6.1 Digestion Flashcards
esophagus
hollow tube connecting to the oral cavity (that is separated from the trachea by the epliglottis)
- food is mixed with saliva (salivary amylase) and is then moved in a bolus via action of peristalsis
stomach
temporary storage tank where food is mixed by churning (physical) and protein digestion begins - lined by gastric pits that release digestive juices which create an acidic environment
small intestines
long, highly folded tube where usable food substances (nutrients) are absorbed - consisting of duodenum, jejunum, ileum - food is broken down by enzymes
large intestines
final section of alimentary canal - water and dissolved minerals (ions) are absorbed
saliva gland
release saliva to moisten food (it contains amylase enzyme) to initiate starch breakdown
salivary glands include parotid gland, submandibular gland, sublingual gland (collection of different glands)
pancreas
produces enzymes that are released into small intestine via duodenum (very first bit of small intestines and secretes hormones (i.e. insulin, glucagon,) which regulate blood sugar concentrations
liver
taking raw materials absorbed by small intestines and used to make key chemicals
roles include detoxification, storage, metabolism, bile production, hemaglobin breakdown
gallbladder
stores biles produced by the liver (bile salts are used to emulsify fats)
bile is released into small intestines via common bile duct
what is peristalsis
muscle contractions that move food through the digestive tract - contractions behind the food, relaxations before it - uses radial muscles (rings of muscles circular and longitudinal muscles)
where does mechanical digestion of food occur
chewing (mouth - food is broken down by grinding action of the teeth- tongue moves food t back of the throat as a bolus); churning (stomach - stomach wall contains muscles which physically squeeze and mix food with digestive juices)
why is pepsin secreted as an inactive pepsinogen
pepsin is activated by hydrochloric acid and could kill many of the bacteria in food, however, if there is no HCl, the pepsin could self digest the proteins in the stomach wall
what is chyme
chyme is the acidic and produced from the mixture of food with digestive juices - acidic white creamy paste!!!!
what occurs during chemical digestion
large insoluble molecules are broken down into small soluble particles that can be absorbed by the small intestines
what occurs in the duodenum
the acidic chyme (combo of food with digestive juices) is neutralized by the alkaline bile produced from the liver
what is bile
a strong alkaline neutralizing chyme that lowers surface tension of large fat globules - making them break into tiny droplets -> emulsification
pancreatic juices
secreted by the exocrine glands of the pancreas
what does pancreatic juice contain
pancreatic amylase (catalyzes hydrolysis of amylose into maltose) -
water,
trypsin secreted inactive as trypsinogen (helps to digest proteins)
pancreatic lipase - hydrolysis of fats to fatty acids and glycerol
carboxypeptidase (protease) chymotrypsin - hydrogencarbonate ions (helps to neutralize stomach acid)
segmentation
process by which all of the enzymes in the pancreatic juice combine with bile and chyme and are mixed together by a form of peristalsis
what products are generally absorbed in the small intestines
amino acids, fatty acids, glycerol, monosaccharide sugars, vitamins, mineral ions
describe the structure of the small intestines
serosa - outer coat
muscularis (composed of longitudinal muscle fibers and circular muscle fibers - particularly involved in peristalsis)
submucosa - composed of connective tissues, blood vessels, some glands
mucosa - series of finger-like villi which increase surface area of absorption
lumen
important features of the small intestines
microvilli - foldings on the epithelial cell membranes further increase surface area
rich blood supply - dense capillary network rapidly absorbs and transports products of chemical digestion - flow of blood helps maintain concentration gradient
single layer epithelium - minimizes diffusion distance between lumen and blood
lacteals - absorbs lipids from the intestine into the lymphatic system
intestinal glands - exocrine pits (crypts of Lieberkuhm) release digestive juices
membrane proteins - faciltates transport of digested materials into epithelial cells
what are the four methods of absorption
simple diffusion - occurs when molecules are small and hydrophobic
facilitated diffusion - for hydrophilic monomers to diffuse through protein channels
active transport
pinocytosis (draws in small droplets of liquid surrounded by a small seciton of the phospholipid membrane
why is active transport necessary
it is necessary for when concentrations are lower in the lumen of the small intestines than in the blood so movement needs to occur against a concentration gradient - requires ATP - useful in the digestive system because diffusion would not be able to move small amounts against the concentration gradients once equilibrium has been established - therefore, there are lots of mitochondria that can synthesize ATP for this process
what is dextrin
disaccharide formed from the digestion of amylopectin - containing 1-4 and 1-6 glycosidic linkages - it is larger a fragment that cannot be hydrolyzed and it remains
