The Digestive System

Digestion is the process of breaking down food into molecules the body can

use

How is food digested?Digestion involves:

Breaking down of food into smaller pieces

The mixing of food Movement through the digestive

tract Chemical breakdown of the large

molecules of food into smaller molecules.

Two Types of Digestion Mechanical – physically changing the

size of food– Ex: grinding action of teeth – Ex: churning action of stomach

Chemical – a change in the chemical nature of the nutrients– Ex: amylase (in saliva) working on

starch

Gastrointestinal Tract

a series of hollow organs that food passes through

Also known as the alimentary canal– Alimentary: of or

relating to nourishment or nutrition

Identify the organs of the digestive system

Identify the organs of the digestive system

Mouth (oral cavity)Teeth

-mechanical digestion

Chemical Digestion: – Amylase Enzymes in saliva

chemically digest carbohydrates.

Mouth (oral cavity)Tongue:o Keeps food in placeo Push bolus to back of

moutho Bolus: a soft mass of

chewed food

More to the Mouth Uvula

– Dangling “thing” in back of throat

– Catches bacteria and dirt particles

– Can be destroyed by bulimics

Pharynx Open area at back

of the mouth Passageway for both

food & air Epiglottis – thin flap

that prevents food from entering the trachea

http://www.cortexity.com:8080/nicksblog/images/pharynx.jpg

Esophagus Tube about 25cm

long connects the

pharynx to the stomach.

2 layers of muscle.

http://www.massgeneral.org/cancer/crr/types/thoracic/illustrations/images/esophagus_front.jpg

Esophogus peristalsis

– Wavelike, involuntary muscle contractions that pushes food through the digestive tract

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html

http://www.easttroy.k12.wi.us/hs/dept/science/bottum/Adv%20Biology/digestive/danatomy/images/peristalsis.gif

Stomach

Both mechanical and chemical digestion

Mechanical Digestion– 3 layers of muscle

that twist and turn the stomach

– Results in churning action = mechanical

– Makes your stomach “growl”

Stomach Chemical digestion:

– Stomach lining produces HCl (hydrochloric acid) to breakdown and dissolve nutrients

– Enzyme – Pepsin begins to digest proteins

– Bolus becomes Chyme

http://www.health.com/health/static/hw/media/medical/hw/hwkb17_010.jpg

Small Intestine 7 meters long

(22feet) Site of nutrient

diffusion into blood from mesentary

http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/19221.jpg

Small Intestine Mesentary:

– Contains blood vessels that Absorb the nutrients

Large Intestine Water and Minerals

(NaCl) are absorbed back into the blood

The remains are formed into brown, semi-solid feces

Large Intestine Diarriaha

– Water was not reabsorbed

Constipation– Too much water

was reabsorbed

Rectum and Anus Rectum = store the feces.

Anus: ring of muscle that squeezes the feces out of the body.

Accessory Organs Aid (help with) in digestion but food

never travels through Liver, Pancreas, Gall bladder

Liver The liver is like a processing factory

with more than 200 different jobs. – Produces bile

Bile: breaks down fats in the small intestine.– Stores some nutrients

brought from the blood after the small intestine

– Produces cholesterol– Detoxifies

Pancreas Produce insulin and

enzymes Enzymatic juices

travel through the common bile duct into the small intestine

http://www.fairview.org/healthlibrary/content/pancreas.gif

Gall Bladder A small baglike sac

under the liver.

It stores bile.

Empties the bile into the small intestine via the common bile duct

Common Bile Duct Collects from liver,

gallbladder, pancreas and empties into the small intestine

To quiz yourself over the parts of the digestive

system, click here:http://www.tvdsb.on.ca/westmin/science/sbi3a1/digest/digdiag.htm

Describe water Most of the nutrients in your body

can't be used unless they are carried in a solution. This means that they have to be dissolved in water.

In cells, chemical reactions take place in solutions.

Describe water Most of the material absorbed from

the cavity of the small intestine is water in which salt is dissolved.

The salt and water come from the food and liquid we swallow and the juices secreted by the many digestive glands.

For more information about the digestive system, click here:

http://kidshealth.org/kid/body/digest_noSW.html