The Breathing System
-When we breathe:
● Air fills the lungs
● Oxygen passes to the bloodstream
● The blood carries the oxygen to cells where it’s used to release energy from food. This release of
energy is called respiration.
● Carbon dioxide and water vapour waste products are released by respiration and are passed
out through the mouth/nose.
Word Equation: Glucose + Oxygen-> energy + CO2 + water vapor
-The breathing system is made up of the following parts:
➔ Nose: We are meant to breathe in through the nose because hair and mucus traps dirt particles and
bacteria in the nose and because air is warmed and moistened in the nose. Warm air helps oxygen
pass into the blood easily.
➔ Trachea: This carries air from the nose to the lungs and back.
➔ Bronchus and Bronchioles: We have two bronchi, each carries air between the windpipe and the
lungs. They subdivide many times to form the bronchioles which carry air to and from the air-sacs or
alveoli.
➔ Alveolus: Each lung has millions of alveoli, each with a thin lining surrounded by capillaries. The
function of these is gas exchange. Oxygen passes from the air into the alveoli and then into the
bloodstream, at the same time carbon dioxide and water enter the alveoli. The gases pass in each
direction by diffusion. Site of gaseous exchange.
➔ Diaphragm: This is a sheet of muscle that forms the base of the chest. It causes air to move in and
out of the lungs along with the ribs and intercostal muscles.
➔ Larynx: Allows us to make sounds.
➔ Rings of Cartilage: Keep the air tubes open.
➔ Lungs: Our breathing organs, made of spongy
material.
WHAT HAPPENS WHEN WE BREATHE?
WHEN INHALING
WHEN EXHALING
The rib cage expands
The rib cage contracts
The lungs expand
The lungs contract
The diaphragm pulls downwards
The diaphragm is pushed upwards into a
dome shaped structure
GASEOUS EXCHANGE DURING BREATHING:
GAS
INHALED AIR
EXHALED AIR
Nitrogen
78%
78%
Oxygen
21%
15%
Carbon Dioxide
.04%
4.6%
-Smoking is bad for these reasons:
➢ Tar damages the bronchioles
➢ Nicotine can damage the heart and blood vessels
➢ Carbon monoxide can cause heart strain
➢ Smoking causes lung cancer and is very bad for a developing child
-The average person takes 12-16 breaths per minute.
Exercise and the breathing rate
• When we exercise, the cells in our body need more energy and so respiration
increases.
• This means there is a greater concentration of CO2 in the body. Too much CO2 is
poisonous to the body.
• We breathe faster to remove this excess CO2.