Four types of bones


The skeleton is the skeleton of the body. It provides a framework for other structures to adhere to and helps create our shape. All skeletal bones can be divided into four types: short, long, flat, and irregular. Each type of bone has a specific purpose, and some types have multiple functions.

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Long bones

The skeleton of the arms and legs is mainly made up of long bones. Long bones are so named because they are longer than they are wide. The long bones of the hand include the humerus , radius , ulna , metacarpals, and phalanges. The long bones of the leg include the femur , tibia , fibula , metatarsal bones, and phalanges. The clavicles (clavicles) are also long bones.

Long bones provide the lever necessary to move our bodies and manipulate our environment. All long bones consist of two main parts: the diaphysis and the pineal gland.


The diaphysis is the nucleus of the long bone, the main organ. The shaft is a tube with a hollow center called the medullary canal (or bone marrow cavity). The wall of the shaft is made up of compact, dense, and very hard bone. For most of the life of a long bone, the center of the shaft is filled with yellow bone marrow. Yellow bone marrow is primarily fat, also known as adipose tissue.


Each end of a long bone is called a pineal gland. The shape of each pineal gland corresponds to its connective bone at the junction, which is called the joint, and the shape of the pineal gland is based on the functioning of the joint. The proximal epiphysis (closest to the body) of the humerus and the proximal epiphysis of the femur have a rounded shape, called the head, and look somewhat like the middle of a ball. This shape allows these two long bones to rotate in different directions. The femoral head fits into a socket in the pelvis. The head of the humerus fits into a socket in the shoulder. This type of connection is called a ball joint. Joints that only allow movement along one axis are called jointed joints.

The wall of the pineal gland is made up of a compact bone, similar to the diaphysis, and in the center is the cancellous bone. Cancellous bone is made up of many small cavities (also called medullary cavities) filled with red bone marrow. The red bone marrow produces red blood cells and is very well connected to the circulatory system. So much blood passes through the cancellous bone that needles inserted into the cancellous bone of the humerus, femur, or sternum (not the long bone, as you will see below) can be used to inject fluids or medications. like an IV.

Epiphyseal plate

There is a line that can be seen on pictures of the pineal gland and it is called the epiphyseal plate. This is where new bone is added to increase the length of the long bone during development (this is called ossification). This is commonly known as a growth plate. Fractures (fractures and cracks in the bone), including the epiphyseal lamina, can interfere with proper bone development in children.

Short bones

Short bones are so named because they are as wide as long bones. There is no shaft in the short bone. It consists of cancellous bone surrounded by compact bone, such as the pineal gland. Short bones also contain red bone marrow.

There are 32 short bones in the human skeleton. Short bones generally help move and strengthen complex wrist and ankle joints by sliding and shifting relative to each other.

The wrists (the wrist bones), the tarsus (the ankles and heel bones), and the patella (kneecap) are short bones. Some experts consider the patella to be the sesamoid bone (discussed below) because it primarily provides an anchor point for tendons and ligaments. However, the patella is common to everyone, while the sesamoid bones develop differently from person to person.

Flat bones

Flat bones are body armor. Flat bones provide structure, such as the shape of the head and torso, as well as the base of the shoulders and hips. Flat bones can also protect the underlying soft tissue. Like short bones, flat bones have walls made of compact bone and a spongy bone center that forms something like a sandwich.

The bones of the skull, scapula (scapula), sternum (breastbone), ribs, and ilium (thigh) are all flat bones. Of these, the scapula, sternum, ribs, and ilium provide secure attachment points for tendons and muscles.


The skull bones are the part of the skull that contains the brain. The bones of the skull are connected to each other by joints called sutures, which appear to be stitched together. Sometimes extra small bones can develop between the stitched bones of the skull along the suture lines. These small bones are called suture bones. They develop randomly and are not called bones.

Jagged bones

Bones that are neither long, short, or flat are considered irregular in shape. The shape of these bones has very specific functions. Facial bones and bones of the spine – vertebrae – abnormal bones. These bones have a complex shape that is unique to their function. Most irregular bones appear only once in the body along the midline, for example, in each of the vertebrae. Some bones of the face appear in a mirror image, such as the cheekbones (cheekbones).

Irregularly shaped bones are often complex in shape and are used as attachment points for muscles, tendons, and ligaments. The most common shape is called a stem, which looks like a bump. Each vertebra has three processes: a spinous process along the back (back) in the center (midline) and transverse processes on either side of the spinous process.

Sesamoid bones

Sometimes bones develop due to friction on tendons or ligaments. They are usually very small bones that develop randomly between people. They are not named. Some anatomists consider the patella to be an example of the sesamoid bone.

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