Chapter 6
Digestion and Excretion
Why do you eat?
Energy:
Food provides your body with the energy and
nutrients it needs to survive.
 The amount of energy in food is measured in
Calories. A Calorie (Cal) is the amount of
energy it takes to raise the temperature of 1 kg
of water by 1°C.

Why do you eat?
Nutrients:
Food is made of nutrients substances that
provide energy and materials for cell
development, growth, and repair.
 The types and amounts of nutrients a person
needs depend on age, gender, and activity level.
level.
 There are six groups of nutrients that play an
important roles in maintaining your health.

Groups of Nutrients
1- Proteins:
Proteins have many functions:
a) build and repair cells
b) provide the structure of bones, skin, nails, and
hair
c) transfer signals between cells
d) speed up chemical reactions
e) fight and protect the body against diseases
Homeostasis is the regulation of an organism’s internal
condition.
Groups of Nutrients
1- Proteins:
Amino acids:
a)
b)
c)
20 different amino acids make up the proteins
in your body.
Your cells can make more than half of these
amino acids.
The remaining amino acids must come from
the foods that you eat.
Groups of Nutrients
1- Proteins:
Sources:
Meat, dairy products, eggs, beans, and nuts are
a good source of protein.
Groups of Nutrients
2- Carbohydrates:
Carbohydrates are the body's major source of
energy
They are commonly in one of three forms:
a) Starches
b) Sugars
c) Fibers.
Groups of Nutrients
2- Carbohydrates:
Carbohydrates are molecules made of carbon,
hydrogen, and oxygen atoms and are usually the
body’s major source of energy.
Groups of Nutrients
2- Carbohydrates:
Sources:
Bread, fruits, vegetables, rice, oatmeal, and pasta
are high in carbohydrates.
Groups of Nutrients
2- Carbohydrates:

All of them are made of sugar molecules that
are linked together like a chain.

It is best to eat foods that contain carbohydrates
carbohydrates from whole grains because they
are easier to digest.
Groups of Nutrients
3- Fats:

Fats, also called lipids, provide energy and help
help your body absorb vitamins.

Fats have many functions:
a) provide the body with energy and insulation
b) help the body absorb vitamins
c) are a major part of the cell membrane
Groups of Nutrients
3- Fats:
Sources:
Fish, vegetables, nuts, and vegetable oils are rich
in unsaturated fats. Butter is rich in saturated fats.
fats.
Groups of Nutrients
3- Fats:



Fats are often classified as either saturated or
unsaturated.
A diet high in saturated fats can increase levels
of cholesterol, which can increase the risk of
heart disease.
Most of the fat in your diet should come from
unsaturated fats.
– Fish, nuts, and liquid vegetable oils contain
unsaturated fats.
Groups of Nutrients
4- Vitamins:
Vitamins have many functions:
a) growth
b) regulation of body functions
c) prevention of some diseases.
If you do not consume enough of one or more
vitamins, then you might develop symptoms of
vitamin deficiency.
Groups of Nutrients
4- Vitamins:
Groups of Nutrients
4- Vitamins:
What foods are good sources of vitamin A?
Carrots, milk, sweet potatoes, and broccoli are all good
sources of vitamin A
What is a good source of both vitamin B2 and iron?
iron?
Meat provides both of these nutrients.
Groups of Nutrients
5- Minerals:
Minerals are inorganic nutrients that do not
contain carbon that help the body regulate many
chemical reactions.
Groups of Nutrients
6- Water:



Your body is mostly water.
You need water for chemical reactions to occur
occur in your body.
Your body takes in water when you eat or
drink. You lose water when you sweat, urinate,
and breathe.
Groups of Nutrients
6- Water:


