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GI Midterm > Lecture 9-Small And Large Intestines > Flashcards

Lecture 9-Small And Large Intestines Flashcards

1
Q

Small intestine secretes what chemicals?

A

CCK, VIP, and secretin (enteroendocrine substances)

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2
Q

Four degrees of folding?

A
  • Plicae circularis
  • Intestinal villi
  • Intestinal glands
  • Microvilli (on the apical surface of the enterocytes)
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3
Q

What is the function of the four degrees of folding?

A

To increase surface area

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4
Q

Enterocytes

A

Epithelial cells lining the lumen

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5
Q

Plicae circularis

  • What are they?
  • Where do they begin and end?
A
  • Permanent folds of mucosa and submucosa

- Begin in the duodenum, distinct in the jejunum, disappear in mid-ileum

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6
Q

Intestinal villi

-Extend deep into the mucosa to form?

A

-Villi extend deep into the mucosa to form crypts (of Lieberkuhn) ending at the muscularis mucosae

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7
Q

Intestinal villi

-The length of the villi depends on?

A
  • the degree of distension of the intestinal wall

- the contraction of smooth muscle fibers in the villus core

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8
Q 
Intestinal glands (Crypts of Lieberkuhn)
   -function?
A

Simple tubular glands that increase the intestinal surface area

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9
Q 
Intestinal glands (Crypts of Lieberkuhn)
   -Formed by?
A

Invaginations of the mucosa between adjacent intestinal villi

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10
Q 
Intestinal glands (Crypts of Lieberkuhn)
   -Cell types include?
A

Absorptive, goblet, paneth, and enteroendocrine cells

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11
Q

Microvilli

  • What are they?
  • Function?
A
  • Evaginations of the apical part of the enterocytes to increase surface area
  • Produce a brush border on the apical border of enterocytes
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12
Q

Muscularis mucosa

-Boundary between?

A

Mucosa and submucosa

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13
Q

Muscularis externa

-Responsible for?

A

Segmentation and peristalsis

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14
Q

Serosa

-description?

A
  • Thin layer of loose CT covered by visceral peritoneum (mesothelium)
    • mesothelium-a membrane composed of simple squamous cells that forms the lining of several body cavities
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15
Q

Segmentation

  • What is it?
  • Controlled by?
  • When does it occur?
A
  • Contraction of smooth muscle layers that mixes the chyme within the small intestine
  • Controlled by the ANS
  • Occurs when the contraction above is NOT COORDINATED
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16
Q

Peristalsis

-When does it occur?

A

Occurs when proximal contraction is COORDINATED

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17
Q

Microcirculation of the small intestine

-main distribution site of blood and lymphatic flow?

A

Intestinal submucosa

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18
Q

Microcirculation of the small intestine
-Arterioles derived from the submucosal plexus enter the mucosa of the small intestine and give rise to two capillary networks?

A
  • Villus capillary plexus

- Pericryptal capillary plexus

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19
Q

Microcirculation of the small intestine

-Villus capillary plexus supplies?

A

The intestinal villus and upper portion of the crypts of Lieberkuhn

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20
Q

Microcirculation of the small intestine

-The pericryptal capillary plexus supplies?

A

The lower half of the crypts of Lieberkuhn

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21
Q

Lacteals

-Function?

A

-Convey chyle (lymph containing lipids absorbed from the meal and packaged in chylomicrons) from the intestine to the lymphatic circulation and thereby to the thoracic duct and then to the systemic blood circulation

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22
Q

Innervation and motility of the small intestine

  • Motility controlled by ANS through?
  • What do each of them do?
A

Submucosal-secretion

Myenteric plexi-contraction of muscle

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23
Q

Innervation and motility of the small intestine

-Intrinsic input is received from?

A

The mucosa and muscle wall of the small intestine

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24
Q

Innervation and motility of the small intestine

-Extrinsic input received from? Through?

A

Extrinsic input received from CNS through PS (vagus) and symp nerve trunks

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25
Q
  • Histologic differences between duodenum, jejunum, and ileum*
    • Duodenum?
A
  • Brunner’s glands in submucosa

- Few goblet cells

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26
Q

Jejunum?

A
  • Well developed plicae circularis (no brunners glands or peyer’s patches)
  • more goblet cells
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27
Q

Ileum?

A
  • Peyer’s patches

- Most goblet cells

28
Q

Villi and Crypts of Lieberkuhn

-Epithelium

A

Simple columnar

29
Q

Absorptive cells/enterocytes

  • Characteristics?
    • microvilli contain?
A
  • Prominent brush border

- Microvilli contain intramembranous enzymes (sucrase, lactase, maltase) used for terminal digestion of carbs

30
Q

Absorptive cells/enterocytes

  • Microvilli contain intramembranous enzymes (sucrase, lactase, maltase) used for terminal digestion of carbs
    • reduce carbs to hexoses, which can be?
A

Transported out of the lumen and into the cell by carrier proteins

31
Q

Lactose intolerance

-What happens in normal lactose digestion?

A

Lactose is broken down by lactase

32
Q

Lactose intolerance

-What happens in lactose intolerance?

A

Lactose is broken down by bacteria via fermentation creating gases, irritation, and increased motility

33
Q

Goblet cells

-function?

A

Mucus secreting cells

34
Q

Goblet cells

-Released by what process?

