As you watch your cat slink through the house and leap effortlessly onto your counter, consider what's underneath her sleek fur coat: a skeletal system comprised of bones, ligaments and cartilage. A complex network, a cat's skeletal system helps her move, keeps her upright and protects her.
Parts of the Skeletal System
A cat has an average of 244 bones in her body, depending on how many toes she has and how long her tail is. Her skeleton is made of three skeletal subunits:
- Axial skeleton: bones of the spine, ribs, skull and sternum.
- Appendicular skeleton: limb bones.
- Visceral skeleton: bones that are part of an organ, such as the ossicles in her middle ear.
Additionally, your cat's bones are classified according to their shape.
- Long bones are in her limbs.
- Short bones are found in her ankles and wrists.
- Flat bones are in her head, surrounding and protecting her brain, eyes, ears and sinuses.
- Sesamoid bones are close to her freely moving joints, such as her knees and wrists.
- Irregular bones include many of the bones in the axial skeleton, including the vertebral column, parts of the hip bone and the bones in the skull that aren't flat bones.
Not all cats have the same size and shape of bones, which can differ in thickness and length, according to the breed of cat.
Purpose of the Cat's Skeletal System
Your cat's skeletal system serves a number of vital functions. It serves as her framework, giving her support and keeping her upright. It also protects her organs; her ribs protect her heart and lungs and her skull protects her brain and eyes. Her bones help her move, serving as levers for her muscles, tendons and ligaments. Her bones also produce red and white blood cells and store fat.
If you've ever taken a look at a bone, it may be difficult to envision it as an organ, however your cat's bones are organs, each with a network of blood vessels and nerves. Bones are primarily made of the minerals phosphorus and calcium and contain several layers of tissue. The majority of her skeletal bone mass is cortical bone, the hard, dense outer layer of bone, which carries most of her weight. The cancellous or trabecular bone is the inner material with the honeycomb structure; though it's pliable, it provides important support for her bones. Bone marrow resides in the center shaft of the bone; marrow is red when it's producing blood cells and yellow when it's comprised mainly of fat. The periosteum is the fibrous membrane that covers the outside of the bone. The membrane feeds the bone with its network of capillaries.
Skeletal System Conditions
Your cat's skeletal system can suffer from a variety of diseases. Nutritional disorders can cause problems, such as rickets, a weakening in the bone from calcium deficiency or poor nutrition. Congenital diseases are not seen often in cats, though some occasionally present, such as the bone inflammation osteomyelitis. Trauma is far more common in cats; falls, fights and car accidents can cause fractures and dislocations. Bone cancer is rare in cats.
Cat Skeletal System Facts
Your cat's skeletal system has many things in common with other animals -- including humans -- but it does offer her a unique attribute when it works with her muscular system: She's able to quickly adjust her body when she falls, a trick that's unique to cats. She is also one of the few mammals who can arch her back in her signature "scaredy-cat" shape. Other cat skeletal system facts include:
- Cats have 13 ribs.
- Cats have 13 thoracic vertebrae; one for each pair of ribs.
- Cats' collar bones aren't attached to other bones.
- Cats have five regions to their spinal column: cervical, thoracic, lumbar, sacral and caudal.
- There are usually between 18 to 23 caudal vertebrae in a cat's tail.
- The most frequently broken bones in cats are the forelegs, hind legs and the pelvis.