※2021年10月23日現在作成途中のページとなる。

 

概要
・喉頭の骨組み(喉頭軟骨)
関節および靭帯
筋肉
脈管・神経
働き
関連語句
Wikipedia
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注意)喉頭が位置する高さに関しては年齢により違いがみられ、「日本人体解剖学」には以下のような解説文が見られる。

「位置は年齢によって異なる。すなわち、新生児では成人よりも2~3椎体上位に位置し(新生児は授乳と呼吸を同時にすることができる)、固有の位置を取るのは4歳以降である。また、老人になると、喉頭の位置はさらに1から2椎体下がる。」

   

 喉頭における軟骨は、喉頭の重要な骨組みとなる働きをしている。以下のように大きく、対性のものと無対性のものの2種類に分類することができる。

詳細な解説はそれぞれのページを参照のこと。

 

 

以下が喉頭部に見られる靭帯の一覧となる。 参考:日本人体解剖学(下巻)

1

 舌骨下面と甲状軟骨上縁の間に張る弾性繊維に富む結合組織性の膜  

 部位的:正中甲状舌骨靭帯外側甲状舌骨靭帯

2
 舌骨体の上縁から起こり喉頭蓋軟骨の舌骨面に付着する。
3
4

 輪状軟骨弓下甲状切痕を結ぶ。

部位的:正中輪状甲状靭帯、外側輪状甲状靭帯

5
 輪状軟骨の下縁と気管軟骨を結ぶ。
6

 上下に3脚を有し、2脚は小角軟骨に、残りの1脚は輪状軟骨に付着

 上脚を小角咽頭靭帯、下脚を輪状咽頭靭帯という。

7
 甲状軟骨の両板間の角の内面と披裂軟骨小丘との間に張る。 
8
 甲状軟骨の後面正中線の外側方と披裂軟骨底を結ぶ。
 

 

以下は「日本人体解剖学」の解説文となる。

「喉頭には、喉頭の運動をつかさどる多数の小さな筋がみられる。外喉頭筋および内喉頭筋からなる。」

以下は「日本人体解剖学」を参考にして作成した内喉頭筋の簡単な一覧となる。

 

 

       

The larynx (/ˈlærɪŋks/), commonly called the voice box, is an organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about 4–5 centimeters in diameter.[1] The larynx houses the vocal cords, and manipulates pitch and volume, which is essential for phonation. It is situated just below where the tract of the pharynx splits into the trachea and the esophagus. The word larynx (plural larynges) comes from a similar Ancient Greek word (λάρυγξ lárynx).[2]


Structure[edit]

The triangle-shaped larynx consists largely of cartilages that are attached to one another, and to surrounding structures, by muscles or by fibrous and elastic tissue components. The larynx is lined by a ciliated columnar epithelium. The cavity of the larynx extends from its triangle-shaped inlet, to the epiglottis, and to the circular outlet at the lower border of the cricoid cartilage, where it is continuous with the lumen of the trachea. The mucous membrane lining the larynx forms two pairs of lateral folds that project inward into its cavity. The upper folds are called the vestibular folds. They are also sometimes called the false vocal cords for the rather obvious reason that they play no part in vocalization. The lower pair of folds are known as the vocal cords, which produce sounds needed for speech and other vocalizations. The slit-like space between the left and right vocal cords, called the rima glottidis, is the narrowest part of the larynx. The vocal cords and the rima glottidis are together designated as the glottis. The laryngeal cavity above the vestibular folds is called the vestibule. The very middle portion of the cavity between the vestibular folds and the vocal cords is the ventricle of the larynx, or laryngeal ventricle. The infraglottic cavity is the open space below the glottis.
Location[edit]
In adult humans, the larynx is found in the anterior neck at the level of the cervical vertebrae C3–C6. It connects the inferior part of the pharynx (hypopharynx) with the trachea. The laryngeal skeleton consists of nine cartilages: three single (epiglotticthyroid and cricoid) and three paired (arytenoidcorniculate, and cuneiform).[3] The hyoid bone is not part of the larynx, though the larynx is suspended from the hyoid. The larynx extends vertically from the tip of the epiglottis to the inferior border of the cricoid cartilage. Its interior can be divided in supraglottis, glottis and subglottis.

