DigestionDigestion

Stages of Food ProcessingStages of Food Processing IngestionIngestion – the act of taking in food – the act of taking in food DigestionDigestion – the process of breaking food down into – the process of breaking food down into

molecules small enough for the body to absorbmolecules small enough for the body to absorb– Enzymatic hydrolysisEnzymatic hydrolysis process in digestion in which process in digestion in which

macromolecules are split from food by the enzymatic macromolecules are split from food by the enzymatic addition of wateraddition of water

AbsorptionAbsorption – an animal’s cells take up small – an animal’s cells take up small molecules such as amino acids and simple sugars molecules such as amino acids and simple sugars from the digestive compartmentfrom the digestive compartment

EliminationElimination – undigested material passes out of the – undigested material passes out of the digestive compartmentdigestive compartment

Digestion TypesDigestion Types How do you digest food How do you digest food

without digesting without digesting yourself?yourself?

Intracellular digestionIntracellular digestion – – digestion within food digestion within food vacuoles (membrane vacuoles (membrane bound organelles)bound organelles)

A cell engulfs food by A cell engulfs food by phagocytosis or phagocytosis or pinocytosispinocytosis

Newly formed food Newly formed food vacuoles fuse with vacuoles fuse with lysosomes containing lysosomes containing enzymesenzymes

Examples include spongesExamples include sponges

Digestion Types Cont.Digestion Types Cont. Extracellular digestionExtracellular digestion – within – within

compartments that are continuous compartments that are continuous with outside of animal’s bodywith outside of animal’s body

Allows for consumption of larger Allows for consumption of larger preyprey

Many animals with simple body Many animals with simple body plans have a digestive sac with a plans have a digestive sac with a single opening (single opening (gastrovascular gastrovascular cavitycavity))

Functions in both digestion and Functions in both digestion and distribution of nutrientsdistribution of nutrients– Ex. hydrasEx. hydras

More Complex Extracellular More Complex Extracellular Digestion Digestion

Most animals have a digestive tube Most animals have a digestive tube extending between two openings extending between two openings (mouth and anus) (called a (mouth and anus) (called a complete complete digestivedigestive tract or tract or alimentary canalalimentary canal))

b/c food moves in single direction, tube b/c food moves in single direction, tube can be organized into specialized can be organized into specialized sectionssections

Another advantage is that it allows for Another advantage is that it allows for the ingestion of additional food before the ingestion of additional food before earlier meals being completely digestedearlier meals being completely digested

Mammalian DigestionMammalian Digestion Food travels along the Food travels along the

digestive tract by digestive tract by peristalsisperistalsis (contraction (contraction of smooth muscles)of smooth muscles)

At some points the At some points the muscular layer is muscular layer is modified into ring-like modified into ring-like valves which regulate valves which regulate the passage of material the passage of material between chambers of between chambers of the tract (the tract (sphincterssphincters) )

In Your MouthIn Your Mouth Oral CavityOral Cavity – uhhh yeah.....its the mouth – uhhh yeah.....its the mouth Saliva contains Saliva contains salivary amylasesalivary amylase that that

hydrolyzes starch and glycogenhydrolyzes starch and glycogen Chewed food is molded into a ball by your Chewed food is molded into a ball by your

tongue (tongue (bolusbolus) and ) and pushed to the back pushed to the back of your throatof your throat

EpiglottisEpiglottis(flap of cartilage) (flap of cartilage) – up during breathingup during breathing– down during eatingdown during eating

Pharynx – junction leading to lungs or stomach

video

StomachStomach Stomach breaks down proteins with the Stomach breaks down proteins with the

enzyme enzyme pepsinpepsin. It works to break the . It works to break the peptide bonds of amino acids. peptide bonds of amino acids.

Afterwards the Afterwards the chyme flows tochyme flows to the duodenum the duodenum

StomachStomach In order to prevent self-digestion....In order to prevent self-digestion.... One, pepsin is secreted in an inactive One, pepsin is secreted in an inactive

form (form (pepsinogenpepsinogen) which doesn’t ) which doesn’t activate until it comes in contact with activate until it comes in contact with hydrochloric acidhydrochloric acid

HCl is released when food is presentHCl is released when food is present Two, there is a layer of mucus covering Two, there is a layer of mucus covering

the stomach. It is eroded and replaced the stomach. It is eroded and replaced constantlyconstantly

More StomachMore Stomach Acid chymeAcid chyme – name for the nutrient- – name for the nutrient-

rich broth that leaves the stomachrich broth that leaves the stomach The acid chyme leaves the stomach The acid chyme leaves the stomach

through an opening known as the through an opening known as the pyloric sphincter pyloric sphincter

It takes about 2-6hrs for a meal to It takes about 2-6hrs for a meal to leave the stomachleave the stomach

LiverLiver Used for Used for

– detoxificationdetoxification– protein synthesisprotein synthesis– production of biochemicals necessary production of biochemicals necessary

for digestion for digestion – Produces bile which performs the Produces bile which performs the

emulsificationemulsification of fats (cleaving the C-C of fats (cleaving the C-C bonds within a fatty acid chain, breaks bonds within a fatty acid chain, breaks down globs of fat).down globs of fat).

