Histology of the Lower GI

Question 1

What is chyme?

Answer 1

The semifluid mass of partly digested food expelled by the stomach into the duodenum.

Question 2

Name the four degrees of folding in the small intestine which aids in increasing surface area.

Answer 2

1. Plicae circulares
2. Intestinal Villi
3. Intestinal glands (crypts of lieberkuhn
4. microvilli on the apical surface of the enterocytes

Question 3

What are plicae circulares?

Answer 3

Permanent folds of mucosa and submucosa.

Question 4

Where would you find the most and well defined plicae circulares?

Answer 4

In the jejunum. PC begins in the duodenum, distinct in the jejunum, and disapear in the mid-ileum.

Question 5

What are intestinal villi?

Answer 5

Finger-like projections of the mucosa covering the entire surface of the small intestine.

Question 6

What forms the crypts of lieberkhn (intestinal glands)?

Answer 6

They are simple tubular glands that are formed by invaginations of the mucosa between adjacent intestinal villi.

Question 7

What cell types are found in the intestinal crypts?

Answer 7

1. Absorptive
2. goblet cells
3. Paneth cells
4. enteroendocrine cells

Question 8

What creates the brush border of the intestinal lining?

Answer 8

Evaginations of the apical part of the enterocytes to increase surface area.

Question 9

In what layer of the intestinal lining are you likely to find arterial and venous supply?

Answer 9

Muscularis Mucosa

Question 10

What layer of the intestinal lining is responsible for peristalsis and segmentation?

Answer 10

Muscularis externa

Question 11

What is segmentation?

Answer 11

A pattern of annular contraction of the smooth muscle layer int he walls of the small intestine which temporarily cut the region affected into individual compartments; this activity serves to mix the chyme within the small intestine.

Question 12

In order for segmentation to function as a mixer, how must the area above and below act?

Answer 12

The above must not be coordinated with the relaxation of the part below.

Question 13

In order for peristalsis to function as moving things along how must the area above and below act?

Answer 13

Contents advance along when proximal contraction is coordinated with the relaxation below.

Question 14

In what layer of the intestinal wall are larger vessels found from where they distribute out to enter the mucosa?

Answer 14

Submucosa.

Question 15

What are two capillary networks found on the linings of the intestinal wall?

Answer 15

1. the villus capillary plexus which supplies the intestinal villus and upper portion of crypts of lieberkuhn
2. the pericryptal capillary plexus supplies the lower half of the crypts of lieberkuhn

Question 16

what part of the intestinal folds are lacteals found in?

Answer 16

At the core of a villus

Question 17

What are chyles?

Answer 17

lymph containing lipids absorbed from the meal and packaged in chylomicrons.

Question 18

That is the flow of chyle from the intestine to systemic circulation?

Answer 18

Lacteals convey chyle from the intestine to the lymphatic circulation and thereby to the thoracic duct and then to the systemic blood circulation

Question 19

How is motility of the small intestine controlled?

Answer 19

Controlled by the ANS thorugh submucsoal and myenteric plexi.

Question 20

Which autonomic innervation causes contraction of intestinal wall?

Answer 20

parasympathetic

Question 21

True or False: Contraction of intestinal wall smooth muscle leads to both peristalsis AND segmentation

Answer 21

True

Question 22

Where are Brunner’s glands found? Be specific.

Answer 22

Found in the duodenum in the portion of the duodenum that’s above the hepatopanreatic sphincter.

Question 23

What is the main function of the brunner’s glands?

Answer 23

The main function is to produce a mucus-rich alkaline secretion (containing bicoarbonate) in order to protect the duodenum from the acidic content of chyme.

Question 24

What are the distinctive features of duodenum that seprates it form jejunum and ileum?

Answer 24

Presence of Brunner’s glands in submucosa

• relatively few goblet cells
• leaf-like villi

Question 25

Whare the distinctive features of the jejunum?

Answer 25

- well-developped plicae circulares - irregular vili - more goblet cells - NO brunner's glands and NO peyer's patches

Question 26

What are the distinctive features of the eleum?

Answer 26

- Peyer's patches in LP and submucosa - Finger-like villi - most goblet cells

Question 27

What type of epithelium lines the crypts of lieberkhun?

Answer 27

Simple columnar epithelium

Question 28

what enzymes are you likely to find on the microvilli lining of the absorptive cells in the small intestine?

Answer 28

lactose, maltose, sucrose for terminal digestion of carbs.

Question 29

In persons with lactose intolerance, what happens to lactose once ingested?

Answer 29

It passes through undigested until large intestine. In the large intestine it is fermented via intestinal bacteria into gas, organic acids and etc.

Question 30

Where are Paneth cells found? Be specific.

Answer 30

Found at the base of crypts in the small intestine.

Question 31

What function do Paneth cells serve?

Answer 31

Secrete antimicrobial proteins to limit bacteria-enterocyte contact, which also kills bacteria directly by enzymatic degredation of bacterial wall or by disrupting the bacterial inner membrane.

Question 32

What hormones do enteroendocrine cells of the SI produce?

Answer 32

Gastrin, secretin and CCK

Question 33

There are several protective mechanism that which protect the small intestine from pathogens and abrasions and etc. What are these mechanisms?

Answer 33

1. A viscous gel-like balnket produced by goblet cells 2. An intestinal tight junction barrier between enterocytes 3. Peyer's patches which participates in the cellular surveilance of antigens 4. IgA secreted by intestinal epithelium in the bile 5. Inactivation of microbial pathogen by antimicrobial proteins produced by paneth cells. 6. the propulsive intestinal motility that prevents bacterial colonization

Question 34

What is the initial alteration of the intestinal mucosa caused by leading to IBD?

Answer 34

infiltration of neutrphils in the crypts of lieberkhun which results in destruction of the intestinal blands by formation of crypts abscesses and progressive atrophy and ulceration of the mucosa.

Question 35

one of the major complication of ___ are occusion of the intestinal lumen by fibrosis and the formation of fistulas in other segments of the small intestine?

Answer 35

IBD

Question 36

What are the symptoms of c. diff colitis and how can it treated?

Answer 36

debiliating, sometimes fatal diarrhea. TX: fecal Microbiota transplant (FMT)

Question 37

Would you find intestinal villi in the large intestine?

Answer 37

No

Question 38

Would you find crypts of lieberkhun in the large intestine?

Answer 38

Yes

Question 39

What cells are found on the epithelial surface of the tubular glands of the large intestine?

Answer 39

1. Absorptive cells 2. Goblet cells 3. Stem cells 4. Enteroendocrine cells.

Question 40

what are Taenia Coli?

Answer 40

Feature of large intestine, formed by fused bundles of the outer smooth muscle layer

Question 41

What produces the saccular s Haustra?

Answer 41

contraction of the taenia coli and the inner circular smooth msucle .

Question 42

is the most distinctive feature of the appendix that makes it different from the rest of the GI?

Answer 42

Thickening of it's wall which is mainly due to large accumulation of lymphoid tissue int he lamina propria and submucsoa.

Question 43

where is the pectinate line?

Answer 43

It's the transformation zone at the ano-rectal junction where the epithelium changes from simple columnar to stratified squamous.

Question 44

What forms the internal anal sphincter?

Answer 44

The inner circular layer of smooth muscle thickens to form the internal anal sphincter

Question 45

what is the external anal sphincter formed by?

Answer 45

skeletal muscle

Question 46

Familial polyposis and colectal tumriogeneis is determined by a defect in what gene?

Answer 46

APC gene (adenomatous polyposis coli)

Question 47

Sigmoidal colon cancer metastesize via what route?

Answer 47

Inferior mesenteric vein.