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The hyoid bone (hyoid) is a small U-shaped (horseshoe-shaped) solitary bone, located in the midline of the neck anteriorly at the base that the mandible and posteriorly at the 4th cervical vertebra. The anatomical place is simply superior to the thyroid cartilage. It is closely linked with an extended tendon-muscular complicated but not specifically interconnected come any adjacent bones and also hence is considered by countless anatomists and also anthropologists to be an unconventional bone. That is anchored in the anterior triangle that the neck by muscles from the larynx, pharynx, tongue, and also the floor the the mouth. The surname hyoid derives native the Greek native “hyodeides,” which method “shaped like the letter Upsilon.” Although dubbed as an unconventional bone, the hyoid being a component of the hyoid-larynx complex is undoubtedly a bone of clinical and forensic significance.
Structure and Function
The hyoid consists of a body, two better horns, and also two lesser horns.<1> The body creates the central quadrilateral-shaped broad segment of the hyoid. The greater horns are larger and also longer than the lesser horns of the hyoid. The greater horns and also lesser horns are additionally known as cornu majus and cornu minus, respectively. The body and the higher horns appear to give the hyoid that U-shape with the higher horns creating the limbs of the "U" top top either next of the body. The greater and lesser horns normally unite come the body of the hyoid via fibrous tissue or a true joint.<2> As period progresses, there is a physiological progression of ankylosis that the joints connecting the greater and also lesser horns v the body of the hyoid.
The hyoid takes part in all feasible functional plot of the orofacial complex. That preserves the patency that the airway in between the oropharynx over and tracheal ring below. It likewise connects come the larynx and also hence dram a role in phonation. Various other functions include tongue movement, mastication, swallowing, avoidance of regurgitation, and even respiration.<1><3> Furthermore, the hyoid maintains the posture of the head, because of the complicated connection the presumes between the mandible and the cervical spine.<1>
The second pharyngeal arch develops the lesser horn (cornu) and also the upper body of the hyoid, when the greater horn (cornu) and also the lower portion of the human body derive from the third pharyngeal arch. This embryonic breakthrough of the hyoid remains controversial.<1> The ossification that the higher horns occurs toward the end of the typical gestational duration of the fetus; this is followed by the ossification the the human body of the hyoid shortly after birth. Eventually, ossification the the lesser horns occurs during the very first or second year after birth. Later on in adulthood, usually the horns fuse with the body, but this might not take place in all individuals. The hyoid is located anterior to the 2nd and third cervical vertebra during infancy, and ultimately in adulthood, that descends come the level the the fourth and fifth cervical vertebra. The lower takes place simultaneously with the various other functionally relevant structures consisting of the epiglottis and also the larynx.<3>
The hyoid functions as one anchor for the suprahyoid muscle (digastric, stylohyoid, mylohyoid and also geniohyoid) as well as the infrahyoid muscles (sternohyoid, sternothyroid, omohyoid, and also thyrohyoid).<2> The stylohyoid ligament suspends the hyoid indigenous the temporal styloid process on either side. The is restricted by the ligamentous attachments inferiorly to the superior aspect of the thyroid cartilage v the thyrohyoid membrane. Additionally, the hyoid is attached to the cervical spine posteriorly via the cervical fascia.<1>
The suprahyoid muscles are 4 in number top top either next of the anterior midline above the level of the hyoid (Media Image, Table 1). They attach the hyoid to the mandible, tongue, and skull. The digastric muscle has two bellies, posterior and anterior. The anterior belly originates indigenous the digastric fossa that the mandible, while the posterior ship originates from the mastoid notch. Both the digastric bellies insert come the intermediate tendon of the digastric muscle i m sorry is attached come the hyoid. The stylohyoid muscle originates from the temporal styloid process; that is a thin and also long muscle the lies parallel to the posterior ship of the digastric. The mylohyoid muscle originates native the mylohyoid heat of the mandible; the is a slim muscle the upholds and also makes up the floor that the mouth while additionally creating a sling worse to the tongue. The geniohyoid muscle is a narrow and short muscle that originates native the internal mental spine the the symphysis menti. The stylohyoid, mylohyoid, and also geniohyoid insert ~ above the body of the hyoid.<1>
