Types of Bones

Four Major Classes of Bones

long bones, short bones, flat bones, and irregular bones.

Short Bones

short bones, such as those found in the wrist and ankle, are nearly as long as they are wide and thick. This gives the bones an almost cubelike shape, like the shape of dice

Shaft

The shaft of a bone is also called the diaphysis, and the ends are called the epiphyses (singular, epiphysis)

How Many Bones?

There are 206 bones of the human body are classified according to their shape.

Sesamoid

These bones usually have one rounded end and a more pointed end. Their shape is similar to sesame seeds, thus the name "sesamoid." The patella, or kneecap, is an example of a sesamoid bone.

Flat Bones

Flat bones tend to be wider than they are thick. Flat bones include the sternum, or breastbone; the scapulae (singular, scapula) or shoulder blades; the ribs-the series of bones that protect the chest cavity; and most of the skull-the bones that make up the head and jaw.

Long Bones

Long bones are much longer than they are wide. The central portion of a long bone, called the shaft, is surrounded by the ends

Sesamoid Bones

One special group of short bones

Irregular Bones

This class of bones includes those that do not fit neatly into one of the other three categories. These are called irregular bones. Among the irregular bones are the hip bones; the vertebrae (singular, vertebra), the bones that form the backbone; and the bones of the inner ear.