# S0 DFBC 5 B8

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```					Name:_______________________                          Date:________________________
SBI3U
The Human Digestive System: Nutrition
Taking care of your body by eating well and maintaining a balanced diet is very important in order to
keep fit, have more energy and be healthy.
Males generally have _____ energy needs than females mainly because of differences in body ___.
We need food to make energy (cellular respiration and the production of ATP). We also need food
for the nutrients in order to ______, ___________ and ___________ cells

Vocabulary
Nutrient: any substance that has a useful function when taken up by body cells.
Joule: the unit used to measure energy.
We still use the unit the calorie to measure energy in foods. Calorie is actually a measurement of
heat needed to increase the temperature of water by 1°C.

All foods can be grouped into _______________ (produced by living things: carbohydrates, fats,
proteins, vitamins) and ________________ (come from rock, soil, sea: minerals and water)

Metabolism: Chemical Reactions
Your body performs many different chemical reactions to stay
alive. All of these grouped together are called your metabolism.
The ________________of materials is called catabolism
The _________________ of small molecules into larger ones is
called anabolism

Metabolic Rate
The rate at which the body converts __________ energy into
____________ energy.
Everybody’s metabolic rate is different because it depends on a
number of factors:
Body size: ____________ burns more energy
Physical activity: more ____________, burn more energy
Age: _____________ with age
Hereditary factors: some have __________________ higher.

Basal Metabolic Rate
Is the amount of energy you would use per day if you
stayed in bed all day, with your body only performing
_________ ____________________
BMR is accurately calculated by measuring the
amount of ______________ used, but we can
estimate using a formula:

Female BMR = [655 + (9.6 x mass in kg) + (1.8 x
height in cm) - (4.7 x age in years)] x 4.18

Male BMR = [66 + (13.7 x mass in kg) + (5.0 x height
in cm) - (6.8 x age in years)] x 4.18

BMR is measured in KJ (kilojoules)
Macronutrients: Carbohydrates
Macronutrients are consumed in large amounts daily:

Carbohydrates: made of ____________, _____________ and _________________.
major source of energy
starch, sugar, cellulose
provide glucose
potatoes, rice, fruits, vegetables
when too many carbs are taken in,
stored as _____________ in liver and
muscle cells, or as ______

Three main types: monosaccharides
(simple sugars), disaccharides (lactose,
sucrose), and polysaccharides (starch,
cellulose)

Should make up 55% of your diet if healthy.

Macronutrients: Proteins

Proteins: provide structure in the body

Some are _____________, some are
_______________, some act as cell surface
markers that are targets for specific
hormones, provide _______________ in the
membrane of cells for transport.

Differ in size and shape and function

Built from _________ _____________
(joined together by peptide bonds)

We have 20 different amino acids and our
body can make 12 of them, so there are
another 8 that are _______________ for us
to get from our foods.

Sources of protein: meat, fish, eggs, milk,
cheese, beans, nuts, and lentils.

We need 60g of protein each day or 10%-
30% of your energy requirement from
protein.
Macronutrients: Fats

Fats: (or lipids) are a part of a balanced diet, in moderate amounts.
Lipids are used in various ways:
Phospholipid bilayer in the cell ________________
________________ in the cell membrane
Surround vital organs and joints as a protective ____________
Surround nerves for ________ signals
Layer just underneath the skin provides ___________________
Concentrated __________ of energy
Some are hormones (sex hormones)
Linoleic, linolenic, and arachidonic are ________________ ______________ because the
body needs them and cannot make them from other substances

Fats and oils are made of 3 fatty acids bonded to a __________ molecule to make a triglyceride
If fatty acid chains have multiple bonds, they are called unsaturated (oils)
If fatty acid chains have all single bonds, they are saturated fats (meat, butter)

Micronutrents: Vitamins
Micronutrients are vitamins and minerals that are taken in small quantities.

Vitamins are _______________ compounds that are vital to life.
Contain atoms of carbon, hydrogen, oxygen, nitrogen and some other elements.
Most vitamins act as coenzymes that join onto other _____________ to make sure _____________
take place properly.
Can be divided into two types:
Fat-soluble vitamins
Water-soluble vitamins

Micronutrents: Minerals & Water
Minerals: important _____________ molecules.
Examples: iron (hemoglobin), calcium (nerve and muscle cells, bones and teeth, sodium (muscle,
nerve cells), potassium (nerves, heart), and iodine (thyroid).
Water: not an ____________ source, but we cannot live without it.
most of the weight of our bodies is from water
plasma (blood) is more than ____% water
every time we breathe out, some ________________ is lost to the air, so it must be replaced.

