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RUSOM_GI Histo I
Esophagus to Anus
| Question | Answer |
|---|---|
| What are the 4 layers of the digestive tract, from superficial to deep? | 1. Mucosa 2. Submucosa 3. Muscularis externa 4. Serosa or adventitia |
| What type of epithelium is normally found in the mucosa layer? | Non-keratinized stratified squamous epithelium |
| What is GALT? | Gut-Associated Lymphatic Tissue: Immune system tissue found in digestrive tract |
| Which layers is GALT found in? | Mucosa & Submucosa |
| What is the function of muscularis mucosae? | Localized movement of the mucosa |
| Which part of the digestive tract does NOT have muscularis mucosae? | Gallbladder |
| What is the function of muscularis externa? | Peristalsis: constricts & shortens the GI tube to propel food towards the caudal end of the GI tract |
| Where is Meissner's plexus located? | Submucosa |
| Where is Myenteric plexus located? | Muscularis externa |
| What type of ganglia are found in Meissner's plexus? | Parasympathetic |
| What type of ganglia are found in Myenteric plexus? | Parasympathetic |
| Do intraperotineal organs have a serosa or an adventitia layer? | Serosa |
| Do retroperotineal organs have a serosa or an adventitia layer? | Adventitia |
| Is mesothelium found in serosa or in adventitia? | Serosa |
| What is the embryological derivative of mesothelium? | Mesoderm |
| Which condition presents with a cardiac gland in the lamina propria of the cardia region of the stomach? | Chronic acid reflux |
| What shape lumen is found in the esophagus? | Stellate-shaped lumen |
| Where is the physiological sphincter of the stomach? | Cardia |
| Where is the anatomical sphincter of the stomach? | Pylorus |
| What are the 2 layers of muscularis externa? | Inner circular & outer longitudinal |
| What is found in the lamina propria of the mucosa layer? | GALT |
| Which condition is related to a lack of protection for the esophageal mucosa from esophageal mucus? | GERD (Gastro-Esophageal-Reflux-Disease) |
| Which condition is found in patients who allow GERD to persist for too long? | Barrett's esophagus |
| Which types of epithelia are affected in Barrett's esophagus? | Gastric & intestinal epithelia |
| What type of metaplasia occurs in patients with Barrett's esophagus? | Stratified squamous epithelium is replaced by simple columnar epithelium |
| What does congenital metaplasia in the esophagus indicate? | The metaplasia is not precancerous (ie, found in babies) |
| What does acquired metaplasia in the esophagus indicate? | The metaplasia is precancerous |
| What could result from chronic heartburn? | Barrett's esophagus --- then esophageal cancer |
| What pH is found in the stomach? | 1-2 |
| What types of digestion occur in the stomach? | Chemical & physical digestion |
| What is the function of pepsin? | Breaks down dietary proteins into peptides |
| What condition would occur if self-digestion of the stomach is not prevented? | Gastric ulcers |
| Which region of the stomach has a dome shape? | Fundus |
| What happens to the rugae when the stomach is full? | The rugae 'disappear' or flatten out as the stomach fills. |
| What are gastric pits? | Invaginations of mucosa that terminate as gastric glands |
| What type of epithelium is found in mucosal pits and glands? | Simple columnar |
| What is the function of the mucosa in the stomach? | To produce a thick mucus layer to protect the stomach from self-digestion |
| What does PAS stain + for? | Sugar residues, such as mucin (a glycoprotein) in mucus |
| What color is a PAS+ cell? | Magenta |
| What is the major type of gland in the cardia? | EEC (Enteroendocrine cells) |
| Where are parietal cells found? (Be specific.) | Fundus of stomach - neck of deep glands |
| What is the function of parietal cells? | Produce HCl & Intrinsic factor |
| Where are chief cells found? (Be specific.) | Fundus of stomach - base of deep glands |
| What is the function of chief cells? | Produce pepsinogen & weak lipase |
| Where are stem cells found in the fundus? (Be specific.) | Neck of deep glands |
| Are parietal cells acidophilic or basophilic? Why? | Acidophilic - they have a lot of mitochondria for active transport |
| Are chief cells acidophilic or basophilic? Why? | Basophilic - they have a lot of Rough ER |
| What is another name for parietal cells? | Oxyntic cells |
