The Internal Anatomy of a Shark
The internal anatomy of a shark differs from that of bony fishes. One
major difference is that all sharks and rays (elasmobranchs) posess a cartilaginous
skeleton as opposed
to one composed of calcareous bone like that of goldfish, tunas, and most
other bony fishes (hence the designation "bony fishes"!). Moreover,
as you can see, the shark has a very large liver
which is filled with copious amounts of oil. Sharks also have a unique
structure known as the spiral valve in their intestines
to aid in digestion.
photo taken from:
Cailliet, G. M.; Love, M. S.;
Ebeling, A. W. 1986.
FISHES - A Field and Laboratory Manual on Their Structure,
Identification, and Natural History.