Histology of the small and large intestines

Question 1

What is the principal location for digestion of food and absorption of digestive products?

Answer 1

Duodenum, jejunum, ileum

Question 2

What is the black arrow and the bracket?

Answer 2

Arrow: microvilli

Bracket: plica circularis

Question 3

What are intestinal villi?

Answer 3

• Mucosal folds that project into the lumen and cover surface of the small intestine. They are covered with a simple collumnar epi of enterocytes and goblet cells with a core of loose CT

Question 4

Describe the 4 layers of the intestine

Answer 4

1. Mucosa: simple columnar with tubular intestinal glands, includes the lamina propria and muscularis mucosae
2. Submucosa: dense irregular CT, including neurovasculature, lymphatics, glads may be there
3. Muscularis: inner circular and outer longitudinal layers
4. Seosa: loose CT covered by visceral peritoneum

Question 5

What controls the motility of the SI and LI?

Answer 5

ANS

slide 136

Question 6

Label

Answer 6

• V: intestinal villi
• M: microfold cells
• C: crypt of Lieberkun

Question 7

What is this and what is its function?

Answer 7

Paneth cell: Large eosinophilic pyramidal shaped cell at base of the intestinal glands

• functions in innate immunity by secreting antimicrobial substances
• Regulate normal bacterial flora

Stem cells can be found near them

Question 8

What is the function of intestinal stem cells?

Answer 8

• Repopulate epithelial lining, daughter ccells move out of the crypts and differentiate into goblet cells enterocytes and enteroendocrine cells

Question 9

What is the function of M cells?

Answer 9

• Epithelial cells specialized for transepithelial transport of particles and microorganisms
• Found in ileal mucosa on top of peyer patches
• Apical surface expresses receptors that bind gram negative bacteria and specific macromolecules
  
  • cells get internalized and transferred to immune cells functioning as highly specialized antigen transporting cells

Question 10

Enteroendocrine cells?

Answer 10

slide 140

Question 11

Describe the mucosa and submucosa layers of this.

Answer 11

• Duodenum- has bruners glands
• Mucosa: simple columnar with scattered goblet cells
• Submucosa: duodenal glands: tubuloacinar mucous glands producing alkalkine secretion
• Neutralizes acidic chyme

Question 12

Describe the mucosa and submucosal layer of this, and what are the deep purple staining circles?

Answer 12

• Ileum
• Mucosa:
  
  • simple columnar with scattered goblet cells
  • Vili shorter than jejunum
  • Peyers patches
  • Paneth cells at base of intestinal glands
• No submucosal glands

Peyers patches

Question 13

What is this describe mucosa and submucosa

Answer 13

• Jejunum
• Mucosa:
  
  • simple oclumnar epi with scattered goblet cells
  • Long finger like villi, villus core has well developed lacteal
  • Tubular intestinal glands
  • Lymphoid nodues in lamina propria
• Submucosa: no glands

Question 14

What is this?

Answer 14

Duodenum

Question 15

What is this

Answer 15

Ileum

Question 16

What is the Pyloris?

Answer 16

• Part of the stomach, it has a thick wall due to presence of pyloric sphincter muscle
• Pyloric glands are found at the base of each gastric pit

Question 17

What is this, and describe it.

Answer 17

Gastroduodenal Junction

• can see bruners glands in the duodenum on the right
• can see pyloric sphincter muscle on left

Question 18

Function of the large intestine?

Answer 18

• Absorbs water sodium vitamins and minerals
• Can uptake sedatives, anesthetics and steroids as well
• Openings of tubular intestinal glands are hallmark of mucosa
• Many goblet cells
• NO intestinal villi

Question 19

What is this, describe the first three layers.

Answer 19

• Large Intestine
• Mucosa:
  
  • glandular simiple columnar epi, colonocytes, goblet cells, stem cells nd enteroendocrine cells
  • Lam ina propria nad mucsularis mucosae are present and GALT is extensive
• Submucosa: dense irregular CT and vascularized
• Muscularis:
  
  • inner layer typical
  • Outer layer reorganized into Taeniae coli forming haustra of LI
• Serosa covers the intraperitoneal portions while retroperitoneal has adventitia

Question 20

What is this?

Answer 20

Large Intestine glands consitsitng of simple columnar epi with goblet cells- hallmark of LI

Question 21

What is this and what are the layers

Answer 21

LI

Mucosa

Submucosa

ME

Question 22

What is this

Answer 22

• Goblet cells at cross section in the LI
• Bottom is longitudinal section of a gland in LI showing goblet cells and colonocytes

Question 23

What is Hirschprung’s disease, what mutation causes this?

Answer 23

• Aganglionosis in the distal colon
• Mutations in the RET gene cause failure of neural crest cells to migrate and develop both plexuses of the bowel segment

Question 24

How does Hirschprung’s disease present? How do you diagnose? How do you treat?

Answer 24

• Constipation
• Poor feeding
• Progressive abdominal distension

Delayed BM <48 hrs after brith, rectal biopsy, barium enema

Surgical removal of the affected segment

Question 25

Describe the Rectum proper.

Answer 25

• typical mucosa with tu;bular intestinal glands and transverse rectal folds

Question 26

Describe the anal canal

Answer 26

• Inferior to the rectum proper
• Contains anal colums with mucosal folds
• Anal sinuses within the columns
• Anal glands extend into submucosa and muscularis externa
• Circumanal glands- large apocrine glands surrounding anal orifice

Question 27

What is this

Answer 27

Anal Canal

• Colorectal zone (CRZ): simple columnar epithelium identical to rectum
• Anal transitional zone (ATZ): simple columnar epithelium transitioning to stratified squamous epithelium of perianal skin
• Squamous zone (SQZ): stratified squamous epithelium continuous with perineal skin lower 1/3

Question 28

Answer 28

Question 29

Answer 29

duodenal villi with microvili

Question 30

what is this

Answer 30

jejunum

Question 31

What is this and what is black line?

Answer 31

LI and Taniae coli

Question 32

Answer 32