| What is the function of intrinsic factor? | It binds to Vitamin B12 so that it can be taken up in the ileum. |
| What condition results from gastric atrophy? Why? | Pernicious anemia - A patient will not produce intrinsic factor, so they will not bind Vitamin B12, which leads to a Vitamin B12 deficiency. |
| What cell types are found in the cardia? | Mucus-secreting cells & EEC |
| What cell types are found in the fundus/body? | Mucus-neck cell, PARIETAL cells, CHIEF cells, EEC |
| What cell types are found in the pylorus? | Mucus-secreting cell, EEC |
| What is another name for chief cells? | Zymogenic cells or Peptic cells |
| What do G cells produce? | Gastrin |
| What does gastrin stimulate? | HCl production in parietal cells |
| What do D cells produce? | Somatostatin |
| What does somatostatin stimulate? | Decrease in gastrin production |
| What does HCl stimulate? | Somatostatin production in D cells |
| What is the protective mechanism of the stomach? | 1. Mucus 2. Bicarbonate 3. Prostaglandins |
| What is the function of prostaglandins in the stomach? | They inhibit gastric HCl production by inhibiting parietal cells |
| How long does it take to regenerate surface cells in the stomach? | 3-7 days |
| What can cause an acute insult to the stomach? | Alcohol, aspirin, toxins, chemotherapy drugs, radiation treatments |
| What happens to the stomach as a result of an acute insult? | Surface mucus cells are damaged, stem cells in pits & glands migrate up and cover the surface |
| What condition results from a failure of protective mechanisms in the stomach following an acute insult? | Ulcers and bleeding |
| What is the pH range in normal pits & glands in the stomach? | Surface layer = pH 1-2; bottom of pit/gland = pH 7 |
| What is unique about the muscularis externa in the stomach? | There are 3 layers: 1. Inner oblique 2. Middle circular 3. Outer longitudinal |
| Does the stomach have serosa or adventitia? | Serosa (it's an intraperotineal organ) |
| What are the 3 regions of the small intestine, in order? | Duodenum, Jejunum, Ileum (DJ Ileum) |
| What are the characteristic features of the small intestine? | Villi, crypts in the mucosa Transverse folds (plicae circulares) |
| What 5 cell types are found in the epithelium of the small intestine? | 1. Enterocytes/absorptive cells 2. Goblet cells 3. EEC (APUD cells) 4. Paneth's cells 5. Stem cells |
| What are the characteristics of the Enterocytes in the Small intestine? | Brush border of microvilli, glycocalyx coating, decreased frequency towards large intestine |
| What is the function of Goblet cells? | Secret mucus, increased frequency towards large intestine |
| What immune protections are found in the small intestine? | sIgA tight junctions between enterocytes GALT |
| What cells can a stem cell in the small intestine produce? | enterocytes EEC Goblet cells Paneth's cells |
| What is the function of EEC/ APUD cells in the small intestine? | Hormone production (gastrin, secretin, CCK, somatostatin); hormones are released locally and modulate GI activities |
| Where are EEC/ APUD cells found? | In crypts of the small intestine |
| What is the function of Paneth's cells in teh small intestine? | Produce lysozyme (antimicrobial; kills bacteria by breaking down cell walls) |
| Where are Paneth's cells found? | At the base of crypts in small intestine |
| What is the function of gastrin? | Stimulates parietal cells (HCl) and chief cells (pepsin) |
| What is the function of somatostatin? | Inhibits parietal cells (HCl) and chief cells (pepsin) |
| What is the function of serotonin? | Stimulate smooth muscle contraction (EC cells in small intestine, fundus of stomach) |
| What it the function of CCK (cholecystokinin)? | Stimulate bile production & pancreatic enzyme secretion |
| What is the function of secretin? | Stimulate pancreatic & biliary bicarbonate and water secretion |
| How do Paneth cell granules look? | Black protein core surrounded by clear/white halo |
| What are the characteristics of a closed-type EEC? | Granules are everywhere in cell; hormones are released from the bottom into circulation |
| What is the function of a lactael? | It is a lymph vessel that absorbs chylomicrons |
| Where are Brunner's glands located? | Duodenum |
| Where are Peyer's patches located? | Ileum |
