Types of SHORT BONES

The adult human skeleton is made up of 206 bones but not everything is the same. Our skeleton is made up of long bones like the femur, flat bones like those form the skull, irregular bones with shapes as strange as those of the vertebrae or bones short. Short bones are found in various parts of our body, including the hands and feet. In this lesson from a TEACHER we will see the characteristics that a bone must have in order to classify it as a short bone and what types of short bones can we find in our body. Do you want to learn more about short bones? We invite you to continue reading this lesson!

The human skeleton bones They can be divided according to different characteristics, but one of the most used is its shape and structure.

To understand the structure of different types of bones we have to bear in mind that not all bones are the same if we look at them from the inside, that is, there are two types of bone tissue: compact bone tissue and cancellous bone tissue.

• The compact bone tissue, as its name suggests, it is characterized by having little or no space between the cells that make up the bone. If we look at it with a microscope, this type of bone is made up of cells that roll into one another, forming structures similar to tree rings (osteons). The other type of bone tissue is cancellous bone tissue.
• The spongy bone tissue it is characterized by having more spaces between the cells that form it. Seen under the microscope, in the spongy bone tissue we can see many small holes, which give it the appearance of an anthill or labyrinth. Inside these holes is the red bone marrow, which is responsible for forming blood cells.

Types of bones in the human body

Following this classification, within the human body we can differentiate five types of bones:

• Long bones. The long bones They are tube-shaped and in them epiphysis (ends) and diaphysis (central part) are distinguished. While in the epiphyses there is cancellous bone, in the diaphysis there is compact bone.
• Short bones. They are cube-shaped, that is, all of their sides are more or less the same length. They are made up of spongy bone tissue and, covering this, a layer of outer compact bone tissue.
• Flat bones. They are bones of little thickness, very thin, formed by a layer of spongy bone tissue and, covering this, two almost parallel plates of compact bone tissue.
• Irregular bones. They are usually made up of central cancellous bone tissue and a layer of compact outer bone tissue of variable thickness. Its shape can vary from the shape of the vertebrae to those of the bones of the face.
• Sesamoid bones. They are usually bones that accompany the tendons, protecting them from friction and tears, which is why they usually have a fairly thick outer layer of compact bone tissue. An example is the patella bone, which is found in the knee joint.

In the hands we can find a group of short bones called carpal bones. The carpal bones form the carpus, which is how the bony part of the wrist is called in anatomy. Therefore, the carpal bones are short bones that make up the wrist.

The carpus or wrist is made up of eight short bones, distributed in two rows. The first row, closest to the hand, is the distal row and is made up of four bones: trapezius, trapezoid, large, and hamate. The other four bones form the proximal row, closest to the arm, and are: scaphoid, lunate, pyramidal and pisiform. As you can see, all of them are cube-shaped bones with rounded corners and, if we look at them with a microscope, We could see its structure: a layer of compact bone tissue that surrounds the spongy bone tissue inside each of the bones.

Within the carpal bones we can distinguish different types of short bones. Some carpal bones, such as the great bone and the hamate bone, are larger than others; While the scaphoid has a concave shape, the large bone is convex, and the pisiform bone has an oval face, a rounded face, a concave face, and a convex face. The carpal bones are both the same and different!

If you want to know more about the carpal bones, curiosities, etc. Check out our lesson on Names of wrist bones!

The tarsus or hindfoot is the back of the foot. This part runs from the instep to the heel, and is composed of seven tarsal bones, arranged as in the carpus, in two rows. The first row is made up of the talus and calcaneus, which together form what we commonly call the heel. The second row is made up of the scaphoid (now called navicular), cuboid, and the three wedges or cuneiform bones; As a whole, in a common way, this area is called the instep of the foot and is the area of ​​insertion with the leg.

As in the carpus, in the tarsi there are also different types of short bones: while the talus has no insertion of any muscle and its position varies Depending on the position of the calcaneus and the navicular, the calcaneus is characterized by having six faces, of which some are flat, others concave and others convex.

If you want to know more about the types of short bones in the foot, see the lesson where we review the Names of parts of the foot and bones.