A tubercle is a small, rough prominence.
A spine is a sharp, slender, pointed eminence.
A ridge, line, or crest is a narrow, rough elevation, running some way along the surface.
Non-articular Depressions.—These are of variable form, and are described as notches, sulci, fossae, grooves, furrows, fissures, etc. These non-articular eminences and depressions may serve to increase the extent of surface for the attachment of ligaments and muscles or may receive blood vessels, nerves, tendons, ligaments, or portions of organs.
Canals or foramina are channels or openings in bone through which pass the nerves and blood vessels.
Teeth.
—In the human body we find two sets of teeth. One appearing in childhood, and are known as milk teeth, twenty in number, the permanent teeth replacing these about the sixth year.
There are thirty-two permanent teeth, divided into four incisors, two canines, four bicuspids and six molars.
Teeth are made up of three different substances, which are known as enamel, dentine and cement.
The enamel is a very hard substance, the hardest in the body, and may be compared to quartz. The enamel covers the entire tooth down as far as the gums.