Arteries of the thyroid gland. Superior thyroid artery
1. Superior thyroid artery, a. thyroidea superior(see Fig.,), departs from the external carotid artery immediately at the place where the latter departs from the common carotid artery at the level of the greater horns of the hyoid bone. It goes slightly upward, then bends in an arcuate manner medially and follows the upper edge of the corresponding lobe of the thyroid gland, sending it into its parenchyma anterior glandular branch, r. glandularis anterior, posterior glandular branch, r. glandularis posterior, And lateral glandular branch, r. glandularis lateralis. In the thickness of the gland, the branches of the superior thyroid artery anastomose with the branches of the inferior thyroid artery, a. thyroidea inferior (from the thyrocervical trunk, truncus thyrocervicalis, extending from the subclavian artery, a. subclavia) (see Fig.).
Along the way, the superior thyroid artery gives off a number of branches:
- sublingual branch, r. infrahyoideus, supplies blood to the hyoid bone and the muscles attached to it; anastomoses with the branch of the same name on the opposite side;
- sternocleidomastoid branch, r. sternocleidomastoideus, non-permanent, supplies blood to the muscle of the same name, approaching it from the inner surface, in its upper third;
- superior laryngeal artery, a. laryngea superior, directed to the medial side, passes over the upper edge of the thyroid cartilage, under the thyrohyoid muscle and piercing the thyrohyoid membrane, supplies blood to the muscles, the mucous membrane of the larynx and partially the hyoid bone and epiglottis;
- cricothyroid branch, r. cricothyroideus, supplies blood to the muscle of the same name and forms an arcuate anastomosis with the artery of the opposite side.
2. Lingual artery, a. lingualis(Fig.; see Fig., ,), thicker than the superior thyroid and begins slightly above it, from the anterior wall of the external carotid artery. In rare cases, it leaves a common trunk with the facial artery and is called linguofacial trunk, truncus linguofacialis. The lingual artery follows slightly upward, passes over the greater horns of the hyoid bone, heading forward and inward. Along its course, it is first covered by the posterior belly of the digastric muscle, the stylohyoid muscle, then passes under the hyoid-glossus muscle (between the latter and the middle constrictor of the pharynx from the inside), approaches the lower surface of the tongue, penetrating into the thickness of its muscles.
Along its course, the lingual artery gives off a number of branches:
- suprahyoid branch, r. suprahyoideus, passes along the upper edge of the hyoid bone, anastomoses in an arcuate manner with the branch of the same name on the opposite side; supplies blood to the hyoid bone and adjacent soft tissues;
- dorsal branches of the tongue, rr. dorsales linguae, small in thickness, depart from the lingual artery under the hyoglossus muscle, heading steeply upward, approach the back of the back of the tongue, supplying blood to its mucous membrane and tonsil. Their terminal branches pass to the epiglottis and anastomose with the arteries of the same name on the opposite side;
- hypoglossal artery, a. sublingualis, departs from the lingual artery before it enters the thickness of the tongue, goes anteriorly, passing over the mylohyoid muscle outward from the mandibular duct; then it approaches the sublingual gland, supplying blood to it and the adjacent muscles; ends in the mucous membrane of the floor of the mouth and in the gums. Several branches, perforating the mylohyoid muscle, anastomose with the submental artery, a. submentalis (branch of the facial artery, a. facialis);
- deep artery of the tongue, a. profunda linguae, is the most powerful branch of the lingual artery, which is its continuation. Heading upward, it enters the thickness of the tongue between the genioglossus muscle and the lower longitudinal muscle of the tongue; then, following sinuously forward, it reaches its top.
Along its course, the artery gives off numerous branches that nourish the muscles and mucous membrane of the tongue. The terminal branches of this artery approach the frenulum of the tongue.
3. Facial artery, a. facialis(see Fig. , , ), originates from the anterior surface of the external carotid artery, slightly above the lingual artery, goes forward and upward and passes inward from the posterior belly of the digastric muscle and the stylohyoid muscle into the submandibular triangle. Here it either adjoins the submandibular gland, or pierces its thickness, and then goes outward, bending around the lower edge of the body of the lower jaw in front of the attachment of the masticatory muscle; curving upward onto the side surface of the face, it approaches the area of the medial corner of the eye between the superficial and deep facial muscles.
