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D1 Fall Histology > 11/14: Small and Large Intestine > Flashcards

11/14: Small and Large Intestine Flashcards

1
Q

What is the site of absorption and completion of digestion?

A

Small intestine

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2
Q

What do the modifications on the small intestine do?

A

Increase surface area

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3
Q

How do mucosa and submucosa throughout the small intestine arrange?

A

In valve-like folds/ring called plicae circulares, they contain submucosal cores (villi)

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4
Q

What is the mucosal surface of the small intestine made of?

A

Villi, contain core of lamina propria

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5
Q

What are between villi?

A

Crypts of lieberkuhn

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6
Q

What is the epithelium supported by?

A

CT lamina propria, containing capillaries and lymphatics for absorption of nutrients

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7
Q

What are intestinal villi lined by?

A

Simple columnar epithelium

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8
Q

What does celiac disease cause?

A

Villus blunting, atrophy and loss -> malabsorption and weight loss

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9
Q

What is the presence of lymphocytes epithelial cells?

A

Intraepithelial lymphocytes

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10
Q

What are the 3 functional zone in the epithelium of the small intestine?

A
  1. Villi
  2. Crypts
  3. Neck - where the villi and crypts meet
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11
Q

What are the cells of the SI epithelium?

A
  1. enterocytes
  2. Mucous cells
  3. Paneth cells
  4. Endocrine cells
  5. Stem cells
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12
Q

What are mucosal cells of the small intestine?

A

Enterocytes

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13
Q

What do enterocytes cover?

A

Surface of the villi

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14
Q

What is in the apical/luminal surface?

A

Highly folded, modified into 2-3000 microvilli (striated or brush border)

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15
Q

What is the function of the microvilli?

A

Increase surface area for absorption

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16
Q

What are microvilli coated with?

A

Protective glycocalyx containing enzymes important for digestion

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17
Q

What do the lateral walls of enterocytes have?

A

Complex interdigitations

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18
Q

What and how are enterocytes separated from?

A

Luminal surface by desmosomes and tight junctions

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19
Q

where are mucous cells?

A

Interspersed among enterocytes

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20
Q

What are mucous cells?

A

Mucus secreting goblet cells

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21
Q

Where are goblet cells found?

A

In the upper 2/3 of the crypts

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22
Q

What do goblet cells synthesize?

A

Mucinogen (mucus)

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23
Q

Where is mucinogen stored?

A

In membrane-bound granules

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24
Q

What is the function of mucinogens?

A

Lubricate and protect epithelium

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25
Q

What is the least frequent cell in the duodenum?

A

Mucous cells, frequency increases into the jejunum and ileum (most)

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26
Q

Where are paneth cells found?

A

At base of crypt

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27
Q

What do paneth cells contain?

A

Large eosinophilic granules

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28
Q

What do paneth cells produce?

A

Antibacterial proteins called defensins, and enzymes, including lysozyme

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29
Q

Where are enteroendocrine cells scattered throughout?

A

Mainly in the lower third of the crypt

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30
Q

What do enteroendocrine cells stain like?

A

Pale cytoplasm, broad base and narrow at lumen

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31
Q

What do enteroendocrine cells regulate?

A

GI motility and secretion

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32
Q

What do “s” cells secrete?

A

Secretin

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33
Q

What does secretin do?

A

Stimulates release of bicarbonate from pancreas

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34
Q

What do “I” cells secrete?

A

Cholecystekinin, or CCK

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35
Q

What does CCK do?

A

Pancreatic secretion and contraction of bladder

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36
Q

What do “A” cells secrete?

A

Glucagon (Increase blood sugar)

37
Q

What do “K” cells secrete?

A

GIP (gastric inhibitory peptide)

38
Q

Where are stem cells located?

A

Base of crypts

39
Q

How do cells shed?

A

Migrate up villus, mature, and are shed

40
Q

How often is the epithelial lining replaced?

A

Roughly every 3-5 days

41
Q

Where is the lamina propria seen?

A

In core of cilli but also surrounds and supports glands’ crypts

42
Q

What make up the lamina propria?

A

Collagen, reticular fibers, fibroblasts and GAGs

43
Q

Where is MALT located?

A

In lamina propria and submucosa of small intestine

44
Q

What cells make up MALT?

A

Lymphocytes (T), plasma cells, eosinophils, macrophages, and mast cells, plasma cells, sec IgA

45
Q

What does the epithelium of MALT contain?

A

Enlarged “M” cells (microfolds)

46
Q

What are “M” cells (microfold)?

A

Squamoid enterocytes, modified for Ag sampling, uptake of macromolecules

47
Q

What else is found inside MALT?

A

Peyer’s patches

48
Q

What are Peyer’s patches?

A

dome-shaped areas grossly visible on surface of mucosa, project into lumen

49
Q

What is the dudoenum characterized by?

A

Presence of brunner’s glands in submucosa

50
Q

What are brunner’s glands?

