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A Healthy Cat’s Body
 
In this chapter is a short description of the various systems in normal, healthy cat’s bodies, touching on the differences between cats and humans and among cat breeds. The primary purpose of this chapter is to provide cat owners with a basis of comparison in case a cat’s body seems not to be functioning correctly.
 
In general, cat’s bodies work in much the same way as those of all other mammals, humans included. However, cats are apt to develop different diseases and illnesses than other species do. These specific problems and diseases will be covered in the symptoms section of this book. Cats have also evolved over the ages to have particular abilities that meet their particular needs. For example, they have a very highly developed ability to see and “sense” in the dark; they are able to jump very high, turn their paws inward, and retract and extend their claws. We will learn more about these special skills in this chapter.
 
Although breeds of cats have been developed with a variety of body, face, and ear shapes, tail lengths, and hair coats, all cats are alike physiologically. There are, however, some differences among cat breeds. For example, manx cats, which are tailless, often suffer from congenital abnormalities of their hindquarters.
 
Skin and Hair
 
One of the most noticeable differences among cat breeds is the length of their hair, or coat. Cat’s coats form an insulating layer between their skin and the external environment and protect them from the cold in winter and the sun in summer. Cats have three basic types of hair. Fine hairs make up a soft undercoat, while the outercoat is longer and coarser. There are also the stiff vibrissae, or whiskers, which project from a cat’s body. These tactile, or sinus, hairs are unique to cat’s bodies and include not only the whiskers but the eyelashes and sinus hairs on the insides of the middle forearms. Exceptions are rex cats, both Cornish and Devon. Cornish rex cat’s coats have no guard hairs at all, and Devon rex cats have uneven coats and few whiskers. Both have short, curly coats that lie close to their bodies. Cat’s whiskers are enervated by the fifth cranial nerve of the brain, and are able to act like radar, allowing cats to “feel” air currents and movements. Cat’s hair can stand on end all over their bodies when they are afraid or angry because of tiny muscles that react in an action called piloerection.
 
All cats shed all year long. Outdoor cats shed more in the spring, as days begin to become longer. Different coat lengths and types of hair determine the amount of shedding, although all cats will shed excessively when they are under stress. It is especially important to groom longhaired cats regularly or the shed hairs will become matted and tangled instead of falling out.
 
Cat’s skin plays many important roles. Not only does it protect a cat’s body from loss of fluids, electrolytes, and proteins but it also serves as a barrier against infections. Cats do not perspire through their skin, but the skin does help maintain body temperature. The blood vessels in the skin either dilate to cool the body or constrict to retain body heat when it’s cold. One of the skin’s most important functions is as a sensory perceptor, conveying things like heat, cold, and pain to the brain.
 
A healthy cat’s coat is shiny and full and her skin is clear and free of sores, scabs, redness, or scaly patches. If a cat is born with brown or black spots on her skin it is probably normal pigmentation, but if dark skin spots or discoloration suddenly occur they should be evaluated by a veterinarian.
 
Eyes and Vision
 
Although cat’s eyes have essentially the same parts as humans and other mammals, they differ from all other animals’in several ways, enabling cats to have the best night vision of all domestic animals. Cat’s eyes have a great many more rods than cones, while human eyes have more cones than rods. Because rods respond to very low light, cats can see extremely well in dim light. Also, their pupils are oblong instead of round, which enables them to dilate widely in low light, and thereby let in more light. In bright light cat’s pupils become a very thin slit, protecting their eyes, which are sensitive to light.
 
Owners are sometimes concerned when a cat’s eyes seem to have a bluish or yellowish glare if the animal is looking toward the light; blueeyed cat’s eyes will have a reddish glare. This is the reflection from a region around the retina called the tapetum. The tapetum reflects light back to the retina, further enhancing a cat’s night vision. Older cats sometimes develop a condition called lenticular sclerosis, in which the lens fibers become dense and refract light differently, making the eyes look bluish. This condition does not affect a cat’s vision but should be observed by a veterinarian to distinguish it from cataracts.
 
