What are the bifurcations of the brachiocephalic trunk?
Right subclavian and right common carotid arteries
What three branches does the subclavian artery give rise to?
Internal thoracic, vertebral artery and thyrocervical trunk
What four branches does the thyrocervical trunk give rise to?
Ascending cervical, transverse cervical, inferior thyroid and suprascapular
What are the bifurcations of the common carotid artery?
Internal and external carotid arteries
What are the bifurcations of the external carotid artery?
Maxillary and superficial temporal arteries
The external carotid artery gives rise to six branches in the neck.
What are these branches?
Posterior auricular, lingual, occipital, ascending pharyngeal, facial and superior thyroid
What is the blood supply to the thyroid gland?
Inferior thyroid artery-thyrocervical trunk-subclavian artery
Superior thyroid artery-external carotid artery-common carotid artery
The external carotid artery bifurcates into the superficial temporal and maxillary arteries. Where does this bifurcation take place?
Behind the neck of the mandible within the parotid gland. It is accompanied by the facial nerve and the retromandibular vein
The common carotid artery bifurcates into the internal and external carotid arteries. Where does this bifurcation happen?
At the level of the superior border of the thyroid cartilage
What is the course of the vertebral arteries?
Branch off the subclavian artery, pass through the C1-C6 transverse foramina through the foramen magnum and join to form the basilar artery
How can we distinguish between the internal and external carotid arteries in the neck?
The internal carotid has no branches within the neck
How does the internal carotid artery enter the skull?
Through the carotid canal
Which common carotid artery is longer? And why?
The left common carotid
Because it branches off from the aorta so there is an extra 2cm in the superior mediastinum
How does the facial artery supply the lips?
Courses along the mandible and gives off superior and inferior labial branches supplying the lips
What are the layers of the scalp?
(Dense) connective tissue
Loose connective tissue
What is the blood supply to the scalp?
External carotid (occipital, posterior auricular, superficial temporal)
Internal carotid (supra-orbital, supra-trochlear)
The arteries form many anastomoses
Vessels of the scalp lie in the subcutaneous connective tissue layer.
What is the clinical importance of this?
The walls of the arteries are closely attached to the connective tissue.
This limits constriction, and if an artery is severed there is diffuse bleeding, along with the numerous anastomoses
Why do deep lacerations involving the epicranial aponeurosis cause profuse bleeding?
Because of the opposing pull of the occipitofrontalis muscles
What are the borders of the carotid triangle?
Superior: posterior belly of the digastric
Medial: superior belly of the omohyoid
What can we use the carotid triangle for?
Surgical approach to the carotid arteries and ijv
Accessing the vagus and hypoglossal nerves
Feeling the carotid pulse
What is the course of the common carotid artery?
Known as the carotid line It begins at the sternoclavicular joint
The carotids terminate halfway between the angle of the mandible and the mastoid process of the temporal bone
What two things can be found at the bifurcation of the common carotid artery?
What spinal level is this?
There is a swelling - carotid sinus - baroreceptors for detecting changes in arterial BP Carotid body - peripheral chemoreceptors for detecting arterial pO2
What happens in a carotid massage?
Used to alleviate SVT
Pressure applied in the carotid triangle to mimic an increase in BP, detected by baroreceptors, decreased sympathetic activity to decrease heart rate
Why is the bifurcation of the common carotid artery a common place for atheroma formation?
Turbulent blood flow (heard as a bruit on auscultation)
An embolus can travel upwards to the brain and cause a stroke/TIA
What is the blood supply to the dura and skull?
Mainly by the middle meningeal artery that branches off the maxillary artery.
It divides in to anterior and posterior branches.
The anterior passes beneath the Pterion
What happens in a craniotomy?
To gain access the the cranial cavity, the bone and scalp are reflected inferiorly to preserve blood supply by the middle meningeal artery
What forms the angular vein?
Where is the angular vein formed?
Supra-orbital and supra-trochlear veins unite at the medial angle of the eye to form the angular vein
Name three veins that drain in to the facial vein
Superior and inferior labial
What is the relationship between the SCM and the internal and external jugular veins?
The external jugular vein passes anteriorly to the SCM
The internal jugular vein passes posteriorly to the SCM
Which veins drain in to the common facial vein?
Which vein does the common facial vein drain in to?
Facial and retromandibular
Drains in to the internal jugular
Which vein do the internal and external jugular veins drain in to?
The subclavian vein
How are the veins of the scalp connected to the dural venous sinuses?
What is importance of this?
They are connected by diploid veins of the skull through emissary veins
The emissary veins are valveless.
Infection can spread from the scalp to the cranial cavity and meninges
What is the cavernous sinus?
A plexus of extremely thin-walled veins on the upper surface of the sphenoid bone
What are the contents of the cavernous sinus?
Internal carotid artery, CN 3,4,6, two branches of the trigeminal nerve (ophthalmic and maxillary branches)
How does the facial vein drain in to the cavernous sinus?
How does the facial vein drain in to the pterygoid venous plexus?
At the medial angle of the eye it communicates with the superior ophthalmic vein
By the inferior ophthalmic vein
The cavenous sinus and pterygoid venous plexus are joined.
What is the importance of this?
Infection can spread from the facial vein to the dural venous sinuses
How do we measure jvp?
We use the ijv by having the patient at a 45 degree angle.
We measure the height from the sternal angle plus 5cm