Along its course, the facial artery gives off several branches:
- ascending palatine artery, a. palatina ascendens, departs from the initial section of the facial artery and, rising up the lateral wall of the pharynx, passes between the styloglossus and stylopharyngeal muscles, supplying them with blood. The terminal branches of this artery branch in the area of the pharyngeal opening of the auditory tube, in the palatine tonsils and partially in the mucous membrane of the pharynx, where they anastomose with the ascending pharyngeal artery, a. pharyngea ascendens;
- almond branch, r. tonsillaris, goes up the lateral surface of the pharynx, pierces the upper constrictor of the pharynx and ends with numerous branches in the thickness of the palatine tonsil. Gives off a number of branches to the wall of the pharynx and the root of the tongue;
- branches to the submandibular gland - glandular branches, rr. glandulares, are represented by several branches extending from the main trunk of the facial artery in the place where it is adjacent to the submandibular gland;
- submental artery, a. submentalis, is a fairly powerful branch. Directing anteriorly, it passes between the anterior belly of the digastric muscle and the mylohyoid muscle and supplies them with blood. Anastomosing with the sublingual artery, the submental artery passes through the lower edge of the lower jaw and, following to the anterior surface of the face, supplies the skin and muscles of the chin and lower lip;
- inferior and superior labial arteries, aa. labiales inferior et superior, begin in different ways: the first - slightly below the corner of the mouth, and the second - at the level of the corner, following in the thickness of the orbicularis oris muscle near the edge of the lips. The arteries supply blood to the skin, muscles and mucous membrane of the lips, anastomosing with the vessels of the same name on the opposite side. The superior labial artery gives off the thin branch of the nasal septum, r. septi nasi, blood supply to the skin of the nasal septum in the nostril area;
- lateral branch of the nose, r. lateralis nasi, - a small artery, goes to the wing of the nose and supplies the skin of this area;
- angular artery, a. angularis, is the terminal branch of the facial artery. It goes up the side surface of the nose, giving off small branches to the wing and back of the nose. Then it approaches the corner of the eye, where it anastomoses with the dorsal artery of the nose, a. dorsalis nasi (branch of the ophthalmic artery, a. ophthalmica) (see Fig.
Lateral lobes of the thyroid gland through the fascial capsule, the lateral surfaces come into contact with the fascial sheaths of the common carotid arteries.
Postinternal surfaces lateral lobes of the thyroid gland are adjacent to the larynx, trachea, tracheoesophageal groove, as well as to the esophagus, and therefore, with an increase in the lateral lobes of the thyroid gland, it may be compressed. In the space between the trachea and the esophagus on the right and along the anterior wall of the esophagus on the left, the recurrent laryngeal nerves rise to the cricothyroid ligament. These nerves, unlike those near the thyroid glands, lie outside the fascial capsule of the thyroid gland.
Thus, the area on posterior surface of the lateral lobe of the thyroid gland amounts to "danger zone" of the thyroid gland, to which the branches of the inferior thyroid artery approach, crossing here with the recurrent laryngeal nerve, and the parathyroid glands are located nearby.
When compressed n. laryngeus recurrens or when the inflammatory process passes from the gland to this nerve, the voice becomes hoarse (dysphonia).
Blood supply to the thyroid gland. Vessels of the thyroid gland.
Blood supply to the thyroid gland carried out by two superior thyroid (from the external carotid arteries) and two inferior thyroid (from the thyroid-cervical trunks of the subclavian arteries) arteries. In 6-8% of cases, the unpaired lowest thyroid artery, a. thyroidea ima, arising from the brachiocephalic trunk. The artery ascends to the lower edge of the isthmus of the thyroid gland in the tissue of the previsceral space, which should be remembered when performing a lower tracheotomy.
Superior thyroid artery, a. thyroidea superior supplies blood to the upper poles of the lateral lobes and the upper edge of the isthmus of the thyroid gland.
