Cats are small obligate carnivores, and almost every part of their anatomy is tuned for hunting: a flexible spine, claws that stay sharp because they spend most of their time tucked away, eyes built for dim light and ears that hear better than ours. Whether a cat is a house cat, a feral cat or free roaming, the body underneath is the same.
This guide walks through the cat's body system by system, from the skeleton to the skin, with every number checked against veterinary sources. It is an anatomy reference, not a care guide. If something about your own cat's body worries you, your veterinarian is the person to ask.
The Cat Skeleton
A cat has about 230 to 250 bones, compared with 206 in an adult human. Sources give different totals because the count varies from cat to cat, mostly with the tail: a normal tail has 20 to 24 vertebrae, and bobtailed cats have fewer.
The spine is easiest to understand region by region. This is the normal feline vertebral formula:
Region | Vertebrae | What to know |
|---|---|---|
Cervical (neck) | 7 | The first two are called the atlas and the axis |
Thoracic (chest) | 13 | Each one carries a pair of ribs, so cats have 13 pairs of ribs |
Lumbar (lower back) | 7 | Between the last ribs and the pelvis |
Sacral (pelvis) | 3 | Fused together into one unit |
Caudal (tail) | 20-24 | Fewer in kinked or bobbed tails |
A 2014 X-ray study in the Journal of Feline Medicine and Surgery used this formula as the normal reference and found that kink-tailed Japanese Bobtails averaged 15.8 tail vertebrae.
Why cats bend so well
Two details explain much of that flexibility. Cats lack the nuchal ligament and the supraspinous ligament, two bands that run along the top of the spine in dogs, so the vertebral column can flex further. And the balance structures in a cat's inner ear are highly developed, which is how a falling cat can rapidly turn itself right side up.
The floating collarbone
Some sources say cats have no collarbone. They do. A cat's clavicle is a small, slender bone embedded in a muscle at the front of the shoulder (the brachiocephalicus), with no bony joints to the rest of the skeleton. In people the collarbone links the shoulder to the breastbone. In a cat it simply floats in muscle, and it can show up on X-rays as a small, isolated bone.
Muscles, Paws and Claws
Skeletal muscles hold the cat's posture and move its joints. They attach to bone through tendons, tough collagen cords that do not stretch, while ligaments wrap the joints and keep them stable. The bones are more than scaffolding: they hold the marrow where blood cells are made and act as the body's calcium reservoir.
Unlike dogs, cats can retract their claws. To push a claw out, the cat contracts the deep digital flexor muscle, which pulls on the last bone of the toe (the distal phalanx). Tucked away, the claws don't wear down on the ground, so they stay sharp for climbing, gripping and catching prey.
Because the claw grows from that last toe bone, declawing is not a nail trim. The Merck Veterinary Manual describes it as a surgical procedure that removes the toe bones along with the claws. Our article on feline onychectomy covers the procedure and the case against it, and your veterinarian can talk through alternatives.
The paws also hold the cat's sweat glands, but they play only a minor role in cooling. Cats keep cool mostly by grooming, spreading saliva over the coat.
Cat Senses
Eyes
A cat's retina has many rod cells, the photoreceptors that collect dim light. According to the Merck Veterinary Manual, cats see about 6 times better than people in dim light, which is where the myth that they can see in total darkness comes from. Behind the retina sits the tapetum lucidum, a reflective layer that boosts incoming light and causes the blue or green eyeshine you see in photos at night.
Cone cells give cats sharp vision and good depth perception, useful for judging the speed and distance of prey. Whether cats see color the way we do is still uncertain.
Cats also have a third eyelid, the nictitating membrane, a whitish pink fold tucked into the inner corner of each eye. It slides across to protect the eyeball and also comes up when the eye is inflamed. A third eyelid that stays visible is a good reason to have your veterinarian look at the eye. One more oddity: the University of Minnesota's anatomy lab guide notes that cats have no true eyelashes (cilia) on either eyelid.
Ears
Each outer ear flap (the pinna) moves independently of the other, so a cat can aim each ear at a different sound. Sound travels down a deep ear canal to the eardrum. Behind it, three tiny bones pass the vibrations to the cochlea, the hearing organ, and the fluid-filled semicircular canals next to it handle balance.