Micronutrents: Fibre
Roughage is another important part of a complete diet. It has no ____________ _________, but
aids in good digestion (dietary fibre)
Animals that eat a lot of plants, like rabbits, are able to break down the ____________ into a useful
form due to the special _____________ _________ in their large intestine.

Anorexia nervosa & Bulemia

Two different medical conditions that are categorized as
__________ disorders.

Exercise excessively or abuse laxatives.

Bulimia is characterized by periods of binge eating, fasting,
and self-induced vomiting.

Treatment is a very slow process of a combination of
medical and psychiatric interventions

Overeating

Obesity is sometimes caused by
___________ factors

Usually caused by inappropriate diet and
inactivity.

Percentage of overweight people is
________________ in Canada due to fast
food and other sugary/high-fat foods.

Being overweight increases the risk of heart
diabetes, cancer, high blood pressure, joint
problems.
The Human Digestive System

The Digestive Tract & Accessory Organs
- the human digestive system is made up of a group of organs working together- they are broken
down into two categories: the digestive tract and the accessory organs
Digestive Tract (organs that contain food):

Accessory Organs (structures that aid digestion):

The Mouth & Salivary Glands
- even before you take your first bite of food, the ________
or _________ of food can trigger the salivary glands to
secrete saliva into the mouth

- chemical digestion starts here with an ___________
called amylase that starts to break down starches into
simpler sugars

- saliva dissolves _____________________ food particles,
stimulates the taste buds and lubricates the mouth making
it easier to swallow

- mechanical digestion also starts here as your _________ bite, tear and grind food into smaller
pieces...by breaking the food into smaller pieces a larger surface area is exposed to the saliva,
allowing it to be _______________ more rapidly
The esophagus
- as you chew your food your tongue helps mould and smooth it
into a soft mass called a bolus, that your ____________ pushes
to the back of your mouth

- as you _____________ the bolus enters the top of the
esophagus to begin its passage into your stomach

- the opening of the esophagus is next to the opening of your
trachea and to prevent food from going down the wrong tube to
tracheal opening is closed by the epiglottis (valve of the
trachea)

- the esophagus is
a hollow muscular
tube that transports
each bolus of food
to the stomach in a
series of wave-like
muscular
_______________
called peristalsis

- glands in the lining
of the esophagus
produce
__________, which
keeps the passage ________ and aids in swallowing

- the entrance to the stomach is called the esophageal sphincter and is normally closed to prevent
the ____________ contents of the stomach from backing up into the esophagus, but it relaxes to
allow each bolus of food to enter the stomach

The Stomach
- the stomach is a muscular, J-shaped organ in which
food is ______________ stored while further chemical
and mechanical digestion takes place; the walls of the
stomach are folded like an accordion, allowing the
stomach to expand after a meal

- the stomach is lined with millions of gastric glands that
secrete gastric juice when stimulated by the presence of
food; __________ _________ is made up of HCl, salts,
enzymes, water and mucus
- the mucus coats the walls of the stomach, protecting it
from attack by the strongly acidic gastric juice; while the
rest of the gastric juice continues the _______________
digestion of the food
- the stomach has 3 layers of muscle fibres that _________
and then ___________ to churn and mechanically break up
pieces of food and mix them with the gastric juice- this
results in a thick liquid called chyme

- at the lower end of the stomach is a muscular valve called
the pyloric sphincter, which keeps the food in the stomach
when closed

What prevents the stomach from digesting its own
cells?

1) the stomach secretes gastric juice only when food is
present
2) the stomach secretes mucus, which prevents gastric juice
from harming the cells of the stomach lining
3) the produces a protein-digesting enzyme, pepsin, in a
form that remains inactive until HCl is present

The Small Intestine
- the small intestine is part of the alimentary canal where digestion is completed- the nutrient
macromolecules are finally ___________ _______ into their component molecules and the nutrients
are _____________ through the membranes of the cells that line the small intestine into the
circulatory system

The Duodenum
- the first region of the small
intestine is the duodenum

- to speed up the process of
absorption, the walls of the
small intestine are lined by
_________ that greatly
increase the surface area
through which nutrients can
be absorbed

- the folds are covered by
tiny finger-like projections
called villi which is then
covered with many fine
brush-like microvilli

- as food passes through the duodenum, it receives ______________ from two organs that support
the function of the digestive system: the pancreas and the gall bladder
The Jejunum and Ileum
- following the duodenum is the jejunum, which is
about 2.5 m long and contains more folds that the
duodenum, it breaks down the remaining _________
and __________________ so the end products can
be absorbed into the bloodstream

