Download Digestive System

Digestive System
Ch 29 p636
Digestive System
Main function  break down and absorb
nutrients
 Four parts –
 Ingestion – eating
 Digestion – breaking down
 Absorption – taking in
 Elimination – removal of waste

The Process
Food is taken into the
mouth.
 Teeth begin mechanical
digestion, physically
breaking down food.
 Salivary amylase –
enzyme that begins
chemical digestion

Food passes pharynx
and is swallowed.
 The epiglottis closes
over the windpipe so
you don’t inhale the
food.
 Peristalsis moves the
food through the
esophagus with
wavelike muscle
contractions

Stomach
Uses mechanical as well
as chemical digestion.
 Enzyme called pepsin
works on proteins,
Hydrochloric acid also
breaks down food.
 Absorption begins.
 It takes food 2-6 hours
to leave the stomach
after ingestion

Small Intestine
Liquefied food from the stomach enters
the small intestine
 Digestion is completed
 Bile – helps break apart fat
 Pancreatic juice neutralizes acids and
adds more enzymes.

Small Intestine cont.


Most absorption takes place here.
The SI has villi - small finger-like projections
that increase surface area
» The SA of YOUR intestine could cover the floor
of the class!!
Large Intestine
Also called colon.
 Compacts waste, reabsorbs
water and important
vitamins.
 Contains lots of helpful
bacteria.
 Whatever is left over is
called feces.
 Passed out through rectum
and anus.

Other Helpful Organs
Liver

Liver
– Produces bile
» Stored in gall bladder and released into SI
– Stores energy as glycogen

Pancreas
– Secretes enzymes to digest fats, proteins, and
Gall Bladder
carbs
– Produces insulin
Small Intestine
pancreas

Overview
Diet and Nutrition
Food provides energy
 Cells use carbohydrates, proteins, and fats
to make ATP
 Energy content of food is measured in
Calories
 Each person must consume a minimum
amount of Calories each day for the body to
function

Essential Nutrients
In addition to energy requirements, the body
needs to ingest certain essential nutrients
that it cant make from other molecules
 These include: vitamins, minerals, essential
fatty acids, and essential amino acids

Essential Amino Acids



Bodies cant store
Influenced cultures
around the world
Ethnic food examples:
Mexican corn and
beans, Japanese rice
and soybeans, and
Cajun red beans and
rice
Nutritional Disorders
Obesity – excess storage of energy as fat
cells. Due to: more Calories than needed
are ingested, inadequate exercise, and
genetic and psychological factors.
 Affects an estimated 60% of Americans

Nutritional Disorders (cont.)


Undernutrition – not
enough calories
consumed. Muscles
shrink and body breaks
down its own tissues for
energy
Malnutrition – diet lacks
one or more essential
nutrients. Ex. Scurvy –
lack of Vitamin C, Protein
deficiency in many parts
of world today.
Eating Disorders
Anorexia – self-starvation, leads to body
organ problems and failure, heart failure
 Bulimia – bingeing and purging, often same
problems as with anorexia
 Bingeing – excessive consumption of
Calories, leads to obesity
