A: Swim bladder, also called air bladder, buoyancy organ possessed by most bony fish. The swim bladder is located in the body cavity and is derived from an outpocketing of the digestive tube. It contains gas (usually oxygen) and functions as a hydrostatic, or ballast, organ, enabling the fish to maintain its depth without floating upward or sinking. It also serves as a resonating chamber to produce or receive sound. In some species the swim bladder contains oil instead of gas. In certain primitive fish it functions as a lung or respiratory aid instead of a hydrostatic organ. The swim bladder is missing in some bottom-dwelling and deep-sea bony fish (teleosts) and in all cartilaginous fish (sharks, skates, and rays).
Skip Ad
Teleost fish in cross section.
See all media
Related Topics: Baroreception
The Editors of Encyclopaedia Britannica
This article was most recently revised and updated by Adam Augustyn, Managing Editor, Reference Content.
Learn More in these related Britannica articles:
auditory mechanisms in insects
sound reception: Special stimulation mechanisms
…however, the connections with the swim bladder disappear, leaving the air sacs connected with the saccular...…
human circulatory system
circulatory system: Circulation in jawed vertebrates
…structure in fishes called the swim bladder, a sac that grows out from the anterior part of the gut…
vertebrate: skeleton
skeleton: Buoyancy devices
…or forward, end of the swim bladder to the auditory organs of the head. Sound vibrations cause changes...…
newsletter icon
HISTORY AT YOUR FINGERTIPS
Sign up here to see what happened On This Day, every day in your inbox!
Email address
By signing up, you agree to our Privacy Notice.
BLADDER
Sections & Media
Home
Health & Medicine
Anatomy & Physiology
Bladder
anatomy
Cite
Share
More
BY The Editors of Encyclopaedia Britannica View Edit History
FULL ARTICLE
Bladder, membranous sac in animals that serves as the receptacle of a fluid or gas. See gallbladder; swim bladder; urinary bladder.
Related Topics: Bladder cancer Urinary bladder Swim bladder Ureter
Learn More in these related Britannica articles:
gallbladder; bile ducts
gallbladder
Gallbladder, a muscular membranous sac that stores and concentrates bile, a fluid that...…
Teleost fish in cross section.
swim bladder
Swim bladder, buoyancy organ possessed by most bony fish. The swim bladder is located...…
male urinary bladder and urethra
urinary bladder
Urinary bladder, in most vertebrates, except birds, organ for the temporary storage of...…
newsletter icon
HISTORY AT YOUR FINGERTIPS
Sign up here to see what happened On This Day, every day in your inbox!
Email address
By signing up, you agree to our Privacy Notice.
