chapter 10: digestion and absorption

what is the purpose of digestion

it prepares feedstuff that is consumed for absorption and is complete when molecules are small enough to be absorbed

what are the 3 main methods of digestion?

physical/mechanical action, chemical action, enzymatic action

what are some examples of physical action in digestion?

mastication, grinding in G.I. tract (birds & gizzards), omasum (ruminant), and digestive turbulence

what are some examples of chemical action in digestion?

using HCl to initiate the digestion of proteins in the stomach, bile acids/salts that are used for the digestion/absorption of lipidse

what are some examples of enzymatic action in digestion?

• there are enzymes that aid in the digestion of specific substrates (ex. lactase for lactose)

• cofactors are needed (minerals and vitamins), such as Mg and Zn

• enzymes often function by hydrolysis

define absorption

absorption is the set of processes that results in the passage of small molecules from the lumen of the gut through the cells of the G.I. tract into the bloodstream

how much do folds, villi, and brush borders increase surface area/absorption in the intestines?

• folds: 3x

• villi: 30x

• brush borders: 600x

what are the 4 types of absorption

passive diffusion, active diffusion, facilitated diffusion, and phagocytosis

what is phagocytosis

• a type of absorption where part of the villi cell breaks off from the membrane and engulfs a nutrient

• NO DIGESTION REQUIRED!!! THE ONLY ONE WITH THIS TRAIT

• helps to absorb large molecules

what role does phagocytosis have in neonates?

it’s important for newborns because it allows for the transfer of immunoglobulins from mom to baby through colostrum (milk)

after 24-48 hours, there is “gut closure” and the phagocytes stop

what dictates what an animal can consume?

their digestive tract