The cat skeleton is both strong and light having evolved for speed and agility, which is demonstrated in the cat’s wonderfully graceful movements including its jumping and climbing skills.The back is highly flexible, which is geared for speed. And the shoulder blade (scapula) is unattached to the main skeleton providing more flexibility.The hind leg structure is designed for power not endurance4. The cat’s skull has large eyesockets as the cat has relatively very large eyes4 for twilight hunting and a short jaw that opens widely and bites strongly. The bones of a skeleton are held together by ligaments (fibrous tissue that connects bones to other bones3). A sprain is a torn or stretched ligament5.
You can read about the world’s fastest land animal and how it achieves its speed with the aid of the flexible spine, here: Cheetah Speed. The world’s tallest domestic cat skeleton at 17.1″ to the shoulder belongs to F1 Savannah cat Scarlett’s Magic. The purpose of the cat skeleton is to:
- produce red and white blood cells and store minerals7
- protect the organs of the body
- support the body
- provide leverage for movement in coordination with the muscles4|1
The skeleton of the domestic cat is almost identical to that of the big cats (tiger, lion, jaguar & leopard) except for its size. And lets not forget that the cat walks on its toes (see cat paws). There are more bones in the cat skeleton than the human skeleton, 230-290 (“about 245”4), compared to 206 for humans2, which begs the question why do we not know the exact number, to which we have to answer that we still have things to learn – update 12-3-2010: There are 244 bones5. It is said that the difference is in part due to the bones of the cat’s tail1 as there are 19-28 bones in the standard cat’s tail5.
In the cat skeleton there is a small, vestige, of a collar bone (clavical) allowing for better mobility of the forelimbs. The cat’s legs are slender, some cat breeds have more slender legs than others. Some have slender legs and cobby (stocky) bodies, for example the Chartreux. Some have long legs and slender bodies…the cheetah wild cat and the Savannah wild cat hybridcome to mind.Of the totally domestic cat breeds, the Egyptian Mau is said to the be the fastest (30+ mph) with a slender athletic and flexible frame and a belly flap(lose skin on belly). When a cat walks the shoulder blade rises above the spine.In a three legged cat this is more pronounced as there is extra pressure on the remaining leg. Long legged cats are good jumpers. The picture opposite, right, shows the relative flexibility of the cheetah’s back (and all cats) over horses, as one example. Cats lack endurance because the generation of power is inefficient compared to the horse. The sacrifice of efficiency is compensated for by an advantage in speed.
The refinement of the breeds affecting the cat skeleton
The skeleton of some of the domestic cat breeds has been altered through selective breeding, while random cats have a cat skeleton that is still very similar to the European wild cat (see also the Scottish wild cat) and African wild cat.
The most noticeable “refinements” to the skeletons of the recognised cat breeds are the slender “foreign” frames and long heads of the Modern Siamese and associated cat breeds such as the Oriental Shorthair and the rounded flat face of the Ultra type Persian (see cat head shape and cat body types) and Scottish Fold. A number of cat breeds have been created (selectively bred) around abnormalities of the cat skeleton:
- Manx and Cymric (long haired Manx)- shortened tail or tailless
- Dwarf Cats – dwarfism
- Miniature cats and Teacup cats – small frame
Note: the Scottish Fold has defective cartilage causing the folded ears and it has been bred for a rounded head.
The cat’s skull has large eye sockets. A cat’s eyes are eight times larger than ours in relation to head size. The jaw is strong and specialised as bite strength has to be high to capture, hold and kill prey. The jaw is short and it opens wide.
Cat skeleton – joints and ligments
There are three types of joints in the cat skeleton:
- fibrous — Example: the joints of the fused bones of the skull and mandible (jaw bone) are made of hard fibre and are inflexible. A cat falling from a height does so with great skill and survives well but sometimes this fibrous joint will split giving the appearance of a broken bone.
- cartilaginous — Example: the discs in between the vertebrae. These are more supple and looser in the cat than in humans providing for more flexibility.
- synovial — Example: in legs and jaw. They are hinged ball and socket joints. The contact surfaces are made up of smooth cartilage. The joint is surrounded by synovial fluid.
Ligaments hold the joints together. It is a band of tough, fibrous connective tissue made up of attenuated collagenous fibers. Ligaments do not connect muscles to bones, tendons do that. They are elastic and when they are under tension, they gradually lengthen. Tendons by contrast are inelastic6.
The structure of bone
The primary tissue of bone is osseous tissue. This is a relatively hard and lightweight composite material, which is formed mainly of calcium phosphate. Internally the bone has a latticed structure of hard struts called trabecullae. Bone has a blood supply.
When born the bones of the kitten’s head are separate bones, which fuse together. A soft area can sometimes be felt on the top of the head. The limbs and ribcage begin as cartilage and then calcify, the cartilage being replaced by bone. Dwarf cats have short legs because of a defect in the production of cartilage (see health issues of dwarf cats). Bone outside of the bone produces new bone cells making it thicker.
Bone length is increased as the cat grows by the production of new bone at the growth plates (epiphyses: the epiphysis is the rounded end of a long bone, at its joint with adjacent bone(s)8). Growth and sex hormones affect growth of the cat skeleton. Neutering cats early tends to lead to longer legs so sex hormones inhibit growth slightly. Bone breaks are repaired by the production of new bone to fill the break1. Cats in warmer climates tend to have smaller skeletons as it helps to produce a greater surface to weight ratio resulting in loss of heat more efficiently. Whereas in cold climates the domestic cat is larger1 (e.g. Siberian cat – see also Domestic Cats – description). This may account for the larger than average Maine Coon (other than selective breeding).