Download Science 8 Unit B Section 3.0

Science 8 Unit B Section
3.0
Body Systems
Section Outcomes:
Describe how various body systems work
 Recognize the roles of organs and tissues
in body systems
 Describe how various cells help the body
function
 Show how the body responds to changing
conditions

3.1 – The Digestive System

Purpose:
Our body needs energy from
carbohydrates, lipids and proteins
 The digestive system makes sure that we
can obtain these nutrients from foods that
we eat

The Digestive System
1.
2.
3.
4.
5.
6.
7.
8.
Types of Digestion

Mechanical Digestion

Chemical Digestion

Some parts of the digestive system use
both mechanical and chemical digestion
The Mouth and Esophagus
The mouth carries out both mechanical
digestion and chemical digestion of foods
 The salivary glands release saliva, which
moistens the food and adds the enzyme,
amylase, which breaks down starches
 Once your food has been chewed, the
tongue pushes down into the esophagus

Peristalsis

Peristalsis:

This is similar to pushing little bits of
toothpaste from the end of the tube to the
tip
The Stomach
When food arrives in the stomach, the
stomach reacts in several ways
 It produces gastric juice (mucus, enzymes,
and strong acid) that breaks down
proteins
 It also churns the food using muscular
contractions
 The stomach releases food a little bit at a
time into the small intestine

The Small Intestine
The small intestine is the place where food
from the stomach completes its digestion
and where the nutrients are absorbed
 The small intestine is relatively narrow,
and its inner surface are covered with tiny
finger-like villi
 Each of these villi are covered with even
smaller microvilli

Digestion in the Small Intestine
At the top end of the small intestine, a
duct attached to the pancreas and bile
duct opens into the intestine
 Bile from the liver (which helps emulsify
fats) empties out of this duct
 As well, bicarbonate (a chemical that
neutralizes stomach acid) and various
enzymes are added from the pancreas

The Large Intestine
The large intestine is the place where
water is absorbed into the body
 As well, many vitamins and minerals are
absorbed here as well
 The large intestine collects undigested
foods and forms them into feces

Length of the Intestine
The small intestine is between 4.5 m and
6 m long in humans
 The average length of the large intestine
is about 1.5 m
 Therefore, you have between 6 and 7.5 m
of intestine packed into your abdomen
(about 20 to 25 feet)

3.2 – Respiratory System

Purpose:

Our body needs oxygen to
produce energy within its
cells, and it needs to
remove CO2 before it builds
up in the blood
Breathing
Breathing involves the movement of two
sets of muscles
 The diaphragm is a large muscle beneath
the lungs
 The intercostal muscles are muscles
between the ribs
 The movement of the diaphragm and
intercostal muscles are responsible for
breathing

Exhaling

When you exhale, the intercostal and
diaphragm muscles move to reduce the
lung volume
Inhaling

When you inhale, the intercostal and
diaphragm muscles move to increase lung
volume
Moving Air In & Out
The movement of air actually involves a
pressure difference between the interior of
the lung and the outside atmosphere
 To inhale, the atmospheric pressure must
be higher than the pressure within the
lungs
 To exhale, the pressure in the lungs must
be higher than the atmospheric pressure

Gas Exchange
The airway into the
lungs begins at the
trachea
 The trachea then
branches into two
cartilage-lined bronchi
 These bronchi then eventually branch off
into many bronchioles

The Alveoli
At the very end of the bronchioles, there
are tiny sacs called alveoli
 These alveoli are surrounded by tiny blood
vessels known as capillaries

As blood filled with CO2 reaches the
alveoli, the CO2 diffuses out of the blood
and into the alveoli
 At the same time, oxygen diffuses out of
the air in the alveoli and into the blood
 The oxygenated blood then returns to the
heart to be circulated around the body

3.3 – Circulatory System

Purpose:
The human body contains about 5 L of
blood
 If we lose more than 20% of that blood
volume (about 1 L), then we can go into
shock and die

The Heart
The heart is two
pumps that work
together to move
blood throughout the
body
 The right side of the
heart takes in
deoxygenated blood
and sends it to the
lungs

The Heart
The left side of the heart receives
oxygenated blood from the lungs and
pumps it to the rest of the body
 The chambers of the heart are known as
the atria and the ventricles:
 Atria:


Ventricles:
Blood Vessels

Arteries:

Veins:

Capillaries:
Veins and Valves
All veins have valves
 Reason:

Capillaries

Role:
Capillaries are specially adapted to
perform this task
 They use two adaptations to do this:
1.

