4.2b Mechanics of Breathing (pulmonary ventilation)

What is Tidal Volume?

Normal breathing moves about 500ml of air with each breath

What is Residual Volume?

after exhalation, about 1200 ml of air remains in the lungs

What is Inspiratory Reserve Volume (IRV)

Amount of air that can be taken in forcibly over the tidal volume. (Usually between 2100 and 3200 ml)

What is Expiratory reserve volume (ERV)

Amount of air that can be forcibly exhaled. (Approximately 1200 ml)

What is Vital Capacity

The total amount of exchangeable air.

Vital capacity = Inspiratory reserve volume + tidal volume + expiratory reserve volume

What is Total lung capacity?

The sum of all lung volumes.

Total Lung Capacity = Vital capacity + residual volume

What is a diaphragm?

the dome-shaped skeletal muscle that forms the floor of the thoracic cavity

What happens to diaphragm during inspiration?

It contracts

When does a diaphragm relax?

during exhalation

Give some factors that can cause shortness of breath

1. advanced pregnancy
2. obesity
3. confining clothing
4. increased stomach size by impeding the descent of the diaphragm

What is Pulmonary ventilation?

Moving air in and out of lungs

What is external respiration?

gas exchange between pulmonary blood and alveoli

What is internal respiration?

Gas exchange between blood and tissue cells in systemic capillaries

What is Inspiration?

the flow of air into the lung

What happens during inspiration?

* Diaphragm and intercostal muscles contract
* The size of the thoracic cavity increases
* External air is pulled into the lungs due to an increase in intrapulmonary volume

What is expiration?

air leaving lungs

What happens during expiration?

* Largely a passive process which depends on natural lung elasticity
* As muscles relax, air is pushed out of the lungs
* Forced expiration can occur mostly by contracting internal intercostal muscles to depress the rib cage

What is Boyle’s Law

P1v1 = P2V2