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GI 3 > Intestine histology > Flashcards

Intestine histology Flashcards

1
Q

The luminal surface of the small intestine has modifications that increase its surface area to aid absorption.
They are permanent mucosal folds present in the duodenum,
jejunum, proximal ileum that increase surface area by 2-3 fold

A

Plicae circulares

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2
Q

______are finger like projections of epithelium-covered lamina propria that increase surface area by 10-fold.

A

Villi

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3
Q

_____ are extensions of the epithelial cell apical plasma membrane that
increase surface area 20- fold.

A

Microvilli

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4
Q

These three specialized modifications, plicae circulares, villi, microvilli will cumulatively increase the intestinal surface area by

A

400 - 600 fold

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5
Q

The villi are extensions of ______that are covered in epithelial cells and contain a central lymphatic channel (lacteal) and several capillaries. Smooth muscle fibers, loose connective tissue and lymphoid cells can also be seen in the center of the villus.

A

lamina propria

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6
Q

The epithelial covering of the villi are composed of what 3 things?

A

— absorptive cells (enterocytes)

goblet cells

DNES (enteroendocrine) cells

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7
Q

Crypts of Lieberkuhn extend from the base of the villi into the lamina propria and contain what 3 things?

A

— DNES (enteroendocrine) cells,

stem cells

paneth cells

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8
Q

The enterocytes are ____epithelial cells ~ 25µM high with an elongated nucleus

A

columnar

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9
Q

The principal function of _____ are terminal digestion and absorption of water and nutrients.

A

enterocytes

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10
Q

These cells re-esterify fatty acids into triglycerides, form chylomicrons, and transport the bulk of the absorbed nutrients into the lamina propria for distribution to the rest of the body.

A

Enterocytes

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11
Q

The luminal surface of each enterocyte has a brush (striated)

border constructed of ~3000 microvilli/ that are covered in a____ coat made of glycosylated membrane proteins

A

glycocalyx

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12
Q

The glycocalyx layer has______ roles and also is integrally involved in the
digestion of disaccharides and dipeptides into monomers for adsorption through peptide hydrolases and disaccharidases that are abundant on the____ surface.

A

protective

apical

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13
Q

____ are easily recognizable in H&E stained intestinal sections because they are full of carbohydrate and so remain unstained; can be identified by PAS staining.

A

Goblet cells

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14
Q

Goblet cells act as______ glands that secrete copious amounts of____ that consists of high MW glycoprotein macromolecules that have 20% protein and 80% carbohydrate.

A

unicellular

mucin

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15
Q

mucin is released at reasonably constant levels by exocytosis from goblet cells. Justafter release the mucin granules become hydrated and expand to function in:

A

lubrication and protection

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16
Q

• The Crypts of Lieberkuhn extend from the base of the villi into the lamina propria and addition to enteroendocrine cells, the crypts contain

A

Paneth cells, and stem cells.

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17
Q

What is in the upper half of Crypts of Lieberkuhn?

What about in the basal half?

A

— Surface absorptive and goblet cells occupy the upper half of the crypt

most of the cells are regenerative cells (and their progeny), DNES cells and Paneth cells.

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18
Q

The epithelial lining of the intestine is continuously being renewed by stem cells that proliferate in the______.
• New cells are born from stem cells in the crypts and migrate up the____ and are finally exfoliated from the tips of the villus.

A

crypts

villus

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19
Q

The intestinal epithelium is replaced every ____ days in humans.
• Stem cells can most easily be identified in the crypts as ____since they are the only cells that are proliferating.

A

3-6

mitotic figures

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20
Q

_____cells are long lived and do not participate in the upward migration of epithelial cells - instead they remain resident at the base of the crypts

A

Paneth

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21
Q

Paneth cells are full of secretory granules and they continuously secrete____.

In addition they secrete____ that help neutralize bacterial and viral infections.

A

lysozyme

defensins

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22
Q

Paneth cells stain intensely with____ and also with phloxine-tartrazine which stains the secretory granules scarlet.

A

eosin

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23
Q

forms the core of the villi and extends down to the muscularis layer and is highly vascularized to accept the products of absorption.

A

Lamina propria

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24
Q

Lamnia propria contains an abundance of___ cells that protect the intestinal lining from microbial invasion

A

lymphoid

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25
Q

The muscularis mucosae is present as an

A

inner circular and outer longitudinal layer of smooth muscle fibres.

26
Q

How does a lacteal empty?

A

Some fibers enter the villus and extend to the tip. During digestion the fibers contract causing shortening of the villus.

27
Q

The lamina propria maintains an extensive immune defense system in the form of lymphoid tissue called:

A
  • Gut-Associated Lymphoid Tissue (GALT)
28
Q

GALT exists as individual lymphocytes within the mucosa and epithelium as well as dense aggregates called ______ - in some regions multiple of these
coaelsce to form ______

A

lymphoid nodules

Peyer’s Patches.

29
Q

30 - 40 permanent Peyer’s Patches are found throughout the ileum with some more in the_____, nodules are least numerous in____.

A

jejunum

duodenum

30
Q

* The duodenal submucosa differs from the rest of the G.I. due to the presence of large numbers of glands called ____ these are an identifying histological feature of the duodenum

A

Brunner’s glands -

31
Q

Brunners glands appear similar to______ They ascend through the muscularis mucosae layer and enter the crypts to deposit their secretions into the lumen.

A

mucous acini.

