Examples of Short Bones
Short bones are bones in the body, designed to provide stability and support with almost no movement. They are wide in nature, just as they are also long though not as long as the long bones. These bone are usually found in the hand and foot, known as carpals and tarsals respectively.
These short bones have nearly the shape of a cube with nearly the same horizontal and vertical dimensions. They consist mainly of spongy bone which is concealed by a thin layer of compact bone. The spongy nature of short bones lowers the weight of the skeleton by providing a balancing to denser and heavy compact bone due to its low density and lightweight.
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We have loads of examples of short bones in the body, mostly found in the carpals and tarsals, here are a few examples:
The lunate bone which is also one of the short bones found in the carpals is otherwise known as Semilunar bone. Its outline is concave or curved in nature. It is located at the centre of the proximal row of the carpal bones which articulates laterally, medically and distally with the scaphoid, triquetral bone, and the capitate bone.
Proximally, the lunate bone has a convex and smooth surface which articulates with the radius, while it’s lateral surface is narrow and flat in nature, with a surface almost like the curved shape of the moon, for articulation with the scaphoid. Medially, the surface of a lunate bone has a smooth and quadrilateral side which articulates with the triquetral bone.
The palmar and dorsal branches which are rough in nature, supply blood to the lunate bone. The lunate bone also assists in the movement of the wrist.
• Pisiform Bone
Pisiform is a sesamoid bone that looks like a small knob found in the wrist, with no covering of the periosteum membrane. Where the ulna articulates with the wrist is situated the Pisiform, which lies between the tendon of the flexor carpi ulnaris muscle.
It only has one side that acts as a joint, articulating with the triquetral bone. It is on a plane anterior to the other carpal bones and is spheroidal in form.
Pisiform has four facets which are:
- The lateral surface is rough and concave.
- The palmar surface is rounded and rough and gives attachment to the transverse carpal ligament, the flexor carpi ulnaris and the abductor digiti quinti.
- The medial surface’ is rough and usually convex.
- The dorsal surface is smooth and oval, and articulates with the triquetral: this facet approaches the superior, but not the inferior border of the bone.
• Capitate Bone
If all the carpal bones, capitate bone is the largest. It articulates with the third metacarpal, located at the base of the palm of the hand. The capitate has three parts namely: upper, lower and middle parts.
The upper part is referred to as the Head, the lower part is referred to as the Body, while the middle is called the Neck. Capitate bone is the third bone from the thumb in the distal row of the carpals which lies between the trapezoid and the hamate bones.
At the centre of the wrist is situated the capitate.
The capitate bone is the largest carpal bone with the highest number of articulations which makes it a very important bone in the wrist as it maintains movements and shapes the carpal rows.
The axis of rotation for any wrist motion will pass through the capitate, this is due to the fact that it is located at the centre of the wrist.
The hamate is also one of the carpal bones which also and example of short bone which connects with the capitate, lunate and triquetral which are also carpal bones, and also the two bones of metacarpals which also long bones of the palm. It has a process like a hook which protrudes from the side of the palm of the wrist toward the outside of the body. The hamate forms part of the ulnar canal also known as Guyon’s canal.
Talus, also known as ankle bone forms the lower part of the ankle joint which does the work of transmitting the weight of the body to the foot. Talus is the second largest bone in the tarsals. It has the highest percentage of articular cartilage. It articulates with the tibia and fibula.