The Skeletal System: The Skull

By | December 12, 2009

There are three basic skull shapes in dogs:

1. Dolichocephalic – Long-nosed breeds like the Rough collie, Afghan Hound, Doberman and  Fox Terrier.

2. Brachycephalic – Short, snub-nosed breeds like the Pug, Bulldog and Pekingese.

3. Mesocephalic –  A group including dogs which fall between the other two extremes.

Parts of  the skull

The features of the skull tend to vary with the overall shape and type of the skull.

The eye: The eye sits in the space called the orbit with in the zygomatic arch. The two zygomatic arches govern the total width of the skull. They vary in shape between the breeds – long-nosed breeds have a fairly straight arch while in short-nosed breeds it is very curved.

The jaw:The shape of the jaw varies quite considerably between breeds. The official breeds standards include requirements for the “bite” of each dog.
The jaw muscles are very powerful. It is said that a 20 kg mongrel can exert a bite of 165 kg; the pressure of an average human bite is 20-30 kg.

The cranium: The upper part of the dog’s skull, it houses the brain and also varies between breeds. In the Chihuahua, a high-domed shape has been specially selected over years of breeding. Unfortunately this has led in certain cases to people breeding from dogs with hereditary brain deformities such as hydrocephalus (water on the brain).

The stop: This is the point where the sagittal crest ends and the skull outline drops down to the nasal bones. Some breeds, such as the Boxer, are required by the breeds standards to have a pronounced stop, while others like the Greyhound or Bull Terrier, are not.
At the back of the skull, the sagittal crest ends in the occipital bone, which gives the Basset hound its peak. This feature doesn’t usually appear in puppies until the age of nine to ten weeks.

The brain:The dog’s brain differs from man’s mainly in the cerebrum. Man has much more grey matter than a dog. Although both need to co-ordinate and control bodily functions and movements, man does this with more sophistication. Most of a dog’s brain is involved with senses and recognition. Very little of the brain is available for association of ideas. A dog can be taught to recognize a Ј1 coin, but would never understand the concept of money and how many cans of dog food the coin would buy. A large breed like the St Bernard, which is similar in weight to a man has a brain about 15 percent the weight of a man’s brain. Interestingly, the area of the dog’s brain responsible for the sense of smell has 40 times the number of cells of the equivalent area of a man’s brain.

The teeth: A dog’s teeth adapt it for being a carnivore. It has large, strong shearing teeth (called “carnassials”), which it uses to chew through tough materials. In addition, this last premolar in the upper jaw has become elongated and developed a cutting ridge, which overlaps with the first molar on the lower jaw when the dog bites. The long, pointed and slightly curved incisors, often called “dog teeth”, are useful stabbing weapons for catching and holding prey. In a dog, the different teeth erupt at different times.

Dental formula: This is the number of each type of tooth normally present in one side of the upper and lower jaws of a dog.
Upper jaw: 3 incisors, 1 canine, 4 premolars, 2 molars.
Lower jaw: 3 incisors, 1 canine, 4 premolars, 3 molars.