Bones provide structure for the body, protect internal organs, and support movement. In a frog, the skeleton is adapted for jumping, swimming and eating.
Spinal Column and Skull
The skull of a frog is flattened, except for a small area surrounding the brain. The backbone contains five to nine vertebrae, including a very short, stiff neck with limited mobility. The jaw is designed to grab rather than chew, and to allow tongue extension.
Frogs have a single upper forearm bone, the humerus. Lower forearm bones are fused together, forming the radioulna. Much like humans, frogs have phalanges, metacarpals and carpals forming the hands and wrists. The arms are adapted to begin the push-off of a jump and to absorb shock on landing.
Jumping power comes from the hind legs, which have three segments—upper leg or femur, fused lower leg bones or tibiofibular, and two long tarsals forming the ankle—plus feet. The hind legs are also suited for swimming.
In humans, bones such as the rib cage provide structure to the torso and protect soft inner organs. The frog has no rib cage, and all internal organs are located in a single body cavity called the coelom. The heart is slightly protected by the pericardium and the breastbone.
Urostyle and Pelvis
Vertebrae at the base of the spine are fused into a pillar called the urostyle. The pelvis comprises three fused bones. The stiffness of these skeletal structures provide strength and shock absorption for leaping.