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Histology > Exam3Lec2Digestive2 > Flashcards

Exam3Lec2Digestive2 Flashcards

1
Q

What three structures make up the GI tract?

A

stomach + small intestine + large intestine

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2
Q

What is the junction that connects the stomach and the duodenum (small intestine) and its marked by the transition of what epithelium?

A

Gastro-duodenal Junction
Marked by transition from simple columnar epithelium-> simple columnar epithelium w/ villi + crypts

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3
Q

What type of epithelium lines the small intestine ?

A

Simple columnar w/ microvilii=brushborder

The epithelium is a part of the mucosa, which is folded then termed villi

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4
Q

What are the 3 parts of the small intestine?

A

Duodenum Jejunum, Ileum

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5
Q

Duodenum: 3 points

A
  1. Has plicae circulares only in the distal portion
  2. Has shorter villi
    3. Only structure that has Brunner’s glands (in submucosa)

shortest segment

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6
Q

Jejunum: 2 points

A
  1. Has the most amount of plicae circulares.
  2. Has the most amount of villi
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7
Q

Iluem: 3 points

A
  1. Has plicae circulares only in the proximal portion
  2. Has shorter villi
  3. Only structure that has Peyer’s Patches (lymph nodules)

longest segment
connects to large intestine

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8
Q

What are the 4 structures found in the small intestine?

A
  1. Microvili w/ glycocalyx: on top of epithelium (mucosa)
  2. Vili: folding of mucosa
  3. Crypts of Lieberkuhn: glands b/w the bases of the vili (mucosa)
  4. Plicae circulares: folding of the submucosa

***NOTE: all these structures help to increase surface area!
Glycocalyx sits on top of microvilli + store digestive enzymes

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9
Q

Microvilli in the digestive tract are termed what?

A

the “brush border”

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10
Q

Mucosa= ____ + ____ + ____

A

epithelium + lamina propria (CT) + Muscularis mucosa

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11
Q

What are the cells found in the mucosa of the small intestine?

A
  1. Enterocytes
  2. Goblet cells
  3. Enteroendocrine Cells
  4. Paneth Cells (unique to small intestine)
  5. M-cells (ileum in small intestine + appendix in large intestine)
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12
Q

What are Enterocytes of the SI?

A

absorptive cells
* Make up the epithelium (i.e., they are “THE” cells of the epithelium)
* Connected to microvilli, which sit on top of the epithelium
* Contain glycocalyx of microvilli ->stores digestive enzymes

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13
Q

What are goblet cells in the SI?

A

Found everywhere (but mostly in ileum)-> secrete mucous

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14
Q

What are Enteroendocrine Cells?

A

Secrete hormones (dark staining granules) = gastrin, CCK, secretin

*NOTE: digestive system uses the term “enteric”… so anything “entero” refers to this region of the body

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15
Q

What are Paneth Cells (unique to small intestine)?

A
  • Found near the bottom of the crypts (of Lieberkühn)
  • Secrete lysozyme (pink staining granules) + regulate bacterial flora
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16
Q

M – Cells
Where are they found in the SI?
Act as?
Transports?

A
  • Found in peyer’s patches (lymphatic nodules)
  • Act as antigen presenting cells (APCs) = immune cells
  • Transport Ags from lumen into the lamina propria (loose CT)
17
Q

Summary: Mucosa of the small intestine
* villi:
* crypts of Lieberkühn:
* epithelium:
* Gut Associated Lymphatic Tissue (GALT) in what?
Mucosa and submucosa
* What is there?

A
  • villi – mucosal projections containing lacteal
  • crypts of Lieberkühn – intestinal glands in the mucosa
  • epithelium: simple columnar (covers villi and crypts)
  • Gut Associated Lymphatic Tissue (GALT) in the lamina propria
  • Mucosa: plicae circulares
18
Q

What is the structure of a normal jejunum?

A

The mucosa is folded into villi which helps to increase surface area = good for absorption of nutrients

19
Q

What is celiac disease?
what does it affect?
caused by?
results in?
tx?

A
  • The mucosa is flattened-> loss of villi (mucosal folding) leads to decreased absorption
  • affects only the jejunum
    Caused by an allergy to gluten (wheat protein)
  • Results in immune-mediated inflammation
  • Tx = removal of gluten from diet relieves inflammation->thus, villi return to normal (folded) structure

only in jejunum

There is no cure, but diet alterations prevent patients from feeling the effects of the disease

20
Q

What type of epithelium lines the large intestine?

A

simple columnar w/ microvilli = “brush border”

Mucosa does NOT have villi but still has crypts

21
Q

What 7 structures is the large intestine made of?

