Histology of the SI/LI

Question 1

What are the parts of the small intestine?

Answer 1

duodenum, jejunum, and the ileum

Question 2

what is the function of the small intestine?

Answer 2

principal site for digestion of food and absorption of digestion products

Question 3

what are the transverse folds that are found in the small intestine lumen called? and what are they made up of?

Answer 3

plicae circulares (made up of mucosa with a submucosal core)

Question 4

where are the plicae circulares visible?

Answer 4

they are visible in the jejunum, less so in the ileum

Question 5

what are found on top of the plicae circulares?

Answer 5

intestinal villi

Question 6

what are intestinal villi covered with/ what cells are found in this layer?

Answer 6

simple columnar epithelium of enterocytes and goblet cells

Question 7

what is the core of the intestinal villi made up of?

Answer 7

loose connective tissue with microvasculature and a lacteal

Question 8

what are lacteals important for?

Answer 8

they absorb lipids from the diet

Question 9

what do the enterocytes have on them?

Answer 9

microvilli

Question 10

what do enterocytes produce?

Answer 10

enzymes for digestion and absorption

Question 11

what is the function of goblet cells?

Answer 11

they produce a mucus coating to shield from abrasion and bacterial invasion

Question 12

what type of epithelium makes up the mucosal layer of the SI?

Answer 12

simple columnar epithelium

Question 13

what is found within the simple columnar epithelium of the mucosal layer of the SI?

Answer 13

tubular intestinal glands (aka crypts)

Question 14

besides the epithelium, what else makes up the mucosal layer of the SI?

Answer 14

the lamina propria and the muscularis mucosae

Question 15

what is the submucosa of the SI made up of?

Answer 15

dense irregular CT with neurovasculature, lymphatics, and glands may also be present

Question 16

what is the muscularis layer of the SI made up of?

Answer 16

inner circular and outer longitudinal layers

Question 17

what is the serosa of the SI made up of?

Answer 17

loose CT covered by visceral peritoneum

Question 18

What are the intestinal glands lined by?

Answer 18

simple columnar epithelium

Question 19

what cells are found within the intestinal glands?

Answer 19

paneth cells, M cells, intestinal stem cells, and enteroendocrine cells

Question 20

where do the intestinal glands open into?

Answer 20

the luminal surface of the intestine at the base of the villi

Question 21

What do paneth cells llok like?

Answer 21

they are pyramidal-shaped cells at the base of the intestinal glands; they have large eosinophilic (pink staining) granules in their apical cytoplasm

Question 22

what is the function of Paneth cells?

Answer 22

innate immunity by secreting antimicrobial substances (such as lysozymes and alpha defensins); they also regulate normal bacterial flora via antibacterial action and phagocytosis

Question 23

where do intestinal stem cells reside?

Answer 23

in a niche at the intestinal gland base, near paneth cells

Question 24

what types of cells can the intestinal stem cell repopulate?

Answer 24

goblet cells, enterocytes, and enteroendocrine cells

Question 25

where are M cells located?

Answer 25

in the ileal mucosa-overlying the peyer patches

Question 26

what are M cells main function?

Answer 26

highly specialized antigen-transporting cells

Question 27

what is an example of a specific bacteria that M cells will bind to?

Answer 27

gram-negative bacteria (e.g. E. coli)

Question 28

when looking at the duodenum, what would you expect to see in the mucosal layer?

Answer 28

simple columnar epithelia with scattered goblet cells

Question 29

what is the hallmark for identifying the duodenum?

Answer 29

in the duodenum's submucosal layer, there are duodenal glands

Question 30

what is the composition of the duodenal glands in the submucosal layer?

Answer 30

tubuloacinar mucous glands that produce an alkaline secretion (it neutralizes acidic chyme)

Question 31

when looking at the jejunum, what would you expect to see in the mucosal layer?

Answer 31

long-finger like villi with a villus core containing a well-developed lacteal; tubular intestinal glands; lymphoid follicles in the lamina propria

Question 32

when looking at the ileum, what would you expect to see in the mucosal layer?

Answer 32

the villi are typically shorter than the jejunum; peyer's patches; paneth cells found at the base of the intestinal glands

Question 33

how can you tell that you are looking at the gastroduodenal junction?

Answer 33

the stomach lacks the submucosal glands and then the duodenum has the submucosal glands

Question 34

what is the function of the LI?

Answer 34

absorbs water, sodium, vitamins, and minerals; will uptake sedatives, anesthetics, and steroids

Question 35

what is the hallmark for identifying the large intestine on histological slides?

Answer 35

the intestinal glands and goblet cells; NO INTESTINAL VILLI

Question 36

what cells make up the mucosal layer of the LI?

Answer 36

colonocytes, goblet cells, stem cells, and enteroendocrine cells

Question 37

what is extensive in the mucosal layer of the colon?

Answer 37

the GALT- it may penetrate the submucosa

Question 38

what happens to the outer longitudinal layer in the muscularis layer of the LI?

Answer 38

it gets organized into taeniae coli--> this forms the haustra of the LI

Question 39

what is Hirschprung's disease/ megacolon?

Answer 39

it is when there is aganglionosis of the distal gut tube

Question 40

what causes Hirschprung's disease?

Answer 40

mutations of the RET gene- normally required for migration and differentiation of NCC; so there is a failure of NCC development in both plexuses of the bowel segment

Question 41

what is short-segment hirschprung's disease?

Answer 41

confined to the rectosigmoid region

Question 42

what is long-segment hirschprung's disease?

Answer 42

it extends past the rectosigmoid region to the splenic flexure

Question 43

what is the presentation of hirschprung's disease?

Answer 43

constipation, poor-feeding, and progressive abdominal distention

Question 44

where are the circumanal glands found?

Answer 44

they are large apocrine glands surrounding the anal orifice

Question 45

what are the three zones of the anal canal?

Answer 45

the colorectal zone, the anal transition zone, and the squamous zone

Question 46

what is the colorectal zone?

Answer 46

it is simple columnar epithelium (the upper 1/3 of the anal canal); identical to the rectum

Question 47

what is the anal transitional zone?

Answer 47

the middle 1/3 of the anal canal; area where we have a change from our simple columnar epithelium to stratified squamous epithelium of the perianal skin

Question 48

what is the squamous zone?

Answer 48

it is the external portion of the anal canal; the lower 1/3 of the anal canal; it is stratified squamous epithelium that is continuous with perineal skin

Question 49

how does the internal anal sphincter form?

Answer 49

at the level of the anus, the inner circular layer thickens to form the internal anal sphincter