A

Exocytosis

35
Q

Enteroendocrine cells

-Function?

A

Secrete peptide hormones (gastrin, secretin, and CCK)

36
Q

Enteroendocrine cells

-Gastrin-function?

A

Stimulates gastric motility, HCl release (parietal cells) and insulin release

37
Q

Enteroendocrine cells

-Secretin-function?

A

Stimulates pancreatic bicarbonate secretion and enhances insulin secretion

38
Q

Enteroendocrine cells

-CCK-function?

A

Acts on pyloric sphincter to slow emptying, stimulates release of bile and pancreatic enzymes

39
Q

Paneth cells

-Function?

A

Secrete antimicrobial proteins to limit bacteria-enterocyte contact
-kill bacteria directly

40
Q

Paneth cells

-antimicrobial proteins are retained in the?

A

Intestinal mucus blanket

41
Q

7 things that protect the small intestine?

A
  • Viscous substance produced by goblet cells
  • Tight junction barrier linking adjacent enterocytes
  • Peyer’s patches
  • IgA
  • Antimicrobial proteins produced by paneth cells
  • Acidic gastric juice
  • Peristalsis prevents bacterial colonization
42
Q

Peyer’s patches

-Function?

A

Participate in the cellular surveillance of antigens

43
Q

Irritable Bowel Syndrome

-Where does it occur in the gut?

A

-A defect in the protective system involving the terminal ileum and large intestine

44
Q

IBS

-Pathology?

A
  • Initial alteration of the intestinal mucosa involves the infiltration of neutrophils into the Crypts of Lieberkuhn
  • Results in the destruction of the intestinal glands by the formation of crypt abscesses and progressive atrophy/ulceration of the mucosa
  • Also infiltrates the submucosa and muscularis
45
Q

IBS

-Accumulation of lymphocytes forms?

A

Granulomas

46
Q

IBS

-Major complications?

A

Occlusion of the intestinal lumen by fibrosis and the formation of fistulas in other segments of the small intestine

47
Q

Fecal microbiota transplant

  • procedure?
  • purpose?
A
  • Fecal matter is transplanted to patient

- Purpose is to replace good bacteria that has been killed

48
Q

Fecal microbiota transplant

-How does the normal microflora become suppressed?

A

-Usually by the use of antibiotics-allows C. difficile to overpopulate the colon-C. diff colitis

49
Q

Large intestine

-Major function of enterocytes?

A

Transport of ions and water

50
Q

Mucosa of the large intestine

-Lined by?

A

A simple columnar epithelium formed by enterocytes and abundant goblet cells
Enterocytes have short microvilli

51
Q

Large intestine-crypts of Lieberkuhn compared to?

A
  • Much deeper than small intestine

- Higher proportion of goblet cells

52
Q

Effect of mineralocorticoids on the large intestine?

-example of a mineralocorticoid?

A

Causes the colon to absorb Na and Cl ions facilitated by plasma membrane channels
-Example-Aldosterone

53
Q

Enterocytes

-Aldosterone MOA?

A

Increases the number of Na channels and increases the absorption of Na
-Na ions entering the enterocyte are extruded by an Na pump

54
Q

Glands of Lieberkuhn

-cell types (Compare to small intestine)?

A

Goblet, enteroendocrine, and stem cells (no paneth cells-small intestine only)

55
Q

Taeniae coli

- Characteristic feature of the large intestine
    - formed by?
A

Formed by fused bundles of the outer smooth muscle layer

56
Q

Contraction of the taeniae coli and the inner circular smooth muscle layer produces?

A

Saccular structures called haustra

57
Q

Appendix

-What is it?

A

Small blind-ending diverticulum from the cecum

58
Q

Appendix

-Most important feature?

A

Thick wall due to accumulations of lymphoid tissue in the lamina propria
-No intestinal villi or crypts, often fatty tissue in the submucosa

59
Q

Small intestine-function?

A
  • Use segmentation contractions to complete chemical digestion of food and nutrient absorption
  • Neutralize acidic chyme from the stomach with bicarbonate ions
  • Absorb water
  • Secrete mucous
59
Q

Appedix-most important feature?

-Due to?

A

THICK WALL due to large accumulations of lymphoid tissue in the lamina propria and submucosa

61
Q

Appendix

  - Thickness of the muscularis externa compared to the rest of the large intestine?
  - Notable about the outer longitudinal smooth muscle layer of the muscularis externa?
A
  • Thinner than in the rest of the large intestine

- The outer longitudinal smooth muscle layer of the muscularis externa DOES not aggregate in the taeniae coli

62
Q

Rectum

-2 regions?

A
  • Rectum proper (upper region)

- Anal canal (lower region)

63
Q

Anal canal extends from?

A

Anorectal junction to the anus

64
Q

Anorectal junction

-Epithelium after anorectal junction?

A

Keratinized stratified squamous epithelium (changes from simple columnar at anorectal junction)

65
Q

Internal anal sphincter is formed by?

A

Thickening of the inner circular layer of smooth muscle

66
Q

External anal sphincter

-Formed by?

A

Skeletal muscle

67
Q

Colorectal tumors

-Defective gene?

A

APC gene-causes excess APC (protein) which activates genes leading to colorectal tumorigenesis

GI Midterm (11 decks)

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