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GI > Tubular Gut Histology > Flashcards

Tubular Gut Histology Flashcards

1
Q

In the tubular gut what are the different layers? Which changes the most through the tract?

A

the mucosa (epithelium, lamina propria, and muscularis mucosa), submucosa (containing the blood vessels and nerves which feed into the muscularis externa and the mucosa), the muscularis externa and a serosa or adventitia; mucosa

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2
Q

What is the make up and function of the muscularis mucosa?

A

smooth muscle, movement of just mucosa, for mixing

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3
Q

What are the histological aspects of the mucosa in the esophagus?

A

epithelium- stratified squamous nonkeratinized, lamina propria- blood vessels, lymphatics, lymphatic tissue, glands- light network of collagen and fibers, mucosal glands mostly in distal esophagus similar to cardiac glands of stomach (esophageal cardiac glands), secrete neutral mucus, protect esophagus from gastric juices, longitudinally oriented smooth muscle in muscularis mucosa

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4
Q

What are the histological aspects of the submucosa in the esophagus?

A

dense irregular collagenous connective tissue with some elastic fibers, large blood vessels, mucous secreting esophageal glands proper (glands here and duodenum only) secrete an acid mucin for lubrication

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5
Q

What are the histological aspects of the muscularis externa in the esophagus?

A

inner circular layer- mixes content, outer longitudinal layer- propels food; upper 5% skeletal, middle 45% mixed, lower 50% smooth muscle

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6
Q

What are the histological aspects of the serosa/adventitia in the esophagus?

A

upper esophagus (above diaphragm) is adventitia, fibroelastic connective tissue, lower esophagus (below the diaphragm) is serosa

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7
Q

What are the histological aspects of the mucosa in the esophageal-cardiac junction?

A

stratified squamous epithelium changes abruptly to simple columnar, cardiac glands in stomach portion, some cardiac glands may appear in lamina propria or submucosa, muscularis mucosa continues across junction, includes inner circular and outer longitudinal

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8
Q

What are the histological aspects of the submucosa in the esophageal-cardiac junction?

A

esophageal glands proper

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9
Q

What are the histological aspects of the muscularis externa in the esophageal-cardiac junction?

A

same as the esophagus

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10
Q

What is Barrett’s esophagus?

A

complication of GERD, metaplasia of distal esophagus to glandular epithelium, risk of adenocarcinoma

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11
Q

What is squamous cell carcinoma?

A

pencil-like ridges along, dysplastic and large, loose polarity

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12
Q

What are the three histological regions of the stomach?

A

cardia, fundus and pylorus (fundus and body are the same histologically)

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13
Q

What is the function of the stomach?

A

reservoir for swallowed food, mixes food with gastric secretions to form chime, releases chime into the duodenum for further digestion and absorption

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14
Q

What layers are involved in the rugae?

A

the mucosa and submucosa; folds are transient

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15
Q

What are the histological aspects of the mucosa in the stomach?

A

simple columnar epithelium (surface mucous cells) extends into gastric pits further invagination into the lamina propria forms gastric glands which is relatively thin due to close packing of the gastric glands and pits, muscularis mucosa with two thin indistinct layers, some smooth muscle fibers extend into lamina propria

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16
Q

What are the histological aspects of the cardiac pits in the stomach?

A

pits are short (<1/2 mucosa), wide and gaping, simple or compound tubular glands, coiled, large lumens, mostly mucus secreting (ill defined borders, bubbly cytoplasm), some enteroendocrine, few parietal, chief uncommon

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17
Q

What are the histological aspects of the fundic pits in the stomach?

A

principle glands of the stomach, produce gastric juice with enzymes, pits short (<1/3) and narrow long glands, straight tubular glands, 2-7 glands empty into one pit; mucus neck cells (regenerative), parietal cells (upper half), enteroendocrine (widely scattered among exocrine cells), and chief cells (found largely at the base - stem cells); extensive neck and base

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18
Q

What are the histological aspects of the pyloric pits in the stomach?