The infrahyoid muscles are 4 pairs of muscles located in the anterior part of the neck (Media Image, Table 2). They room found between the hyoid over and the shoulder girdle below. The sternohyoid muscle primarily originates indigenous the back of the manubrium and also inserts top top the medial part of the worse border the the hyoid body. The sternothyroid muscle originates generally from the earlier of the manubrium and inserts ~ above the oblique heat of the thyroid cartilage. The omohyoid muscle has a superior belly and an inferior belly. The remarkable belly that the omohyoid occurs from the intermediary tendon that the omohyoid and inserts ~ above the hyoid. The inferior ship of the omohyoid originates native the scapular premium border and also inserts come the intermediate tendon of the omohyoid. The thyrohyoid muscle originates native the oblique line of the thyroid cartilage and also inserts in ~ the inferior element of the human body of the hyoid and also the greater cornu.<1><4>
Other Muscles regarded the Hyoid
The hyoglossus and the center pharyngeal constrictor originate indigenous the hyoid. These muscles carry out not form the team as mentioned over of muscles pertained to the hyoid.
Elevation the the Hyoid
The digastric, stylohyoid, mylohyoid and geniohyoid role in elevating the hyoid.
Depression of the Hyoid
The sternohyoid, sternothyroid, omohyoid, and thyrohyoid role in boring the hyoid.
The hyoid reflects a wide variety of anatomical variations, most likely owing to the asymmetry of the greater and lesser horns. Therefore, the hyoid is thought about one the the most polymorphic components of the human body. The commonest variation of the hyoid takes ar in the process of ankylosis the the joints between the horns (greater and lesser horns) and the body that the hyoid. Ethnicity, sex, age, height, and weight the the subject add to the morphological variations. These variations can happen unilaterally, bilaterally, and also multiple variations can happen in the same individual.<2> Surprisingly, the absence of the hyoid has been reported too in a male neonate who was also a teratoma case, had actually a mandibular cleft, and suffered from respiratory distress.<5> this anomalies correlate to some clinical conditions such as micrognathia, Pierre Robin sequence, and cleft lip and also palate. Symptoms led to by this anomalies incorporate dysphagia, neck movement limitations and foreign body sensation in the throat.<2>
The Hyoid and also its relationship to Blood Vessels
The pointer of the greater horn the the hyoid is a far-ranging landmark because that cervical surgery in the mid-neck region. The carotid bifurcation, the premium thyroid artery, and the lingual artery are closely related to the pointer of the greater horn. The tip of the higher horn is a beneficial landmark in locating these arteries throughout cervical surgery. The carotid bifurcation is located inferior and also posterior to the tip of the better horn. Also, the origin of the remarkable thyroid artery i beg your pardon is the an initial branch of the interior carotid artery lies below the level the the better horn. The lingual artery is among the very closely related structures to the hyoid, and it branches turn off the outside carotid artery over the level that the better horn.<6>
The Hyoid and also its relation to Nerves
The hypoglossal and the exceptional laryngeal nerve are closely related to the guideline of the better horn the the hyoid. The guideline of the better horn aids the surgeon in locating this nerves throughout cervical surgery. The hypoglossal nerve lies superiorly come the pointer of the higher horn the the hyoid. The premium laryngeal nerve divides right into its external and also internal branches as it overcome behind the better horn, v its external branch gift deeper than the interior one.<6>
The Hyoid and Obstructive Sleep Apnea Syndrome
