Nutrition Ch. 3
Secretin
secreted from duodenal wall in response to acidic chyme in small intestine that stimulates the pancreas and in response bicarbonate-rich juices secreted into small intestine
Cholecystokin
secreted from intestinal wall in response to fat or protein in small intestine that stimulates the gallbladder and pancreas and in response bile is secreted in duodenum and bicarbonate and enzyme rich juices secreted into small intestine
large intestine during digestion
ileocecal valve-beginning of colon-breaks down fiber and water
probiotics
living microorganisms found in foods and dietary supplements that, when consumed in sufficient quantities, are beneficial to health
small intestine during digestion
majority of absorption-fluids drip from gallbladder and pancreas-chyme travels down to 3 segments-duodenum, jejunum, ileum
GI path food follows from ingestion to elimination
mouth esophagus stomach small intestine large intestine rectum anus
simple diffusion
nutrients cross into intestinal cells freely
active transport
nutrients move against concentration gradient, requiring energy
facilitated diffusion
nutrients need a specific carrier to transport
sphincter contractions
open and close periodically to allow contents of GI tract to move at a controlled pace, preventing continuous elimination
Gastrin
secreted from stomach wall in response to food in stomach and stimulates stomach glands and in response hydrochloric acid is secreted in stomach
liver
target gallbladder, secreting bile that is stored until needed
gallbladder
target small intestine, secreting bile that emulsifies fat so enzymes can break it down
intestinal glands
target small intestine, secreting intestinal juice that breakdown carbs, fat and protein, mucus protects intestinal wall
salivary glands
target the mouth, secreting saliva to ease swallowing and breakdown carbohydrates
pancreas
target the small intestine, secreting pancreatic juice that neutralizes acidic juices, enzymes breakdown carbs, fats, and proteins.
gastric glands
target the stomach, secreting gastric juice to mix bolus, and breakdown proteins. mucus protects stomach cells
esophagus during digestion
upper esophageal sphincter opens during swallow, bolus slides down and passes through hole in to stomach, lower esophageal sphincter closes behind bolus
peristalsis
wavelike muscular contractions of GI tract that pushes its contents along
small intestine
where majority of absorption takes place
negative feedback
-food in stomach causes cells of stomach wall to start releasing gastrin. -gastrin stimulates stomach glands to release components of hydrochloric acid -stomach pH reaches 1.5 acidity -acidity in stomach causes cells of stomach wall to stop releasing gastrin
health of your digestive system depends on
1. healthy supply of blood 2. lifestyle factors 3. kinds of foods eaten
3 absorption techniques
1. simple diffusion 2. facilitated diffusion 3. active transport
7 challenges the digestive system must overcome
1. throat must be arranged so swallowing and breathing don't interfere with each other 2. path to allow food from mouth to pass through diaphragm to reach stomach below 3. contents should move forward slowly, but steadily 4. food must be lubricated with right amount of fluid to move smoothly 5. foods must be broken down-withdraw water and leave solid waste 6. cells must be protected against powerful digestive juices they secrete 7. GI tract must evacuate periodically
3 main sphincters
1. upper esophageal sphincter 2. lower esophageal sphincter 3. pyloric sphincter
bacterium in your gut
GI bacteria digest fibers and complex proteins, produce nutrients, vitamins, alleviate diarrhea etc, enhance immune funciton, and protect against colon cancer.
stomach during digestion
PROTEIN digestion- changes food to semiliquid mass called chyme. chyme releases bit by bit through pyloric sphincter
lower portion of small intestine and large intestine are ideal for growing flora
because it has neutral pH and slow peristalsis
blood leaving digestive system
blood carried away goes by way of a vein. the hepatic portal vein directs blood to liver. It branches into a large network of capillaries so every cell of the liver has access to the blood. the blood leaving the liver collects into the hepatic vein, which returns blood to the heart
blood traveling to digestion system
blood is carried by way of an artery, which branches into capillaries to reach every cell
chemical digestion and absorption of stomach
carbohydrate: digestion continues until bolus has been mixed with gastric juices, stomach acid of juices inactivates salivary enzyme and digestion ceases. protein: uncoil when mixed with gastric acid, making them available to gastric protease enzymes that begin to digest proteins. fat: forms a separate layer on top of the watery mixture
chemical digestion and absorption of small intestine
carbohydrate: digestion picks up when pancreas releases pancreatic enzymes to break down carbs. They are then absorbed through intestinal cell walls protein: depends on pancreatic and intestinal proteases. small fragments are liberated and absorbed through cells of intestinal wall and into hepatic portal vein fat: food is emulsified by bile. Pancreatic and intestinal lipase's breakdown fat to be absorbed through cells of small intestinal wall and into lymph.
chemical digestion and absorption of the mouth
carbohydrate: digestions begins as salivary enzyme starts to breakdown carbs. fiber: covering on sesame seeds is crushed by teeth exposing nutrients to digestive enzymes. protein: foods are moistened by saliva fat: digestion is minimal. some hard fats begin to melt as they reach body temp
mouth during digestion
chews and mixes food with saliva *carbohydrates break town -tongue provides taste sensation -food passes pharynx-epiglottis closes off airway so choking doesn't occur -when swallowed, food is called bolus
chemical digestion and absorption of large intestine
fiber: SOME are partly digested by bacteria and some are absorbed, MOST pass through and released through feces
