The larynx is an organ that is part of the upper respiratory tract. It is a cavity surrounded by cartilage. The larynx is located above the trachea at the level of the fourth, fifth and sixth cervical vertebrae. But she is not constantly static at this level. When swallowing and pronouncing sounds, it shifts up or down. Read more about the structure, innervation and blood supply to the larynx later in the article.
Larynx location
Before moving on to examining the blood vessels and innervation of the larynx, you need to figure out where it is located at all, as well as which cartilage and muscles form it. This is really important, as the vessels and nerves are needed specifically for the nutrition of these muscles and cartilage.
The larynx can be palpated well, since it is superficial, almost immediately under the skin. And some protrusions are visible to the naked eye. They serve as anatomical landmarks when performing a tracheostomy. In men, the Adam's apple, which is actually a protrusion of the thyroid cartilage, is well visualized. In girls and children, you can see the arc of the cricoid cartilage.
The upper border of the larynx is the hole, which is called the entrance to the larynx. From below, the larynx smoothly passes into the trachea - the breathing tube. On the sides of it are lobes of the thyroid gland, as well as vessels and nerves of the neck.
Cartilage skeleton
Studying the innervation of the larynx becomes simpler if you know the cartilage that is part of it. After all, the name of the nerve often corresponds to the name of the cartilage.
The main cartilage of the larynx is called cricoid. On the front, it forms an arc, and on the back it is a view of a quadrangular plate. Above it is the thyroid cartilage, which is the largest of all the structures of the larynx. This formation consists of two plates, which are combined in front at a certain angle.
Another laryngeal cartilage is scyphoid. In its form, it resembles a pyramid, in which they distinguish the base and top. Moreover, the apex is turned upward and somewhat posteriorly, and the base is downward and anteriorly.
At the top is the epiglottis - an elastic cartilage. It closes the entrance to the larynx during swallowing, which prevents food from entering the respiratory tract.
Larynx muscles
Separately, attention should be paid to the muscles of the larynx. They are divided into two types: their own and skeletal. The muscles of the first variety are attached to the cartilage of the larynx from the outside with one end, and the other join the bones of the skeleton (sternum, collarbone, lower jaw, scapula, etc.). These muscles include:
- shield-hyoid;
- sterno-thyroid;
- sternum-hyoid;
- double-abdominal;
- scapular-hyoid;
- awl-hyoid.
Own muscles are divided into internal and external. Moreover, there are only two external muscles - the paired ring-thyroid.
Internal muscles are divided into several groups depending on their functional features:
- muscles that regulate the width of the entrance to the larynx;
- muscles that control and change the state of the vocal cords;
- muscles of the epiglottis.
Blood vessels
The blood supply to the larynx is quite plentiful. She receives blood from the laryngeal arteries: the upper and lower. The superior laryngeal artery, in turn, branches off from the superior thyroid artery. This occurs slightly above the edge of the thyroid cartilage. In the hyoid-thyroid septum there is a hole through which this artery penetrates the wall of the larynx.
On the opposite side is the same superior laryngeal artery. They anostomose, that is, connect, with each other, giving another branch to the inner part of the larynx. The middle laryngeal vessel also departs from the superior thyroid artery.
The lower laryngeal artery branches, respectively, from the lower thyroid vessel. The latter, in turn, departs from the subclavian artery. In the larynx, the lower vessel passes behind the joint between the thyroid and cricoid cartilage, supplying blood to the posterior surface of the larynx. This artery forms anastomoses with the upper and middle vessels.
Thus, oxygen-rich blood flows through the arteries to the cartilage and muscles of the larynx. Poor oxygen comes out of the larynx structures through the veins of the same name. It gathers in the venous plexuses, which then pass into the upper and lower laryngeal veins. They, in turn, flow into the superior and inferior thyroid veins. The upper vessel then carries blood to the internal jugular vein. The lower vessel is a tributary of the brachiocephalic vein.
Laryngeal innervation
The transmission of nerve impulses to the skeletal muscles of the larynx is carried out due to the branches of the vagus nerve (10 pairs of cranial nerves). The superior laryngeal nerve belongs to the mixed group. This means that at its expense both the motor and sensitive innervation of the larynx are carried out. That is, he takes part in the movement of muscles, carrying an impulse to the larynx, and also carries an impulse from it to the organs of the central nervous system.
The superior laryngeal nerve branches off from the vagus nerve at the level of its lower node. It goes down and branches into two branches, slightly reaching the level of the hyoid bone. These branches include:
- external - performs a motor function, and carries an impulse to only one muscle - the anterior cricothyroid, and also innervates the lower pharyngeal compressor;
- internal - it is sensitive, penetrates the larynx together with the upper laryngeal artery through an opening in the thyroid hyoid membrane, innervates the mucous membrane of the organ; Thus, the sensitive innervation of the larynx is realized.
The lower laryngeal nerve is purely motor. It provides contraction of all the muscles of the larynx, in addition to the anterior cricothyroid.
Recurrent laryngeal nerves
An essential role in the innervation of the larynx is played by the right and left recurrent nerves. The right branch from the vagus nerve at the level of its intersection with the subclavian artery. Rounding this vessel, the artery rises further along the lateral wall of the larynx. The left recurrent nerve also departs from the vagus nerve, but at the level of the botallal duct, which is obliterated in children soon after birth.
If these nerves are damaged, voice formation and breathing are disturbed, since they innervate the vocal cords.
Thus, the innervation of the larynx is carried out by the following nerves:
- lower and upper laryngeal nerves;
- right and left recurrent laryngeal nerves.