Based on past posts, it seems logical to assume that cats have extremely fine tuned and heightened senses compared to those of humans. Their sense of balance, hearing, smell, and vision (to some extent) is better than what humans could be. However, one sense that falls short of a human’s is a cat’s sense of taste. Humans have approximately 9,000 taste buds compared to the paltry 470 of a feline’s.
A Feline’s Sense of Taste
The tongues of most mammals hold taste receptors, proteins that bind to incoming substance. These receptors are attached to what is known as gustatory cells which are scattered all over the tongue. Through their pores, the cells send filaments to the outside which collect and transmit tastes to the underlying nerves. On a side note, these nerve fibers will also respond to thermal stimuli in addition to taste. Prolonged cooling of the tongue with ice water was found to abolish all responses to gustatory stimuli.
Like humans, cats are responsive to four basic tastes: sour, bitter, salty, and sweet, decreasing in sensitivity in that order. But felines have evolved to exclusively eat meat and as such, sugar and carbohydrates (which is turned into sugar) means very little. As such, they lack the sweet receptor, which is made up of a coupled protein generated by two separate genes known as Tas1r2 and Tas1r3, and the necessary conduction fibers in the glossopharyngeal nerve from the tongue to the cerebrum which is required to taste sweetness. As obligate carnivores, their response to sweet is much weaker, almost non-existent in comparison to other mammals.
Many people will observe that their cats are attracted to sugary processed foods like candies, ice cream, pudding, etc. This might seem that their cats have a “sweet tooth” but in reality, it is probably because the fat content, which they can easily detect, is what attracts them.
On the other hand, the cat’s aversion to bitterness has been duly noted. A recent study published in the journal PLOS One revealed that cats have twelve different receptors in their tongues for bitter taste, at least seven of which are highly active. The bitter taste sensors are important to a cat in that they warn of harmful and/or poisonous foods or objects. Bitter receptors were once thought to have developed to protect herbivores and omnivores from consuming poisonous plants. But now, the science community believes that the bitter taste could exist to minimize intake of toxic compounds from the skin and other components of certain prey species, such as invertebrates, reptiles, and amphibians.
A feline’s high sensitivity to bitterness is evident whenever your cat eats a mouse or another prey, only to leave behind a little blackish blob also known as the gall bladder, which is filled with bitter bile. And over the years, products have been developed using bitter tasting liquids to stop licking and chewing on wounds, furniture, bandaging, etc. for cats.
A Cat’s Teeth
Not only does the cats need to taste their prey, they also need their teeth to tear apart and chew their prey. Although domestic cats can potentially live without teeth, if fed with the right diet, teeth are important for a number of reasons. This includes prehension (grasping and holding food), mastication (cutting food), as well as for self-defense and hunting. Cats are not able to chew because their jaws cannot move laterally.
A cat will have 30 teeth in total (though some short-faced cats only have 28) and 26 as a kitten. Just like humans, cats have deciduous teeth, meaning that they have two sets of teeth. Milk teeth erupt a week or two after birth, first the incisors, canines, and molars, in that order. By the end of the 6th week, all 26 appear. Six months later, a kitten’s milk teeth are gradually replaced with permanent teeth. During this process, while the roots of the milk canines are disappearing and those of the permanent ones are still developing, the canines do not function properly. Therefore, young cats must rely on their mothers for food as they cannot kill their prey yet.
By the time all of the permanent teeth appear, there are 16 teeth on the upper jaw (6 incisors, 2 canines, 6 premolars, and 2 molars) and 14 on the lower jaw, which has the same number of teeth except only 4 premolars.
Each type of tooth have their own function and role.
The six little incisor teeth on each jaw allows the cat to do some ripping and scrapping of meat. Despite having minimal use, they are used most often to help hold prey in the mouth. They only have one root so when diseased, are often unstable and can be easily extracted. In total, there is twelve incisor teeth but quite often, some of these teeth will be lost as a cat gets older. Sometimes, one or more incisors may not even develop in the first place.
The most important teeth a cat can have are its canines. The canines are broader and more robust than those of other carnivores. Because they are somewhat flattened, the teeth can enter the space between two vertebrae in order to sever the spinal cord and skill. There are also nerve receptors in the canines so can they feel the spinal cord when going for the killing bite. They are long teeth with only a single, but long root, which is supported by strong ligaments and deeply embedded in the bone. Cats should have four canines, one on each side of the mouth at both the top and bottom jaw.
Furthermore, the premolars, also known as carnassials, are blade-like, virtually serrated, designed like scissors for shearing and slicing meat off bones. Depending on the placement, the premolars will have one or more roots. There should be six premolars in the upper jaw, three on each side, and four in the lower jaw, two on each side.
Lastly, the molars. There are two upper molars, one on each side, and two lower molars, one on each side and can also used for cutting through meat and bone. But like human wisdom teeth, the molars, for the most part, have lost any function that they may have and are often missing. Unlike the other teeth, the upper and lower molars have different root systems: upper molars have only one root while the lower molars have two roots. When diseased, upper molars are usually easier to remove as they have a short root. However, removing lower molars is another story. Because they have one thick root and one small root with bone and ligament attachment, the lower molars are much more difficult to remove.
What Makes Up a Tooth?
Each tooth sits in a socket in the bone (called an alveolar socket) held firmly in place by ligaments, cementum (a bony-like substance) soft tissue and bone. The tooth itself can divided into the crown visible above the gum line and the root. The point at which the crown and the root meet is termed as the neck.
When dissecting the structure of a tooth, it is made up of three substances:
- Pulp – this lies within the centre of the tooth (called the pulp cavity). Pulp enters this cavity at the tip of the root and contains cells nerves and blood vessels. Because of this, damage or inflammation of the pulp is extremely painful.
- Dentine – this covers the pulp and is the main bulk of the root as well as providing a middle layer between the pulp and the enamel on the crown of the tooth. Dentine is hard and mineralised but is very sensitive making root exposure or enamel damage very painful.
- Enamel – this is a very hard, mineralised substance, which contains no nerves and is insensitive. Enamel covers the crown of the tooth protecting the tooth and the underlying dentine, and therefore prevents sensitivity when the animal is eating. However, cat dental enamel is thin, measuring only around 0.2mm thick compared with around 0.5mm in dogs. Damage to the enamel exposes the underlying dentine and will result in a very sensitive tooth, which is also susceptible to infection.
References + For More Reading
Cat Sense by John Bradshaw
Smithsonian’s Answer Book: Cats by John Seidensticker
Eyewitness Companion: Cat by Dr. Bruce Fogle
Natural History of Cats by Claire Necker
Pieces of a Cat by Carol Brown