A

pits long (approx. 1/2 mucosa) and wide, glands short, branched tubular glands, coiled, extensively coiled and tortuous, mucous cells predominate, occasional parietal, enteroendocrine common, chief uncommon

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19
Q

What are the cellular features of surface mucous cells?

A

tall columnar cells, basal nuclei, secrete an insoluble, cloudy, neutral mucous-> protection of epithelium, secretion not continuous but rather vagal stimulation, serve a protective function, regenerate in 3-5 days

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20
Q

What are the cellular features of mucous neck cells?

A

stem cells, irregular shaped, smaller than surface, singly or in clusters among parietal cells, secrete soluble mucus which is slightly more acidic than surface cells, apical secretory granules less numerous and smaller than surface, oval nucleus near basal surface, little heterochromatin prominent nucleolus, few organelles, abundant ribosomes, high mitotic rate, replace pit and surface 3-5 days, replace chief and enteroendocrine 60-90 days, parietal weeks 150-200days

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21
Q

What are the cellular features of chief cells?

A

fundic mostly, found in lower half of gastric glands, secrete proteins (pepsinogen, rennin, lipase), conspicuous secretory granules, strongly basophilic with abundant RER, prominent Golgi, prominent nucleoli, basal nucleus, regenerated 60-90

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22
Q

What are the cellular features of parietal cells?

A

fundic mostly, central nucleus, mostly in upper and middle part of gastric glands, eosinophilic, stimulated by cholinergic nerves, secrete HCl (enhanced by histamine and gastrin), secrete H2O and gastric intrinsic factor (GIF) a glycoprotein essential for absorption of Vit B12, intracellular canaliculi and tubulovesicular system, abundant mitochondria and H/K ATPase antiporter, receptors for gastrin, histamine H2, acetylcholine M3, regenerate 150-200 days

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23
Q

What are the cellular features of enteroendocrine cells?

A

open and closed types, produce more than 20 GI hormones important in coordination and control of GI functions, small ovoid or pyramidal cells can be found throughout the gland, esp. at base, lack other distinctive organelles, clear halo with H&E, secretory granules at apex or base, aliases (argentaffin, enterochromaffin, EC, argyrophil, APUD, DNES) characterized by immunocytochemistry; 60-90 days

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24
Q

What are the histological aspects of the submucosa in the stomach?

A

dense connective tissue, submucosal plexus (meisner’s), between submucosa and inner layer of smooth muscle, regulates local secretions, blood flow and absorption; autonomic and enteric nervous system- stellate shaped cells, post gang. PS or enteric

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25
Q

What are the histological aspects of the muscularis externa in the stomach?

A

three layers: inner oblique, middle circular, outer longitudinal, thicker than the esophagus, thickening of middle layer creates pyloric sphincter, peristaltic waves mix chime, acid, enzymes

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26
Q

What are the histological aspects of the myenteric (aurbach’s plexus) in the stomach?

A

coordinates motility, autonomic and enteric nervous system, between the inner and outer layer of smooth muscle, neuralemma surround wavy fibers with white between is the nerve plexus

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27
Q

What is a gastric ulcer?

A

mucosal lesion/ inflammation of mucosa caused by helicobacter pylori bacteria or stress

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28
Q

What is Gastrimoma (Zollinger-Ellison Syndrome)?

A

neoplasms producing gastrin

29
Q

What are the surface amplifications of the mucosa in the small intestine?

A

plicae circulares, intestinal villi, intestinal glands (crypts of Lieberkuhn), Microvilli (brush border)

30
Q

What are plicae circulares and where are they found in the small intestine?

A

permanent structures (folds), more prominent in first part of jejunum, diminish in height distally, seldom in ileum, core is submucosa

31
Q

What are intestinal villi? where are they found in the small intestine? Characteristics?