32
Q

What do Brunners glands secreate

A

The secretions contain an alkaline mucus that neutralizes the pH of the gastric chyme and protects the duodenum and epidermal growth factor for stem cell proliferation in the crypts

33
Q

The small intestine secretes about 2 litres of fluid/day. Secretion is mainly under neural control from the submucosal _________ and hormones produced by enteroendocrine cells.

A

(Meissner’s) plexus

34
Q

causes the release of digestive enzymes from the pancreas and bile from the gallbladder.

A

Cholecystokinin

35
Q

regulates the pH of the duodenal contents via control of gastric acid secretion and buffering with bicarbonate.

A

Secretin

36
Q

The muscularis externa is composed of an inner layer of circular
smooth muscle and an outer layer of longitudinal smooth muscle.
• Between the smooth muscle layers lies the

A

myenteric plexis (Auerbach’s).

37
Q

Two purposes of the Myenteric plexis

A

provides motor inervation to the muscularis externa and secretomotor innervation to the mucosa.
— The enteric nervous system is a part of the nervous system which directly controls the GI system

38
Q

Control of peristaltic movement is mediated by the
myenteric plexis in response to

A

gastric distension.

39
Q

The main functions of the small intestine are to complete digestion and
absorb the products into the bloodstream and lymphatic system-

A

7l of fluid, 30g of sodium, 0.5kg of carbohydrate and protein, and 1kg of fat
are absorbed by the intestine daily

40
Q

•Luminal digestion of most foodstuffs results in individual molecules
that can be absorbed by the enterocytes. Enterocytes also generate enzymes that are incorporated into the brush border that digest carbohydrate and polypeptides to

A

monomeric units

41
Q

the shortest segment of the small intestine, only 25
cm in length. It receives bile from the liver and digestive juices from the
pancreas via the common bile duct and pancreatic duct, respectively

A

Duodenum

42
Q

How is the duodenum different then the jejunum and ileum?

A

its villi are broader, taller, and more numerous per unit area. It has fewer goblet cells
per unit area than the other segments, and there are Brunner’s glands in its submucosa

43
Q

villi of the_______ are narrower, shorter, and sparser than those of
the duodenum. The number of goblet cells per unit area is greater in the
______than in the duodenum.

A

jejunum

jejunum

44
Q

Describe the vili in the ileum

A

The villi of the ileum are the sparsest, shortest, and narrowest of the
three regions of the small intestine.

45
Q

The lamina propria of the_______
houses the Peyer’s patches in the wall. In the region of
Peyer’s patches the villi are reduced in height and may even be absent.

A

ileum

46
Q

Large intestine is ~ 1.5M long
composed of the

A

cecum, appendix, colon (ascending, transverse, descending, and sigmoid), rectum and anus.

47
Q

absorbs most of the water from chyme and compacts
the remaining material into feces for excretion.

A

large intestine

48
Q

Cecum and colon are histologically indistinguishable. The ileum enters on the medial side of cecal-colonic boundary and is closed by the _____ that prevents reflux of
cecal/colonic content back into the ileum

A

ileocecal valve

49
Q

The____ is not folded into plicae
cirularis and villi are absent from the
mucosa giving it a relatively smooth
surface.

A

colon

50
Q

The colonic epithelium consists of cells similar to the small intestine,
with the exception of the _____ that are absent from the colonic Crypts

A

Paneth cells

51
Q

• villi are absent but the colonic mucosa is full of _______ that are made up of cell types similar to those of the small intestine.

A

Crypts of Lieberkhun

52
Q

How are the crypts in the colon different than in the small intestine?

A

• The crypts in the colon are longer than in the small intestine and are highly glandular with an abundance of goblet cells. The Crypts open into the lumen at the surface of the colon and can be seen as a regular array of holes across the mucosa.

53
Q

As with the small intestine the mucosal cells are born from stem cells at the base of the crypts and migrate up the walls of the crypts until the are sloughed off from the apex - the colonic mucosa is replaced every

A

6 -7 days.

54
Q

The muscularis externa outer longitudinal muscles are arranged in three distinct bands called ______that remain partially contracted and cause the large intestine to be puckered into sacculations called haustra coli.

A

taenia coli

55
Q

The____ is blind-ended tube extending from the cecum distal to the ileocecal junction.
• In some animals it is involved in digestion of cellulose but in human it has an unknown function.

A

appendix

56
Q

How is the tunic layer in the appendix different then in the intestine?

A

It follows the similar tunic pattern to the intestine in general but a characteristic feature is the presence of masses of lymphoid tissue in the mucosa and submucosa and mucosal glands are more disperse.

57
Q

________is an inflammation of the appendix - left untreated it can rupture resulting in infection of the peritoneal cavity with gut contents that can lead to fatality. Very common with about 1/500 people suffering per year.

A

Appendicitis

58
Q

The terminal 12cm portion of the G.I. tract is the rectum. The rectal mucosa is similar to the colon except that the Crypts are somewhat deeper and the goblet cells more abundant.

A

Recto-anal Junction

59
Q

The end of the rectum joins the anal canal at the recto-anal junction where the epithelium transitions from simple columnar to _______

A

stratified squamous.

60
Q

In Recto-anal junction, the Crypts disappear just prior to this junction and are replaced by ________

A

large circumanal glands.

61
Q

Two venous plexi are found in the submucosa of anal canal - _______ plexus and _____ plexus. In older people and during pregnancy an increase in the size of the vessels in these plexuses can result in hemorrhoids.

A

internal hemorrhoidal

external hemorrhoidal

GI 3 (15 decks)

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