Obstructive sleep apnea is a chronic sleep-related breathing disorder. The is ideal described by recurring narrowing and also obstruction of the pharyngeal airway throughout sleep.<7> This condition is resulted in by pharyngeal collapsibility, i beg your pardon is due to the loss of wakefulness stimulus and also changes in the neuromuscular control. Number of factors add to the pharyngeal collapsibility; the hyoid position is one of these factors. One imbalance between the suprahyoid and infrahyoid muscles may lead to alteration in the place of the hyoid, hence affecting the airway patency and also causing an ext pharyngeal collapsibility.<8> The clinical manifestations incorporate non-refreshing sleep, daytime sleepiness, fatigue, nocturia, irritability and also morning headache. If left unmanaged, it might lead to many complications, including cardiovascular diseases, cognitive impairment, and decreased productivity and also concentration, i m sorry may bring about road web traffic accidents.<7> The therapy of selection is the nasal continuous positive airway pressure; if unsuccessful, other choices include oral devices, positional therapy,<9> upper airway surgical treatment such together genioglossus advancement,<10> hyoidothyroidopexy (hyoid suspension),<11> hyoid myotomy and also sliding genioplasty.<10>
Hyoid Bone Insertion Tendinitis
Hyoid bone insertion tendinitis is likewise known together hyoid bone syndrome. Patients describe it together neck pains that increases with swallowing and also movement that the neck. The ache is characteristically one of two people dull or sharp, radiating come the temporal area, posterior pharyngeal wall, sternocleidomastoid muscle, ear, and also supraclavicular region. ~ above examination, tenderness over the higher horn of the hyoid is noted upon palpation. The condition is diagnosed mainly by background and physical examination. Imaging might be supplied to exclude, the other differential diagnoses. Medical therapy is the initial treatment of choice. It has topical and systemic non-steroidal anti-inflammatory medications, local anesthetics and steroid injections. If medical therapy fails, then surgical procedure is the following consideration.<12>
Calcified Stylohyoid Ligament and Eagle Syndrome
There are two species of Eagle syndrome. The first type is the classic Eagle syndrome or the standard styloid syndrome, usually seen after tonsillectomy as pharyngodynia found in the tonsillar fossa, occasionally linked with odynophagia, dysphagia, foreign body sensation, hypersalivation, and also seldom, momentary voice changes. All of these symptoms show up when the tightened tonsillectomy scar tissue moves follow me the reminder of an elongated styloid procedure through functional movements.
Forensic Anatomy that the Hyoid
The forensic profile of the hyoid concerned forensic sociology primarily includes estimation the age and determination of sex. Combination of the hyoid is especially helpful to predict period in adulthood. The bone thickness of the hyoid is a beneficial predictor of both age and also sex <3>. However, that is precious noting that the literature reports a wide range of variability in the degree and also timing of blend of the greater horns v the human body of the hyoid. Using discriminant role analysis, various metric measurements of the hyoid are uncovered to be helpful in determining the sex of the bone.<17>
Forensic significance of Hyoid Fracture
Trauma to the hyoid and also laryngeal cartilages (thyroid cartilage and also cricoid cartilage), is one of the far-ranging signs of hands-on strangulation or throttling discovered during a forensic autopsy. Fractures that the hyoid-laryngeal complex are current in instances of fatality due come a constricting force roughly the neck. Forensic pathologists have actually intensively studied traumatic lesions of the hyoid-laryngeal complicated in strangulation, consisting of manual strangulation and ligature strangulation, and hanging. Other develops of blunt force influence to the neck can additionally cause fracture of the hyoid.
The damage commonly affects the greater horns or the region between the human body of the hyoid and also the horns. Injuries are greatly in the type of vertical or tilt fractures. Displacements the the fracture segments are likewise observed. Bilateral fractures of the hyoid and double fractures of one of the better horns are not uncommon.<18> The frequency of a fractured hyoid is more in situations of strangulation in comparison to instances of hanging. However, a hyoid fracture is existing in only around a third of all homicides native strangulation.<19> Therefore, the merits noting that an intact hyoid does not constantly rule the end strangulation as the underlying cause of death. The hyoid is fractured more frequently in the older victims of strangulation and also is less likely to occur in younger victim of strangulation in the period group 20 to 40.
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<19> The differences in the age-related frequency of hyoid fracture room dependent ~ above the degree of ankylosis of the hyoid that progresses with age. The mobility in the region of the junction between the higher horns and also the human body of the hyoid need to not it is in mistaken because that a fracture.