【 語 句 】

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Cartilages[edit]

 

Posterior view of the larynx; disarticulated cartilages (left) and intrinsic muscles (right)
There are nine cartilages, three unpaired and three paired (3 pairs=6), that support the mammalian larynx and form its skeleton.
Unpaired cartilages:

  • Thyroid cartilage: This forms the Adam's apple (also called the laryngeal prominence). It is usually larger in males than in females. The thyrohyoid membrane is a ligament associated with the thyroid cartilage that connects it with the hyoid bone. It supports the front portion of the larynx.
  • Cricoid cartilage: A ring of hyaline cartilage that forms the inferior wall of the larynx. It is attached to the top of the trachea. The median cricothyroid ligament connects the cricoid cartilage to the thyroid cartilage.
  • Epiglottis: A large, spoon-shaped piece of elastic cartilage. During swallowing, the pharynx and larynx rise. Elevation of the pharynx widens it to receive food and drink; elevation of the larynx causes the epiglottis to move down and form a lid over the glottis, closing it off.

Paired cartilages:

  • Arytenoid cartilages: Of the paired cartilages, the arytenoid cartilages are the most important because they influence the position and tension of the vocal cords. These are triangular pieces of mostly hyaline cartilage located at the posterosuperior border of the cricoid cartilage.
  • Corniculate cartilages: Horn-shaped pieces of elastic cartilage located at the apex of each arytenoid cartilage.
  • Cuneiform cartilages: Club-shaped pieces of elastic cartilage located anterior to the corniculate cartilages.

【 語 句 】

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Muscles[edit]
The muscles of the larynx are divided into intrinsic and extrinsic muscles. The extrinsic muscles act on the region and pass between the larynx and parts around it but have their origin elsewhere; the intrinsic muscles are confined entirely within the larynx and have their origin and insertion there.[4]
The intrinsic muscles are divided into respiratory and the phonatory muscles (the muscles of phonation). The respiratory muscles move the vocal cords apart and serve breathing. The phonatory muscles move the vocal cords together and serve the production of voice. The main respiratory muscles are the posterior cricoarytenoid muscles. The phonatory muscles are divided into adductors (lateral cricoarytenoid musclesarytenoid muscles) and tensors (cricothyroid musclesthyroarytenoid muscles).
Intrinsic[edit]
The intrinsic laryngeal muscles are responsible for controlling sound production.

Notably the only muscle capable of separating the vocal cords for normal breathing is the posterior cricoarytenoid. If this muscle is incapacitated on both sides, the inability to pull the vocal cords apart (abduct) will cause difficulty breathing. Bilateral injury to the recurrent laryngeal nerve would cause this condition. It is also worth noting that all muscles are innervated by the recurrent laryngeal branch of the vagus except the cricothyroid muscle, which is innervated by the external laryngeal branch of the superior laryngeal nerve (a branch of the vagus).
Additionally, intrinsic laryngeal muscles present a constitutive Ca2+-buffering profile that predicts their better ability to handle calcium changes in comparison to other muscles.[6] This profile is in agreement with their function as very fast muscles with a well-developed capacity for prolonged work. Studies suggests that mechanisms involved in the prompt sequestering of Ca2+ (sarcoplasmic reticulum Ca2+-reuptake proteins, plasma membrane pumps, and cytosolic Ca2+-buffering proteins) are particularly elevated in laryngeal muscles, indicating their importance for the myofiber function and protection against disease, such as Duchenne muscular dystrophy.[7] Furthermore, different levels of Orai1 in rat intrinsic laryngeal muscles and extraocular muscles over the limb muscle suggests a role for store operated calcium entry channels in those muscles' functional properties and signaling mechanisms.

【 語 句 】

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Extrinsic[edit]
The extrinsic laryngeal muscles support and position the larynx within the mid-cervical region. [trachea.]

Nerve supply[edit]
The larynx is innervated by branches of the vagus nerve on each side. Sensory innervation to the glottis and laryngeal vestibule is by the internal branch of the superior laryngeal nerve. The external branch of the superior laryngeal nerve innervates the cricothyroid muscle. Motor innervation to all other muscles of the larynx and sensory innervation to the subglottis is by the recurrent laryngeal nerve. While the sensory input described above is (general) visceral sensation (diffuse, poorly localized), the vocal cords also receives general somatic sensory innervation (proprioceptive and touch) by the superior laryngeal nerve.
Injury to the external laryngeal nerve causes weakened phonation because the vocal cords cannot be tightened. Injury to one of the recurrent laryngeal nerves produces hoarseness, if both are damaged the voice may or may not be preserved, but breathing becomes difficult.

