Normal Histology Small and Large Bowel

Question 1

Describe the 3 small intestine surface modifications that increase its surface area, from largest to smallest

Answer 1

1. Plica circulares:

permanent mucosal folds in duodenum, jejunum, proximal ileum

2. Villi:
   - finger like projections of epithelim-covered lamina propria
3. microvilli
   - extensions of epithelium plasma membrane

Question 2

What do you typically see inside a villus?

(5)

Answer 2

1. central lacteal
2. capillaries
3. smooth m fibers
4. loose connective tissue
5. lymphoid tissue

Question 3

Goblet cells:

• function
• characteristic appearance on histology:
  1. H/E stain
  2. PAS stain

Answer 3

-secrete mucin through exocytosis, which lubricates and protects intestinal surface

Histology: located between enterocytes

1. H/E: unstained b/c of carbohydrate content
2. PAS: stain pink b/c of carbohydrate content

Question 4

1. How quickly is intestinal epithelium replaced by stem cells?
2. how to identify stem cells on histology?

Answer 4

1. every 3-6 days
2. mitosis visible in stem cells. located at base of crypts

Question 5

What cells are located in Crypts of Lieberkhun?

(5)

Answer 5

1. enterocytes
2. goblet cells–mucin
3. enteroendocrine cells–hormones
4. Paneth cells–anti microbial peptides
5. stem cells

Question 6

Paneth cells

• secrete what? (2 most important)
• appearance on histology

Answer 6

• secrete:
  1. lysozyme–glycosidase that hydrolyzes peptidoglycan wall
  2. defensins–form pores in microbe membrane
• scarlet color–secretory granules stain with eosin

Question 7

What aspect of villi helps move fats/lymph through lacteals?

Answer 7

-muscularis mucosae (inner circular and outer longitudinal) of each villi contract and empty lacteals

Question 8

Peyer’s patches

1. what are they
2. where located? and how many?

Answer 8

1. aggregates of lymphoid nodules in gut mucosa
2. Mostly in ileum (30-40), some in jejunum, few in duodenum

Question 9

Brunner’s glands

1. function
2. location

Answer 9

1. Glands that secrete alkaline mucus that neutralizes pH of gastric chyme in duodenum
2. Duodenum submucosa

Question 10

Small intestine secretion is controlled by:

(2 categories)

Answer 10

1. neural control:

submucosal Meissner’s plexus

2. Hormones
   - CCK, Secretin from enteroendocrine cells

Question 11

Name the 2 neural plexuses of the enteric nervous system and what they control

Answer 11

“M’s don’t go together”

1. Meissner’s Submucosal plexus
   - regulate secretions
2. Auerbach’s Myenteric plexus
   - control contraction of muscularis externa (circular and longitudinal) for peristalsis