What does the arterial supply of the head and neck arise from?
Branches of the right and left common carotid arteries and vertebral arteries
What arises from the brachiocephalic trunk on the right?
- Common carotid
What do the subclavian arteries give rise to?
- Internal thoracic
- Thyrocervical trunk
- Vertebral arteries
Where does the internal thoracic artery go?
Inside the ribcage
What is the internal thoracic artery commonly used in?
Coronary artery bypass
What does the thyrocervical trunk give rise to?
- Ascending cervical and transverse cervical
- Inferior thyroid
What does the ascending cervical and transverse cervical supply?
What does the suprascapular artery supply?
What does the inferior thyroid supply?
The lower pole of the thyroid gland
What do the vertebral arteries supply?
The posterior neck and posterior parts of the brain
What course does the vertebral artery take from its origin?
It descends through the transverse foramina of the cervical vertebrae (except C7) and enters the subarachnoid space just between the atlas and occipital bone. It then passes jup through the foramen magnum, curving aroudn the medulla, to join the vertebral artery from the other side
What does the vertebral artery eventually form?
The basilar artery
Where does the basilar artery run?
Along the anterior aspect of the brainstem
What branches does the common carotid give off in the neck?
What does the right common carotid artery originate from?
The brachiocephalic artery
Where does the right common carotid artery branch from the brachiocephalic artery?
Behind the right sternoclavicular joint
Where does the left common carotid artery arise from?
The arch of the aorta
What is the result of the differing origins of the right and left common carotid arteries?
The elft common carotid is slightly longer
Where does the left common carotid course before entering the neck?
In the mediastinum, for about 2cm
What is each common carotid artery enclosed within?
A carotid sheath
What is the carotid sheath?
A fascial envelope enclosing and seperating several structures a
What structures lie in the carotid sheath?
- Carotid artery
- Internal jugular vein
- Vagus nerve
- Deep cervical lymph nodes
How does the sheath differ over the carotid artery compared to other areas?
It is thicker
How does the carotid artery lie in the carotid sheath relative to other structures?
Lies medially within the sheath
How does the sheath over the internal jugular vein differ in comparison to other areas?
It is thinner
Where does the internal jugular vein lie in the carotid sheath relative to other structures?
Behind and inbetween vessels
Where is the carotid sheath found, relative to muscles in the area?
Deep to the sternocleidomastoid muscle
What is the carotid sheath derived from?
- The prevertebral layer of cervical fascia posteriorly
- The pretracheal layer anteromedially
- The investing layer anterolaterally
Where does the sympathetic trunk lie relative to the carotid sheath?
Outside the sheath, medially and behind it
Where do the common carotids terminate?
At the upper border of the thyroid cartilage
How do the common carotid arteries terminate?
They divide into the internal and external carotid arteries
What happens to internal carotid at the divison?
It is more bulbous
Why is the internal carotid more bulbous at the division of the common carotids?
Because of the carotid sinus and the carotid body
What is the carotid sinus?
A swelling at the region of bifurcation
What is the function of the carotid sinus?
Location of baroreceptors for detecting changes in arterial BP
What is the clinical relevance of the carotoid sinus?
Rubbing this area firmly, termed a carotid massage, can alleviate supra-ventricular tachycardias
What is the function of the carotid body?
It's where the peripheral chemoreceptors are
What do peripheral chemoreceptors do?
Detect arterial oxygen
Briefly describe the blood and nerve supply of the carotid body
How is the internal carotid artery distinguished from the external?
By a lack of branches in the neck as it ascends to supply intra-cranial structures
How does the internal carotid artery enter the skull?
Through the carotid canal
What is the external carotid artery the major source of?
Blood supply to extra-cranial structures of the head and neck region
What are the branches of the external carotid artery?
- Superficial thyroid
- Ascending pharyngeal
- Posterior auricular
- Superficial temporal
What are the terminal branches of the external carotid artery?
Maxillary and superficial temporal
Where does the external carotid artery divide into its terminal branches?
At a level behind the neck of the mandible, within the substance of the parotid gland
What does the maxillary artery notably give rise to?
The middle meningeal artery
What do many of the branches of the external carotid artery do?
Make a loop at their origin
What is the clinical relevance of the bifurcation of the carotid artery?
It is a common site for atheroma formation
Why is the bifurcation of the carotid artery a common site for atheroma formation?
Because where blood meets the bifurcation, there is turbulence, leading to increased risk of atheroma formation
What does atheroma formation at the bifurcation of the common carotid lead to?
Narrowing (stenosis) of the artery, limiting blood to the brain
What can a rupture of the atheroma at the bifucation of the carotid artery cause?
An embolus to travel to the brain and get lodged in an artery there, leading to TIA or stroke
What do most of the superficial arteries of the face arise from?
What are the superficial arteries of the face?
- Transverse facial
- Lateral nasal
- Superior and inferior labial
What superficial arteries of the face do not arise from the common carotid?
Supra-orbital and supra-trochlear
Where do the supra-orbital and supra-trochlear arteries arise from?
The opthalmic, which is a branch of the internal carotid
What are the vessels that supply blood to the scalp largely branches of?
The external carotid artery
What vessels supply blood to the scalp?
- Superficial temporal
- Posterior auricular
What is the result of the scalp being supplied by a rich blood supply of anastomoses?
Can get profuse bleeding
Where do the vessels of the scalp lie?
In the subcutaneous connective tissue layer
What are the walls of the arteries supplying the scalp attached closely to?
What is the result of the walls of the arteries of the scalp being closely attached to connective tissue?
Limits constriction, so can get profuse bleeding
Why can deep lacerations to the epicranial aponeurosis cause profuse bleeding?
Due to the opposing pull of the occipitofrontalis muscle
Does loss of scalp blood supply lead to bone necrosis?
Why does loss of scalp blood supply not lead to bone necrosis?
Because blood supply to the scalp is largely from the middle meningeal artery
What is the middle meningeal artery a branch of?
The maxillary artery
What does the middle meningeal artery supply?
Skull and dura
What is formed by the middle meningeal artery on the inside of the calvaria?
What are the branches of the middle meningeal artery?
Anterior and posterior
Where does the anterior branch of the middle meningeal artery run?
Under the pterion
What is the pterion?
A relatively thin area where a number of bones meet
When is the pterion prone to damage?
When there is a blow to the side of the skull
What can a fracture of the skull at the pterion cause?
Rupture of the middle meningel artery
What happens when the middle meningeal artery is ruptured?
Bleeding occurs, causing an extradural haemorrhage. Blood builds up and rips the periosteal layer of dura away from bone, and blood compresses the brain
What is the function of a craniotomy?
To gain access to the cranial cavity
What happens in a craniotomy?
The bone and scalp flap is reflected inferiorly to preserve blood supply
Why is the bone and scalp flap reflected inferiorly in a craniotomy?
Because that's how the arterial supply runs
What is the purpose of preserving the arterial supply to scalp and bone in a craniotomy?
So they can be replaced