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

11/14: Small and Large Intestine Flashcards

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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
What is the least frequent cell in the duodenum?
Mucous cells, frequency increases into the jejunum and ileum (most)
26
Where are paneth cells found?
At base of crypt
27
What do paneth cells contain?
Large eosinophilic granules
28
What do paneth cells produce?
Antibacterial proteins called defensins, and enzymes, including lysozyme
29
Where are enteroendocrine cells scattered throughout?
Mainly in the lower third of the crypt
30
What do enteroendocrine cells stain like?
Pale cytoplasm, broad base and narrow at lumen
31
What do enteroendocrine cells regulate?
GI motility and secretion
32
What do "s" cells secrete?
Secretin
33
What does secretin do?
Stimulates release of bicarbonate from pancreas
34
What do "I" cells secrete?
Cholecystekinin, or CCK
35
What does CCK do?
Pancreatic secretion and contraction of bladder
36
What do "A" cells secrete?
Glucagon (Increase blood sugar)
37
What do "K" cells secrete?
GIP (gastric inhibitory peptide)
38
Where are stem cells located?
Base of crypts
39
How do cells shed?
Migrate up villus, mature, and are shed
40
How often is the epithelial lining replaced?
Roughly every 3-5 days
41
Where is the lamina propria seen?
In core of cilli but also surrounds and supports glands' crypts
42
What make up the lamina propria?
Collagen, reticular fibers, fibroblasts and GAGs
43
Where is MALT located?
In lamina propria and submucosa of small intestine
44
What cells make up MALT?
Lymphocytes (T), plasma cells, eosinophils, macrophages, and mast cells, plasma cells, sec IgA
45
What does the epithelium of MALT contain?
Enlarged "M" cells (microfolds)
46
What are "M" cells (microfold)?
Squamoid enterocytes, modified for Ag sampling, uptake of macromolecules
47
What else is found inside MALT?
Peyer's patches
48
What are Peyer's patches?
dome-shaped areas grossly visible on surface of mucosa, project into lumen
49
What is the dudoenum characterized by?
Presence of brunner's glands in submucosa
50
What are brunner's glands?
Large #’s of highly convoluted, branched, tubuloalveolar submucosal glands
51
What do brunner's glands secrete?
Alkaline mucus (8-9.5) and zymogens; unique to duodenum
52
What is the main function of the duodenum?
Neutralize gastric acid and pepsin, assisted by pancreas and gallbladder
53
What does the alkaline mucus the brunner's glands secrete function for?
Protection against stomach contents entering the duodenum
54
What does the alkaline mucus do to the duodenal contents?
Brings them closer to the pH at which pancreatic enzymes are most effective
55
What is the function of the large intestine?
Modifies fluid content of fecies Specialzied for mucus secretion and salt/water absorption
56
What is the lining of the large intestine?
Mix of absorptive and mucosu cells 1. Columnar cells 2. Mucous cells 3. Endocrine cells 4. Stem cells
57
What is included in the large intestine?
cecum, appendix; ascending, transverse, descending, & sigmoid colon, & rectum
58
What does the large intestine lack?
Villi and plicae circulares
59
What is the primary function of the colon?
H2O & electrolyte resorption; also produces mucus for elimination of undigested food & waste
60
What is found in the colon?
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
What do the mucosal folds of the colon contain?
Core of lamina propria
62
What is the mucosal epithelium similar to in the colon?
Small intestine, but paneth cells generally absent in adults
63
What are the surface cells in the colon?
Mainly columnar with little mucin Rest of the glands shows columnar and mucous (goblet) cells
64
What is the cell population at the base of the colon glands?
Uncommitted stem cells Goblet cells Columnar cells occsaional palestaining endocrine cells
65
What do columnar cells absorb?
Soluble salt and water No brush border enzymes
66
Where can the quality of mucus change?
Colon
67
MALT in the large intestine does NOT form _____
Peyer's patches
68
No _______ present in lamina propria
Lacteals
69
What is the turnover/cell replacement in the large intestine?
Epithelial cell replacement 5 days from stem cells located at base of glandular crypts
70
What bacteria is present in the large intestine?
Commensal ("Coliforms")
71
Describe the outer longitudinal M layer in muscularis externa?
Reduced or incomplete - forms 3 longitudinal strips, taenia coli
72
What is taenia coli responsible for?
Formation of haustra, sacculations of large intestine
73
What is the appendix?
Small, blind-ended sac, distal to ileo-cecal junction
74
What is the appendix used for?
Vestigial cecum; used for bacterial digestion in herbivores
75
What does the appendix contain?
Large amounts of submucosal MALT, active in children
76
What occurs if appendix is inflamed?
Appendicitis, removed by appendectomy
77
Any mass arising from the wall of the colon that protrudes into the lumen
Polyps - adenoma Generally asymptomatic; most common sign, rectal bleeding Tx: Sx removal
78
What can decrease the risk of colon cancer (adenocarcinoma)?
↑ 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
What is treatment of colon cancer?
Tx: Surgical removal; if extensive, may require resection of portion of colon
80
What is contained in the rectum?
Transverse rectal folds and large numbers of mucus glands
81
Describe the epithelium transition between rectum and anal canal
Mucosa from simple columnar epithelium to stratified squamous epithelium at anal canal
82
What folds are contained in the anal canal?
Contain longitudinal folds called anal columns
83
Describe the anal galnds within the anal canal
extend into submucosa & muscularis externa (branched, straight, tubular glands—secrete mucus)
84
What does the surrounding muscle in the rectum form?
internal & external anal sphincters (external— voluntary, skeletal Mm; internal—involuntary, smooth Mm)
85
What are occasional enlargement and irritation of submucosal Vv?
Hemorrhoids
86
What is the anus?
external opening; exit of GI tract
87
Where can hemorrhoids develop?
inside the rectum (internal hemorrhoids) or under the skin around the anus (external hemorrhoids)
88
Describe the difference in referred pain of hemorrhoids
Internal hemorrhoids - follows autonomics, diffuse External hemorrhoids - somatic pain, sharp on well-localized

D1 Fall - Histology (20 decks)

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