Superficial Blood Vessels of the Head and Neck Flashcards
Describe the arteries that supply the head and neck and their branches. (not external carotid ones yet)
On the right brachiocephalic trunk splits into the subclavian and common carotid arteries. The vertebral, internal thoracic and thyrocervical arteries all arise from the subclavian artery in the base of the neck. There are no branches off the common carotid artery in the neck until it bifurcates into the external carotid artery. There are no branches off the internal carotid artery either in the neck.
What three arteries branch off the thyrocervical trunk?
Ascending and transverse cervical supply the neck. Suprascapular supplies the shoulder and inferior thyroid supplies the lower pole of the thyroid gland.
What is the path of the vertebral arteries and what structure does it form with the internal carotid artery?
Vertebral arteries arise from the subclavian artery through the transverse foramina of the cervical vertebrae and after this through the foramen magnum, they supply the brain along with the internal carotid arteries which enter the brain through the carotid canal. These two then unite to form the circle of willis.
Where does the common carotid bifurcate and what important structure are present here?
The common carotid bifurcates at about the level of the superior border of the thyroid cartilage. Carotid sinus is a swelling at the region of this bifurcation. This is the location of the baroreceptors for detecting changes in arterial BP. The carotid body are peripheral chemoreceptors that detect changes in O2.
Which sensory nerve supplies the carotid sinus?
The glossopharyngeal nerve is the sensory efferent fibre from the carotid sinus.
What pathology commonly occurs at the bifurcation of the common carotid?
Carotid artery atheroma commonly occurs at the bifurcation of the carotid artery. Causes narrowing of the artery, rupture of the clot can cause an embolus to travel to the brain causing a TIA (transient ischaemic attack) or stroke.
What are the boundaries of the carotid triangle and what does it contain?
Superior boundary – posterior bell of diagastric
Lateral boundary – anterior/medial border of the sternocleidomastoid
Medial boundary – superior belly of the omohyoid muscle. This triangle contains the internal jugular vein and the bifurcation of the common carotid.
What is the clinical importance of the carotid triangle?
This triangle is important for surgical approach to the carotid arteries or internal jugular vein. Can also access vagus and hypoglossal nerves. Finally, can feel the carotid pulse and give a carotid sinus massage (used in supraventricular tachycardia but must first listen for Bruits).
What are the branches of the external carotid artery?
Superior thyroid, lingual, facial, ascending pharyngeal, occipital and posterior auricular.
Terminal branches – superficial temporal and maxillary.
Which arteries feed the scalp and where do they lie?
Scalp arteries run in the dense connective tissue. The main ones are superficial temporal, posterior auricular and occipital arteries form the external carotid and the supra-orbital and supratrochlear from the internal carotid artery.
What is the clinical correlate about scalp arteries?
Clinical relevance of blood supply to the scalp
Walls of arteries are closely attached to the connective tissue limits constriction so can get profuse bleeding. Numerous anastomoses, deep lacerations involving aponeurosis cause profuse bleeding because of opposing pull of occiptofrontalis. Note blood supply to the skull mostly middle meningeal artery so loss of scalp does not lead to bone necrosis.
Describe the venous drainage of the face and scalp?
Superficial veins generally accompany the arteries (superficial temporal, occipital and posterior auricular. Supraorbital and supratrochlear veins unite at medial angle of eye to form angular veins which drain into the facial vein. Some deep parts of scalp in temporal have veins which drain into the pterygoid venous plexus.
What is the clinical risk of infection in the scalp?
Infection risk – connection between venous drainage of scalp and dural venous sinuses. The scalp veins connect to diploic veins through several emissary veins and thus to dural venous sinuses. Emissary veins are valve less so infection can spread to the cranial cavity and affect meninges.
What arteries supply the dura and skull?
Brain covered by double layer of dura matter. Blood supply to the skull comes from the middle meningeal artery from the maxillary artery. It splits into two the anterior and posterior branch, the anterior passes under the pterion region – extradural haemorrhage.
How do you gain access to the brain without destroying the skull’s blood supply?
Craniotomy – gain access to cranial cavity. Bone and scalp reflected inferiorly to preserve blood supply.
What are the superficial arteries of the face and what is the important branch from the maxillary artery?
Supra-orbital, supratrochlear, transverse facial, angular, lateral nasal, maxillary, superior and inferior labial and the facial artery. Again, these all arise from the external carotid artery except the supra-orbital and supratrochlear arteries which are from the ophthalmic artery from the internal carotid artery.
Branches of maxillary artery – lots but we only need to know middle meningeal.
What are dural venous sinuses - give names?
Endothelium lined spaces between periosteal and meningeal layers of the dura. Form at dural septae and receive blood from large veins draining the brain.
Superior sagittal sinus, inferior sagittal sinus, cavernous sinus, sigmoid sinus and transverse sinus. They all eventually drain into the sigmoid sinus which continues as the internal jugular vein leaving the skull through the jugular foramina.
What are the venous plexuses?
The venous plexuses – cavernous sinus and pterygoid venous plexus. The Cavernous sinuses has internal carotid artery and a number of cranial nerves in surrounded by many thin walled veins on the upper surface of the sphenoid bone.
What is the clinical relevance of the venous sinuses?
Facial veins can drain backwards into this sinus because veins in face are valve less – blood can flow in either direction. As a result infection can be taken back deep into the brain. This creates what we know as the danger triangle of face of infections.
Describe the path of the internal and external jugular veins?
External jugular vein courses superficially over the sternocleidomastoid, Internal jugular vein is deep to the SCM. The internal jugular vein lies underneath the sternocleidomastoid muscle, lateral to the common carotid artery.
How do you measure JVP?
Internal jugular vein (especially on right side) is better for JVP as it resembles that of the atria better. Cannot palpate this. Can only look for pulsations through the muscle – patient lies at 45 degrees look at how high they come from the sternal angle.
What does the sternal angle/angle of louis mark
Sternal Angle or angle of louis marks the beginning and ending of the aortic arch as well as the level that the trachea bifurcates. It is also in line with the articulation between T4 and T5.