Inferior thyroid artery, a. The thyroidea inferior departs from the truncus thyrocervicalis in the scalene-vertebral space and rises under the 5th fascia of the neck along the anterior scalene muscle up to the level of the VI cervical vertebra, forming a loop or arch here. Then it descends downwards and inwards, perforating the 4th fascia, to the lower third of the posterior surface of the lateral lobe of the gland. The ascending part of the inferior thyroid artery runs medially from the phrenic nerve. At the posterior surface of the lateral lobe of the thyroid gland, the branches of the inferior thyroid artery cross the recurrent laryngeal nerve, being anterior or posterior to it, and sometimes cover the nerve in the form of a vascular loop.
Thyroid gland surrounded by a well-developed venous plexus located between the fibrous and fascial capsules (Fig. 6.16).
From him superior thyroid veins, accompanying the arteries, blood flows into the facial vein or directly into the internal jugular vein. The inferior thyroid veins are formed from the venous plexus on the anterior surface of the gland, as well as from the unpaired venous plexus, plexus thyroideus impar, located at the lower edge of the isthmus of the thyroid gland and in front of the trachea, and flow into the right and left brachiocephalic veins, respectively.
Innervation of the thyroid gland. Nerves of the thyroid gland.
Innervation of the thyroid gland carried out by the branches of the sympathetic trunk, superior and recurrent laryngeal nerves.
Lymphatic drainage from the thyroid gland occurs in the pretracheal and paratracheal lymph nodes, and then in the deep lymph nodes of the neck.
The thyroid gland secretes regulators of all types of metabolism - the hormones triiodothyronine (T 3) and thyroxine (T 4), as well as calcitonin and catalcin, endocrine regulators of Ca 2+ metabolism.
The rudiment of the thyroid gland in the form of a protrusion of the pharynx between the first and second pairs of pharyngeal pouches (at the root of the tongue) appears at the 3-4th week. intrauterine development. The epithelial rudiment of the gland grows neutrally than the cartilages of the larynx and by the 7th week. reaches the site of final localization, forming two lobes and an isthmus. The weight of the thyroid gland is 15-30 g.
The gland primordium is first connected to the pharynx by a hollow cord that opens on the surface of the root of the tongue (later Foramen coecum). Normally this cord degenerates. With incomplete degeneration of the epithelial cord along its length, cervical cysts may appear.
The remnant of the cord closest to the body of the gland is the pyramidal lobe. The two lateral and isthmus lobes make up the bulk of the thyroid tissue.
Blood supply to the thyroid gland
Arterial blood supply.
a) The superior thyroid arteries (branches of the external carotid arteries) supply the upper poles of the lobes of the gland.
b) The inferior thyroid arteries begin from the thyroid-cervical trunks (branches of the subclavian arteries) and supply the lower poles of the gland.
c) The azygos artery of the thyroid gland, found in 12% of cases, originates from the aortic arch. Its branches take part in the blood supply to the isthmus of the thyroid gland. Venous drainage occurs through:
Paired superior thyroid veins, which run along the arteries of the same name and empty into the internal jugular veins;
The middle veins of the thyroid gland (veins of Kocher), which arise from the lateral surfaces of the lobes and also flow into the internal jugular veins;
The inferior thyroid veins drain either directly into the internal jugular or innominate veins.
Lymphatic drainage from the thyroid gland occurs in the lymph nodes located in the esophageal tracheal groove, in front and on the sides of the trachea.
Involvement of the lymph nodes of the esophageal-tracheal groove during metastasis of thyroid tumors contributes to the spread of the tumor to the underlying recurrent laryngeal nerve, trachea and esophagus.
Innervation of the larynx
1. Recurrent laryngeal nerve
The recurrent laryngeal nerves arise from the vagus nerves and pass in the esophagotracheal groove, adjacent to the posteromedial surface of the thyroid gland.
On the right side, the nerve bends around the subclavian artery and ascends in an oblique direction from the outside to the inside, crossing the inferior thyroid artery at the posterior surface of the lower lobe of the thyroid gland.
On the left, the nerve begins below, at the level of the aortic arch, goes around it and lies in the left esophageal-tracheal groove.
The recurrent nerve has an external branch that provides sensory innervation to the larynx and an internal branch that goes to the muscles of the pharynx.
Damage to the recurrent laryngeal nerve, with the development of paralysis of the laryngeal muscles and impaired phonation, most often occurs either where it crosses the inferior thyroid artery or where it pierces the membrane between the cricoid and thyroid cartilages. Damage to the nerve during surgery requiring removal of a lobe of the gland can be prevented by first isolating it.
