Sesamoid bone

src: anatomystructure.net

In anatomy, bone sesamoid ( ) is a bone embedded in the tendon or muscle. It comes from the Latin word "sesamum" (sesame seed), because of its smallest size of sesamoid. Often, these bones are formed in response to strain, or can be present as a normal variant. The kneecap is the largest sesamoid bone in the body. Sesamoids act like pulleys, providing a smooth surface for the tendon gliding over, improving the ability of the tendon to transmit muscle strength.

The sesamoid is the most commonly present small nodular bone embedded in the tendons in the thumb area. Calcification of sesamoid bone is one of the important features of the accelerated growth of puberty, which is earlier in women than in men. The absence of a sesamoid bone shows a delay in reaching puberty.

Video Sesamoid bone

Structure

Cellamoid bones can be found in joints throughout the body, including:

• On the knee - patella (in the quadriceps tendon). This is the largest sesamoid bone.
• In the hands - two sesamoid bones are commonly found in the distal portion of the first metacarpal bone (within the adductor pollicis tendon and flexor pollicis brevis). There is also a sesamoid bone in the distal portion of the second metacarpal bone.
• On the wrist - The wrist biphorm is a sesamoid bone (in flexor tendon carpi ulnaris). It begins to harden on children ages 9-12.
• At the foot - the first metatarsal bone usually has two sesamoid bones in its joint with the big toe (both in the hallucis brevis flexor tendon). One is found on the lateral side of the first metatarsal while the other is found on the medial side. In some people, only a single sesamoid is found in the first metatarsal bone.
• In the neck - Although hyoid bones are free to float, it is not technically a sesamoid bone. All sesamoid bones are formed directly from the connective tissue found in the tendons and ligaments. In contrast, hyoid bones are formed from cartilaginum precursors like most other bones in the body.
• In the ear - the incent lenticular process is a sesamoid bone and is therefore considered the fourth ossicle of the middle ear.

Maps Sesamoid bone

Common variant

• One or both sesamoid bones beneath the first metatarsophalangeal joint (index finger) can be multipartite - in two or three parts (mostly bipartite - in two parts). (See the x-ray of the foot on the right.)
• The fabella is a small sesamoid bone found in some mammals embedded in the lateral head tendon of the gastrocnemius muscle behind the lateral condyle of the femur. This is a normal anatomical variant and is present in humans in 10% to 30% of individuals. Fabella can also be mutipartite or bipartite.
• Cyamella is a small sesamoid bone embedded in popliteal muscle tendons. This is a normal anatomical variant. It is rarely seen in humans, but has been described more frequently in other primates and certain other animals.

src: droualb.faculty.mjc.edu

Clinical interests

• The common foot disease in dancers is sesamoiditis (inflammation of the sesamoid bone beneath the first metatarsophiliary joint of the big toe). This is a form of tendinitis that results from tendons surrounding the sesamoid becoming inflamed or irritated.
• Selamoid bones generally have very limited blood supply, making them susceptible to avascular necrosis (bone death due to lack of blood supply), which is very difficult to treat.

src: 52.62.202.235

Other animals

In horse anatomy, the term sesamoid bone usually refers to two sesamoid bones found in the back of the fetlock joint or metacarpophalangeal/metatarsophenangeal in both hindlimb and forelimbs. Precisely this should be called proximal sesamoid bones while the navicular bone should be referred to as a distal sesamoid bone. Patella is also a form of sesamoid bone in a horse.

Although many carnivores have radial sesamoid bones, giant pandas and red pandas independently evolve to have an enlarged radial sesamoid bone. This evolution has caused two different species from other carnivores. The red panda probably initially evolved "pseudo-thumb" to aid in arboreal drive. When the red panda then evolves to consume a bamboo diet, the enlarged bone undergoes an exampuration to aid in grasping the bamboo. Giant pandas, however, evolved the radial sesamoid bone enlarged around the same time as the bamboo diet evolved. In giant pandas, bones allow movement like clasps and are used for grasping bamboo. In these two panda species, the DYNC2H1 and PCNT genes have been identified as possible causes of pseudo-thumb development.

Recently, bone marrow bone enlarged radial mice have been studied. Their enlarged radial selamide and huge panda bones have the same morphology and size relative to the rest of the hand. The reason for this evolutionary change is still unknown, but it is possible to aid in grasping small objects and thin branches.

src: vetwerxequine.com

See also

• Accessory bone

src: 52.62.202.235

Footnote

src: vetwerxequine.com

References

• Gray's Anatomy (1918) (Bartleby)

src: anatomystructure.net

External links

• Media related to Sesamoid bone in Wikimedia Commons

Source of the article : Wikipedia