A

distinguishing feature of the small intestine, narrow folate or finger like projections, consist of extensions of lamina propria covered with simple columnar epithelium, longer in duodenum and proximal jejunum shorter and narrower in distal jejunum and ilium, contain lacteals, core of lamina propria contains plasma cells, B cells, mast cells (basophils), lymphocytes, eosinophils, macrophages, and smooth muscle

32
Q

What are the characteristics of the crypts of Lieberkuhn?

A

intestinal glands which appear as invaginations of epithelium, simple tubular glands which open into intervillous spaces, lined by absorptive cells, goblet, enteroendocrine, Paneth and stem cells

33
Q

What are the characteristics of the microvilli or brush border?

A

extensions of plasma membrane, core contains actin filaments which associate with plasma membrane and terminal web, junctional complex at apical lateral surface of columnar cell, surface covered with glycocalyx, PAS positive, digestive enzymes attached

34
Q

What is the small intestine epithelium adapted for?

A

final digestion of food, absorption of nutrients, secretion of hormones, and protection

35
Q

What are the characteristics of the enterocytes?

A

simple columnar with numerous microvilli (striated border), thick glycocalyx and junctional complexes near lumen; absorptive cell

36
Q

What are the characteristics of the goblet cells?

A

mucous secreting, function to protect mucosa and lubricate food; increase in number from duodenum to ileum

37
Q

What are the characteristics of the enteroendocrine?

A

like enteroendocrine in the stomach, largely at bases of glands, clear halo, eosinophilic granules at base, sometimes euchromatic nucleus; secretes: gastrin, secretin, cholecystokinin, somatostatin, and motilin

38
Q

What does gastrin do?

A

stimulates HCl secretion from stomach

39
Q

What does secretin do?

A

stimulates pancreatic and biliary bicarbonate and water secretion

40
Q

What does cholecystokinin?

A

stimulates secretion of enzymes and bicarbonate from pancreas and stimulates gallbladder contraction

41
Q

What does somatostatin do?

A

inhibits secretion of CCK, GIP, and motilin

42
Q

What does motilin do?

A

increases motility of stomach and intestines

43
Q

What are the characteristics of the Paneth cells?

A

found at bases of crypts in small intestine (rarely in normal colons), basophilic basal cytoplasm, acidophilic zymogen granules containing lysozyme (helps regulate normal bacterial flora of small intestine)

44
Q

What are the membrane glycoproteins in the microvilli? Purpose?

A

intramembranous, enzymes and used to trap things to absorb

45
Q

What is GALT?

A

gut associated lymphoid tissue, diffuse network of lymph with IEL, LPL, MLPL or organized nodules solitary or grouped in tonsils, appendix, peyer’s patches

46
Q

How is the formation of the sIgA? How does it work?

A

plasma cell secretes monomeric IgA, it is dimerized in LP, bind to receptors on enterocyte, endocytose into the enterocyte after attaching to a receptor, when released into the lumen the receptor remains attached to the IgA making it sIgA, binds toxins and bacteria to prevent absorption into the body

47
Q

What are M cells and what are their characteristics?

A

microfold cells, FAE (follicle associated epithelium) overlaying Peyer’s patches, lack microvilli, create a pocket for lymphocytes on basolateral surface (contain lymphocytes)

48
Q

What is the sequence for the release of IgA through microfold cells?

A

microfold cell trancytoses antigen from lumen to cell bases and presents antigen lymphocytes act as APC, B lymphocyte moves to regional node and proliferates, then to blood stream or efferent lymphatics, travels distantly or homes back to original site of antigen exposure, end result is B-cells secretion of IgA

49
Q

where are the stem cells located and how many days do they take to renew the epithelium?

A

deep in crypts, renewal in 2-6 days

50
Q

What are the characteristics of the lamina propria in the small intestine?

A

loose areolar connective tissue containing fibroblasts, macrophages, smooth muscle, and heavily populated with cells of the immune system (lymphatic tissue)

51
Q

What are the characteristics of the muscularis mucosa in the small intestine?