2. The superior laryngeal nerve is intimately intertwined with branches of the superior thyroid artery and gives a sensory external branch innervating the larynx and a motor branch to the cricothyroid muscle.
We'll talk about antidiuretic hormone. You can see that I have already started drawing it. I'm not a great artist, I wanted to play it safe in advance. On one side I drew the pituitary gland... so, the pituitary gland. and on the other - the brain. So, antidiuretic hormone. I emphasized ADH because that is what it is commonly called. People call it ADH. Some call it vasopressin. In fact, vasopressin is a good name because it is descriptive. It consists of parts “vaso-”, which refers to blood vessels, and “pressin”, which reflects the compression of blood vessels. This indicates what the hormone does. So, I drew the hypothalamus. Let's write it down: hypothalamus. And now directly below it there will be a pituitary gland funnel, similar to the neck. Funnel of the pituitary gland. At the very bottom is the pituitary gland. So, at the bottom is the pituitary gland. Its front and back. The anterior part, directed forward, closer to the eyes, is the anterior lobe of the pituitary gland. She is here. This lobe will be the posterior lobe of the pituitary gland because it is slightly behind. Since we are giving names, let's move on. Here is the chiasmus. It is related to vision. I'll write down "chiasmus" so you know what we're talking about. The only reason I mention it... Right above it, in this area, right here... If I drew it on my little diagram, it would be here. There is a “supra”... S-U-P-R-A - the supraoptic core. The word “nucleus” here refers to a collection of nerve cell bodies. Not the nucleus that we usually talk about, not the one that is inside the cell and directs the flow of movement, controlling it. These are, after all, different things. So here the nucleus is just a collection of small nerve cell bodies. I will only draw two, but you understand that there are many more. This is for the diagram only. If you draw the rest of this nerve, you need to go down and point out the interesting features of the hypothalamus and the posterior part of the pituitary gland here. You can see that these nerve cells start in one place and go down to the posterior pituitary gland through the infundibulum. This is the connection between the hypothalamus and the posterior pituitary gland through nerves. And these nerves are filled with ADH. We've already talked about how this is related to ADH, but now you can see exactly how. ADH is produced in these nerve cells. He sits here and waits for the right moment to be released by these nerves. ADH is a small protein. Little squirrel. It consists of 9 amino acids. It's actually very small. So this is ADH. 9 amino acids. So it's a very small hormone. If we know that this is a hormone of amino acid nature, then we can consider it a hormone of peptide or protein nature and distinguish it from steroid hormones. This is how ADH is produced. In these nerve cells. And the next topic for discussion is how it stands out. We have a small capillary bed here with small arteries and capillaries running together into small venules on this side. Right here. What happens when the trigger signal appears? It's probably better to put it in bold. Let's say red. This is my favorite highlight color. When the trigger is triggered, these nerve cells release ADH. They release all the ADH and throw it out here in this very area where all the capillaries are. Of course, the blood flow will carry all the ADH into the small vein. Now I will draw a venule and a vein. And the hormone is transferred to the rest of the body. This releases ADH from the nerve cells of the supraoptic nucleus. How does it enter the body? This occurs by release into the posterior pituitary gland. The hormone is carried by these small capillaries and venules. I guess the next question to figure out is: what is the trigger? What is the trigger for this little supraoptic core I've drawn here? Let's talk about this. What are the trigger signals that our body uses to know when to release ADH. The main signal is the one that needs to be highlighted, the trigger. Even if you forget everything else, try to remember this. The main signal is high blood concentration. We talk about blood concentration in terms of osmolarity. Let's write it down. Osmolarity. What does the concept of osmolarity mean? You take all the solutes that are in the blood. Absolutely everything: from protein to sodium and potassium. Anything that retains water in the blood vessels. And you add it all up. What will be the total concentration? Let's imagine this in the form of a measuring device. Let's draw a small measuring device. On one side... So, something like that. So, on one side, let's say, 260, and on the other, 320. We mean concentrations. So 280 and 300. That's osmolarity per liter. This is a unit of measurement. So, osmolarity is defined as the number of osmoles in a liter. This is concentration. It is best to stay in this area, here. This is your green zone. Here the body feels comfortable. But if we are here, in this area or here, then the body is not very happy. Let's say we are in the first zone. This means that your body notices that the blood is too dilute. Too divorced. And in this area, your body notices that it is too salty. The body signals that the blood is too salty. In this case, if you have, as I said, a