Pulmonary ventilation refers to the ___.

• flow of air into and out of the alveoli (where gas exchange occurs)

• alternating flow of air into and out of the lungs

• flow of air only into the lungs

• flow of air only out of the lungs

Muscles that expand the rib cage; drive airflow into the lungs are ___ muscles.

Muscles that force air out of the lungs are ___ muscles.

The ___ pleura wraps around the lung itself.

The ___ pleura is the outermost layer of the lung, and it touches the inside of the chest cavity.

The primary inspiratory muscle is the ___.

During quiet breathing, what are the muscles used for inspiration?

• diaphragm

• external intercostal muscles

• sternocleidomastoid

• scalenes

During labored breathing, what muscles are involved in inspiration?

• diaphragm

• external intercostal muscles

• sternocleidomastoid

• scalenes

What muscles are involved in forced expiration?

• internal intercostal muscles

• abdominal muscles

• diaphragm

• sternocleidomastoid

What occurs when pressure in the lungs is less than the
atmospheric pressure?