th
8
Grade Science
Wednesday November 14
Levels of Organization
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Cells (such as a lung cell)
Tissues (such as lung tissue)
Organs (such as lungs)
Organ systems (such as the respiratory
system)
Feeding Cells
• The foods you eat are filled with the chemicals
that your body needs to grow strong and
healthy
The Digestive System
• Your digestive system is like a
disassembly line
• Digestion is the breakdown of
foods that you eat into smaller
and simpler molecules that can
be used by the cells in your body
• The digestive system is like a
long tube that runs through
your body
The Digestive System
• Food is taken into the body
through the mouth, where it
is chewed and broken down
into smaller pieces
– This is called mechanical
digestion
• As the food passes through
the digestion tube, it is
broken down further
– This is called chemical
digestion
Mechanical and Chemical Digestion
• Both mechanical and
chemical digestion are
necessary for
providing materials
necessary for survival
of the cell and
organism
Helping Digestion
• Other body systems help the
digestive system
– Such as your brain which tells
some cells in your mouth to
produce saliva when you see,
smell, taste or just think about
food
• Enzymes help with the
digestive process
Circulation and Digestion
• The body’s circulatory system
transports blood that provides
nutrients for the cells of the
digestive system
• This exchange happens in the small
intestine
• By the time food reaches the small
intestine, it has been broken down
into molecules that can pass
through the walls of the villi
– This is called absorption
Circulation and Digestion
• After nutrients are
absorbed into the
bloodstream, they are
carried to cells
throughout the body
• Materials that are not
absorbed pass out of the
body as wastes
Energy For the Body
• The body's cells release
energy from food in in order
to carry out different body
activities
– This is called cellular
respiration and happens
in the mitochondria
• Carbon dioxide and water are
wastes
Energy for the Body
• Cellular Respiration is a series of chemical
processes in which oxygen combines with
food molecules and energy is released
Respiration Equation
• Food + Oxygen = energy
for the body to do work
(as a result carbon
dioxide and water are
what is left over)
What we need to survive!
• In order for your body
to live, your body must
have a constant supply
of nutrients (FOOD)
and oxygen
• Without oxygen, your
body cannot release
energy you need from
food
Living things need it!
• living organisms need
food and oxygen to
release the energy from
that food
• People and animals have
similar structures that
serve the same functions
(for example animals
must have body systems
in place that help them
eliminate waste such as
an excretory system)
Respiratory System
• When you inhale,
oxygen enters your
body
• When you exhale,
carbon dioxide is
released through
your respiratory
system
Oxygen Absorption
• The exchange of oxygen and carbon dioxide takes place
in the lungs
• In the lungs, alveoli exchange oxygen with the
surrounding capillaries
• This is how oxygen gets into your blood in your
circulatory system
• Oxygen is then taken to the body’s cells and is
exchanged for carbon dioxide to be returned to the
lungs for elimination
•
Picture on the next slide
Respiratory System
Circulatory and Respiratory Systems
• When oxygen enters the body it passes into
the bloodstream and is transported into the
cell
• Carbon dioxide is transported out of the cell
and passes into the blood stream and exits the
body
Getting Rid of Wastes
• Carbon dioxide gas is released
from your body through the
combined efforts of the
circulatory and respiratory
systems
• Undigested material is
eliminated by your digestive
system but waste is also
removed by sweat
• All of these systems work
together to make up your
excretory system
If you don’t get rid of the waste…
• Wastes can build
up to toxic levels
and damage cells
and eventually
the whole
organism
The Urinary System
• This body system removes
wastes also
• In this system, waste
products are removed
from blood in the kidneys
by nephrons
Nephrons in the Kidneys
• Blood is filtered in the nephrons in the kidneys
• Water, salt, sugar and wastes from your blood
first pass into the nephron
• Capillaries or small blood vessels surrounding
the nephrons reabsorb nutrients and anything
left behind is waste and sent to be excreted
Nephrons
Interdependence of Body Systems
• The body senses changes in
the environment and
responds by making
changes in body functions
• When your body is in
stable internal condition it
is said to be in homeostasis
Interdependence of Body Systems
• Your body responds to changes
such as
– Increased activity (heart rate and
breathing increase)
– Increase or decreased
temperatures (body shivers or
sweats)
– Slowed metabolism when food
supply is low or you are
dehydrated
– Adrenaline rush when you are
frightened (increased heart rate)
Cell Membrane
• The cell membrane helps regulate the transfer
of materials (such as nutrients and waste) in
and out of the cell
Nervous and Muscular Systems
• The nervous system
(including your brain
and spinal cord) sends
messages to your
muscles to move
• This is done through
electrical impulses that
tell muscles to contract
or expand resulting in
movement