A

Large #’s of highly convoluted,
branched, tubuloalveolar submucosal glands

51
Q

What do brunner’s glands secrete?

A

Alkaline mucus (8-9.5) and zymogens; unique to duodenum

52
Q

What is the main function of the duodenum?

A

Neutralize gastric acid and pepsin, assisted by pancreas and gallbladder

53
Q

What does the alkaline mucus the brunner’s glands secrete function for?

A

Protection against stomach contents entering the duodenum

54
Q

What does the alkaline mucus do to the duodenal contents?

A

Brings them closer to the pH at which pancreatic enzymes are most effective

55
Q

What is the function of the large intestine?

A

Modifies fluid content of fecies
Specialzied for mucus secretion and salt/water absorption

56
Q

What is the lining of the large intestine?

A

Mix of absorptive and mucosu cells
1. Columnar cells
2. Mucous cells
3. Endocrine cells
4. Stem cells

57
Q

What is included in the large intestine?

A

cecum, appendix; ascending,
transverse, descending, & sigmoid colon, & rectum

58
Q

What does the large intestine lack?

A

Villi and plicae circulares

59
Q

What is the primary function of the colon?

A

H2O & electrolyte resorption; also produces mucus for elimination of undigested food & waste

60
Q

What is found in the colon?

A

Large #s of goblet cells in epithelium and colonic glands in submucosa
NO brunner’s glands
NO villi for nutrient absorption
NO plicae circulares

61
Q

What do the mucosal folds of the colon contain?

A

Core of lamina propria

62
Q

What is the mucosal epithelium similar to in the colon?

A

Small intestine, but paneth cells generally absent in adults

63
Q

What are the surface cells in the colon?

A

Mainly columnar with little mucin
Rest of the glands shows columnar and mucous (goblet) cells

64
Q

What is the cell population at the base of the colon glands?

A

Uncommitted stem cells
Goblet cells
Columnar cells
occsaional palestaining endocrine cells

65
Q

What do columnar cells absorb?

A

Soluble salt and water
No brush border enzymes

66
Q

Where can the quality of mucus change?

A

Colon

67
Q

MALT in the large intestine does NOT form _____

A

Peyer’s patches

68
Q

No _______ present in lamina propria

A

Lacteals

69
Q

What is the turnover/cell replacement in the large intestine?

A

Epithelial cell replacement 5 days from stem cells located at base of glandular crypts

70
Q

What bacteria is present in the large intestine?

A

Commensal (“Coliforms”)

71
Q

Describe the outer longitudinal M layer in muscularis externa?

A

Reduced or incomplete - forms 3 longitudinal strips, taenia coli

72
Q

What is taenia coli responsible for?

A

Formation of haustra, sacculations of large intestine

73
Q

What is the appendix?

A

Small, blind-ended sac, distal to ileo-cecal junction

74
Q

What is the appendix used for?

A

Vestigial cecum; used for bacterial digestion in herbivores

75
Q

What does the appendix contain?

A

Large amounts of submucosal MALT, active in children

76
Q

What occurs if appendix is inflamed?

A

Appendicitis, removed by appendectomy

77
Q

Any mass arising from the wall of the colon that protrudes into the lumen

A

Polyps - adenoma
Generally asymptomatic; most common sign, rectal bleeding
Tx: Sx removal

78
Q

What can decrease the risk of colon cancer (adenocarcinoma)?

A

↑ roughage & fiber in diet ↓ colon cancer by ↓ transit time & ↑ GI motility
New test kits for early detection; detect tumor Ab; also colonoscopy screening over 50

79
Q

What is treatment of colon cancer?

A

Tx: Surgical removal; if extensive, may require resection of portion of
colon

80
Q

What is contained in the rectum?

A

Transverse rectal folds and large numbers of mucus glands

81
Q

Describe the epithelium transition between rectum and anal canal

A

Mucosa from simple columnar epithelium to stratified squamous epithelium at anal canal

82
Q

What folds are contained in the anal canal?

A

Contain longitudinal folds called anal columns

83
Q

Describe the anal galnds within the anal canal

A

extend into submucosa & muscularis externa (branched, straight, tubular glands—secrete mucus)

84
Q

What does the surrounding muscle in the rectum form?

A

internal & external anal sphincters (external— voluntary, skeletal Mm; internal—involuntary, smooth Mm)

85
Q

What are occasional enlargement and irritation of submucosal Vv?

A

Hemorrhoids

86
Q

What is the anus?

A

external opening; exit of GI tract

87
Q

Where can hemorrhoids develop?

A

inside the rectum (internal hemorrhoids) or under the skin around the anus (external hemorrhoids)

88
Q

Describe the difference in referred pain of hemorrhoids

A

Internal hemorrhoids - follows autonomics, diffuse
External hemorrhoids - somatic pain, sharp on well-localized

D1 Fall Histology (20 decks)

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