- the ileum, which is about 3 m long, contains ______
and ____________ villi than either the duodenum or
the jejunum; its function is also to absorb nutrients, as
well as to push the remaining undigested material into
the large intestine

- the pancreas and gall bladder are not part of the
_____________________ ____________ itself, but
they are connected to the canal by ducts and because
of this close association they are referred to as
accessory organs

Pancreas
of pancreatic fluid into the duodenum each day, this
fluid contains ____________ that chemically digest
carbohydrates, lipids and proteins

- the pancreatic fluid also contains bicarbonate, which alters the pH of __________ from 1 to 8;
providing conditions in which enzymes in the pancreatic fluid can work most efficiently

- the liver is the _____________ internal organ of the
human body, in adult humans it is the size of a football

- the main digestion-related secretion of the liver is bile, a
greenish-yellow fluid mixture that is made up of bile
pigments and bile salts; bile pigments do not take part in
digestion they are ________ products from the liver's
destruction of old ____________________________
- after bile is produced by the liver it is sent to the gall bladder, which stores the bile _____________
meals; the bile salts contained in bile are essential for the digestion of _________

- because fats are _______________ in water they are suspended in the chyme as small droplets-
the bile salts break down the fats into small enough pieces to be broken down by digestive enzymes

Chemical Digestion & Absorption
- the bile and pancreatic fluid in the duodenum help break down carbohydrates, proteins and lipids
into smaller molecules that can then be absorbed by the small cells which line the small intestine
Complex             Proteins              Fats            Nucleic Acids
Carbohydrates

Mouth

Stomach

Small Intestine

The Large Intestine
- after the nutrients in digested food have been
absorbed from the small intestine into the
_______________, the remaining material moves into
the large intestine or colon, which is much
__________ and _________ than the small intestine

- the main function of the large intestine is to absorb
________ from the alimentary canal, about 90% is
absorbed back into the blood and extra-cellular fluids
and the volume of indigestible food matter (mostly
plant matter) is reduced by 2/3
–
- billions of ______________ bacteria in the colon
break down undigested matter further, some of which
produce important ____________ which are absorbed
into the blood stream through the colon

- the leftover matter forms ______, which are pushed
by muscular contractions of the colon into the rectum
Time Required For Human Digestion:

Digestive Structure                    Primary Function                      Time Food Spends in
Each Structure
Mouth

Esophagus

Stomach

Small Intestine

Large Intestine

Homework:

1) Look up a malady of the digestive system on the internet and state its causes and symptoms.
2) Create a graphic organizer, such as a flowchart or a table, that compares the chemical digestion of
the four types of macromolecules as they move through the following body parts: oral cavity,
esophagus, small intestine and large intestine. Include any enzymatic digestion that occurs along the
way.
3) The small intestine is divided into three different regions. Describe the structure and function of
each of these regions.
4) Your friend is convinced that digestion begins in the stomach. Is this true or false? Explain your
5) Infer how the food reaches an astronaut’s stomach when he or she is floating in zero gravity.
6) Why does the acid in gastric juice not damage the stomach?
7) Which structural feature of the small intestine increases surface area? Why is this important?
8) A nutritionist recommends drinking water before or after a meal, but not during a meal. Why might
Diseases & Disorders of the Digestive System
- the most commonly used _______________ _______ for diseases and disorders of the digestive
system is endoscopy, where a camera is inserted into either the _______ or the ______ of the
patient and guided through the digestive system to detect any
abnormalities

- this is an incredibly ___________ procedure and for this reason the
capsule endoscope was created, this remote endoscope is similar
to a large pill that patients swallow and ___________ the video to a

Ulcers
- ulcers are small _____________ in the gastrointestinal
tract and can occur in the mouth, esophagus, stomach
and intestine

- ulcers are caused by an imbalance in the thickness of
the ____________ _________ of the organ in question
and the acid it contains, this imbalance allows the acid to
eat away and make a hole 1/8 to 3/4 of an inch in
diameter

- the main symptom of an ulcer is ______ which is more
severe when the stomach is empty and is often
misinterpreted as heartburn, indigestion or hunger

- ulcers can be treated with medication to
increase the ____ of the various digestive
fluids or to encourage the development of
the mucosal lining; in severe cases
______ may be required to repair an ulcer

Acid Reflux & Heartburn

- Acid reflux occurs when the lower
esophageal ____________ fails to
prevent the stomach acid from moving
into the lower esophagus and the
extremely low pH of the stomach acid
irritates the esophagus

- it is usually treated with ___________ to
increase the pH of the stomach acid and soothe the irritated esophagus

- many patients are encourage to change their ______________ to reduce the severity of their
symptoms; this usually includes decreasing consumption of high-acid foods and leading a healthier
lifestyle

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