The Digestive System Digestion is the process of breaking down food into molecules the body can use.
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Transcript of 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
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
Large Intestine
Water and Minerals (NaCl) are absorbed back into the blood
The remains are formed into brown, semi-solid feces
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
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