6. Small/Large Intestine Histo

Question 1

What is the principal site for digestion of food and absorption of digested products?

Answer 1

Small intestine: duodenum, jejunum and ileum

Question 2

What is the main hallmark for the small intestine which is more visible in the jejunum rather than the ileum?

Answer 2

Plicae Circulares which are transverse folds with submucosal core with intestinal villi

Question 3

Intestinal villi are in the mucosa and project into the lumen of the small intestine to increase absorptive area. The core contains loose CT with a lacteal. What other two things are important in the intestinal villi?

Answer 3

Enterocytes which produce enzymes for digestion/absorption

Goblet cells which provide mucus to sheild from abrasion

Question 4

What is contained inside a lacteal in the intestinal villi?

Answer 4

Blood supply and a lacteal which helps absorb nutrients from the SI

Question 5

Where are plicae circulares with intestinal villi absent?

Answer 5

duodenum

Question 6

Enterocyte microvilli have striated border, increasing luminal surface. What does the terminal web allow?

Answer 6

Terminal web has actin/myosin allowing for contraction of microvilli

Question 7

The mucosa of the SI is simple columnar epithelium with tubular intestinal glands, lamina propria and muscularis mucosae to release gland contents. What about the submucosa, muscularis externa and serosa layers?

Answer 7

all the same as esophagus.
Dense ireg CT
inner circular/outer longitudinal
serosa w loose CT and peritoneum

Question 8

Motility of the SI and LI is controlled mainly by the ANS. What does the enteric (intrinsic) nervous system consist of? (2)

Answer 8

Submucosal plexus of meissner

myenteric plexus of auerbach (in muscularis externa between inner and outer)

Question 9

The intestinal glands are simple tubular glands lined by simple columnar epithelium which is continuous with the epithelium that covers the intestinal villi. What are the 4 types of cells in the intestinal glands?

Answer 9

Enteroendocrine
Paneth
Intestinal Stem cells
M (microfold) cells

Question 10

Enteroendocrine cells are found throughout the intestinal glands and secrete hormones to control gut motility, HCl, bile and other things. What are some of the main hormones they secrete? (5)

Answer 10

Gastrin
Secretin
Gastric Inhibitory polypeptide (GIP)
Motilin
Cholecystokinin (CCK)

Question 11

What type of cells are at the base of intestinal glands mainly only in the SI, which function in innate immunity by secreting antimicrobial substances such as lysozymes?

Answer 11

Paneth cells

Question 12

Paneth cells regulate normal bacterial flora. When these cells are found in the normal colon, what could it suggest?

Answer 12

Pathological conditions

Question 13

Intestinal stem cells (ISCs) reside at the crypt base near paneth cells. They repopulate epithelial lining and can move out a crypts to differentiate into?

Answer 13

Goblet cells, enterocytes, and enterendocrine cells

Question 14

What cell has a deep pocket like recess which houses dendritic, macrophages and T/B cells. It also has microfolds and glycocalyx and overlie PEYER’s patches?

Answer 14

M (microfold) Cells

Question 15

The apical surfaces of M cells express receptors that bind macromolecules and bacteria to do what?

Answer 15

internalize and transfer to immune cells

M CELLS ARE HIGHLY SPECIALIZED ANTIGEN-TRANSPORTING CELLS

Question 16

When differentiating the pyloris (thick d/t sphincter) of the stomach and the duodenum of the SI, what layer is important to look at?

Answer 16

the submucosal layer

Question 17

What is different about the submucosal layer of the of the duodenum compared to the pyloris? hallmark

Answer 17

There are abundant Brunner’s glands in the submucosa, deep to muscularis mucosae

Question 18

Brunner’s glands in the duodenum in the intial SI produce alkaline secretion which neutralize the acidic chyme. What does the duodenum collect?

