 Dr. Sanjay Sanyal, professor department chair. So this is going to be a demonstration of the strap muscles of the neck That is the infrahoid and the suprahoid muscles and the branches the answer survive callus We supply them and a few of the triangles formed by these strap muscles. This is a supine cadaver There's the right side of the neck. I'm standing on the right side the camera person is also on the right side So first let's take a look at this muscle here. This is the sternocleidomastoid We have cut it here the distal portion is here the proximal portion is here Let's take a look at this triangle. This is carotid triangle What are the boundaries of the carotid triangle? The posterior boundaries formed by the anti-border of the sternocleidomastoid the inferior boundaries formed by the superior belly of the Omohyde and the superior boundary is formed by this muscle here This is the posterior belly of digastric and under that this muscle here This is the stylohyde muscle. So therefore this triangle that we see here is the carotid triangle And as you would have already guessed it contains the common carotid artery and its bifurcation into The internal and the external carotid artery it contains the internal jugular vein and the vagus nerve It also contains the carotid sinus and the carotid body, which is located in the bifurcation Roof of this triangle is the platysma and the floor of the triangle is the muscular part of the tracheal fascia The next triangle that we going to see is this triangle. So let's take a look at the boundaries in the midline We have an imaginary line in the middle of the neck Postero superiorly we have this line. This is again the superior belly of the Omohyde on the right side and Postero inferiorly we have the continuation of the sternocleomastoid which had been present here It would have been like this. So therefore we can see another triangle here This is the omotracheal or the muscular triangle again The roof of this triangle is formed by the platysma and the floor of the triangle is formed by the visceral part of the Pre tracheal fascia. The contents of this triangle are number one this structure here The anterior jugular vein and the jugular venous arch and we can see that here So I'm going to reflect this up. Next content is Infra-hyoid strap muscles which are incidentally covered by the muscular part of pre tracheal fascia And the next content is thyroid gland, which is located here. Having mentioned that now Let's take a look at this strap muscles here. Neck muscles are divided into two groups. This is the hyoid bone Muscles below the hyoid are called Infra-hyoid muscles and the muscles above the hyoid are called the suprahyoid muscles So let's take a look at this infra-hyoid muscles first. This is inferior belly of the Omohyde It was cut here because during the process of embalming they cut this This inferior belly of the Omohyde takes origin from this scapula and it goes up like this under the sternocleomastoid It becomes tenderness and we can see the intermediate tendon here And the intermediate tendon is attached by means of facial slaying which also goes under the sternocleomastoid and gets attached to the clavicle Therefore at the intermediate tendon the muscle changes direction and thereafter we have the superior belly of the Omohyde Which is attached to the high bone. So this is one infra-hyoid strap muscle Then we have the next strap muscle that we can see here. That is this one here This is the sternohyoid muscle It extends from the posterior surface of the manor brim sterni and it goes up and gets attached to the hyoid bone Once we reflect this then we see the next muscle under that. This is the sternohyroid This also takes attachment from the inner surface of the manor brim sterni and it goes up And it gets attached to the oblique line of the thyroid cartilage and we can see that line here so this is the sternohyroid and Exactly from the place where this muscle gets inserted We have the next muscle starting up and we can see that muscle here. I'm going to lift it up here This is the thyrohyoid muscle which extends from the oblique line of the thyroid cartilage and gets attached to the hyoid bone So therefore the infra-hyoid strap muscles are Omohyoid, sternohyoid, sternothyroid and the thyrohyoid. What is the function of these infra-hyoid strap muscles? They pull down the hyoid bone or to stabilize it to enable the suprahyoid muscles to work Now let's come to the suprahyoid. We can see only a few of them. We can see this muscle here This is the posterior belly of digastric. Digastric means it has got two bellies The posterior belly takes origin from the mastoid process Again, it becomes an intermediate tendon here in the region of the hyoid bone and it is attached to the hyoid bone by means of a facial sling and after that we have the anterior belly of digastric, which is this one here Which gets attached to the inner surface of the mandible and this forms the boundaries of the digastric or the mandibular triangle Just under the posterior belly of digastric. We have this muscle This is the stylohyoid muscle which also forms the posterior boundary of the digastric triangle This extends from the stylohyoid process to the hyoid bone and at the place where it is getting inserted on the hyoid bone The tendon splits to allow the tendon intermediate tendon of the digastric to pass through What is not visible here in this dissection under this anterior belly of digastric We have the mylohyoid and under that will be the geniohyoid. So these are the suprahyoid muscles What are the functions of the suprahyoid strap muscles? Number one, they pull up the hyoid bone and that is necessary during swallowing or deglutition More specifically during the second phase of swallowing pharyngeal phase of swallowing and the other function of the suprahyoid strap muscles is to depress the mandible When it has been fixed by the infrared strap muscles So therefore they also act as accessory muscles of mastication that brings me to the nerve supply of these Neck muscles. We can see this nerve here This is the hypoglossal nerve It comes from the hypoglossal canal and it crosses in front of the internal and external carotid and it enters the tongue By going deep to the mylohyoid muscle superficial to the hyoglossus and here it gives a branch We can see that branch here. This is the branch to the hyrohyoid and deeper inside It gives a branch to the geniohyde These two branches to the geniohyde and the thyroid strictly speaking are not from the hypoglossal nerve They are coming from the C1 C2 loop. That is the superior limb of answers are vicalis and we can see clearly the branch going to the thyroid So this is the supply to the geniohyde and the thyroid Accompanying this again the hypoglossal nerve We had the rest of the superior limb of answers are vicalis which comes from the C1 C2 loop and we can see it is Applying the omohide. So this is the superior limb of answers are vicalis. What is not visible is We'll have another loop which comes from the C2 and C3 and which forms the descending limb of answers are vicalis or the descending survey callus and that forms a loop of answers are vicalis and That supplies the rest of the strap muscles Namely the sternohyoid the sternothyroid and the Omohyoid and we can see the nerve supply to the omohyroid also here the posterior bilia of digastric and the stylohyoid They are supplied by branches of the facial nerve So therefore these are derived from the second pharyngeal arch the anterior bilia of digastric and the mylohyoid is supplied by CN5V3 mandibular nerve. So therefore they are derived from the first pharyngeal arch So these are the nerve supply of the hyphrahyde and the suprahyde muscles and we have already seen how these Muscles form the triangles of the neck before I conclude just to complete the picture I will draw your attention again to the omohyoid muscle here inferior belly of the omohyoid divides the lateral cervical region into a lower portion which is referred to as the subclavian triangle and an upper portion Which is referred to as the occipital triangle Subclavian triangle contains the subclavian artery and we can see the subclavian artery here That's why it is called the subclavian triangle It is also referred to as omoclavicular triangle and the superior portion of the triangle is referred to as the occipital triangle Because it contains the occipital artery, which we can see here So therefore this inferior belly of omohyro also helps to divide the lateral cervical region into two triangles So these are the triangles and the synphrahyde and the suprahyde muscles that I wanted to show you Thank you very much for watching. Dr. Sanjay Sanyal Sanyal, Mr. Kedl, Kumbh Batch is the camera person If you have any questions or comments, please put them in the comment section below. Have a nice day