 Hello everyone welcome back to another session in dentistry and what today we have a very interesting topic in human anatomy that is triangles of the neck the topic is very important for exam point of view it is very frequently asked short note short essay or a long essay because we have a big anterior and posterior triangles so the triangles of the neck could be a long essay or it could be anterior triangle or posterior triangle could be a short essay and the individual triangles such as digastric triangle and a very important carotid triangle or could be a muscular triangle occipital or any individual triangle could be a short note so studying triangles of neck is very easy only thing you need to understand the anatomy so you can easily make out the boundaries and the content of this individual triangle so let us learn the triangles of the neck so before moving on to the anterior and posterior triangles we need to learn some anatomical landmarks and structures so it will be very easy to understand the boundaries of the individual and anterior and posterior triangle so the structures are we need to learn three bonds four muscles and two imaginary lines so the muscles are the trapezius muscle which is present at the back of the neck and the sternocleinomastoid which is starting from the clavicle and ending to mastoid and occipital bone and the omohired muscle which is starting from the hired bone which is crossing the sternocleinomastoid which has two bellies that is a superior belly which is superior omohired and this is inferior omohired and the last muscle is digastric muscle which has two bellies again but which is known as anterior digastric and posterior digastric so these are the four muscles which divides the lateral side of neck into various triangles and the bones are one is mandible that is lower border of mandible the second one is hyoid bone and third one is clavicle okay so the muscles are trapezius sternocleinomastoid omohired digastric bones are mandible lower border of mandible hyoid bone and clavicle and two imaginary lines the first line is the anterior medial line that is the anterior part of the neck line and the second line is a line joining from the ankle of mandible to the mastoid process this extension of this lower border of mandible so here it is angle of mandible and from here to mastoid process that is an imaginary line okay now let's see the lateral side of neck so lateral side of neck the anterior lateral side it looks like a quadrilateral shape looks like a quadrilateral shape okay with four boundaries okay so these four boundaries are the superior boundary so this boundary is the base of the mandible and a line continued from the angle of mandible to the mastoid process so this is the base of the mandible and line continuing from angle of mandible to the mastoid process this is the superior boundary and the inferior boundary is the upper border of clavicle so this is the inferior boundary so I'm talking about this quadrilateral area okay so this is a inferior boundary and the anteriorly by the anterior medial line this is the anterior medial line okay the anterior medial line this is the same structure I just redrawn here with more detailing the quadrilateral shape the superior border inferior border anterior border and the posterior border is the anterior part of trapezius muscle the anterior margin of trapezius muscle okay so this will be the quadrilateral area okay the quadrilateral area which has a superior border that is a base of the mandible and a line joining from angle of mandible to mastoid process anterior medial line upper border of clavicle and the anterior margin of trapezius line so why it is important because this quadrilateral area is divided by the sternocleidomastoid muscle okay so it is dividing the sternocleidomastoid muscle this area and it is dividing this quadrilateral shape into two triangles okay so you can see one triangle is here like this with base at the superior border and another triangle is here base is here okay so it is opposite one is this format and another one is this format so the diagonal line or the separating line is sternocleidomastoid so this muscle separating the quadrilateral area into anterior triangle and posterior triangle so this is a posterior triangle and this is the anterior triangle okay clear with this so this was a quadrilateral area this was a quadrilateral area and it is divided into anterior triangle and posterior triangle like this this is the anterior triangle and this is the posterior triangle now let's see the anterior and posterior triangle the anterior triangle and posterior triangle now let's learn the anterior triangle boundaries okay anterior triangle boundaries the anterior part so this is a anterior triangle okay so anterior part is anterior, the medial line is anterior part and posteriorly by the anterior margin of sternocleidomastoid. This is a sternocleidomastoid, this is anterior margin, this is a posterior margin. So, anteriorly by the anterior medial line, posteriorly by the anterior margin of sternocleidomastoid and its apex is at the manuprium sternum. So, this is the apex, this is the manuprium sternum where the clavicle meets the sternum. So, this point is the apex, that is the manuprium sternum and its base is the inferior border of mandible. So, inferior border of mandible is the base, anterior border is anterior medial line, posterior border is anterior margin of sternocleidomastoid and apex is manuprium sternum. So, this anterior triangle is further divided into digastric triangle, carotid triangle, muscular triangle and submental triangle. That is anterior triangle is further divided into submental carotid, digastric and muscular. So, the digastric muscles are dividing the space, the omohide muscle is dividing the space and making it into four further individual triangles. We are talking about anterior triangle. Now, let us see we will come to one by one later. Now, let us see the posterior triangle. So, posterior triangle, posterior triangle which has having boundaries. So, what are the boundaries of posterior triangle? Posterior triangle anteriorly by sternocleidomastoid. So, this is the posterior triangle, like