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Hyoid bone

life science Maturity 11-13 Next article →

The hyoid bone is a unique and vital structure located in the human neck. It is shaped like a horseshoe and sits in the anterior midline. This means it is positioned in the front center of your neck. You can find it between your chin and the thyroid cartilage, which is often called the Adam's apple.

Hyoid bone hariadhi
Hyoid bone hariadhi

At rest, the bone sits between the base of the mandible and the third cervical vertebra. Most bones in the body connect directly to other bones. However, the hyoid is the only bone in the human body that does not connect to any other bone. Instead, it is anchored in place by muscles and ligaments. It is pulled from the front, the back, and from below. This floating position allows it to move freely, which is essential for many bodily functions.

Because it is not fixed to other bones, the hyoid acts as a mobile anchor for several systems. It provides an attachment point for the muscles of the tongue and the floor of the mouth. It also connects to the larynx, which is the voice box, located below it. Behind the bone, it attaches to the epiglottis and the pharynx. These connections allow the hyoid to assist in swallowing and tongue movement. The bone is classified as an irregular bone. It consists of a central part called the body and two pairs of horns.

Gray186
Gray186

These horns are known as the greater horns and the lesser horns.

The body is the central, thickened part of the bone. Its front surface is convex and curves upward and forward. Many specimens feature a vertical median ridge that divides the body into two lateral halves. It also has a transverse ridge across its upper half. Various muscles attach to different parts of the body. For example, the geniohyoid muscle attaches to the front of the body. Below the transverse ridge, muscles like the mylohyoid and the sternohyoid find their attachment points. At the back, the body is smooth and concave. It is separated from the epiglottis by the hyothyroid membrane and loose areolar tissue.

The two pairs of horns project from the sides of the body. The greater horns project backward from the outer edges of the body. They are flattened and taper toward their ends. These ends form a bony tubercle that connects to the lateral thyrohyoid ligament. The upper surface of these horns is rough to help muscles stay attached. Large muscles, such as the hyoglossus and the middle pharyngeal constrictor, run along the entire length of these horns.

Gray186
Gray186

The lesser horns are smaller and shaped like cones. They are attached to the angles where the body meets the greater horns. These two parts are connected by fibrous tissue. In some cases, they are joined by distinct diarthrodial joints. These joints usually stay throughout a person's life, though they can sometimes become ankylosed, or fused together.

Understanding the history of the hyoid bone helps scientists learn about human evolution. In the Kebara Cave in Israel, researchers discovered a modern-looking hyoid bone belonging to a Neanderthal man.

Larynx external en
Larynx external en

This discovery led some scientists to argue that Neanderthals had a descended larynx. If this is true, it suggests they may have had speech capabilities similar to modern humans. However, other researchers disagree. They argue that the shape of the hyoid does not necessarily show where the larynx was located. Other theories suggest the hyoid bone evolved alongside lactation. This change might have helped mammals suckle their young more effectively.

The development of the hyoid bone is a complex process called ossification. This is how soft cartilage turns into hard bone. The bone begins forming from six different centers. Two centers create the body, while one center creates each of the four horns. Ossification starts in the greater horns toward the end of fetal development. The body begins to harden shortly after. The lesser horns are the last to ossify, usually during the first or second year after birth.

Hyoid bone hariadhi
Hyoid bone hariadhi

In early life, the body and the greater horns are connected by synchondroses. As a person reaches middle age, these parts usually join through bony union.

The hyoid bone is also medically significant for breathing and sleep. It helps keep the upper airway open while you sleep. If the hyoid is positioned too low, it can be associated with obstructive sleep apnea (OSA). This is a condition where the airway collapses repeatedly during sleep. Doctors sometimes use a procedure called hyoid suspension to help improve the airway. Because of its protected position in the neck, the bone does not fracture easily. In forensic science, a fractured hyoid in an adult can be a strong indicator of strangulation. However, in children, the bone is still flexible due to incomplete ossification, so it is less likely to break.

Many other animals have specialized hyoid structures that serve unique purposes. In birds, the hyoid is often very long. In woodpeckers, the horns wrap around the back of the skull to cushion the brain from pecking.

Hyoid bone hariadhi
Hyoid bone hariadhi

In the world of big cats, the hyoid determines how an animal communicates. A lion has an incompletely ossified hyoid, which allows it to roar. A cheetah has a fully ossified hyoid, which allows it to purr and meow instead. This shows how the hardening of this single bone can completely change the sounds an animal can make.

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File:Hyoid_bone_hariadhi.svg
Hyoid_bone_hariadhi.svg
File:Gray186.png
Gray186.png
File:Larynx external en.svg
Larynx external en.svg
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