explain generally how the digestive system (mouth, pharynx, esophagus, stomach, small and large...

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?