Alimentary System II - Intestines

Question 1

What are the three divisions of the small intestine?

Answer 1

Duodenum, jejunum, ileum

Question 2

What are the divisions of the large intestine?

Answer 2

Cecum, colon, rectum, anal canal.

Question 3

Where is the appendix located?

Answer 3

Is is a diverticulum of the cecum.

Question 4

The serosa of the intestines is continuous with what?

Answer 4

The posterior loose CT.

Question 5

Where do blood vessels and nerves enter and exit the intestine (where the lymphatics also exit)?

Answer 5

The mesentery.

Question 6

What is chyme?

Answer 6

Food-acid-stuff in the stomach.

Question 7

Where are Brunner glands located and what do they secrete? Precisely where do they secrete their product?

Answer 7

Located in the submucosa of the proximal duodenum. They secrete a bicarbonate-rich secretion to neutralize acidic chyme. Secretion occurs in the ducts that open to the base of the intestinal crypts.

Question 8

What glands are the ONLY submucosal glands in the intestines?

Answer 8

Brunner glands.

Question 9

What makes up the core of intestinal villi?

Answer 9

Loose CT.

Question 10

What are the lymphatics of intestinal villi called?

Answer 10

Central lacteals.

Question 11

What are the functions of the smooth muscle within the intestinal villi? What layer is this smooth muscle derived from?

Answer 11

Function is to squeeze the lymph out of the lacteal and into the lymphatic circulation. Contraction of these muscles also aids in absorption of nutrients. Derived from muscularis mucosae.

Question 12

Can wandering lymphocytes be found in the intestinal villi?

Answer 12

Yup

Question 13

What is lymph fluid in intestinal villi called?

Answer 13

Chyle

Question 14

What are Crypts of Lieberkuhn? What two important cells are found in them?

Answer 14

Glandular invaginations of intestinal epithelium that project into the lamina propria.

2 cells:

1. Stem cells
2. Paneth cells

Question 15

What do Paneth cells do? Where are they found? What is a histologic identifier of these cells?

Answer 15

They secrete antimicrobial products such as lysozyme. Found in intestinal villi. Histologically these have highly eosinophilic granules.

Question 16

What are Plicae circulares? What cell layer forms the core of these structures? In which intestinal segments are these absent?

Answer 16

Macro-outfoldings that project into the lumen of the small intestine. Submucosal cells form the core, mucosal cells form villi. Absent in proximal duodenum and distal ileum.

Question 17

Do goblet cells increase in number distally in the GI tract?

Answer 17

Yes.

Question 18

What functions does the glycocalyx perform?

Answer 18

Absorbs enzymes from the pancreas and activates them through a cascade.

Question 19

Describe the cascade that is involved in glycocalyx zymogen activation.

Answer 19

Tripsinogen —-> tripsin with enterokinase enzyme. Tripsin leads to zymogen activation.

Question 20

What happens in Celiac disease?

Answer 20

Inflammatory reaction that leads to atrophy of villi, which leads to malabsorption, etc.

Question 21

Describe what goblet cells look like in H&E.

Answer 21

Largely unstained, nuclei are pushed to basal end of the cell. Flower petal appearance.

Question 22

Compare open vs. closed type enteroendocrine cells.

Answer 22

Open enteroendocrine cells reach the gut lumen and can sample the lumenal environment. These are also regulated by the lumenal environment.

Closed enteroendocrine cells do not reach the lumen. They are open to interstitial tissue and can be regulated through neural and paracrine mechanisms.

Both types can secrete products into interstitial CT where they can be taken up via fenestrated capillaries.

Question 23

Where are Auerbach’s plexus neurons located? Where are Meissner’s plexus neurons located?

Answer 23

Auerbach’s are located between muscle walls. Meissner’s are located in the submucosal layer.

Question 24

Where are Peyer’s patches found?

Answer 24

Ileum

Question 25

What are the main functions of the large intestine?

Answer 25

Concentrate feces, resorb water, electrolytes and certain vitamins.

Question 26

Does the large intestine have villi? Does the appendix have teniae coli?

Answer 26

Nope. Just Chuck Testa with another life-like mount.

Nope.

Question 27

What are the three cell types found in the colonic mucosa?

Answer 27

Columnar (absorptive) cells, goblet cells, enteroendocrine cells.

Question 28

What structures do the apical region of colonic mucosal columnar cells have?

Answer 28

Microvilli with a glycocalyx coat.

Question 29

Does the appendix have lymphoid tissues?

Answer 29

Yes, lymphoid nodules and M cells are in the appendix.

Question 30

What is unusual about the muscularis externa of the colon? What is this called?

Answer 30

The outer longitudinal layer is gathered into three thick bands called the teniae coli.

Question 31

The smooth muscle cells found in the core of villi are continuous with which muscle layer?

Answer 31

The inner circular layer of the muscularis mucosae.

Question 32

Where are M cells found in the small intestine?

Answer 32

Intervillar epithelium.

Question 33

Is enterokinase membrane-bound?

Answer 33

Nope.