this. So, anteriorly by the posterior border of sternocleidomastoid, posteriorly by the anterior border of trapezius and the base or the inferior border is the middle third of clavicle. So, this is the middle third of clavicle that is the inferior border or base of this triangle. And where is the apex? The apex is between the attachment of sternocleidomastoid and trapezius to the occipit and it is often blended. So, sometimes it is making this triangle equadrilateral shape. So, this apex is sometimes blended and making it equadrilateral shape. Quadrilateral means four sides. So, it is not very pointed. This sternocleidomastoid and this trapezius it is blended, not very pointed one. So, making the triangle equadrilateral shape. So, that is a posterior triangle. Posterior triangle boundaries are the posterior border of sternocleidomastoid anteriorly posteriorly by the posterior border of trapezius and inferior your base is the middle third of clavicle and the apex is the two muscles that is sternocleidomastoid and trapezius at the occipit and it is blended to make the triangle equadrilateral shape. And the floor of the mouth. The floor of the mouth is having pre-vertible fascia and some muscles such as spleenis, capitals, levator, scapula and scaliness muscle. And the roof of the posterior triangle is formed by investing layer of deep cervical fascia. Okay roof and floor you know this if it is a triangle if it is a triangle this is a floor and we should say this is a roof okay roof. So, you need to visualize in a three dimensional format it has a floor and roof okay. So, we will start with the first triangle that is digastric triangle okay. The digastric triangle boundaries the abo the base of the mandible and its projection into the mastoid process. So, this is a digastric triangle this pink one which is between the anterior belly and posterior belly of digastric and the hyoid bone here the mandible and the line joining from angle of mandible to mastoid okay. So, abo the angle or the base of the mandible and its projection to mastoid process and the posterior inferiorly by the posterior belly of digastric anterior inferiorly the anterior belly of digastric okay and the floor is formed by mylohyoid and hyoglossus muscle and which is also known as submandibular triangle because it contains submandibular gland and there is the contents include submental mylohyoid arteries and nerves and along with submandibular gland and also submandibular lymph nodes are present and the external carotid artery which is moving deep to stylohyoid and also internal carotid artery internal jugular vein vagus nerve also lies deep to this external carotid artery and also styloglossus stylofaryngeus and also glosopharyngeal nerve is present. So, those are the contents of digastric triangle or submandibular triangle its boundaries are anterior inferiorly and posterior inferiorly by the anterior belly and posterior belly of digastric and the base by the clover border of mandible. So, that is about digastric triangle or submandibular triangle. Now, we have submental triangle okay. Submental triangle is demarcated by the anterior belly of both digastric muscle its apex is at chin okay. So, here it is apex it is like this apex is a chin and the base is a body of the hyoid bone okay this is hyoid bone. So, base is here. So, it is like base is here in this format here is the chin and this is the base hyoid bone this is the chin. So, what would be the other boundaries? So, it will be the digastric muscle and the anterior midline okay. So, the floor is formed by mylohyoid muscles and the content includes lymph nodes and small veins. So, this is a very small triangle that is submental triangle which is starting from the base is the hyoid bone and apex is a chin. So, the boundaries are anterior midline anterior belly of digastric and the hyoid bone and apex is a chin okay and the content includes lymph nodes and small veins which unite to form anterior jugular vein okay that is about submental triangle. Next we have the muscular triangle it is mainly composed of muscles that is why it got this name muscular triangle. So, muscular triangle. So, what would be the boundaries of muscular triangle? So, muscular triangle again anteriorly by the anterior anterior midline just like the submental triangle and posterior superiorly this is the posterior border which is this one omohide muscle that is superior belly of omohide this is posterior superior and inferior posterior it is by the anterior margin of sternoclein. So, muscular triangle the boundaries are sternocleidomastoid and superior sternocleidomastoid and superior belly of omohide and anterior border of anterior midline okay which is known as muscular triangle because it consists of lots of muscles such as omohide sternohyoid sternothyroid and thyroid. All muscles are intrahyoid muscles intrahyoid muscles means muscles which is present below the hyoid bone this is a hyoid bone just present below the hyoid bone and all are present in this triangle which is that is why this triangle got that peculiar name muscular triangle. So, whenever you are explaining about or writing the answer for triangle without diagram you won't get any mugs. So, you need to draw not very detailed diagram at least you can mention it in triangular format with boundaries and once you draw the picture with four muscles and the three bonds it is very easy to find out the boundaries even if you don't remember the exact boundaries after drawing the picture you will easily understand the boundaries where exactly the floor comes the roof comes and the anterior and anterior posterior and inferior border. So, such things it is very easy when you draw a picture of the triangle. So, that is about muscular triangle now we are moving on to a very important triangle that is carotid triangle. So, this is a carotid triangle. So, carotid triangle which is bounded our boundaries are posteriorly by so carotid triangle is in this format posteriorly by the anterior border of sternocleidomastoid anterior inferiorly by the superior belly of omohyroid and superiorly by the stylohyoid and posterior belly of digastric. So, here both the muscles are present one is digastric that is