A

two thin smooth muscle layers, may be absent near Peyer’s patches. Contributes to movement of mucosa (villi); inner circular and outer longitudinal

52
Q

What are the characteristics of the submucosa in the small intestine?

A

differs from lamina propria- collagen bundles are coarser, elastic fibers present, adipose tissue present and vasculature are larger sized vessels; brunners glands, and submucosal plexus (Meissner’s plexus)

53
Q

What are the characteristics of brunner’s glands in duodenum?

A

mucous glands; coiled tubuloacinar glands which open into lumen, secrete an alkaline (pH 8.2-9.3) mucin with a high content of bicarbonate, protects intestinal mucosa, raises pH to optimal range for pancreatic enzymes, produces EGF (polypeptide that inhibits HCl production and enhances cell division

54
Q

What are the characteristics of the muscularis externa in the small intestine?

A

inner circular and outer longitudinal, myenteric plexus (Auerbach’s plexus)

55
Q

What is the make up of serosa or adventitia of the small intestine?

A

lined with simple squamous epithelium or mesothelium, contains connective tissue

56
Q

What is the make up of the mucosa in the large intestine?

A

no plicae (except distal portion of rectum), no villi, straight tubular glands (crypts of lieberkuhn) similar to small intestine but longer and more goblet cells; cell types: simple columnar epithelium, goblet cells increase towards rectum, rarely paneth, enteroendocrine, single stem cell population, lamina propria and muscularis mucosa

57
Q

what is the function of the simple columnar epithelium?

A

absorptive cells with microvilli, water absorption passive, follows active transport of sodium across basal surface

58
Q

Where is the stem cell population located in the large intestine? How does the cell renewal take place in the large intestine?

A

single stem cell population at base of crypt, zone of replication lowest 1/3 of crypt, absorptive and goblet 5-6 days, enteroendocrine 3-4 weeks

59
Q

what is the make up of the muscularis externa of the large intestine?

A

thin inner circular, outer longitudinal not uniform thickness rather forms 3 longitudinal bands teniae coli when partially contracted forming haustrae

60
Q

What is the make up of the serosa or adventitia in the large intestine?

A

serosa or adventitia depending on location, serosa has appendices epiplicae

61
Q

What are the characteristics of the appendix?

A

recently theorized to be a safe-house for bacterial flora, all layers of typical GI, most similar to large intestine (glands shorter, fewer and no teniae coli)

62
Q

What are the features of the anal rectal junction?

A

rectum has transverse folds, anus longitudinal folds, abrupt transition from columnar epithelium (rectum) to stratified squamous (anus), anal columns, anal valves, and the pectinate line; transition similar to esophageal cardiac junction except no submucosal glands, many goblet cells, and muscularis mucosa discontinuous

63
Q

What are the anal columns?

A

permanent longitudinal folds of mucosa and lamina propria in rectum

64
Q

What are the anal valves?

A

small crescentic mucosal folds producing the anal sinuses

65
Q

What is the pectinate line?

A

opposite middle of sphincter ani internis, junction of endodermal (autonomic n., superior and middle rectal artery) and ectodermal derivatives (spinal n. and inferior rectal a.)

66
Q

What are the characteristics of the submucosa in the anal rectal junction?

A

superior, middle and inferior rectal arteries from inferior mesenteric; internal iliac and internal pudendal respectively; rectal venous plexus- internal and external hemorrhoids

67
Q

What are the characteristics of the muscularis externa in the anal rectal junction?

A

teniae coli absent in rectum- outer layer of muscle is continuous, inner circular layer of smooth muscle thickened a level of anus (internal anal sphincter, 1/2 way=pectinate), outer longitudinal layer of smooth muscle becomes a mixture of elastic fibers and smooth muscle (fibromuscular, blend into levator ani)

68
Q

What are the components of the external anal sphincter?

A

circumferential ring of skeletal muscle consisting of three parts: deep, superficial and subcutaneous

GI (9 decks)

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