explain generally how the digestive system (mouth, pharynx, esophagus, stomach, small and large...
TRANSCRIPT
Explain generally how the digestive system (mouth, pharynx, esophagus, stomach, small and large intestines, rectum) converts macromolecules from food into smaller molecules that can be used by cells for energy and for repair and growth.
List the major organs of the digestive systemRelate the structure of each organ with its function in mechanical digestionIdentify the source of each major digestive enzyme, and describe the function of the enzymeSummarize the process of absorption in both the small and large intestine
To make energy using:
foodoxygen
O2
food
ATP
All animals eat other organismsHerbivores
eat mainly plantsgorillas, cows, rabbits, snails
Carnivoreseat other animals
sharks, hawks, spiders, snakes
Omnivoreseat animals & plants
cockroaches, bears, raccoons, humanshumans evolved as hunters, scavengers & gatherers
1. Ingesttaking in food-mouth; pharynx and esophagus
2. Digestmechanical digestion
breaking up food into smaller pieceschemical digestion
breaking down food into molecules small enough to be absorbed into cellsenzymes (hydrolysis)
3. Absorbabsorb across cell membrane
diffusionactive transport
4. Eliminate undigested extracellular material passes out of digestive system
Movement & Control peristalsis
push food along by rhythmic waves of smooth muscle contraction in walls of digestive system
sphinctersmuscular ring-like valves, regulate the passage of material between sections of digestive system
Accessory glandssalivary glands, pancreas, liver & gall bladder
secrete digestive juices (enzymes & fluid)
Epiglottis problem: breathe & swallow through same orificeflap of cartilagecloses trachea (windpipe) when swallowingfood travels down esophagus
Esophagus
move food along to stomach by peristalsis
Mouthmechanical digestion
teethbreaking up food
chemical digestionsaliva
amylaseenzyme digests starch
mucin slippery protein (mucus)protects soft lining of digestive systemlubricates food for easier swallowing
buffers neutralizes acid to prevent tooth decay
anti-bacterial chemicals kill bacteria that enter mouth with food
mouthbreak up foodmoisten food digest starchkill germs
Food is chewed in the mouth and forms a bolus The bolus travels down the esophagus-a long tube- by peristalsisIt then enters the stomach through a sphincter
mouthbreak up foodmoisten food digest starchkill germs
Functionsfood storagedisinfect foodchemical digestion
pepsinenzyme breaks down proteinssecreted as pepsinogen
activated by HClBut the stomach is made out of protein!What stops the stomach from digesting itself?
mucus secreted by stomach cells protects stomach lining
stomachkills germs store food break up fooddigest proteins
cardiacsphincter
pyloricsphincter
mouthbreak up foodmoisten food digest starchkill germs
esophagus
Doctors used to think ulcers were caused by stress
tried to control with antacids
Now we know ulcers are caused by bacterial infection of stomach
Helicobacter pylorinow cure with antibiotics
inflammation of stomach
inflammation of esophagus
Colonized by H. pylori
Free of H. pylori
H. pylori
Functionmajor organ of digestion & absorption chemical digestion
digestive enzymes
absorption through liningover 6 meters! small intestine has huge surface area
= 300m2 (~size of tennis court)
Structure3 sections
duodenum = most digestionjejunum = absorption of nutrients & waterileum = absorption of nutrients & water
1st section of small intestines is still digestingacid food from stomach mixes with digestive juices from accessory glands: pancreas liver gall bladder
Releases digestive enzymes to further break down macromolecules into smaller onesBuffers
Help reduce acidity of chyme from the stomach-bicarbonate
small intestinessmall intestines
stomachkills germs break up fooddigest proteinsstore food
pancreasproduces enzymes to digest proteins & starch
mouthbreak up foodmoisten food digest starchkill germs
Helps the digestive systemproduce bile
stored in gallbladder until neededbreaks up fats
act like detergents to breakup fats
pancreasproduces enzymes to digest proteins & starch
stomachkills germs break up fooddigest proteinsstore food
liverproduces bile
- stored in gall bladderbreak up fats
mouthbreak up foodmoisten food digest starchkill germs
Absorption through villi & microvillifinger-like projections
increase surface area for absorption
How is the villi’s structure related to it’s
function?
How is the villi’s structure related to it’s
function?
Passive transportfructose
Active (protein pumps) transportpump amino acids, vitamins & glucose
against concentration gradients across intestinal cell membranesallows intestine to absorb much higher proportion of nutrients in the intestine than would be possible with passive diffusion
worth the cost of ATP!
small intestinesbreakdown all foods
- proteins- starch- fats- nucleic acids
absorb nutrients
stomachkills germs break up fooddigest proteinsstore food
pancreasproduces enzymes to digest proteins & starch
liverproduces bile
- stored in gall bladderbreak up fats
mouthbreak up foodmoisten food digest starchkill germs
Functionre-absorb water
use ~9 liters of water every day in digestive juices> 90% of water reabsorbed
not enough water absorbed back to body
diarrhea too much water absorbed
back to bodyconstipation
Living in the large intestine is a richflora of harmless, helpful bacteria
Escherichia coli (E. coli)a favorite research organism
bacteria produce vitamins vitamin K; biotin, folic acid & other B vitamins
generate gasesby-product of bacterial metabolism methane, hydrogen sulfide
Last section of colon (large intestines)eliminate feces
undigested materialsextracellular waste
mainly cellulose from plantsroughage or fiber
saltsmasses of bacteria appendix
stomachkills germs break up fooddigest proteinsstore food
small intestinesbreakdown food
- proteins- starch- fats
absorb nutrients
pancreasproduces enzymes to digest proteins & carbs
liverproduces bile
- stored in gall bladderbreak up fats
large intestinesabsorb water
mouthbreak up foodmoisten food digest starchkill germs
Ingestion: mouth & esophagusDigestion: stomach, small intestineAbsorption: small intestine; large intestineElimination: larges intestine, rectum, anus
Review
1.Name 2 types of digestion2.What are the 4 processes of the digestive system?3.List in order the 5 organs food passes through.4.List 4 accessory organs5.Name what organs break down which organic molecules.6.How do organic molecules, vitamins and nutrients get to where they are needed in the body?