6.1 Flashcards
what are the 8 main organs in the body
- mouth
- oesophagus
- stomach
- liver
- pancreas
- small intestine
- large intestine
- rectum
whats the function of the mouth?
- performs ingestion of food
- followed by chemical digestion of carbohydrates and mechanical digestion by teeth
whats the function of the oesophagus?
- to transport food to the stomach through peristalsis
whats the function of the stomach?
- epithelial cells secrete H+ ions to create stomach acid
- which kills pathogens and activates enzymes for proteins digestion
- forming chyme
whats chyme?
the pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food
whats the function of the liver?
- produces bile
where is bile stored?
- in the gallbladder
whats the function of the pancreas?
- produces juices containing enzymes for carbohydrates, lipids and proteins
whats the function of the small intestine?
- mixes chyme, bile and pancreatic juices together
- to promote digestion and absorbs the digested products
whats the function of the large intestine?
- completes carbohydrate digestion
- conducts water reabsorption to form feces
whats the function of the rectum?
- stores feces
- feces leaves through the anus via egestion
define digestion
- the breakdown of large insoluble macromolecules into smaller soluble monomers
how is starch digested?
amylase digests 1,4-linkages of starch to form molecules of maltose and leave 1,6-linkages behind, called dextrins
how is maltose digested?
maltase digests maltose to form 2 glucose molecules
how are dextrins digested?
dextrinase digests dextrins to form 2 glucose molecules
how are lipids digested?
lipases breaks down lipids to form 2 fatty acids and monoglycerides
how are proteins digested?
proteases breaks down proteins to form amino acids
define peristalsis
a wave of muscle contraction that passes along the entire digestive tract
describe the process of peristalsis in 3 steps
- inner circular muscles contract behind the bolus, pinching the bolus off
- outer longitudinal muscles contract ahead, shortening the oesophagus
- inner circular muscles contract closer behind the bolus to push it along the alimentary canal
define absorption
the movement of digest products from the lumen of the small intestine into the blood
describe the use of villi
- villi increases the surface area of the small intestine
- thus the surface area for absorbing of food
what are the functions of a villi (including the thin epithelium, mucosa and the muscular propria)
thin epithelium
- shortens the absorption pathway
mucosa
- has a rich blood supply to maintain a high conc gradient for absorption
- lacteals absorb lipids
muscular propria
- containing inner circular muscle
- outer longitudinal muscle to perform peristalsis
define amphipathic
having both hydrophilic and hydrophobic parts
describe the process of lipid digestion
- bile salts are amphipathic, allowing them to perform emulsification
- the hydrophobic ends bind to triglyceride molecules to form smaller droplets for easier digestion
- the hydrophilic ends then allow lipase to bind and break down the triglyceride into a monoglyceride and 2 fatty acids
define emulsification
the process by which the dispersed phase is broken up into small droplets
describe the process of lipid absorption
- simple diffusion of fatty acids and monoglycerides
- exocytosis of chylomicron (fatty acids and cholesterols)
- simple diffusion of lacteal
what does emulsify mean and what emulsifies lipids?
- means to break large fat droplets into smaller droplets
- bile salts emulsifies lipids
what is the fat-digesting enzyme?
pancreatic lipase
describe the process of Na+/K+ absorption and how it links to glucose absorption
- absorption of sodium ions via active transport
- creates a sodium concentration gradient from the lumen to the intestinal cell
- the transport of glucose across the membrane needs ATP and this energy is from the transport of sodium ions using ATP
- because the glucose-sodium pump is not fueled by ATP directly, this is called secondary active transport
