Digestion and Absorption

obtaining nutrients essential for body processes from food includes acquisition and dividing of foods into smaller parts

prepare nutrients for absorption store nutrients build useful products reject unused and broken down residue

crossing the epithelium and entering the blood must have absorption to utilize nutrients

food not ingested in a suitable state physical nature of feed determines -gathering apparatus for uptake -type of digestive system required for digestion

meat eaters simplest digestive tract (monogastric)

plant eaters most complex digestive tract ruminant or monogastric and hind gut fermenters (horses)

plant and meat eaters intermediate digestive tract

• selection: selection of appropriate food relies on all 5 senses, also learned aversions • prehension: process of getting food into mouth, claws and paws, lips, tongue, teeth 3.mastication: chewing, divides food particles, mixes with saliva • deglutition: swallowing • digestion: physical changes-chewing, swallowing, crushing, peristaltic potions,, chemical changes- enzymes, bacteria, microorganisms, digestive juices 6.absorption: crossing epithelium, utilization of nutrients 7.circulation: transport of nutrients to site of storage and use via blood or lymph • metabolism: cell level utilization- anabolism(tissue growth) and catabolism (tissue breakdown) • excretion: body voids material- defecation, urination, sweat, exhale, wearing off cells

lack of teeth- lack of digestion in mouth gizzard-super muscular, can breakdown tough feed and crop- enlargements of esophagus proventriculus- like a stomach small intestine ceca- between small and large intestine, where fermentation takes place of forage

functions: take in food, prehension differs with species, taste, chew (mastication), mix with saliva mastication: physical reduction of feed to increase surface area carnivores- large canines and incisors for tearing and little chewing herbivores- specialized molars for chewing and grinding saliva: add moisture to feed, aid in chewing, aid in swallowing amylase- digestive enzyme that starts to breakdown simple sugars in the feed

muscular tube pharynx to stomach (cardia) begins with striated (voluntary) –> ends with smooth muscle (involuntary) dogs and ruminants striated throughout angle of attachment in horses discourages regurgitation

“honeycomb” -where food first drops, grinding and transfer -traps objects “hardwear disease” reticular groove -young ruminants -transfer milk from esophagus to abomasum (bypass rumen system to true stomach) -non functional after weaning

-young ruminants -transfer milk from esophagus to abomasum (bypass rumen system to true stomach) -non functional after weaning -muscular contractions close the groove

covered in papilla -increased surface area for absorption and function fermentation vat- anaerobic breakdown of feed (without oxygen) largest compartment >40 gallons ecosystem of microbes -bacteria, protozoa, and fungi -produce volatile fatty acids (VFAs) and microbial cell protein

only abomasum developed in newborn ruminant -little fermentative capability: size, musculature, microbial population development requires solid feed and microbes 2-3 months of age

milk only diet: papillae is very smooth milk and hay: more developed papillae milk and grain: ^^

occurs primarily in reticulum and rumen rumen microbial population: symbiotic relationship (both benefiting) majority bacteria, then protozoa, with fungi and yeast in smaller amounts products of fermentation: VFA, gas (methane, carbon dioxide), heat, microbial crude protein, B vitamins, vitamin K

re-chewing coarse material -diet dependent 6-10 hours per day steps in the process: -regurgutation -remastifaction -reensalivation -reswallowing reduces particle size and increases salivary flow

expelling gases produced from microbial fermentation peak fermentation = 12-30L of gas/hr failure to expel gases= bloat

“many plies”, pages of a book -moves particles from rumen to abomasum -continue to grind roughage -aborption of water

“true stomach” functions exactly like a monogastric stomach glandular portion of stomach uses hydrochloric acid and other enzymes to digest feed

ruminant: 4 compartments (3/4 of abdominal cavity) monogastric (non ruminant): one compartment, size varies

stomach in monogastric, abomasum in ruminants function: -mixing action -acid secretion -enzyme secretion digested food leaves the stomach as chyme -mixture of food and digestive juices

regions: -esophagel (non glandular) -cardiac (mucus) -fundic (mucus, HCl (parietal cells), pepsin (chief cells) -pyloric (mucus)