Exam3Lec2Digestive2

Question 1

What three structures make up the GI tract?

Answer 1

stomach + small intestine + large intestine

Question 2

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

Answer 2

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

Question 3

What type of epithelium lines the small intestine ?

Answer 3

Simple columnar w/ microvilii=brushborder

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

Question 4

What are the 3 parts of the small intestine?

Answer 4

Duodenum Jejunum, Ileum

Question 5

Duodenum: 3 points

Answer 5

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

Question 6

Jejunum: 2 points

Answer 6

1. Has the most amount of plicae circulares.
2. Has the most amount of villi

Question 7

Iluem: 3 points

Answer 7

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

Question 8

What are the 4 structures found in the small intestine?

Answer 8

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

Question 9

Microvilli in the digestive tract are termed what?

Answer 9

the “brush border”

Question 10

Mucosa= ____ + ____ + ____

Answer 10

epithelium + lamina propria (CT) + Muscularis mucosa

Question 11

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

Answer 11

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)

Question 12

What are Enterocytes of the SI?

Answer 12

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

Question 13

What are goblet cells in the SI?

Answer 13

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

Question 14

What are Enteroendocrine Cells?

Answer 14

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

Question 15

What are Paneth Cells (unique to small intestine)?

Answer 15

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

Question 16

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

Answer 16

• 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)

Question 17

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

Answer 17

• 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

Question 18

What is the structure of a normal jejunum?

Answer 18

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

Question 19

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

Answer 19

• 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

Question 20

What type of epithelium lines the large intestine?

Answer 20

simple columnar w/ microvilli = “brush border”

Mucosa does NOT have villi but still has crypts

Question 21

What 7 structures is the large intestine made of?

Answer 21

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

Question 22

What is the large intestine formed into?

Answer 22

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

Question 23

What are the cells found in the large intestine?

Answer 23

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

Question 24

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

Answer 24

• 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)

Question 25

What structures does the vermiform appendix NOT have?

Answer 25

Lymph nodules located in the mucosa + submucosa -> but there is **NO folding of the mucosa**, thus **NO villi** Also, **does NOT have tenia coli** ## Footnote NOTE: lymph nodules in the ileum have villi, but nodules in the appendix do NOT have villi

Question 26

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

Answer 26

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

Question 27

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

Answer 27

Recto-anal junction Marked by transition from simple columnar epithelium-> stratified squamous epithelium ## Footnote NOTE: recto-anal jxn is reverse of the esophago-gastric jxn

Question 28

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

Answer 28

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

Question 29

What is Hirschsprung's Disease (Congenital Megacolon)?

Answer 29

* Defect of neural crest cell migration -: incomplete development of large intestine ->lack of haustra + ganglion cells | lack of haustra ## Footnote Ganglion cells = Auerbach’s plexus of nerves (musc. externa) + Meissner’s plexus of nerves (submucosa)

Question 30

What is Inflammatory Bowel Disease?

Answer 30

umbrella term for Ulcerative Colitis + Crohn’s Disease

Question 31

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

Answer 31

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

Question 32

What is crohn's disease? Sx?

Answer 32

**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

Question 33

What is Celiac disease?

Answer 33

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

Question 34

What triggers Celiac disease?

Answer 34

allergy to wheat protein and gluten

Question 35

How is Celiac dieases treated?

Answer 35

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

Question 36

What causes IBD?

Answer 36

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

Question 37

What happens when we have dysfunction of paneth cells?

Answer 37

the pathogenesis of chronic inflammatory bowel disease