measuring device, and if the needle hits this area, then the trigger signal will go off to highlight the ADH. This is the first trigger we can talk about. Why don't I go back and add this to the diagram? I'll put this on the diagram. Clearly we are seeing one of the trigger signals. Let's imagine that there is a small nerve cell here. Here in this place. I'll draw it this way on purpose because we don't know where these little osmoreceptors are. We know they work great, but we don't know exactly where they are. Here's my little diagram that I drew. Now you guessed it: if the osmoreceptors tell us that we are in this zone, then there is a problem. Why don't I get ahead of myself and call it an osmoreceptor? Osmoreceptor. My osmoreceptor is set up to tell me that the salt concentration is too high, which is one of the signals that triggers the release of ADH. What is the second trigger? What is another reason that promotes the release of ADH? Low blood volume. Think about this for a second. How does your body know that your blood volume is low? Let's get back to basics. Let's return to the heart. I'll start this way because I always think about it this way. It’s very simple: what goes into the heart and what comes out of the heart? We know we have blood vessels. Large vessels, such as large veins, that carry blood to the heart. We have the superior and inferior vena cava. This is the superior vena cava - the large vein, and this is the inferior vena cava. There are not only large veins, but these two are an example of large ones. We also have a right atrium. We have a couple of points here that are in the blood vessels where small nerves end. Nerves ending in these places will recognize the moment when blood volume becomes low. Because, remember, the venous system... Let me remind you of what we discussed a long time ago. The venous system becomes a large-volume system. If a decrease in volume ever occurs, this will be one of the most suitable points to determine this moment. Information appears in the walls: nerve fibers will determine that the walls of the vessels will be less stretched. They will wonder, “Why are we less stretched?” And the answer will be: because the blood volume has become smaller. When they are less stretched, they will send a signal and say, “Something is happening. We have less blood volume, probably the brain should know about this.” This way the signal is sent to the brain. It can be depicted like this. Let's put a little receptor here. Next we go down; here the low volume is determined through these... through these receptors in the large veins and in the right atrium. Fine. What is the other trigger? You see that there are many signals. I post one by one. Let's put another trigger signal here. What is another reason for the release of ADH? This could be a decrease in blood pressure. We now know that veins tell us a lot of information about volume. If we go even further, we learn that arteries can also tell us about volume. Remember from the other video where we talked about baroreceptors that they are a great way to get information about blood pressure. I'll draw some baroreceptors. Baroreceptors refer only to pressure receptors. We have baroreceptors here in the aortic arch. There are also baroreceptors in the carotid sinuses on both sides. These baroreceptors will recognize when blood pressure is low. They will send a signal up to the brain to say, “We have a problem again. Our blood pressure is low." This is another signal to the brain. Let's draw it here. Like this. Something like this. This will be a signal... a signal of low... Let's write it down here: low pressure. Now we have signals for high osmolarity, low volume, low pressure. Can we remember any other signals? I remembered another one - angiotensin 2. Angiotensin 2 Remember, angiotensin 2 is part of the whole renin-angiotensin system. I will write: angiotensin-aldosterone system, in other words. Angiotensin 2 will be another trigger. Let's imagine a blood vessel and the nerve located next to it. The trigger will start the angiotensin molecule, consisting of 8 small amino acids. It will serve as a signal to this nerve, which, in turn, will let the body, or rather the brain, know that the pressure is low. This is another signal. Let's draw it here on our diagram. Another signal could be something like this. Right here. The placement I chose is actually arbitrary, but the point is that angiotensin 2 also has an effect in the brain. This little molecule will let the brain know that even the kidneys are trying to do something about your blood pressure. It would be great if the brain participated in the release of ADH if necessary. These are the different trigger signals. As I said at the beginning, the main signal related to ADH that you need to remember is the osmoreceptor. He is truly the most important, everything else is secondary to him. This is definitely the main function of ADH. Subtitles by the Amara.org community
The blood supply to the thyroid gland ensures the smooth functioning of the organ. The thyroid gland needs a constant supply of nutrients; subsequently, stimulated hormones are distributed throughout the body through the bloodstream. Blood enters the thyroid gland simultaneously through 4 arteries. The rate of blood flow is 5 milliliters per 1 gram of tissue, so surgical intervention is accompanied by great risks (damage to the bloodstream, opening of internal bleeding).