【 語 句 】

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Development[edit]
In newborn infants, the larynx is initially at the level of the C2–C3 vertebrae, and is further forward and higher relative to its position in the adult body.[8] The larynx descends as the child grows.[9][10]


Function[edit]

Sound generation[edit]
Sound is generated in the larynx, and that is where pitch and volume are manipulated. The strength of expiration from the lungs also contributes to loudness.
Manipulation of the larynx is used to generate a source sound with a particular fundamental frequency, or pitch. This source sound is altered as it travels through the vocal tract, configured differently based on the position of the tonguelipsmouth, and pharynx. The process of altering a source sound as it passes through the filter of the vocal tract creates the many different vowel and consonant sounds of the world's languages as well as tone, certain realizations of stress and other types of linguistic prosody. The larynx also has a similar function to the lungs in creating pressure differences required for sound production; a constricted larynx can be raised or lowered affecting the volume of the oral cavity as necessary in glottalic consonants.
The vocal cords can be held close together (by adducting the arytenoid cartilages) so that they vibrate (see phonation). The muscles attached to the arytenoid cartilages control the degree of opening. Vocal cord length and tension can be controlled by rocking the thyroid cartilage forward and backward on the cricoid cartilage (either directly by contracting the cricothyroids or indirectly by changing the vertical position of the larynx), by manipulating the tension of the muscles within the vocal cords, and by moving the arytenoids forward or backward. This causes the pitch produced during phonation to rise or fall. In most males the vocal cords are longer and with a greater mass than most females' vocal cords, producing a lower pitch.
The vocal apparatus consists of two pairs of folds, the vestibular folds (false vocal cords) and the true vocal cords. The vestibular folds are covered by respiratory epithelium, while the vocal cords are covered by stratified squamous epithelium. The vestibular folds are not responsible for sound production, but rather for resonance. The exceptions to this are found in Tibetan chanting and Kargyraa, a style of Tuvan throat singing. Both make use of the vestibular folds to create an undertone. These false vocal cords do not contain muscle, while the true vocal cords do have skeletal muscle.
Other[edit]
The most important role of the larynx is its protecting function; the prevention of foreign objects from entering the lungs by coughing and other reflexive actions. A cough is initiated by a deep inhalation through the vocal cords, followed by the elevation of the larynx and the tight adduction (closing) of the vocal cords. The forced expiration that follows, assisted by tissue recoil and the muscles of expiration, blows the vocal cords apart, and the high pressure expels the irritating object out of the throat. Throat clearing is less violent than coughing, but is a similar increased respiratory effort countered by the tightening of the laryngeal musculature. Both coughing and throat clearing are predictable and necessary actions because they clear the respiratory passageway, but both place the vocal cords under significant strain.[11]
Another important role of the larynx is abdominal fixation, a kind of Valsalva maneuver in which the lungs are filled with air in order to stiffen the thorax so that forces applied for lifting can be translated down to the legs. This is achieved by a deep inhalation followed by the adduction of the vocal cords. Grunting while lifting heavy objects is the result of some air escaping through the adducted vocal cords ready for phonation.[11]
Abduction of the vocal cords is important during physical exertion. The vocal cords are separated by about 8 mm (0.31 in) during normal respiration, but this width is doubled during forced respiration.[11]
During swallowing, elevation of the posterior portion of the tongue levers (inverts) the epiglottis over the glottis' opening to prevent swallowed material from entering the larynx which leads to the lungs, and provides a path for a food or liquid bolus to "slide" into the esophagus; the hyo-laryngeal complex is also pulled upwards to assist this process. Stimulation of the larynx by aspirated food or liquid produces a strong cough reflex to protect the lungs.
In addition, intrinsic laryngeal muscles are spared from some muscle wasting disorders, such as Duchenne muscular dystrophy, may facilitate the development of novel strategies for the prevention and treatment of muscle wasting in a variety of clinical scenarios. ILM have a calcium regulation system profile suggestive of a better ability to handle calcium changes in comparison to other muscles, and this may provide a mechanistic insight for their unique pathophysiological properties[12]

 

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