 This is the supine cadaver. We have dissected out the right side of the neck. I'm standing on the right side and the camera person is also on the right side. So let's take a look at the boundaries of the carotid triangle. This is the upper part of the sternocolomastoid. This is the posterior boundary. Entering clearly we have the superior belly of the omohide and superiorly we have this muscle here. This is the posterior belly of digastric and under that we have this muscle. This is the stylohyde muscle. So this is the carotid triangle and as we have already guessed, contents of the carotid triangle will be the carotid sheath which I am going to describe in more detail. The roof of the strangle is formed by the platysma and we can see a remnant of the platysma muscle here and the floor is formed by the muscular part of the pre tracheal fascia that is that component of the pre tracheal fascia which covers the infrahyde muscles. Now let's take a look at the contents and for that I'm going to reflect the sternocolomastoid here and I'm going to reflect the omohide here. So therefore we have completely exposed the carotid triangle and we have also shown the continuity with the infratemporal fossa. So let's take a look at this structure here. This is the internal jugular vein. The internal jugular vein, the carotid artery and the vagus nerve were all enclosed in the carotid sheath and we have completely removed it. The internal jugular vein starts here and we can see the origin of the internal jugular vein right here where my instrument has disappeared. It is a continuation of the sigmoid sinus which comes out through the jugular foremen and we can see there's a dilatation here. This is the superior bulb of the internal jugular vein and there is a valve there, the superior valve of the internal jugular vein. The internal jugular vein descends lateral to the carotid and it continues down and it opens here by combining with the subclavian vein and this union is referred to as the venous angle. So this is the course of the internal jugular vein. This is a conventional sinus venogram to show the continuity of the sigmoid sinus as the internal jugular vein, lateral view and reverse review and this is an MR sinus venogram to show the same thing, a magnetic resonance sinus venogram. Let us now focus on the carotid artery. This is the origin of the carotid artery on the right side. The common carotid artery arises from the bracocephalic trunk. We can see the bracocephalic trunk here. The bracocephalic trunk divides into this, this is the subclavian artery on the right side and this is the common carotid artery. This is a digital suppression angiogram to show the bracocephalic trunk dividing into common carotid and the right subclavian artery. The common carotid artery is situated medial to the internal jugular vein and we can see that here. This segment of the common carotid artery is badly damaged because they had used this portion for embomic purposes and therefore this portion has been completely lacerated. This is the other continuation of the common carotid artery. The common carotid artery then divides into an internal carotid and external carotid and we can see that this division is taking place at the level of the superior thyroid notch. We can identify the internal carotid by means of its dilatation and this is the carotid sinus. The carotid sinus acts as a baroreceptor. It helps to regulate the systemic blood pressure and after that if we trace the internal carotid artery we see that it disappears. It goes into the carotid canal and it enters into the cranial cavity and forms an anterior circulation of the brain. This is a three-time traditional camouflage SPGR MRI angiogram to show the anterior and posterior cerebral circulation. The next branch is this one here. This is the external carotid. The word internal and external refers not to the location as in the neck but by the virtue of the fact that the external carotid artery supplies all the structures outside the skull and internal carotid artery supplies all the structures inside the cranial cavity with some exceptions. But here it is looking, the internal carotid artery is lateral and the external carotid artery is medial. At the bifurcation in this connective tissue there is located the carotid body which we cannot see because it's very small and that carotid body acts as a peripheral chemoreceptor. Both carotid sinus and carotid body are supplied by branches from the glosopharyngeal and that is known as a carotid sinus nerve. The peripheral chemoreceptors help to maintain the arterial PAO2 oxygen saturation at sea level. Thank you very much for watching. Don't send your sunny out please like and subscribe if you have any questions or comments. Please put them in the comment section below. Have a nice day.