the journey of air
1)enters the body and is warmed as it travels through the mouth and nose.
2)It then enters the trachea.
3)The trachea divides into two bronchi. One 4)bronchus enters each lung.
4)Each bronchus branches out into smaller tubes called bronchioles. Air travels through these bronchioles.
5)At the end of the bronchioles, the air enters one of the many millions of alveoli where gaseous exchange takes place.

The respiratory system transports oxygen from the air we breathe, through a system of tubes, into our lungs and then diffuses it into the bloodstream, whilst carbon dioxide makes the opposite journey

The diaphragm contracts and moves downwards. The intercostal muscles contract and move the ribs upwards and outwards. This increases the size of the chest and decreases the air pressure inside it which sucks air into the lungs

The diaphragm relaxes and moves back to its domed shape. The intercostal muscles relax so the ribs move inwards and downwards under their own weight. This decreases the size of the chest and increases the air pressure in the chest so air is forced out of the lungs

Gas exchange occurs at the alveoli in the lungs and takes place by diffusion. The alveoli are surrounded by capillaries so oxygen and carbon dioxide diffuse between the air in the alveoli and the blood in the capillaries

big surface area. they have moist, thin walls (just one cell thick) they have a lot of tiny blood vessels called capillaries

Residual volume is the amount of air that remains in a person's lungs after fully exhaling

Tidal volume is the lung volume representing the normal volume of air displaced between normal inhalation and exhalation when extra effort is not applied

Vital capacity is the maximum amount of air a person can expel from the lungs after a maximum inhalation

Intercostal muscles are several groups of muscles that run between the ribs

thin skeletal muscle that sits at the base of the chest and separates the abdomen from the chest

a short band of tough, flexible fibrous connective tissue which connects two bones or cartilages or holds together a joint

the maximal amount of additional air that can be drawn into the lungs by determined effort after normal inspiration

the additional amount of air that can be expired from the lungs by determined effort after normal expiration — compare inspiratory reserve volume