Microanatomy of stomach and intestines

Question 1

General structure of tubular organs

Answer 1

-Tunica serosa or adventitia-separates organs

-Tunica muscularis

-Tunica submucosa-supplies blood supply

-tunica mucosa-functional layer (organ differences- can be absorptive, secretory etc.)
>can be divided into epithelium, lamina propria (connective tissue and glands), and sometimes muscle layer

Question 2

Why multiple muscle layers?

Answer 2

-need a muscle to do circular contraction and a muscle layer to do a longitudinal contraction
-helps with glands and excretions
-helps move mucosa without moving entire organ

Question 3

Regions of simple stomach

Answer 3

-species differences
-non glandular and glandular regions
>proper gastric gland region
>cardiac gland region
>pyloric gland region

Question 4

Species differences of simple stomach

Answer 4

-dogs and cats have non-glandular part
-horses and pigs have non-glandular part
-cardiac gland region much larger in pig

Question 5

Tunica mucosa of glandular stomach

Answer 5

-pits and glands are contained totally within the lamina propria, while the folds involve the lamina muscularis mucosae
>pits are the holes; glands are at the bottom of the pits

Question 6

Gland differences

Answer 6

-Proper gastric gland- straight and tube shaped
>chief cells producing pepsinogen
>parietal cells producing HCl
>mucous neck cells and surface mucous cells- each produce slightly different types of mucous
>G cells-secrete gastrin in blood

-Cardiac gland-straight and coiled
>mucous producing cells
>parietal cells

-Pyloric gland-straight and coiled
>mucous producing cells

Question 7

Gastric gland cells turnover

Answer 7

-every 3-4 days

Question 8

Small intestine

Answer 8

-duodenum, jejunum, ileum
-lined by simple columnar absorptive epithelium

Question 9

How is SA of small intestine increased?

Answer 9

-plicae circulares: circular folds (x3 times)
-villi: finger like projections (x10times)
>enterocytes on villi with microvilli: on apical surface of columnar cells (x20times)

Question 10

Duodenum glands

Answer 10

-mucosal glands- at base of villi in mucosa producing mucus
>Goblet cells

-sub-mucosal glands- mucus producing type gland present deeper into the submucosa
>only present in the first half of duodenum

Question 11

Intestinal villus

Answer 11

-Epithelium
-Lacteal- lymphatic drainage
-Capillary network
-Lamina propria (immune cells)

Question 12

Enterocytes

Answer 12

-lining the intestines
-terminal bars (tight junctions) between the cells- separates the lumen from interior

Question 13

Enterocytes impact on lipids

Answer 13

-lipids are broken down, transported inside the small intestine
-synthesis of proteins in RER
-form triglycerides

Question 14

Paneth cells

Answer 14

-producing antimicrobial compounds

Question 15

Enteroendocrine cells

Answer 15

-produce secretin etc.
-stimulate further endocrine functions (ex. insulin production)

Question 16

Duodenum histology differences

Answer 16

-cranial part of duodenum=submucosal mucosa producing glands

Question 17

Jejunum histology differences

Answer 17

-no glands
-lowest number of goblet cells

Question 18

Parvovirus receptors

Answer 18

-canine parvovirus and feline panleukopenia (distemper) virus binds the transferrin receptor (TfR) of the proliferating crypt cells in small and large intestines
>killing crypt stem cells depopulates villus enterocytes causing rapidly fatal blood diarrhea

Question 19

Ileum histology differences

Answer 19

-M cells
-Peyer’s patches

Question 20

Large intestine

Answer 20

-composed of cecum, colon, rectum, and anal canal
-absence of circular folds and villi
-straight unbranched tubular glands with many goblet cells

Question 21

Anal canal

Answer 21

-transitions from simple epithelium to keratinized stratified squamous epithelium
-Dogs: mucosa near junction with skin contain sebaceous glands
-outer layer of T. mucosa terminates at anorectal junction
-inner layer terminate as internal anal sphincter muscle
-external anal sphincter muscle covers internal anal sphincter muscle
-ducts of anal sacs open at junction of intermediate and cutaneous zone

Question 22

differences between stomach and small intestine

Answer 22

Mucous
-stomach=surface cells and mucous neck cells
-small intestines= submucosal glands and goblet cells
Absorption
-stomach:stratified squamous keratinized
-small intestine: absorptive cells of simple columnar epithelium
SA increase
-stomach:rugae
-small intestine:plicae circulare, villi and microvilli
Villi
-stomach: absent
-Small intestine:present