Digestive System Flashcards
Sphincters
allow small quantities to pass at one time
upper esophageal sphincter
between pharynx and esophagus
lower esophageal sphincter
between esophagus and stomach
pyloric sphincter
between stomach and small intestine
Ileocecal valve
between small and large intestine
Chewing
moistening and digestion of food begins.
tongue- taste and move food
teeth- tear food into smaller pieces (mastication)
Salivary glands- release saliva (mainly water, helps moisten food, amylase begin to break down starch)
Swallowing
voluntary aspects:
- food/liquid is chewed and formed into bolus; propulsion of the bolus by the tongue
involuntary:
- pharyngeal swallow; carrying of the bolus along the esophagus through the process of peristalsis
functions of the stomach
- mixes and stores ingested food
- gastric secretions help dissolve and break food particles
- pyloric valve/sphincter helps control passage of food into small intestine
- food is no longer a bolus- called chyme
components of gastric juice
gastrin- stimulates HCI secretion
hydrochloric acid- creates acidic environment, kills microbes in foods
pepsin & trypsin- aid in protein digestion
Gastric lipases- aids in some small fat digestion
intrinsic factor- helps absorb vitamin B12
mucus- protects the stomach lining from acid, enzymes and bacteria
small intestine
- 6 M long
- absorb nutrients through villi that move substances into the blood stream.
1st section: Duodenum- entering chyme triggers hormone signals that stimulate release of digestive enzymes
2nd section: Jejunum- most digestion & nutrient absorption occurs here
3rd section: Ileum
fat digestion
requires pancreatic and intestinal lipases to break down large fat to smaller units.
also requires bile to emulsify fats:
- bile is made by the liver but stores and released by gallbladder in the duodenum
carbohydrate and protein digestion
enzymes released by stomach, intestinal lining & pancreas into the stomach & small intestine
- carbohydrase (e.g. amylase) to digest carbohydrates
- proteases (e.g. trypsin) to digest proteins
Segmentation
– Smooth muscle rings repeatedly contract and relax
– Mixes and fragments chyme with digestive juices
– Brings contents into close contact with absorbing cells
Water-soluble nutrients & small fats
– routed to the liver, then transported by the blood to the cells (blood circulatory system)
Fat-soluble nutrients and larger fats
– enter into the lymph(lymphatic system), bypassing the liver at first, then enter the blood circulatory system
Major enzymes- carbohydrates
salivary amylase:
Released by- saliva glands
active in- mouth and stomach
breaks down- polysaccharides to di- and oligosaccharides
Pancreatic amylase:
released by- pancreas
active in- small intestine
breaks down- polysaccharides to di- and monosaccharides
Disacharidases:
released by- intestinal lining
active in- small intestine
breaks down - into monosaccharides
Major enzymes- digesting proteins
pepsin:
released by- stomach lining
active in- stomach
breaks down proteins- into protein fragments
trypsin and chymotrypsin:
released by- pancreas
active in-small intestine
breaks down- proteins into proteins fragments
major enzyme- fats
lipases :
released by- pancreas
active in- small intestine
breaks down- triglycerides into fatty acids and monoglycerides
how are water and small lipids absorbed into intestinal cells
simple/passive diffusion- freely
how are water soluble vitamins absorbed through intestinal cells
facilitated diffusion-need a specific carrier to transport them
how are glucose and amino acids absorbed
active transport- requires energy
Large intestine
Anything not absorbed in the small intestine moves into the large intestine, formation of faeces Divided into: -Caecum -Colon -Rectum
Hormones
Gastrin ( responds to food in the stomach- stimulates stomach glands so HCI is secreted into the stomach)
Secretin (responds to acidic chyme in small intestine- stimulates pancreas to release
juices to neutralize chyme
Cholecystokinin (responds to fat or protein in small intestine-
Hormones
Gastrin ( responds to food in the stomach- stimulates stomach glands so HCI is secreted into the stomach)
Secretin (responds to acidic chyme in small intestine- stimulates pancreas to release
juices to neutralize chyme)
Cholecystokinin (responds to fat or protein in small intestine- stimulates gallbladder to secrete bile into duodenum; pancreas to release bicarbonate and enzyme rich juices into small intestine)
Ghrelin (responds to hunger- stimulates brain so you at)