2.
The Blood
55 % of your blood
volume is plasma (the
liquid portion)
 About 1 % is made
up of white blood
cells that fight
infections
 The remainder is red
blood cells

Blood Cell Types

White Blood Cells:

Red Blood Cells:

Platelets:
3.4 – The Excretory System

Purpose:

Without our excretory system, the wastes
that we produce would build up over time
and poison us
Waste Products
Our cells produce a number of toxic waste
products
 When cells break down proteins, ammonia
is produced
 These cells may also release salts and
other waste (including excess water)

The Liver
Aside from its role in digestion, the liver
also helps to clean the blood
 The ammonia in the blood is converted to
a less toxic substance called urea
 However, the urea still has to be removed
from the body
 The liver also metabolizes many other
toxic substances, such as various drugs
and alcohol

The Kidneys
The kidneys
are about 10
cm long and
filter about
180 L of blood
per day
 However, you
only produce
about 1.5 L of
urine in a day

The Nephron
Nephrons are the
tiny structures that
filter the blood
 Blood enters the
kidney via the renal
artery
 The artery branches
into smaller vessels
until the capillaries
enter the nephron

Nephrons
The millions of nephrons in each kidney
filter wastes out of the blood
 At the same time, the nephron reabsorbs
water so that the blood volume is
maintained
 The waste flows through collecting ducts
as urine

Ureters, Bladder, and Urethra
Ureters are long tubes that connect each
kidney to the bladder
 The bladder is a sac covered in muscular
tissue
 The bladder can store less than 1 L of
urine
 When full, the bladder releases urine into
the urethra, which allows the urine to
leave the body

The Skin
Sweat glands
don’t just keep
the body cool
 They also release
excess salt in the
sweat

Urine and Diseases
1.
A number of diseases can be diagnosed
by monitoring urine production and
contents
Diabetes
2.
Kidney disease

Dialysis

People who
have kidney
failure can
still have
their blood
cleaned by a
dialysis
machine
Dialysis
The machine uses osmosis and diffusion
to remove wastes from the blood, while
keeping the appropriate components from
leaving
 It takes about 4 to 6 hours to clean the
blood
 However, this is supposed to be a
temporary solution – a kidney transplant is
the only permanent solution

3.5 – The Nervous System

Purpose:
The nervous system connects to every
other body system
 Therefore, we have nervous tissue
throughout the body

The Neuron
Neurons are the cells
that make up the
nervous system
 Every neuron has the
same structures, but
sensory neurons are
different in shape from
the motor neurons

Parts of the Neuron
Parts of the Neuron

Cell Body

Dendrites

Axon
Organization of the Nervous
System
The nervous system can be divided into
two main parts:
 Central Nervous System (CNS)


Peripheral Nervous System (PNS)
The Peripheral Nervous System
Our peripheral nervous system can be
further divided into two sections:
 Somatic Nervous System


Autonomic Nervous System
The Central Nervous System
The central nervous system is where we
process information from our senses, and
where we produce both voluntary
responses and involuntary responses
 Our brain, the main organ in the central
nervous system, is divided into parts that
carry out different functions

Parts of the Brain
The Reflex Arc
To prevent injury, our body has reflex arcs
 The reflex arc involves sensory and motor
neurons working together without the aid
of the brain
 This speeds up our reaction to pain and
other stimuli to prevent injury

Reflex Arc
The Distribution of Sensory
Neurons
Our sensory neurons are not evenly
distributed throughout the body
 Some areas of our body, for instance, are
much more sensitive to touch than others
 As well, we have special sensory receptors
that are bundled together in our sense
organs
