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Heterotrophic Nutrition
&
The Human Digestive System
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Heterotrophic Nutrition
Heterotrophs are organisms who are unable
to produce their own food and therefore must
obtain food from an external source.
 Examples:

–
–
–
–
Bacteria
Protozoans (amebas)
Fungi
Animals
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Processes involved in Heterotrophic Nutrition
1. Ingestion – taking in food by mouth (eating)
2. Digestion – breaking down large molecules
into small ones
There are two types of digestion:
– Mechanical digestion – food is broken down by
cutting, grinding, and tearing.
 Increase the food’s surface area for chemical digestion
– Chemical digestion – large molecules are broken
down into smaller ones by enzymatic hydrolysis.
 Hydrolysis – splitting molecules by adding water
Digestion = Hydrolysis
3. Egestion – removal of undigested or
undigestible material.
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Products of Chemical Digestion
Before Hydrolysis
After Hydrolysis
Complex
Carbohydrates
Sugars
Proteins
Amino
Acids
Lipids
Fatty acids &
glycerol
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Human Nutrition
Nutrients – substances an organism
needs to live.
 There are 6 basic nutrients in food.


Some must be digested
before being absorbed:
– Carbohydrates
– Proteins
– Lipids

Some do not have to be
digested before being
absorbed:
– Vitamins
– Minerals
– Water
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Human Nutritional Requirements

Nutrient requirements vary with age
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What are some important Nutrients?

Roughage (Fiber, a carbohydrate) indigestible materials in food (Fruits,
vegetables, grains). Roughage stimulates
proper functioning of muscles in the
digestive tract.

Proteins are made from 20 different amino
acids. We can synthesize 12 of those amino
acids. The other 8 must be from our diet and
are called the 8 essential amino acids.

Water is needed for chemical reactions to
occur in the body.
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Roles of Nutrients
Without vitamins and minerals, your body
will not function properly.
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Roles of Nutrients
Not all forms of nutrients are good for you:

Saturated Fats - are solid at room temperature
and are linked to cardiovascular disease.

Polyunsaturated Fats - are liquid at room
temperature and are not linked to
cardiovascular disease.
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Human Digestive System
The human digestive system breaks down food
into smaller molecules that can be absorbed
into the blood and transported to cells
throughout the body.
 It is a one way tube that travels from the
mouth to the anus.
 Also called:

– The Alimentary Canal
– The Gastrointestinal Tract
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Human Digestive System
Mouth
Epiglottis
Liver
Gallbladder
Large Intestine
Anus
Salivary Glands
Esophagus
Stomach
Pancreas
Small Intestine
Rectum
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Human Digestive System
The Oral Cavity (Mouth) Structures & Functions
Teeth – perform mechanical
digestion by tearing, crushing
and grinding food into smaller
pieces.
 Salivary Glands – perform
chemical digestion of
carbohydrates through
amylase (enzyme that digests
starch).
 Tongue – pushes food to the
back of the mouth so it can be
swallowed.

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Human Digestive System
The Epiglottis


It is a flap at the back of
the throat that covers
the esophagus & trachea
(windpipe).
It covers the trachea
during swallowing to
keep food from entering
the respiratory system
(prevents choking).
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Human Digestive System
The Esophagus

A tube that connects the
mouth to the stomach.

No digestion occurs here.

Food moves through by
peristalsis (involuntary
muscle contractions).
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Human Digestive System
The Stomach
A muscular organ
 Performs mechanical
digestion (churns and
mixes food)
 Releases gastric juice
(a mixture of HCl,
hydrochloric acid, and
proteases) to begin
the chemical
digestion of proteins.

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Human Digestive System
The Small Intestine





A long, tubular organ (20–25 feet
long)
Digestive enzymes are released
into the small intestine from the
gall bladder and pancreas.
All chemical digestion is finished
here.
End products of digestion are
absorbed through villi.
Peristalsis moves materials
through the small intestine.
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Human Digestive System
The Small Intestine - Villi



Villi are small finger-like projections in the small
intestine.
They increase surface area in the small intestine.
Villi absorb products of digestion into the blood
stream.
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Human Digestive System
The Large Intestine





A tubular organ
(5 feet long)
No digestion occurs here.
Water is absorbed.
Undigested materials pass
through and are left behind
to be egested as feces.
Peristalsis moves materials
through the large intestine.
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Human Digestive System
The Rectum and Anus
The rectum stores feces
before egestion.
 Feces are egested through
the anus.
 No digestion or absorption
occurs here.
 Peristalsis moves materials
through the rectum and
anus.

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Additional Structures of the Human Digestive System
1. Liver – produces bile, which
emulsifies fats.
2. Gallbladder – stores bile
and releases it into the
small intestine.
3. Pancreas – produces
proteases and releases
them into the small
intestine.
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Human Digestive System
Emulsification

Emulsification is an example of mechanical digestion.

Bile emulsifies fats by breaking fat globules down into
small droplets that can easily be chemically digested in
the small intestine.
Fat
Globule
Bile
Fat Droplets
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Disorders of the Human Digestive System
1. Ulcers - an erosion of the surface
of the alimentary canal. Caused
by bacteria, NOT stress!
2. Constipation - too much water is
absorbed by the large intestine
and egestion is difficult.
3. Diarrhea – too little water is
absorbed by the large intestine,
combined with increased
peristaltic activity of the large
intestine.
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Disorders of the Human Digestive System
4. Appendicitis inflammation of the
appendix.
5. Gall Stones - hardened
cholesterol deposits in the
gall bladder. Blocks the
release of bile into the
small intestine.
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Name that Body Part – Digestive System Edition!
Salivary Glands
Mouth (oral cavity)
Epiglottis
Tongue
Esophagus
Liver
Stomach
Pancreas
Large Intestine
Small Intestine
Appendix
Anus
Rectum
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