Merck notes that cats hear better than people and even most dogs. In a classic 1985 study in Hearing Research, the hearing range of cats for sounds at 70 decibels ran from 48 Hz to 85 kHz, one of the broadest ranges measured in any mammal.
Whiskers
Whiskers (vibrissae) are specialized hairs linked to sensory cells, and they give cats an extra-fine sense of touch. They help a cat judge the size of an opening before it commits its body to it. Cats have them on more than the face: there is also a patch of whiskers on the back of each front leg, at the wrist. If a cat loses some, our article on whether cat whiskers grow back has the details.
Smell and the vomeronasal organ
A cat's sense of smell is much stronger than a person's, and it shapes how food tastes to them. Cats also have a second scent system, the vomeronasal organ (Jacobson's organ), which picks up pheromones. You may have seen a cat sniff something, then lift its head, open its mouth slightly and pull back its upper lip. That expression is the flehmen response, and it wafts the scent toward the vomeronasal organ.
Taste
Cats most likely cannot taste sweetness. A 2005 study in PLoS Genetics found that one of the two genes needed to build the sweet taste receptor, Tas1r2, is broken in cats and no longer makes a working protein. The rest of a cat's sense of taste works normally, which suits an obligate carnivore.
Teeth and Tongue
Most cats have 26 deciduous (baby) teeth and 30 permanent teeth. The baby incisors start coming in at 2 to 4 weeks of age and the baby premolars at 5 to 6 weeks. Permanent teeth usually begin to appear at around 4 to 7 months.
Tooth type | Adult cat | Kitten |
|---|---|---|
Incisors | 12 | 12 |
Canines | 4 | 4 |
Premolars | 10 (6 upper, 4 lower) | 10 |
Molars | 4 | 0 |
Total | 30 | 26 |
For how these numbers become a dental formula, and how cats compare with dogs and horses, see our guide to dental formulas in animals.
The tongue feels like sandpaper because it is covered with tiny, backward-facing spines called papillae. They help a cat pick small pieces of food off a bone and trap loose fur when it grooms.
Organ Functions
The labeled diagram above shows where the main internal organs sit. What each one does:
- Esophagus: moves food to the stomach with waves of muscle contraction (peristalsis).
- Trachea: the windpipe. It splits into the left and right bronchi, which branch into smaller airways inside the lungs.
- Lungs: oxygen passes into the blood and carbon dioxide passes out in tiny air sacs called alveoli. The airways also warm, humidify and filter the air on the way in.
- Heart: a four-chambered pump. The right side sends blood to the lungs to pick up oxygen, and the left side pumps it out to the rest of the body. In a resting cat, the heart's natural pacemaker fires more than 120 times a minute. Veterinarians usually feel a cat's pulse at the femoral artery, inside the thigh.
- Stomach: stores, mixes and churns food and continues breaking it down chemically.
- Liver: produces bile acids needed for digestion, stores vitamins, minerals and glycogen, makes proteins such as clotting factors, and detoxifies harmful substances.
- Pancreas: its secretions are needed to digest food properly.
- Intestines: the small intestine absorbs nutrients, and the large intestine and rectum form and pass feces.
- Spleen: can contract to push extra red blood cells into circulation when oxygen levels drop. Along with the thymus, it also helps develop some blood cells, although most are made in the bone marrow.
- Kidneys: filter waste out of the blood, keep water and electrolytes (salts) in balance, make the hormones erythropoietin (which drives red blood cell production) and renin (involved in blood pressure), and process vitamin D.
- Ureters, bladder and urethra: the ureters carry urine from the kidneys to the bladder, which stores it until it leaves through the urethra.
- Brain and spinal cord: the central nervous system. The brain has three main parts: the brainstem (basic life functions), the cerebrum (conscious decisions) and the cerebellum (movement and coordination). The spinal cord runs through the vertebrae in cervical, thoracic, lumbar, sacral and caudal segments, and spinal nerves branch out to the legs, bladder, anus and tail.
