Lungs/Gas Exchange

Mechanism of Inspiration

1. Ribcage up and out by external intercostal muscles contracting and internal intercostal muscles relaxing (pulled into their elongated state)

2. Diaphragm contracting moves downward and pushes the abdominal wall out due to the muscles relaxing

Mechanism of Expiration

1. Ribcage pulled down and in by intercostal muscles contracting (only in forced exhalation) and external intercostal muscles relaxing (pulled into their elongated state)

2. Diaphragm contracting moves downward and pushes the abdominal wall out due to the muscles relaxing

Tidal Volume

Volume of fresh air inhaled and the amount of stale air that is exhaled in each ventiliation

Ventilation Rate

Number of times that air is drawn in or expelled per minute

Inspiratory Reserve Volume

Amount of air a person can inhale forcefully after a normal tidal volume inspiration

Expriatory Reserve Volume

Amount of air a person can exhale forcefully after a normal exhalation

Vital capacity

Total volume of air that can be exhaled after a maximum inhalation or total volume of air that can be inhaled after a maximum exhalation

Gas exchange surfaces are characterize by:

• being thin to keep diffusion distances short

• being most, encourging gas diffusion

• having a large surface area for maximum diffusion

• being permeable to respiratory gases

Diffusion

The passive movement of gas molecules (like O and CO2) from an area of higher concentration to an area of lower concentration

Larger SA

Allow more gases to enter

Air gets drawn into lungs by

Trachea → branches to the left and right bronchi → bronchioles (branches in the lungs) → alveolar ducts → 5 or 6 alveoli

When does diffusion occur?

Due to a high concentration of oxygen in the alveoli and a low concentration of oxygen in the blood

Surfactant

Reduced the surface tension and prevents the water from causing the sides of the alveoli to adhere when the air is exhaled from the lungs (prevents collapsing)

Alveoli

Where oxygen goes, they are adapted to recieve the air and transport it easily into the blood.