells
Which of the 4 layers,
mucosa, submucosa, muscularis externa, or serosa will demonstrate the most variation in histological structure. How does the variation in structure
impact function
The epithelium of mucosa exhibits the most variation of all layers due to different functions of protection, absorption, or secretion
What tissue layer gives rise to colorectal polyps.
mucosal lining (occurs from a development as an abnormal proliferation)
Where would you expect to find Brunner’s (submucosal) glands in the highest numbers. Explain the physiological significance of having Brunner’s glands in high numbers in this part of the tubular gut
proximal part of the duodenum (1st and 2nd) near pyloric sphincter due to high amount of acid from stomach. glands secrete alkaline mucus rich in bicarbonate to neutralize chyme and facilitate activation of pancreatic enzymes
What structure (ducts) opens into the second part of the duodenum and what is the anatomical significance of the duct opening into this part of small intestine. What products are released from this from this duct and how is the activity of this product dependent on Brunner’s glands.
common bile and pancreatic duct open in the 2nd part of the duodenum and bile & pancreatic enzymes are released into the lumen of the duodenum
What type of neuron cell bodies are found within the submucosal (Meissner’s) and myenteric (Auerbach’s) plexuses – be specific ??? i.e Somatic efferent; somatic afferent ; visceral efferent, visceral afferent
visceral efferent and visceral afferent (ANS from vagal and splanchnic, ENS, and visceral afferent from sensory receptors)
How can you histologically distinguish between Auerbach’s vs Meissner’s’ plexus when viewed at high power
Meissners: visible collagen fibers, in submucosa, DICT surrounding large neuron cell bodies
Auerbach’s: in b/w layers of muscle in muscularis externa, large nuclei of ganglion nerve cells
What is the name of the multicellular exocrine glands found within the wall of jejunum –and what layer are these glands located
Crypts of lieberkuhn - lamina propria
What is name of the cell that represents a unicellular exocrine gland that is also found in the jejunum ? When do these cells first appear and where along the tubular gut are these cells located? Where do they appear in highest numbers ?
Goblet cells -> increase in number as you move distally as they lubricate mucosa to bind digested food together for ease of passage
What are the key histological features that may be used to distinguish between the duodenum and ileum for these two tissue sections?
Duodenum: Brunner’s glands
Ileum: Peyer’s parches, Paneth cells, large lacteals, no submucosal glands
What is name for the epithelial cell that is responsible for nutrient absorption in small intestine ? What is the significance of pancreatic enzymes being released in response to chyme entering the duodenum. (hint: pancreatic enzymes activate the enterocytes to start digestive process. )
Enterocytes produce and secrete enterokinase and activate pancreatic proteolytic enzymes
What parts of the tubular gut have submucosal glands, which have only mucosal glands? Which parts have both types of glands? What do the submucosal glands secrete –what about the mucosal glands –is it dependent on type of cells found in mucosal glands?
submucosal: esophagus, duodenum
musocal: esophagus, stomach, small intestine, large intestine
What layer of the wall will be most useful for identifying the level from which the tissue section of the esophagus has been taken and why?
muscularis externa
What product is secreted by parietal, chief, mucus neck, enteroendocrine in stomach and in which specific layer of the gut wall are these cells found? Which region will exhibit the highest number and therefore be the easiest region in which to identify these cells?
all in mucosa (highest glands in fundic)
parietal: HCl and IF (IF is necessary for vit B12 absorption and loss can lead to faulty RBC synthesis and anemia)
chief: pepsinogen (active), pepsin is activated in stomach by HCl and necessary for protein digestion
mucus: line epithelial surface (alkaline to protect against self digetion of HCl) and pit/neck of gland (acid to protect mucosa against pathogens)
enteroendocrine: hormones (histamine to stimulate acid secretion by acting on parietal cells and gastrin to stimulate gastric motility and indirectly stimulates HCl) into fenestrated capillaries in lamina propria
Explain the potential clinical outcome if intrinsic factor is not secreted? How would damage of chief cells prevent Vit B12 absorption
F is necessary for vit B12 absorption and loss can lead to faulty RBC synthesis and anemia
What is the name of the nerve that if damaged would prevent the passage of food through the lower esophageal sphincter and cause food to accumulate in the esophagus
vagus nerve - causes food to accumulate and can cause gastric reflux
Which part of the GI contains enterocytes, goblet, Paneth and the enteroendocrine cells which secrete CCK and secretin. In what specific layer/structure of the gut wall are these cells found? What is the function of these cells/products produced. What other cell type is found in this same region (hint – it is common throughout the mucosal glands in the GI tract and is does not secrete anything)
small intestinal mucosa (also includes stem cells)
enterocytes: enterokinase
goblet cells: mucin
Enteroendocrine cells: secretin & cholecystokinin
Paneth cells: lysozymes
What is the main type of epithelium in the digestive wall?
simple columnar (except esophagus)
What type of epithelium is present in the esophagus?
SSNK
What is a key feature of lamina propria?
Glands throughout GI tract
What are the glands in the lamina propria called when present in the esophagus? Stomach? Intestine (small and large)?
esophageal cardiac glands; gastric glands (named for regions); intesinal glands or crypts of Lieberkuhn
