Getting & Using Food Ingest

taking in food

Digest mechanical digestion

breaking up food into smaller pieces chemical digestion

breaking down food into molecules small enough to be absorbed into cells

enzymes (hydrolysis)

Absorb absorb across cell membrane

diffusion active transport

Eliminate undigested extracellular material passes out of

digestive system

intracellulardigestion

extracellulardigestion

Purpose of Digestion Convert large molecules into smaller ones cable

of being used by the cell.

How do animals get their food?

filter (suspension) feeding substrate feeding

fluid feeding bulk feeding

Digestive systemsEverybody’s got one!

Parts of the body

Common processes & structuresMovement & Control

peristalsispush 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)

Swallowing (& not choking)

Epiglottis problem: breathe & swallow through same orificeflap of cartilagecloses trachea (windpipe) when swallowingfood travels down esophagus

Esophagus

move food along to stomach by peristalsis

IngestionMouth

mechanical digestionteeth

breaking up food

chemical digestionsaliva

amylaseenzyme digests starch

mouthbreak up foodmoisten food digest starchkill germs

StomachFunctions

food storagecan stretch to fit ~2L food

disinfect foodHCl = pH 2

kills bacteriabreaks apart cells

chemical digestionpepsin

enzyme 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

Ooooooh!Zymogen!

stomachkills germs store food break up fooddigest proteins

cardiacsphincter

pyloricsphincter

mouthbreak up foodmoisten food digest starchkill germs

Small intestineFunction

major 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

Absorption by Small IntestinesAbsorption through villi & microvilli

finger-like projectionsincrease surface area for absorption

Ooooh…Structure-Functiontheme!

Duodenum 1st section of small intestines

acid food from stomach mixes with digestive juices from accessory glands:

pancreas liver gall bladder

Pancreas Digestive enzymes

peptidasestrypsin

trypsinogenchymotrypsin

chimotrypsinogencarboxypeptidase

procarboxypeptidase

pancreatic amylase

Buffers reduces acidity

alkaline solution rich in bicarbonate (HCO3-)

buffers acidity of material from stomach

small intestines

stomachkills germs break up fooddigest proteinsstore food

pancreasproduces enzymes to digest proteins & starch

mouthbreak up foodmoisten food digest starchkill germs

Liver Digestive System Functions

produces bilestored in gallbladder until neededbreaks up fats

act like detergents to breakup fats

Circulatory System ConnectionCirculatory System Connection

bile contains colors from old red blood cells collected in liver =

iron in RBC rusts & makes feces brown

bile contains colors from old red blood cells collected in liver =

iron in RBC rusts & makes feces brown

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 of Nutrients Passive transport

fructose

Active (protein pumps) transportpump amino acids, vitamins & glucose

against concentration gradients across intestinal cell membranes

allows intestine to absorb much higher proportion of nutrients in the intestine than would be possible with passive diffusion

worth the cost of ATP!

nutrients are valuable…grab all you can get!

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

Large intestines (colon)Function

re-absorb wateruse ~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 bodyConstipationhttp://www.youtube.com/watch?NR=1&v=cdijh

32NiLs&feature=fvwp

Flora of large intestinesLiving in the large intestine is a rich

flora of harmless, helpful bacteriaEscherichia 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

You’ve gotcompany!

Rectum Last section of colon (large intestines)

eliminate feces

undigested materialsextracellular waste

mainly cellulose from plantsroughage or fiber

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