BIO181 animal digestion

ruminant stomach

rumen, reticulum, omasum, abomasum

rumen

the large fermentation chamber

loaded with microorganisms such as bacteria, chytrids, and protists

breaks down vegetation and releases nutrients such as vitamin K, vitamin B, and fatty acids

reticulum

where the breakdown of vegetation continues

omasum

aids in the absorption of water

abomasum

true stomach

contains digestion enzymes that complete the digestive process

chewing the cud

process of regurgitating the food for further chewing and swallowing it

chewing

chewing or maceration of food

peristalsis

muscular contractions that move food along the tubular structures of the digestive tract such as the esophagus and intestines

churning

mixing bu muscular action in the stomach

segmentation

a specific peristaltic movement in the intestines

chemical action

digestion caused by enzymatic secretions throughout the digestive tract

mechanical action

digestion when chewing, peristalsis, churning, and segmentation occur

organs of digestion

accessory salivary glands

liver

pancreas

gallbladder

stomach

small intestine

large intestine

parts of the stomach

cardiac sphincter

pyloric sphincter

parotoid gland

produces salivary amylase which helps with the breakdown of carbs

sublingual gland

produces mucin and helps with lubrication

submandibular gland

produces salivary amylase and mucin

chyme

a semi-fluid pulp formed in the stomach made of partly digested food and the secretions of the gastrointestinal tract

mucus cells

lubricates and protects the stomach walls

secretes mucus

chief cells

produces pepsinogen which is the inactive form of pepsin

parietal cells

secretes HCL

HCL helps breakdown cellulose and activate pepsinogen to pepsin

helicobacter pylori

bacterium that consumes gastric mucus and erodes the stomach walls which can cause ulcers

structure of the small intestinal lining

villi and microvilli

capillary system in villi

lacteal

where does carb digestion start?

mouth: digestion of carbs begins in the mouth, salivary amylase starts breaking down complex carbs (starch) into simpler sugar(maltose)

where is carb digestion completed?

small intestine: pancreatic amylase continues breaking down starch into maltose

where does protein digestion start?

stomach: pepsin breaks proteins into smaller polypeptides

where is protein digestion completed?

small intestine: pancreatic enzymes continue breaking polypeptides into smaller peptides and amino acids

brush border enzymes complete the process by breaking peptides into individual amino acids, which are absorbed

where does fat digestion start?

small intestine: lingual lipase and gastric lipase play minor roles but the main digestion occurs in the small intestine

where is fat digestion completed?

small intestine: bile salts from the liver emulsify fats into smaller droplets, pancreatic lipase breaks down triglycerides into monoglycerides and free fatty acids

salivary amylase

carb, from the salivary glands, secreted in the mouth

breaks down starch into maltose

pancreatic amylase

carb, from the pancreas, secreted in the small intestine

continues breaking down starch into maltose

brush border enzymes

carb, in small intestine lining, secreted in the small intestine

break disaccharides (maltose, sucrose, lactose) into monosaccharides (glucose)

bile

fats, in the liver, secreted by the gallbladder

emulsifies fats into smaller droplets to aid enzymatic action

pancreatic lipase

fats, in pancreas, secreted by the small intestine

breaks triglycerides into monoglycerides and free fatty acids

gastric lipase

fats, in the stomach, secreted by the stomach

breaks down fats into fatty acids and glycerol

pepsin

protein, in the stomach and secreted by the stomach

breaks down proteins into smaller polypeptides

HCL

protein, in the stomach lining, secreted by the stomach

activates pepsinogen into pepsin and provides an acidic environment for protein digestion

trypsin and chymotrypsin

protein, in the pancreas, secreted by the small intestine

breaks polypeptides into smaller peptides

carboxypeptidase

protein, in the pancreas, secreted by the small intestine

cleaves amino acids from the carboxyl end of peptides

function of bile

produced by the liver

stored and released by the gallbladder

bile salts

produced in the liver, stored in the gallbladder, and transported to the small intestine via the biliary system

duedenum

the first section of the small intestine

receives chyme

neutralize stomach acid with bicarbonate secretions to prevent damage to the intestinal lining

begin the chemical digestion of nutrients using enzymes and bile

bicarbonate

secreted by the pancreas and Brunner’s glands in the duodenum to neutralize acidic chyme

amylase

digests carbohydrates

lipase

breaks down fats

proteases

digests proteins

duodenal gland secretions

mucus protects the mucosal lining and provides a slightly alkaline environment

jejunum

main site of nutrient absorption in small intestine

contains a highly folded mucosa with villi and microvilli to increase surface area for absorption

Ileum

continues absorption of nutrients not absorbed in the jejunum

water absorption is too LOW

results in diarrhea

leads to dehydration and electrolyte imbalances

water absorption is too HIGH

results in constipation

feces become hard and difficult to pass

water

maintains hydration and softens stool

fiber

soluble version absorbs water, forming a gel like consistency that eases stool movement

insoluble version adds bulk to stool and stimulates intestinal movement

gut microbiota

ferment undigested carbohydrates, producing short-chain fatty acids that nourish colon cells

synthesize vitamins

protect against harmful pathogens by competing for space and resources

appendix

small tubular structure attached to the cecum

thought to play a minor role in immunity by harboring beneficial gut bacteria