air sac

noun

1. a sac containing air.
2. alveolus ( def 2 ).
3. any of certain cavities in a bird's body connected with the lungs.
4. a saclike dilation of the wall of a trachea in many insects.

air sac

noun

1. any of the membranous air-filled extensions of the lungs of birds, which increase the efficiency of gaseous exchange in the lungs
2. any of the thin-walled extensions of the tracheae of insects having a similar function

air sac

1. An air-filled space in the body of a bird that forms a connection between the lungs and bone cavities and aids in breathing and temperature regulation.
2. See alveolus
3. A saclike enlargement in the trachea of an insect.
4. A baglike piece of skin or tissue below the jaw of certain animals, such as the bullfrog and orangutan, that can be inflated to increase sound production.

Word History and Origins

Origin of air sac¹

First recorded in 1820–30

Example Sentences

During intense exercise, the heart can become overworked, which may lead to some fluid buildup in the small air sacs of the lungs, known as pulmonary edema, a condition commonly connected to heart problems.

From Washington Post

The virus invades the lining of the lungs, including the alveoli, tiny air sacs that capture oxygen from each breath and quickly pass it into the bloodstream.

From Nautilus

Pneumonia occurs when “air sacs in the lungs fill with fluid, limiting their ability to take in oxygen and causing shortness of breath, cough and other symptoms,” Galiatsatos writes.

From Washington Post

ARDS occurs when air sacs become filled with fluid leaking from the tiny blood vessels in the lungs, causing the lungs to fail.

From Popular-Science

But the joints of the backbone in front of the sacrum receive their air from the cervical air sac.

From Project Gutenberg

These animals are said to possess an air-sac in the throat, at the back of the trachea (or windpipe), as in Ateles.

From Project Gutenberg

The cheek-bones enormously swollen along the side of the nose; in the neck a large air-sac.

From Project Gutenberg