Functional development of GI tract Flashcards
Mammals at birth
-an immediate change from amniotic fluid to milk
-at weaning, a gradual or immediate change from milk to solid food
Mammals in utero
-weight of fetus increases dramatically during the last 1/3 of gestation which is linked to growth of GIT
-adrenal gland rapidly develops during last 1/3rd of gestation which is linked to cortisol production as it is known to play a role in GI development
-development of gastric function includes stomach acid and gastrin secretion, and enzymes (chymosin, pepsin, amylase, lactase, aminopeptidases)
Mammals stomach development
-thickening of glandular region and maturation of chief cells (secrete zymogens)
-Pepsin and HCl increases gradually following birth
-pH at birth is high at birth, and HCl secretion begins a couple days after birth
Mammal small intestine development
-increases in length and diameter from birth to adulthood
-early on, it is permeable to large molecules
-crypts and villi organized and functioning at birth
-enzymes present at birth (lactase levels are higher in neonate than adult; alkaline phosphatase activity minimal at birth and increases gradually)
Intestinal weight growth (piglet)
-allometric
-small intestines grow drastically compared to other tissues (as long as they are actually suckling)
Intestinal growth in dogs
-decrease in length, weight, and surface area when weaned
-also a decline in villus heigh and increase in crypt death following weaning
**don’t see overall increase in s. intestine growth like you see in piglets
Enzymes during post-natal development of dogs
-observed trypsin, amylase, lipase, chymotrypsin
-low protease activity at birth , allowing for acquisition of passive immunity
-lipase, amylase and ribonuclease activity is low initially. Important so they can digest milk properly. note consequence of milk replacers
Alterations in piglet small intestines structure at weaning
-provide some food (creep food) to help with weaning transition. Hope is that they see some food before complete weaning
-saw that there was a decrease in villi heigh/crypt depth due to weaning regardless of access to creep
can’t tell which animals were eating the creep or how much they were eating
Lactase activity in dogs during development
-enzyme activity in proximal part of intestines is highest
-decrease in lactase activity proximal to distal and at weaning
Peptidases activity in dogs during development
-less of an effect due to intestinal segment
-tendency of dipeptidases IV to increase with age
Pancreatic enzymes in pigs
-increase prior to weaning, then sudden decrease at weaning and then increase in amylase (starch digestion)
-shows impact of weaning on enzyme development
Barrier Function of GIT
-controls entry into the animal of substances that may be toxic/infectious if they could freely enter
-forms a barrier to the outside (inside GIT can be considered outside animal)»_space;achieved by epithelial cells joined together by tight junctions
Tight junctions
-formed by proteins (occludens, claudens, junctional adhesion molecules) that act as a permeability seal and facilitate communication between cells
Intestinal barrier
-consists of an apical and basolateral barrier
-has many different entry mechanisms (diffusion, and transporters)
Dysfunction of intestinal epithelial barrier
-results in leaky gut
-associated with intestinal disorders such as IBD, Crohn’s disease, ulcerative colitis, diabetes, COPD
