Histology of SI and LI

Question 1

What are plicae circulares?

Answer 1

transverse folds with submucosal core that cannot lay flat if distended, visible in jeju less so in ileum

Question 2

Where are intestinal villi found? What are they covered with?

Answer 2

mucosal folds that project into lumen and cover surface of SI

Simple columnar epithelium of enterocytes and goblet cells, core of loose CT with microvasculature and a lacteal

Question 3

Describe the mucosa, submucosa, muscularis, and serosa of the small intestine

Answer 3

Mucosa= simple columnar epi with tubular intestinal glands, lamina propria and muscularis mucosae

Submucosa= dense irregular CT, neurovasculature lymphatics and glands

Muscularis= inner circular and outer longitudinal layers

Serosa= loose CT covered by visceral peritoneum

Question 4

What is the structure of intestinal glands?

Answer 4

simple tubular glands lined by simple columnar, continuous with simple column that covers intestinal villi, open onto luminal surface of intestine at base of the villi

Question 5

Where are enteroendocrine cells found? What do they secrete and regulate?

Answer 5

throughout intestinal glands

secrete peptide hormones to control gut motility
regulate secretion of enzymes HCL and bile, gastrin, secretin, GIP, motilin, CCK

Question 6

Where are paneth cells found? What do they secrete?

Answer 6

pyramidal shaped cells at base of intestinal glands,

eosinophilic secretory granules secrete antimicrobial substances, regulate bacterial flora and part of innate immunity

Question 7

What are microfold cells? Where are they located?

Answer 7

epithelial cells specialized for transepithelial transport of particles and microorganism

located in ileal mucosa overlying Peyer patches, pocket formed by deeply invaginated membrane and contain lymphocytes and macrophages

Question 8

Where are intestinal stem sounds found? What is their job?

Answer 8

in niche at crypt base near Paneth

repopulate epithelial lining: daughter cells move out of crypts and differentiate into goblet enterocyte and enteroendocrine cells

Question 9

What is the role of microfold cells?

Answer 9

apical surface expresses receptor for macromolecules and gram-negative bacteria which are internalized and transferred to immune cells
highly specialized antigen-transporting cells

Question 10

What glands are found in the duodenum submucosa?

Answer 10

Brunner’s glands which are tubuloacinar mucous glands, produce alkaline secretion, neutralize acidic chime

Question 11

What is the role of the hepatopancreatic ampulla in the duo?

Answer 11

Collect bile and pancreatic secretions

Question 12

Does the jejunum have submucosal glands?

Answer 12

No but have villi

Question 13

Describe the villi of the jejunum

Answer 13

Long finger like villi, tubular intestinal glands, villus core with well-developed lacteal for fat absorption

Question 14

What is found in the ileum?

Answer 14

finger like villi (shorter than jeju)
Peyer’s patches of mucosal lymphoid modules specific to ileum
Paneth cells at base of intestinal glands

Question 15

What abrupt transition occurs at the ileocecal junction?

Answer 15

villi of SI –> glandular epithelium of LI

Question 16

What is critical to the function of the ileocecal vlave?

Answer 16

thickened extension of muscular mucosae which to limit reflux of colon into ileum

Question 17

Does the large intestine have intestinal villi?

Answer 17

NO

Question 18

What makes up the mucosa of the large intestine?

Answer 18

glandular simple columnar epi: colonocytes goblet cells stem cells and enteroendocrine, lamina propria and muscularis mucosae present, GALT extens

Question 19

What makes up the submucosa of the LI?

Answer 19

dense irregular vascularized CT

Question 20

What makes up the muscularis of the LI?

Answer 20

inner layer typical, outer long organized into taeniae coli which form haustra of LI

Question 21

What parts of the colon have serosa?

Answer 21

intraperitoneal

Question 22

What causes Hischprung’s Disease? What are the symptoms?

Answer 22

Aganglionsois in distal colon from mutations of RET required for migration and differentiaon of NNC  failure of NCC development in both plexuses of bowel segment

Constipation, poor feeding, and progressive abdominal distention

Question 23

What makes up the proper part of the rectum?

Answer 23

Upper part with typical mucosa of tubular intestinal glands and transverse rectal folds

Question 24

What defines the canal/lower part of the rectum?

Answer 24

Anal columns with mucosal folds, anal sinuses aka depressions between columns, and anal glands that extend into submucosa and muscularis

Question 25

What kind of glands are circumanal glands?

Answer 25

large apocrine glands surrounding anal orifice

Question 26

What cells make up the colorectal zone of the anal canal?

Answer 26

simple columnar epi identical to rectum

Question 27

What cell type does the anal canal transition to at the anal transition zone?

Answer 27

simple columnar –> stratified squamous of perianal skin

Question 28

How does the internal anal sphincter form?

Answer 28

level of anus inner circular layer thicken