Types of Bones

The human skeletal system consists of a total of 206 bones. These bones are divided into various groups based on their shape and composition.

All these bones collaborate to build the fundamental structure of the human body, uphold the body’s mass, allow mobility, and safeguard all the internal organs.

Contents

Distinct Categories of Bones in the Human Body
1. Elongated Bones
2. Cuboidal Bones
3. Planar Bones
4. Anomalous Bones
5. Sesamoid Bones
References

Distinct Categories of Bones in the Human Body

As stated earlier, there are 5 primary types of bones in the human body, categorized by their shape: 1) elongated bones, 2) cuboidal bones, 3) planar bones, 4) anomalous bones, and 5) sesamoid bones. Here is an illustrative chart demonstrating all the bones in the skeletal system, according to their category:

Discover the characteristics of these bones and their differences:

1. Elongated Bones

As the name suggests, these bones are lengthier than their width, possessing a cylindrical shape. They consist of a long central shaft, known as diaphysis, and two bulky ends known as epiphyses. Mostly, these are the bones in the appendicular skeleton.

Roles:

Sustaining body weight
Serving as levers to facilitate movement

Instances: The bones of the upper limb, humerus, radius, ulna; lower limb bones, tibia, fibula, femur; the metacarpals, metatarsals, phalanges of both fingers and toes, and the clavicles

2. Cuboidal Bones

Relatively smaller cube-shaped bones with more or less similar lengths and widths. These bones have a layer of compact bone covering a large area of spongy bone and marrow, giving them a cuboid shape.

Roles:

Providing stability
Allowing movement (to some extent)

Instances: Carpal bones (scaphoid, lunate, triquetral, hamate, capitate, trapezoid and trapezium); Tarsal bones (calcaneus, talus, navicular, cuboid, lateral cuneiform, intermediate cuneiform, and medial cuneiform)

3. Planar Bones

These bones are thin, broad, and usually curved. They are commonly located in areas around delicate body organs that require additional protection, and where there are numerous muscle attachments.

Roles:

Guarding vital organs, such as the heart, brain, and urinogenital organs
Providing extensive surfaces for muscle attachment

Instances: Most cranial bones (occipital, parietal, frontal, lacrimal, vomer), the scapula, ribs, and sternum

4. Anomalous Bones

As the name implies, these bones do not have a specific shape like the previous three types. Consequently, they have been classified into a separate category. These bones can have relatively intricate shapes, enabling them to protect internal organs.

Roles:

Shielding internal organs

Instances: All 33 vertebrae, pelvic bones (ilium, ischium, and pubis), the cranial bones, sphenoid and ethmoid

5. Sesamoid Bones

This classification is based more on the position of a bone than its shape, as these bones develop embedded in tendons. They are usually found at the ends of long bones and resemble sesame seeds, hence the name.

Roles:

Preserving tendons from regular wear and tear by reducing friction

Instances: The 2 patellae (kneecaps) and the pisiform bones in the carpus

Note: There is another distinct type of bone called the sutural bone found in some people. Although categorized as bones, they are additional bony pieces found between some sutures in the skull. Their shape and position may vary from one individual to another.

Since they are not found in every human body, they are not included in the primary 206 bones, and sutural bones are not one of the primary types.

These bones appear randomly and do not usually have names. Wormian bones, sometimes found embedded in the cranial suture in a child’s skull, can be considered an example of sutural bones.