The thyroid gland is localized along the anterior wall of the cervical spine, curved lobes seem to cover the organs of the neck (trachea, larynx). The shape of the organ resembles a butterfly (shield); the lobes of the gland are connected by an isthmus. In the absence of an isthmus, the halves of the gland fit tightly (to each other). 35-40% of people are diagnosed with a well-developed pyramidal lobe. The apex of the “pyramid” can reach the laryngeal notch, or less often the hyoid bone.
The weight of the gland in a healthy adult varies between 20-35 grams. Hormones produced by the thyroid gland are involved in complex chemical reactions that occur in the human body.
Externally, the thyroid gland is protected by a fibrous capsule. At the stage of intrauterine development, fibrous plates fuse with the parenchyma of the organ, and as a result of processes penetrating deep into the body, lobar division of the gland occurs. In the middle section of the parenchyma, connecting layers are formed, teeming with small capillary vessels and nerve endings.
During adolescence, the glands of the endocrine system sharply increase in volume; With age, the iron decreases in size. The growth of the organ depends on the intensity of the bloodstream.
Blood supply to the thyroid gland
Blood enters the cavity of the thyroid gland through the lower and upper paired arteries; less often, the hollow “lowest” artery is involved in the blood supply system. A volume of blood passes through the gland tissue in a single period of time equal to the throughput of the brain. The intensity of blood supply depends on the functional activity of the body's endocrine system.
The superior thyroid artery, following from the carotid artery, moves to the area of the carotid triangle. A blood channel is attached to the apex of the thyroid gland. And already inside the organ, the vessels are divided into independent branches.
The posterior branch runs along the posterior wall of the thyroid gland and helps fill the tissues with blood. At a conventional point, the blood channel connects with the branch leaving the inferior thyroid artery.
The posterior branch, originating from the superior thyroid artery, connects with the arteries of the neck organs (air canals, esophagus).
The anterior branch is somewhat larger than its counterpart running along the posterior wall of the gland. The blood supply wire runs along the anterior wall, at the upper point of the area connecting the lobes, and connects with a similar branch belonging to the inferior artery of the thyroid gland. The superior arterial branch predominantly supplies blood to the anterior cavity of the gland.
The inferior thyroid artery arises from the subclavian artery. Based on its function, it can be noted that it pumps 20-25% more blood than its “sister” located above. At the branching stage, the artery located in the lower part of the organ is transformed into several branches, mainly supplying blood to the posterior surface of the gland. Along the path of the artery lies the laryngeal nerve and the parathyroid glands, with which it intersects.
In the case of surgery, there is a high probability of damage to a nerve or artery, which leads to partial paralysis of the laryngeal muscles.
Inferior unpaired thyroid artery
The inferior azygos thyroid artery (lowest) is found in 10-12% of people. It begins at the aortic arch and runs along the anterior wall of the pretracheal space. Less commonly, the artery branches off from the common carotid and inferior thyroid. The artery approaches the organ from below and exclusively supplies blood to the “island” connecting the lobes of the thyroid gland.
The paired arteries of the thyroid gland become fundamental to a branched circulatory network, which plays a key role in supplying blood to the organs of the neck and head.
The bloodstream of the thyroid gland is conventionally classified into:
- Intraorgan.
- Extraorganic.
Damage to blood channels becomes the main cause of internal bleeding.
Innervation
The innervation of the thyroid gland is a collection of nerve cells.
The organ is literally permeated with fibers of nerve endings of the parasympathetic and sympathetic systems. The innervation of the autonomic nervous system is driven by the vagus nerves; The sympathetic system is “powered” with the help of nodes located in the neck and forms a tight corset of thyroid vessels.
The innervation effect of nerve fibers, the impact of nerve impulses on the functioning of the thyroid follicles is minimal.