Why male cats are prone to urinary blockages
Male cats have a longer and narrower urethra than females, so it can become blocked. A urinary blockage is a medical emergency. If a male cat keeps trying to urinate with little or nothing coming out, cries in the litter box, or becomes lethargic and stops eating, call your veterinarian right away. Our guide to feline lower urinary tract disease explains the conditions behind it.
Blood Types in Cats
Cats have three main blood types: A, B and AB. Type A is by far the most common, at about 99% of cats in the US. Some pure breeds are more likely to be type B, and type AB is rare. Researchers have since found other feline blood groups outside this system, such as Mik.
There is no universal donor cat. A cat's immune system makes antibodies against the blood group antigens it doesn't carry, so a cat's blood type must be known, and a crossmatch done, before a transfusion.
Skin and Coat
The skin is a cat's largest organ. It has three main layers: the epidermis on the outside, the dermis in the middle with its blood vessels and nerves, and the subcutis underneath, which holds fat and the twitch muscle.
Cat hair grows in clusters. Each follicle is compound: one central hair surrounded by 3 to 15 smaller hairs, all exiting from the same pore. Oil (sebaceous) glands are plentiful on the face, chin, paws, back of the neck, rump and tail, and they are part of the cat's scent-marking system. When a cat rubs its face on objects, it leaves a layer of sebum carrying its facial pheromones.
Interesting Cat Anatomy Facts
- Cats are crepuscular, most active around dawn and dusk. They sleep about 40% of the day and spend another 22% resting, according to the Merck Veterinary Manual.
- The tiger genome is 95.6% similar to the domestic cat's. The two lineages split about 10.8 million years ago.
- Purring may not need constant signals from the brain. In a 2023 study in Current Biology, cat larynges removed after death still produced purr-range sounds of 25 to 30 Hz, helped by pads of connective tissue up to 4 mm across in the vocal folds. The researchers did not rule out a role for muscle contractions.
- Cats use their whiskers to judge whether they can fit through an opening.
- Cats have sweat glands on their paws, but they cool themselves mainly by grooming.
- Cats do have a collarbone. It floats in a shoulder muscle with no bony joints.
If you are studying feline anatomy, our article on pyometra in cats looks at a serious uterine infection in intact female cats. For a large-animal comparison, see our guide to horse anatomy.
Originally written by Amber LaRock. Updated by the I Love Veterinary editorial team.
Sources
- Merck Veterinary Manual: Physical Description of Cats
- Merck Veterinary Manual: Eye Structure and Function in Cats
- Merck Veterinary Manual: Ear Structure and Function in Cats
- Merck Veterinary Manual: Structure of the Skin in Cats
- Merck Veterinary Manual: Components of the Musculoskeletal System in Cats
- Merck Veterinary Manual: Dental Development of Cats
- Merck Veterinary Manual: Introduction to Digestive Disorders of Cats
- Merck Veterinary Manual: Disorders of the Liver and Gallbladder in Cats
- Merck Veterinary Manual: Introduction to Heart and Blood Vessel Disorders in Cats
- Merck Veterinary Manual: Introduction to Lung and Airway Disorders of Cats
- Merck Veterinary Manual: Introduction to Blood Disorders of Cats
- Merck Veterinary Manual: Blood Groups and Blood Transfusions in Cats
- Merck Veterinary Manual: The Urinary System of Cats
- Merck Veterinary Manual: Noninfectious Diseases of the Urinary System of Cats
- Merck Veterinary Manual: Parts of the Nervous System in Cats
- Merck Veterinary Manual: Social Behavior of Cats
- University of Minnesota: Dissection Lab Guide for Dog and Cat Anatomy, feline anatomy appendix
- Washington State University Extension: Cat Anatomy and Physiology, 4-H Cat Project Unit 3 (hosted copy)
- Purina: Cat Anatomy 101
- Journal of Feline Medicine and Surgery: Japanese Bobtail: vertebral morphology and genetic characterization of an established cat breed
- Hearing Research: Hearing range of the domestic cat
- PLoS Genetics: Pseudogenization of a sweet-receptor gene accounts for cats' indifference toward sugar
- Nature Communications: The tiger genome and comparative analysis with lion and snow leopard genomes
- Current Biology: Domestic cat larynges can produce purring frequencies without neural input
This article is for general information and is not a substitute for advice from your veterinarian.
