Human Digestion &
Human Nutrition
Nutrition
• All the activities by which
an organism obtains and
uses food for growth and
repair of cells.
Nutrients
• The substances in food that
an organism needs and uses
for its life functions.
Function of Nutrients
1. They act as a fuel to provide energy
for the life activities of cells.
2. They supply chemicals needed for
growth and repair of cells.
3. They regulate the metabolic
processes needed for the proper
functioning of the cell.
Nutritional
requirements vary with
an individuals:
age
sex
activities
Six Types of Nutrients
1. Carbohydrates
2. Proteins
3. Lipids
4. Vitamins
5. Minerals
6. Water
Carbohydrates
• Main source of energy
for body functions.
Ex: bread, pasta, and
fruits
Lipids
• Supply of energy
• Part of cell membrane
• Storage form of excess
food in the body.
Ex: butter, bacon, and nuts
Proteins
• Used for growth and
repair of body tissue.
Ex: meat, milk , eggs, and
fish
Water
• Solvent in which
chemical reactions take
place.
• Aids in the transport of
materials in the body.
Minerals
• Make up the body structures.
Ex: calcium- make up bone
and teeth
iron- part of hemoglobin
(red blood cells)
Vitamins
• Needed for normal
metabolism.
Ex: vegetables, fruits,
and meats
• Carbohydrates, proteins, and
lipids need to be digested by
the body in order to be
absorbed into the blood.
• Vitamins, minerals, and water
do not need to be digested and
are easily absorbed into the
blood.
Digestive Tract
• Also known as the GI tract
• Consists of a one-way digestive
tract.
• Food is moved through the tract
by slow, rhythmic muscular
contractions called peristalsis.
Organs of the Digestive
System
•
1. pharynx (throat)
2. mouth (teeth)
3. tongue
4. stomach
5. pancreas
6. small intestine
7. rectum
8. salivary glands
9. esophagus
10. liver
11. gall bladder
12. large intestine
13. appendix
14. anus
(II) Sequence
(way food travels)
oral cavity (mouth)  esophagus 
stomach  small intestine  large
intestine  rectum  anus  toilet
1. Oral Cavity
• Ingestion of food
• Teeth are used in the mechanical
breakdown of food which serves to
increase surface area for enzyme action.
• Carbohydrate digestion begins in the
mouth by enzymes secreted from the
salivary glands.
Ex: amylase
http://www.innerbody.com/anim/mouth.html
2. Esophagus
• Connects mouth
to stomach.
• Peristaltic
action of the
esophagus
moves food to
the stomach.
3. Stomach
• Lining of the stomach contains
gastric glands that secrete gastric
juice.
• This gastric juice contains
enzymes and hydrochloric acid.
• Protein digestion begins here.
4. Small Intestine
• Carbohydrate, protein, and lipid
digestion is completed here.
• Nutrient absorption occurs in the
small intestine.
• Structures like the gall bladder
and pancreas secrete enzymes
into the small intestine for
digestion.
Gall Bladder
• Bile is produced in the liver and
stored in the gall bladder.
• Bile is secreted by the gall bladder
into the small intestine for
emulsification.
• Emulsification- the breakdown of
fats.
Pancreas
• Located near the stomach
• For digestive purposes, the
pancreas secretes:
protease- breakdown of proteins
lipase- breakdown of lipids (fats)
5. Large Intestine
• Water absorption only
• NO nutrient absorption occurs
here.
• Undigested material is known as
feces.
• The large intestine passes the
feces into the rectum.
6. Rectum
Temporarily stores the
feces.
7. Anus
Opening through which
feces passes out of the body.
(Egestion)
(III) Nutrient Absorption
• Takes place in the small
intestine.
• Chemical digestion in humans
is accomplished by Hydrolysis
and the use of enzymes.
End Products of Digestion
Proteins  amino acids
Carbohydrates  glucose
Lipids  3 fatty acids + glycerol
• The end products of digestion
are absorbed in the small
intestine by finger-like
projections called villi.
Villus
• Lacteal- absorption of
fatty acids and
glycerol.
• Capillary networkabsorption of glucose
and amino acids.
Roughage
• Is an indigestible material in
food that provides bulk, which
stimulates the muscles of the
digestive tube and thus keeps
food moving through it.
sources: fruits, vegetables, and
grains.
Lack of roughage in the diet is one
cause of constipation.
Disorders
of the
Digestive Tract
Anorexia Nervosa
• A condition in which there is a severe
loss of weight accompanied by
symptoms of nutritional deficiencies.
• Psychological condition where a
person is unable to take or retain
food due to an excessive concern
about obesity.
Ulcers
* An erosion of the
surface of the digestive
tract associated with
pain, nausea, and
vomiting.
Constipation
* Too
much water is
absorbed in the large
intestine.
*Also can exist due to
lack of roughage.
Diarrhea
* Decreased water
absorption and increased
peristaltic activity of large
intestine.
* Results in an increased,
multiple, watery feces.
Appendicitis
*An inflammation of the
appendix.
*Usually feces that infects
the appendix.
Gallstones
* An accumulation of
hardened cholesterol
deposits in the
gall bladder.