Answer 18

Collects bile and pancreatic secretion via the hepatopancreatic ampulla (2nd descening part of duodenum at L2-L3)

Question 19

What part has the longest finger-like villi of the SI, with no submucosal glands or peyer’s patches?

Answer 19

Jejunum

Question 20

What part of the SI has shorter finger-like villi than the jejunum, and has island like PEYER’s patches?

Answer 20

Ileum

Question 21

Food is propelled from the ileum to cecum through the ileoceccal valve. Here we can see an abrupt transition from villi of SI to?

Answer 21

glandular epithelium of LI

Question 22

What is the main job of the large intestine?

Answer 22

absorb water, sodium, vitamins, minerals

Question 23

Opening of tubular intestinal glands (crypts of Lieberkuhn) are hallmark of the LI mucosa. What are 3 other hallmarks!

Answer 23

intestinal glands
goblet cells
NO intestinal villi

Question 24

The mucosa of the LI ha simple columnar epithelium and a lamina propria and muscularis mucosae are present. What is extensive here and may penetrate the submucosa?

Answer 24

GALT

Question 25

The LI submucosa is typical along with the inner layer of muscularis externa. What is different about the outer longitudinal layer?

Answer 25

it is organized into taeniae coli which form the haustra to help propel food

Question 26

The veriform appendix is a diverticulum of the cecum with layers similar to those of LI. What are characteristic of the mucosa, submucosa, muscularis and serosa here?

Answer 26

Mucosa has simple columnar epithelium and goblet cells
Sub has ADIPOCYTES and dense ireg CT
Muscularis has undeveloped outer longitudinal layer
Covered in Serosa!

Question 27

What disease is due to mutations in the RET gene which causes failure of neural crest cells (NCC) to migrate and develop the plexuses of the bowel segment?

Answer 27

Hirschprung’s Disease
(85% are short segment confined to rectosigmoid, 10% long-segment from rectosigmoid to splenic flexure, 5% affects entire colon)

Question 28

Hirschprung’s disease occurs 1:5000 neonates. Presents with constipation, poor feeding and abdominal distention. How does one treat this?

Answer 28

Surgical removal of the affected colon segment and reattach ends

Question 29

IBD, inflammatory bowel disease, includes ulcerative colitis and chron’s disease. Characterized by diarrhea, pain and relapses. Chron’s can affect any reion while ulcerative colitis affects?

Answer 29

the mucosa of the LI

Question 30

Chrons is observed in the LI and terminal ileum. Inflammatory cells produce cytokines that damage the intestinal mucosa. Neutrophils infiltrate into the crypts of lieberkuhn and destroy intestinal glands due to crypt abscesses

Answer 30

just FYI I think

Question 31

The rectum proper (upper part) has typical mucosa with tubular intestinal glands and transverse folds. The anal canal (lower part) has what three things?

Answer 31

Anal columns with mucosal folds
Anal sinuses: depressions between columns
Anal glands: extend into submucosa/muscularis externa

Question 32

What is the main job of anal sinuses?

Answer 32

to keep poop inside :)

Question 33

The ENS stops at the pectinate line and what begins for the external anal sphincter?

Answer 33

skeletal muscle

Question 34

The anal canal has three zones, what are they?

Answer 34

colorectal zone
anal transitional zone (ATZ)
squamous zone

Question 35

The colorectal zone is simple columnar epithelium identical to the rectum (upper 1/3 of anal canal) while the squamous zone is?

Answer 35

nonkeratinized stratified squamous epithelium continous with perineal skin (lower 1/3 of anal canal)

Question 36

The ATZ is where simple squamous epithelium becomes?

Answer 36

Stratified squamous epithelium of perianal skin (middle 1/3 of anal canal)

Question 37

What layer forms the internal anal sphincter?

Answer 37

the inner circular layer of the muscularis externa thickens

Question 38

At the recto-anal junction, what two types of cells can be seen?

Answer 38

nonkeratinized stratified squamous epithelium and simple columnar with tubular intestinal glands