posterior belly of digastric and stylohyoid muscle. Stylohyoid muscles which starting from hyoid bone to the styloid process. So, that is a posterior superior border and anterior inferior is the superior belly of omohyroid. So, carotid triangle is important because it has carotid sheath. Carotid sheath we have already learned. So, components of carotid sheets are external carotid artery, internal carotid artery, internal jugular vein and vagus nerve all are present in carotid triangle. So, it is very important triangle because it contains main arteries. So, along with external carotid artery its branches such as superior thyroid artery, then lingual artery, facial artery and occipital artery all are present here. And many of the veins such as superior thyroid, lingual, facial, ascending, pharyngeal and occipital veins also present along with hypoglossal nerve. So, that is about carotid triangle and we finish the anterior triangles. Okay, anterior triangle of neck that is submental carotid digastric and muscular. This is submental from hyoid bone to chin with anterior belly of digastric and the anterior medial line. Carotid is sternocleidomastoid superior belly of omohyroid and posterior belly of digastric and stylohyoid. Then digastric anterior and posterior belly of digastric and the floor of the lower border of mandible and lying to mastoid process. Muscular superior belly of omohyroid sternocleidomastoid and anterior midline and the structures present in this triangles. Now, we are moving on to the posterior triangle. Posterior triangle are this format okay. So, posterior triangle boundaries we already discussed the middle part of clavicle posterior border of sternocleidomastoid anterior border of trapezius and joining here it might be a little quadrilateral in shape. The posterior triangle is divided into two by the inferior belly of omohyroid into a larger and upper occipital triangle and the smaller and lower supraclavicular triangle. This is supraclavicular triangle because it is present above the clavicle. Supra means above the clavicle. Supra means above we have learned this is intrahyoid muscles which is present in the muscular triangle which is below the hyoid bone okay. This is supraclavicular muscle this is occipital triangle. Now, let us learn the occipital triangle. Oxypital triangle the boundaries are sternocleidomastoid trapezius inferior belly of omohyroid okay. So, it will be somewhat like this and occipital triangle which consists of the most important nerve that is spinal accessory nerve which supplies all these muscles trapezius muscle and sternocleidomastoid all muscles supplied by the spinal accessory nerve spinal accessory nerve okay. That is occipital triangle and it was also having supraclavicular nerves and the next one is supraclavicular triangle okay. Its boundaries are the base is clavicle and posterior border of sternocleidomastoid and inferior belly of omohyroid. So, supraclavicular triangle it has superficial and deep fascia and platysma which is crossing the supraclavicular nerves and it is also having subclavian vein and subclavian artery subclavian artery. So, this is also known as subclavian triangle because it is having subclavian artery and subclavian vein and also brachial plexus okay. So, three things subclavian artery and vein and brachial plexus all are present in supraclavicular triangle and also it has external jugular vein okay. So, these are the triangles of neck. So, I will recap it we have four muscles three bones and two lines trapezius sternocleidomastoid digastric anterior and posterior belly and superior and inferior omohyroid belly of omohyroid mandible hyoid bone clavicle the anterior midline and the line joining from lower border of mandible to mastoid process. So, anteriorly we have four triangles submental carotid digastric and muscular posteriorly we have occipital and supraclavicular. So, this is a digastric which has boundaries anterior and posterior belly of digastric lower border of mandible carotid which is having sternocleidomastoid superior belly of omohyroid stylohyoid and posterior belly of digastric. Digastric then we have submental anterior midline then the hyoid bone and anteriorly of digastric. Muscular triangle anterior midline superior belly of omohyroid and sternocleidomastoid and its content okay carotid triangle is very very important because it has carotid sheath and other structures posterior triangle is again it is somewhat quadrilateral shape as the apex is not very much pointed the fibers are blended that is sternocleidot and trapezius muscle fibers are blended but the base is the middle part of clavicle. So, it is dividing into a bigger and larger upper occipital triangle and lower supraclavicular triangle which is also known as subclavian triangle because it has subclavian artery subclavian vein external jugular vein this is occipital triangle which is the most important nerve which is a spinal accessorina which supplies all these muscles that is a posterior triangle. So, this question might come as I mentioned it has it can come as a bigger longer essay you need to draw the entire picture explain all the triangles and its contents you can make a tabular column and write about its boundaries then you could expect anterior triangle or posterior triangle as a short note or you could expect short note the carotid triangle is very important. So, the main point is make a quadrilateral shape divide into two then change into various triangles this is a submental triangle digastric triangle carotid triangle muscular triangle then again divide this occipital triangle and subclavian or supraclavicular triangle. So, understanding the anatomy is very important to write the boundaries the borders very precisely because you may you might get confused very easily only thing is you need to understand the anterior and posterior border of digastric this is superior and this is the inferior billy of omohide rest all is very easy just two other muscles sternocleidomastoid and trapezius. So, that is about triangles of the neck hope you understood this. So, whenever you are writing this question always draw the picture okay I will come up with a new topic in anatomy thank you.