A
  1. Cecum : connects to ileum of small intestine
  2. Vermiform Appendix: Contains lymph nodules in large intestine
  3. Ascending Colon
  4. Transverse Colon
  5. Descending Colon
  6. Sigmoid Colon
  7. Rectum = connects to anus
22
Q

What is the large intestine formed into?

A

Formed into haustra (segmented pouches) w/ tenia coli (muscle)

23
Q

What are the cells found in the large intestine?

A
  1. Enterocytes (absorptive cells) = epithelial cells w/ microvilli
    2.Goblet cells = most numerous in descending colon
  2. Enteroendocrine cells
  3. M-cells = only in appendix of large intestine + ileum of small intestine

bolded is hy for exam

Microvilli does NOT have digestive enzymes b/c there is no digestion occurring
***NOTE: large intestine has same cells as small intestine except Paneth cells

24
Q

What type of epithelium lines the Vermiform Appendix of the large intestine and what type of cells does it contain?

A
  • Epithelium = simple columnar
  • Contains enterocytes (absorptive cells) + M-cells (immune) + few goblet cells
  • M-cells: act as APCs in the lymph nodules

Only location in the large intestine where M-cells are found
NOTE: M – cells also found in lymph nodules (peyer’s patches) of ileum (small intestine)

25
Q

What structures does the vermiform appendix NOT have?

A

Lymph nodules located in the mucosa + submucosa -> but there is NO folding of the mucosa, thus NO villi

Also, does NOT have tenia coli

NOTE: lymph nodules in the ileum have villi, but nodules in the appendix do NOT have villi

26
Q

What type of epithelium do the following structures have?
A. Rectus
B. Anal canal
C. Anus

A

A. Rectus:simple columnar
B. Anal canal: stratified squamous
C. Anus:keratinized stratified squamous

27
Q

What connects the rectum to the anal canal and its marked by transion of what type of epithelium?

A

Recto-anal junction
Marked by transition from simple columnar epithelium-> stratified squamous epithelium

NOTE: recto-anal jxn is reverse of the esophago-gastric jxn

28
Q

For the Enteric Nervous system of the Large intestine, what are the ganglions that form the nerve plexuses and their location?

A

Auerbach’s plexus ->located b/n the outer longitudinal + inner circular layers of muscularis externa
Meissner’s plexus ->located in the submucosa

Ganglions located in the large intestine establish nervous system role in digestive tract

NOTE: muscularis mucosa is part of the mucosa, muscularis externa is not

29
Q

What is Hirschsprung’s Disease (Congenital Megacolon)?

A
  • Defect of neural crest cell migration -: incomplete development of large intestine ->lack of haustra + ganglion cells

lack of haustra

Ganglion cells = Auerbach’s plexus of nerves (musc. externa) + Meissner’s plexus of nerves (submucosa)

30
Q

What is Inflammatory Bowel Disease?

A

umbrella term for Ulcerative Colitis + Crohn’s Disease

31
Q

What is Ulcerative Colitis?
What does it affect?
Sx?
Tx?

A

only affects colon
* Formation of granulation tissue ->disrupts normal tissue -> loss of mucosa = loss of absorptive function of epithelium
* Increased expression of VEGF (vascular endothelial growth factor) causes proliferation of blood vessels
* Sx = decreased water resorption resulting in watery diarrhea + bleeding
* Tx = INFLIXIMAB = anti-TNF (tumor necrosis factor) therapy

lack of mucosa

Granulation tissue associated w/ proliferation of blood + lymphatic vessels in the lamina propria (loose CT of mucosa)

32
Q

What is crohn’s disease?
Sx?

A

affects any part of large intestine
* Formation of granulation tissue -> multiple “skip lesions” throughout areas of the large intestine-> gives cobblestone appearance to mucosa
* Sx = decreased water resorption resulting in watery diarrhea + bleeding

33
Q

What is Celiac disease?

A

immune-mediated inflammation which leads to flattening of jejunal surface = extensive loss of villi

34
Q

What triggers Celiac disease?

A

allergy to wheat protein and gluten

35
Q

How is Celiac dieases treated?

A

No cure
villi usually returns to normal structure when wheat and its products are excluded from diet

36
Q

What causes IBD?

A

Cause is unknown
Believed it results from:
* errant host reactions with intestinal microbiota
* intestinal epithelial dysfunction
* aberrant mucosal immune responses

37
Q

What happens when we have dysfunction of paneth cells?

A

the pathogenesis of chronic inflammatory bowel disease

Histology (39 decks)

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