GallbladderGallbladder a small non-a small non-

vital organ that vital organ that sits beneath sits beneath the liverthe liver

Stores the bile Stores the bile produced in produced in the liverthe liver

Bile becomes Bile becomes more more concentratedconcentrated

PancreasPancreas a gland organ in the digestive and a gland organ in the digestive and

endocrine system. endocrine system. It produces several important hormones, It produces several important hormones,

including insulinincluding insulin secretes pancreatic juice containing secretes pancreatic juice containing

digestive enzymes (including bicarbonate digestive enzymes (including bicarbonate which neutralizes the chyme) which neutralizes the chyme)

these enzymes help in breakdown of the these enzymes help in breakdown of the carbohydrates, protein, and fat in the carbohydrates, protein, and fat in the chyme. chyme.

Within the Small IntestineWithin the Small Intestine– peptidasespeptidases and and trypsintrypsin digest proteins digest proteins

into smaller proteinsinto smaller proteins– dipeptidasesdipeptidases digest small proteins into digest small proteins into

single amino acidssingle amino acids– nucleasesnucleases digest DNA. digest DNA.– lipaseslipases finishes lipid digestion (breaks finishes lipid digestion (breaks

fatty acid chains from glycerol)fatty acid chains from glycerol)– amylasesamylases & & disaccharidasesdisaccharidases- digests - digests

carbohydratescarbohydrates

Duodenum Duodenum the first section (25cm) of the the first section (25cm) of the

small intestine small intestine Most of the actual digestion is Most of the actual digestion is

done heredone here ““Stuff” from the stomach, Stuff” from the stomach,

gallbladdergallbladder, and , and pancreaspancreas all find all find their way here their way here

Other “stuff” found here includes Other “stuff” found here includes maltase, lactase and sucrase maltase, lactase and sucrase

So....we end up with bile, chyme, So....we end up with bile, chyme, and various digestive enzymes and various digestive enzymes presentpresent

AbsorptionAbsorption Now that all the food is digested the small Now that all the food is digested the small

intestine absorbs all the nutrients through intestine absorbs all the nutrients through villivilli and and microvillimicrovilli..– Increases Increases

absorption areaabsorption area– Inside each villi thereInside each villi there

is a net of capillariesis a net of capillarieswhich absorb nutrientswhich absorb nutrients(diffusion) into bloodstream(diffusion) into bloodstreamas well as as well as lacteallacteal which which absorb nutrients intoabsorb nutrients intothe lymphatic systemthe lymphatic system

All nutrient-rich blood is carried to the hepatic portal vein which is a blood vessel that leads directly to the liver. This allows the liver to regulate the level of glucose concentration (about 90mg/100mL). Blood then heads to the heart

Large IntestineLarge Intestine Large intestineLarge intestine- also called the colon. Aprox - also called the colon. Aprox

4.9ft long (small intestine aprox 23ft.) 4.9ft long (small intestine aprox 23ft.) Its primary job is to reabsorb whatever water Its primary job is to reabsorb whatever water

is left in the chymeis left in the chyme Takes about 12-24hrsTakes about 12-24hrs Food not broken down in this stage of Food not broken down in this stage of

digestiondigestion Simply absorbs vitamins created by bacteria Simply absorbs vitamins created by bacteria

inhabiting the coloninhabiting the colon Also important in absorbing water and Also important in absorbing water and

compacting the fecescompacting the feces Stores fecal matter in the rectumStores fecal matter in the rectum

El ColonEl Colon The The cecumcecum hosts a large hosts a large

number of bacteria that aid number of bacteria that aid in the breakdown of plant in the breakdown of plant material such as cellulosematerial such as cellulose

Herbivores have a very Herbivores have a very large cecum compared to large cecum compared to carnivorescarnivores

AppendixAppendix- branches off the - branches off the beginning of the large beginning of the large intestine. Function intestine. Function unknownunknown

FactsFacts About 7L of fluid are used in the About 7L of fluid are used in the

digestive tract each day, 90% of this is digestive tract each day, 90% of this is reabsorbed and reusedreabsorbed and reused

If less water then normal is reabsorbed If less water then normal is reabsorbed then diarrhea, if more then constipationthen diarrhea, if more then constipation

E. Coli is one of most common bacteria E. Coli is one of most common bacteria in colonin colon

RectumRectum is final portion of colon is final portion of colon

Evolutionary AdaptationsEvolutionary Adaptations Teeth – mammals have very specialized teethTeeth – mammals have very specialized teeth Stomach – large and expandable for Stomach – large and expandable for

carnivorescarnivores Omni/herbivores tend to have longer Omni/herbivores tend to have longer

digestive tracts cause plants are harder to digestive tracts cause plants are harder to digest due to cell wallsdigest due to cell walls

Symbiotic relationships with bacteria to Symbiotic relationships with bacteria to digest plantsdigest plants

The most elaborate adaptations for The most elaborate adaptations for herbivores is in the group of animals called herbivores is in the group of animals called ruminantsruminants (cattle, deer, sheep) (cattle, deer, sheep)

OtherOther http://www.youtube.com/watch?http://www.youtube.com/watch?

v=Og9-cikC3a0v=Og9-cikC3a0