Another cause for possible owner concern is a pinkish membrane that sometimes appears in the inside corner of a cat’s eye, partially covering the eyeball. This membrane is called a third eyelid (nictitating membrane) and is present in all mammals except humans. The third eyelid pops up automatically when a cat retracts her eyes (pulls them back into the eye sockets). It protects and cleans the eyeball, and may become more noticeable if a cat’s eye is irritated or if she is suffering from an illness. Burmese cats occasionally develop an eversion (outward turning) of the gland-, of the third eyelid, which can be surgically corrected. Cats with prominent eyes and flat faces (brachycephalic breeds) such as Persians and Himalayans are more susceptible to eye damage because their eyes are not set deep in their sockets.
 
Ears and Hearing
 
Cat’s internal ears have the same parts as humans’. All cats have pointed, upright ear flaps, or pinnae. Variations occur in Scottish Folds, whose ear tips are flipped forward, and American Curls, whose ears flip backward at the tips. Cat’s upright ears help capture sounds and direct them down the ear canal to the eardrum, from where they are transmitted to the brain.
 
Cat’s hearing is estimated to be at least three times more acute than humans’and they are able to hear high-pitched sounds much better than people. It is common for white cats with two blue eyes to suffer from congenital deafness.
 
Noses and a Sense of Smell
 
Cat noses come in variations of two basic shapes; pointed and flat-faced, or brachycephalic Longhaired cats, such as Persians and Himalayans, have been bred to have extremely flat faces. Some shorthaired cat breeds such as British Shorthairs and Scottish Folds have somewhat flattened faces and protuberant eyes, but are not truly brachycephalic Extremely brachycephalic cats may have upper respiratory problems due to their very small nasal openings (nares).
 
Cat’s sense of smell is very acute because the olfactory (smell-sensing) areas of their brains are highly developed. Their appetite is mostly controlled by smell. Therefore, if a cat’s nose is stuffed up, she will not be very interested in eating.
 
Mouth and Teeth
 
Cat’s teeth serve two purposes. They are both offensive and defensive weapons, and also are designed to fit cat’s particular style of eating. Cats grasp and then shred or tear their food before swallowing. Adult cat’s canine teeth are slanted inward in order to trap prey better.
 
Kittens have twenty-six teeth, which are replaced by thirty adult teeth by the time a kitten is six months old. The teeth are evenly divided between the upper and lower jaws.
 
Cat tongues are very rough and serve primarily as grooming tools, smoothing fur and removing loose hair like a comb. If too much loose hair is swallowed, a cat will develop hair balls in the stomach.
 
Cardiovascular System
 
Cat’s cardiovascular systems are similar to those of humans and other mammals. Cats have a four-chambered heart with two atria and two ventricles. A cat’s heart is primarily responsible for pumping and circulating blood through an elaborate network of arteries, which deliver oxygenated blood to tissues, and veins, which drain deoxygenated blood from tissues and return it to the heart. It is then pumped into the lungs for reoxygenation during respiration.
 
In general, cats do not suffer from the types of cardiovascular disease that humans do. For example, arteriosclerosis, or plaques on the inside of arteries caused by an excess of cholesterol, is virtually nonexistent in cats. Nor do they suffer from heart attacks brought on by clogged arteries. Cats do, however, have other types of heart problems, which we will discuss later.
 
Digestive System
 
The digestive system of the cat is made up of components that transport food and fluids into and through the body. On the way through the digestive system, nutrients and fluid are absorbed and utilized by the body tissues. The remaining waste products are eventually eliminated.
 
The mouth and teeth grab and grind food until it can be swallowed and passed via the esophagus, a long muscular tube running from the back of the throat, to the stomach. In the stomach, food is further ground and churned. Stomach acids and small amounts of enzymes begin the digestive process. The resulting gruel then moves into the small intestine, where pancreatic enzymes, intestinal enzymes, and bile (produced by the liver) break it down into absorbable components. Fluids and these nutrients are absorbed through the lining of the small intestines. Remaining nonabsorbed material, including wastes for excretion, then move into the large intestine or colon. Most fluid is removed from this waste, and firm stool is produced and excreted via the rectum.
 
The liver is the largest organ in a cat’s body. It is responsible for a myriad of important functions. In addition to producing bile to aid digestion, it acts to metabolize and detoxify any drugs, chemicals, or poisons that enter a cat’s body. It manufactures the major blood-clotting factors, and stores sugar to provide energy between meals.