Cheetah
Internal anatomy

Sharply contrasting with the other big cats in its morphology, the cheetah shows several specialized adaptations for prolonged chases to catch prey at some of the fastest speeds reached by land animals. Its light, streamlined body makes it well-suited to short, explosive bursts of speed, rapid acceleration, and an ability to execute extreme changes in direction while moving at high speed. The large nasal passages, accommodated well due to the smaller size of the canine teeth, ensure fast flow of sufficient air, and the enlarged heart and lungs allow the enrichment of blood with oxygen in a short time. This allows cheetahs to rapidly regain their stamina after a chase. During a typical chase, their respiratory rate increases from 60 to 150 breaths per minute. The cheetah has a fast heart rate, averaging 126–173 beats per minute at resting without arrhythmia. Moreover, the reduced viscosity of the blood at higher temperatures (common in frequently moving muscles) could ease blood flow and increase oxygen transport. While running, in addition to having good traction due to their semi-retractable claws, cheetahs use their tail as a rudder-like means of steering that enables them to make sharp turns, necessary to outflank antelopes which often change direction to escape during a chase. The protracted claws increase grip over the ground, while rough paw pads make the sprint more convenient over tough ground. The limbs of the cheetah are longer than what is typical for other cats its size; the thigh muscles are large, and the tibia and fibula are held close together making the lower legs less likely to rotate. This reduces the risk of losing balance during runs, but compromises the cat's ability to climb trees. The highly reduced clavicle is connected through ligaments to the scapula, whose pendulum-like motion increases the stride length and assists in shock absorption. The extension of the vertebral column can add as much as 76 cm (30 in) to the stride length.

Muscle tissue has been analized in the cheetah and it has been found that there are little diferences in type IIx muscle fibers concentration, type IIx MHC concentration, as well anaerobic LDH enzyme activity between sexes, in contrast to humans where women had type IIx MHC and LDH activity much lower that men, although type IIx muscle fibers concentration were similar. Cheetah males had larger cross-sectional area fibers.

The cheetah resembles the smaller cats in cranial features, and in having a long and flexible spine, as opposed to the stiff and short one in other large felids. The roughly triangular skull has light, narrow bones and the sagittal crest is poorly developed, possibly to reduce weight and enhance speed. The mouth can not be opened as widely as in other cats given the shorter length of muscles between the jaw and the skull. A study suggested that the limited retraction of the cheetah's claws may result from the earlier truncation of the development of the middle phalanx bone in cheetahs.

The cheetah has a total of 30 teeth; the dental formula is 3.1.3.1 3.1.2.1. The sharp, narrow carnassial molars are larger than those of leopards and lions, suggesting the cheetah can consume a larger amount of food in a given time period. The small, flat canines are used to bite the throat and suffocate the prey. A study gave the bite force quotient (BFQ) of the cheetah as 119, close to that for the lion (112), suggesting that adaptations for a lighter skull may not have reduced the power of the cheetah's bite. Unlike other cats, the cheetah's canines have no gap or diastema behind them when the jaws close, as the top and bottom cheek teeth show extensive overlap; this equips the upper and lower teeth to effectively tear through the meat, and prevent the canines of penetrate fully the hide and meat so the cheetah has to kill by closing the trachea and suffocating its prey. The slightly curved claws, shorter and straighter than those of other cats, lack a protective sheath and are partly retractable. The claws are blunt due to lack of protection, but the large and strongly curved dewclaw is remarkably sharp. Cheetahs have a high concentration of nerve cells arranged in a band in the centre of the eyes, a visual streak, the most efficient among felids. This significantly sharpens the vision and enables the cheetah to swiftly locate prey against the horizon. The cheetah is unable to roar due to the presence of a sharp-edged vocal fold within the larynx.
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