Histology of the SI/LI Flashcards

1
Q

What are the parts of the small intestine?

A

duodenum, jejunum, and the ileum

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2
Q

what is the function of the small intestine?

A

principal site for digestion of food and absorption of digestion products

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3
Q

what are the transverse folds that are found in the small intestine lumen called? and what are they made up of?

A

plicae circulares (made up of mucosa with a submucosal core)

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4
Q

where are the plicae circulares visible?

A

they are visible in the jejunum, less so in the ileum

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5
Q

what are found on top of the plicae circulares?

A

intestinal villi

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6
Q

what are intestinal villi covered with/ what cells are found in this layer?

A

simple columnar epithelium of enterocytes and goblet cells

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7
Q

what is the core of the intestinal villi made up of?

A

loose connective tissue with microvasculature and a lacteal

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8
Q

what are lacteals important for?

A

they absorb lipids from the diet

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9
Q

what do the enterocytes have on them?

A

microvilli

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10
Q

what do enterocytes produce?

A

enzymes for digestion and absorption

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11
Q

what is the function of goblet cells?

A

they produce a mucus coating to shield from abrasion and bacterial invasion

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12
Q

what type of epithelium makes up the mucosal layer of the SI?

A

simple columnar epithelium

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13
Q

what is found within the simple columnar epithelium of the mucosal layer of the SI?

A

tubular intestinal glands (aka crypts)

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14
Q

besides the epithelium, what else makes up the mucosal layer of the SI?

A

the lamina propria and the muscularis mucosae

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15
Q

what is the submucosa of the SI made up of?

A

dense irregular CT with neurovasculature, lymphatics, and glands may also be present

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16
Q

what is the muscularis layer of the SI made up of?

A

inner circular and outer longitudinal layers

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17
Q

what is the serosa of the SI made up of?

A

loose CT covered by visceral peritoneum

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18
Q

What are the intestinal glands lined by?

A

simple columnar epithelium

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19
Q

what cells are found within the intestinal glands?

A

paneth cells, M cells, intestinal stem cells, and enteroendocrine cells

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20
Q

where do the intestinal glands open into?

A

the luminal surface of the intestine at the base of the villi

21
Q

What do paneth cells llok like?

A

they are pyramidal-shaped cells at the base of the intestinal glands; they have large eosinophilic (pink staining) granules in their apical cytoplasm

22
Q

what is the function of Paneth cells?

A

innate immunity by secreting antimicrobial substances (such as lysozymes and alpha defensins); they also regulate normal bacterial flora via antibacterial action and phagocytosis

23
Q

where do intestinal stem cells reside?

A

in a niche at the intestinal gland base, near paneth cells

24
Q

what types of cells can the intestinal stem cell repopulate?

A

goblet cells, enterocytes, and enteroendocrine cells

25
Q

where are M cells located?

A

in the ileal mucosa-overlying the peyer patches

26
Q

what are M cells main function?

A

highly specialized antigen-transporting cells

27
Q

what is an example of a specific bacteria that M cells will bind to?

A

gram-negative bacteria (e.g. E. coli)

28
Q

when looking at the duodenum, what would you expect to see in the mucosal layer?

A

simple columnar epithelia with scattered goblet cells

29
Q

what is the hallmark for identifying the duodenum?

A

in the duodenum’s submucosal layer, there are duodenal glands

30
Q

what is the composition of the duodenal glands in the submucosal layer?

A

tubuloacinar mucous glands that produce an alkaline secretion (it neutralizes acidic chyme)

31
Q

when looking at the jejunum, what would you expect to see in the mucosal layer?

A

long-finger like villi with a villus core containing a well-developed lacteal; tubular intestinal glands; lymphoid follicles in the lamina propria

32
Q

when looking at the ileum, what would you expect to see in the mucosal layer?

A

the villi are typically shorter than the jejunum; peyer’s patches; paneth cells found at the base of the intestinal glands

33
Q

how can you tell that you are looking at the gastroduodenal junction?

A

the stomach lacks the submucosal glands and then the duodenum has the submucosal glands

34
Q

what is the function of the LI?

A

absorbs water, sodium, vitamins, and minerals; will uptake sedatives, anesthetics, and steroids

35
Q

what is the hallmark for identifying the large intestine on histological slides?

A

the intestinal glands and goblet cells; NO INTESTINAL VILLI

36
Q

what cells make up the mucosal layer of the LI?

A

colonocytes, goblet cells, stem cells, and enteroendocrine cells

37
Q

what is extensive in the mucosal layer of the colon?

A

the GALT- it may penetrate the submucosa

38
Q

what happens to the outer longitudinal layer in the muscularis layer of the LI?

A

it gets organized into taeniae coli–> this forms the haustra of the LI

39
Q

what is Hirschprung’s disease/ megacolon?

A

it is when there is aganglionosis of the distal gut tube

40
Q

what causes Hirschprung’s disease?

A

mutations of the RET gene- normally required for migration and differentiation of NCC; so there is a failure of NCC development in both plexuses of the bowel segment

41
Q

what is short-segment hirschprung’s disease?

A

confined to the rectosigmoid region

42
Q

what is long-segment hirschprung’s disease?

A

it extends past the rectosigmoid region to the splenic flexure

43
Q

what is the presentation of hirschprung’s disease?

A

constipation, poor-feeding, and progressive abdominal distention

44
Q

where are the circumanal glands found?

A

they are large apocrine glands surrounding the anal orifice

45
Q

what are the three zones of the anal canal?

A

the colorectal zone, the anal transition zone, and the squamous zone

46
Q

what is the colorectal zone?

A

it is simple columnar epithelium (the upper 1/3 of the anal canal); identical to the rectum

47
Q

what is the anal transitional zone?

A

the middle 1/3 of the anal canal; area where we have a change from our simple columnar epithelium to stratified squamous epithelium of the perianal skin

48
Q

what is the squamous zone?

A

it is the external portion of the anal canal; the lower 1/3 of the anal canal; it is stratified squamous epithelium that is continuous with perineal skin

49
Q

how does the internal anal sphincter form?

A

at the level of the anus, the inner circular layer thickens to form the internal anal sphincter