When lost water is not replaced, you might
become dehydrated.
Symptoms of dehydration include thirst,
headache, weakness, dizziness, and little or no
urination.
Groups of Nutrients
6- Water:
Water have many functions:
a)
b)
c)
d)
regulates your body temperature
protects your body tissues
helps your body remove wastes
prevents you from becoming dehydrated
Healthful Eating
A balanced Diet:
Healthful Eating
Food Labels:
Food labels help you
determine the amount
of protein,
carbohydrates, fats,
and other substances
in food
Lesson 6.2 The Digestive System
Define
 The digestive system is a
group of organs that work
together to convert the food
into energy and basic
nutrients needed to feed the
body.
• Digestion is the process by which food is
broken down into a form that can be
used by the body.
Lesson 6.2 The Digestive System
Functions of the Digestive System
a)
b)
c)
Ingests food
Breaks it down so nutrients can be absorbed
Eliminates what cannot be digested
Digestion occurs in the following order:
1.
Ingestion is the act of eating, or putting food
in your mouth.
2.
Digestion is the mechanical and chemical
breakdown of food into small particles and
molecules that your body can absorb and use.
Digestion occurs in the following order:
3.
Absorption occurs when the cells of the
digestive system take in small molecules of
digested food.
4.
Elimination is the removal of undigested
food and other wastes from your body.
Types of digestion
Ingestion
 Mechanical digestion
 Involves chewing food
to break it down into
smaller pieces
 Chemical digestion
 The action of enzymes in breaking down large
molecules into smaller molecules
Enzymes


Enzymes are proteins that help break down
larger molecules into smaller molecules.
Enzymes also speed up, or catalyze, the rate of
chemical reactions.
The Role of Enzymes in Digestion

The digestive system produces enzymes to
break down each type of food molecule.

The enzyme amylase helps break down
carbohydrates.

The enzymes pepsin and papain help break
down proteins.

