digestive physiology

Question 1

list the four basic tissues of the GIT

Answer 1

Mucosa, Submucosa, Muscularis externa, serosa

Question 2

The Mucosa tissue layer is comprised of?

Answer 2

Epithelium, Lamina Propriam and Muscularis mucosa.

Question 3

The gastric mucosa (foregut)

Answer 3

A simple columnar epithelial tissue; surface mucous cells (faveolar), and mucous neck cells producing HCO3- rich mucous. gastric pits lead to gastric glands.

Question 4

four regions of the foregut

Answer 4

oesophageal region and cardia (mammals and reptiles) ; fundus; body and pylorus (leading to pyloric sphincter).

Question 5

The Cardia

Answer 5

storage, chemical and microbial digestion, Cardiac glands ( primarily secrete mucus) .

Question 6

The fundus

Answer 6

storage and mixing, oxyntic glands extreting gastric juice, mucous cells, parietal cells secreting HCL and intrinsic factor; chief cells, secrete enzymes: pepsinogen, gastric lipase, rennin etc.

Question 7

the plyorus

Answer 7

mixing (physical digestion), plyoric glands (endocrine) , made up of mucous glands and g-cells secreting gastrin.

Question 8

HCL in the foregut.

Answer 8

activates pepsinogen, kills microorganisms, connective tissue breakdown, protein degredation

Question 9

intrinsic factor

Answer 9

facilitates vitamin b12 absorption thru the ileum

Question 10

small intestinal layers that allow the surface area to be increased by ~600x

Answer 10

sub-mucosa folds: plicae(3x) ; Mucosal folds: villi (10x) ; epithelial: microvilli (20x)

Question 11

relevance of the crypts of leiberkuhns at the base of villi (small intestines)

Answer 11

invaginations inbetween villi; contain Stem cells, replacing enterocytes shed from the tip of villi, enterendocrine cells ( CCK, GIP, secretin) , paneth cells, which secrete antimicrobial peptides.

Question 12

regions of the small intestine

Answer 12

jejunum, duodenum and ileum.

Question 13

regional variations of small intestine constituents.

Answer 13

duodenum: Brunners glands, mucus, protects epithelium from acid chyme arriving from foregut.
jejunum: prominant in villi and plicae
ileum: Peyers patches (aggregated lymphoid nodules), produce and secrete lymphocytes protecting the small intestine from the large bacterial population of the large intestine.

Question 14

the Liver as an ancillary organ of the midgut

Answer 14

producing bile ( bile salts and HCO3-)
Gall bladder is absent in some species of mammals and fish.

Question 15

the pancreas as an ancillary organ of the midgut

Answer 15

secreting pancreatic juice (enzymes and HCO3-)

Question 16

Hindgut- caecum

Answer 16

contains the ileocaecal valve which prevents the movement of colonic content back into the ileum.

Question 17

structure of the colon

Answer 17

Huastra- pouches formed by sacculations along the caecum and colon. sacculations caused by longitudinal muscles reduced to bands ( taeniae caeca/coli

Question 18

hindgut- large intestine functions

Answer 18

absorption of water, electrolytes and some vitamins. fermentative digestion and storage.

Question 19

structure of the ruminant stomach

Answer 19

rumen and reticulum separated by reticuloruminal fold, rumen divided into sacs by muscular pillars; mucosal papillae cover the rumen. reticulo-omasal orifice, borders the reticulum and omasum; abomasum before small intestine.

Question 20

ruminant stomach functions

Answer 20

rumen divided by muscular pillars, providing food retention, ensuring microbial fermentation of all matter; mucosal pappilae for absorption, high SA, abumasom, the glandular stomach, major secretions of HCL and many digestive enzymes.