| Which portion of the small intestine does not contain Brunner's glands or Peyer's patches? | Jejunum |
| What is produced by Brunner's glands? | Alkaline mucin pH 8.2-9.3 |
| Where does alkaline mucin empty into? | Neck of crypts in duodenum |
| What is the function of alkaline mucin? | Protects against acid chyme; creates optimal pH for pancreatic enzymes |
| What is the function of Peyer's patches? | Part of GALT system; covered by M (microfold cells)--- important for immune response |
| Are M cells APC (antigen-presenting cells)? | No. |
| Does small intestine have serosa or adventitia? | Both. Serosa where small intestine lies free in abdominal cavity; Adventitia where small intestine is attached to the body wall |
| What is the shape of Brunner's gland? | Leaf-like villi |
| What is the shape of Peyer's patches? | Finger-like villi |
| Which digestive enzymes are secreted by the pancreas into the small intestine? | Amylase, lipase, peptidase, trypsin |
| What cleaves trypsinogen to trypsin? | Enterokinase from enterocytes |
| What are the functions of trypsin? | Cleaves pancreatic enzymes into active form; Breaks polypeptides |
| Where is bile reabsorbed? | In the small intestine |
| What are the protective mechanisms of the small intestine? | 1. Glycocalyx 2. Goblet cells 3. Brunner's glands 4. Bile 5. Pancreatic fluid |
| What type of secretions are released into the small intestine, and why? | Alkaline; to neutralize stomach acid |
| Where are ulcers more common; in the stomach or in the duodenum? | Duodenum (8%) > Stomach (2%) |
| What is usually found in patients with GI ulcers? | + for H. pylori bacteria |
| What are the basic functions of the Large intestine? | Reabsorption of water & salts from feces; propel feces out of body |
| Does digestion occur in the Large intestine? | No. |
| What is the role of Flora & Fauna in the Large intestine? | Extraction of vitamins |
| Which part(s) of the Large intestine have serosa? | Trans-colon (Intraperotineal) |
| Which part(s) of the Large intestine have adventitia? | Ascending colon, Descending colon (Retroperotineal) |
| What cell types are found in Large intestine epithelia? | Columnar absorptive, Goblet cells (***), EEC, Stem cells |
| What is special about the muscularis externa of Large intestine? | Outer longitudinal layer has 3 longitudinal stripes -- taeniae coli |
| What are the characteristics of the appendix? | Same histology as Large intestine, filled entirely with diffuse lymphatic tissue and nodules, contains plasma cells |
| What could result from a burst appendix? | Infection could spread into abdomen (peritoneal cavity) |
| What leads to infection of the appendix? | Small lumen becomes obstructed, invaded by bacteria |
| How does the rectum differ from the colon? | It lacks taeniae coli |
| What causes Congenital megacolon (Hirschsprung's disease)? | Absence of parasympathetic ganglia in bowel wall |
| What is the embryological origin of parasympathetic ganglia in the bowel wall? | NCC |
| What signs/symptoms are present in a patient with Congenital megacolon (Hirschsprung's disease)? | Aganglionic sone permanently contracted (no relaxation from parasympathetic system), proximal bowel becomes dilated, bowel obstruction starts at anus and progresses upwards |
| What are the Columns of Morgagni (Anal columns)? | Vertical folds produced by infolding of mucus membrane & muscular tissue in the upper hald of the lumen of the anal canal |
| What artery supplies the upper 1/2 of the anal columns? | Superior rectal a. (branches of IMA) |
| What artery supplies the lower 1/2 of the anal columns? | Inferior rectal a. (branches of internal Pudendal a.) |
| What separates the anal canal into upper and lower parts? | Pectinate line |
| Why is the pectinate line an important landmark? | Above the pectinate line -- sup. rectal a. & v., columnar epithelium, ENDODERM Below the pectinate line -- inf. rectal a. & v., stratified squamous epithelium, ECTODERM |
| Where are hemorrhoids found within the anal canal? | Surrounding the pectinate line; plexus of large veins in lamina propria |
| What type of muscle is found in the internal anal sphincter? | Thickened inner circular layer of muscularis externa |
| What type of muscle is found in the external anal sphincter? | Skeletal muscle |
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