Fats are broken down with the help of the
enzyme lipase.
The Role of Enzymes in Digestion
Notice in Figure 4 that the food molecule
breaks apart, but the enzyme itself does
not change.
Therefore, the enzyme can immediately be used
used to break down another food molecule
Organs of the Digestive System
1- Mouth
• Mechanical digestion of food begins
in your mouth.
• Your salivary glands produce saliva,
they produce more than 1 L of saliva
every day.
• Saliva contains an enzyme that helps
break down carbohydrates.
• Saliva also contains substances that
neutralize acidic foods.
• It also contains a slippery substance
that makes food easier to swallow.
Organs of the Digestive System
2- The Esophagus
 Muscular tube that connects
the mouth, or throat, to the
stomach
Peristalsis
 Smooth muscles contract
rhythmically to move food
through the digestive
system.
Organs of the Digestive System
3- The Stomach
• The stomach changes food into a
liquid-like substance, and it slowly
empties the semi-liquid food into
the small intestine.
• Stomach temporarily store food.
• Aid in chemical digestion
Organs of the Digestive System
Organs of the Digestive System
3- The Stomach
• Folds enable the stomach to expand and hold large amounts of
food and produce chemicals that help break down proteins.
• Gastric juice makes the stomach acidic to break down some of the
structures that hold plant and animal cells together.
• Gastric juice also contains pepsin, an enzyme that helps break
down proteins in foods into amino acids.
• As food mixes with gastric juice in the stomach, it forms a thin,
watery liquid called chyme.
Organs of the Digestive System
4- The Small Intestine
• The small intestine is a long tube
connected to the stomach. It is where
chemical digestion and nutrient
absorption occur
• Much of the body's chemical digestion
takes place in the first part of the
small intestine, called the duodenum.
• The absorption of nutrients occurs
through finger-shaped villi in the
small intestine.
Organs of the Digestive System
4- The Small Intestine
Organs of the Digestive System
4- The Small Intestine
• The pancreas and the liver produce
substances that enter the small intestine
and help with chemical digestion.
• The pancreas produces an enzyme
called amylase that helps break down
carbohydrates and a substance that
neutralizes stomach acid.
• The liver produces a substance called
bile. Bile makes it easier to digest fats.
The gallbladder stores bile until it is
needed in the small intestine.
Organs of the Digestive System
5- The Large Intestine
• Materials that pass through the large
intestine are the waste products of
digestion. The waste products become
more solid as excess water is absorbed.
• Peristalsis continues to force the
remaining semisolid waste material
into the last section of the large
intestine, called the rectum.
• Muscles in the rectum and anus
control the release of this semisolid
waste, called feces.
The Role of Enzymes in Digestion
Organs of the Digestive System
Bacteria and Digestion
• Some bacteria have an
important role in the
digestive system. Bacteria
digest food and produce
important vitamins and
amino acids.
• Bacteria in the intestines
are essential for proper
digestion.
Lesson 6.3 The Excretory System
Our body is organized into different body systems. These systems
work together to perform body functions that are necessary to
maintain life.
The Excretory System
•
The excretory system collects and eliminates wastes from the body
and regulates the level of fluid in the body
• The excretory system is made of four body systems that work
together to maintain internal stability.
Types of Excretion
The respiratory system
removes carbon dioxide
and water vapor from the
body.
The digestive system collects
and removes undigested
solids from the foods you eat.
Types of Excretion
The integumentary system,
which includes the skin,
secretes excess salt and water
through sweat glands.
The urinary system processes,
collects, transports, and
releases liquid wastes from the
body.
Organs of the Urinary System
The Urinary System
• The urinary system is responsible
for maintaining the volume and
composition of body fluids
within normal limits.
Organs of the Urinary System
The Urinary System
• The kidneys are bean shaped
organs about the size of your fist.
• They are located near the back
wall of your abdomen, below
your rib cage and above your
waist.
• The kidneys have special
structures that filter waste
products out of the blood and
produce urine.
Organs of the Urinary System
The Urinary System
• The ureters are tube-like
structure that are about 25 cm
long.
• They descend from the kidneys
and are connected to the bladder.
• The urine flows out of the kidneys
and into the ureters. Ureters carry
urine from the kidneys to the
bladder.
Organs of the Urinary System
The Urinary System
• The bladder is a muscular,
hollow organ located in the lower
abdomen.
• The bladder expands to store the
urine it receives. Then it contracts
when it ejects the urine.
Organs of the Urinary System
The Urinary System
• The urethra is a muscular tube
that extends from the bottom of
the bladder to the outside of the
body.
• The urethra contains circular
muscles or sphincters that control
the release of urine outside the
body.
Organs of the Urinary System
Functions of Kidneys
a) Kidneys produce
hormones that stimulate
the production of red
blood cells.
b) Control blood pressure
and help control calcium
levels in the body.
Organs of the Urinary System
Functions of Kidneys
c) Waste products, salts and
toxins are filtered from the
blood as it passes through the
kidneys
d) When blood is filtered, a fluid
called urine is produced.
Organs of the Urinary System
Structure of Kidneys
• The kidneys contain blood
vessels and nephrons.
• Nephrons are networks of
capillaries and small tubes, or
tubules, where filtration of blood
occurs.
• Each kidney contains about
one million nephrons.
Organs of the Urinary System
Filtration of blood
• The nephrons work through a
two-step process:
• The first filtration occurs in
clusters of capillaries in the
nephrons.
• The second filtration occurs in
small tubes in the nephrons.
Organs of the Urinary System
What would happen if all of the
liquid from the first filtration were
excreted outside the body?
Organs of the Urinary System
Important nutrients would be lost
and your body would dehydrate. To
regain some of this water, the kidneys
reabsorb up to 99% of the nutrients
and water from the first filtration.
Urinary Disorders
Urinary Disorders
Kidney disease
• Description:
• Kidney disease, also called kidney failure, occurs when the
ability of the kidneys to remove wastes is reduced.
• Symptoms:
• Fatigue, vomiting, loss of appetite, and shortness of breath
are some symptoms of kidney failure. However, at the
beginning stages a person can experience no symptoms.
• Possible causes:
• high blood pressure, diabetes, poisons, some medicines,
trauma
Urinary Disorders
Kidney stones
• Description:
• Kidney stones are small, hard collections of minerals and
salts that accumulate in the kidney. The presence of kidney
stones interrupts the normal function of the kidneys and
can even block a ureter, causing urine to build up.
• Symptoms:
• Abdominal pain, nausea, and blood in the
urine are some symptoms of kidney stones.
• Possible causes:
• calcium build-up in the kidney
Urinary Disorders
Urinary tract infections
• Description:
• Urinary tract infections (UTIs) are
bacterial infections of any part of the
urinary tract.
• Symptoms:
• Burning during urination, little and
frequent urination, blood in the urine,
and back pain are some symptoms of
urinary tract infections.
• Possible causes:
• bacteria getting into the urinary system
Urinary Disorders
Bladder control problems
• Description:
• Bladder control problems are conditions that cause the
bladder to release urine involuntarily.
• Symptoms:
• Leaking urine without any warning or during performing
everyday activities is a symptom of bladder control problems.
• Possible causes:
• urinary tract infections, muscle weakness, prostate enlargement
The Excretory System and Homeostasis
• Your kidneys have many important jobs that help keep your
body working well. It is essential that you take good care of
them by:
• drinking enough water
• eating healthy food that is rich in nutrients
• staying fit and exercising