Session 2: Major Blood Vessels of the Head & Neck

Question 1

Main arteries of the neck.

Answer 1

Subclavian artery Vertebral artery Internal thoracic artery Thyrocervical trunk Inferior thyroid artery Common carotid artery External carotid artery Internal carotid artery

Question 2

Explain the route of these arteries in the neck.

Answer 2

The aorta branches into the brachiocephalic trunk and on the right side of the body the brachiocephalic trunk divides into subclavian artery and the common carotid artery. The subclavian will run into shoulder and onwards and divide suprasclavicularly into the vertebral artery first. It will then at a similar level divide into the thyrocervical trunk (superiorly) and to the internal thoracic artery (inferiorly). The thyrocervical trunk will then divide into inferior thyroid artery (main division of thyrocervical trunk). Brachiocephalic trunk will also divide into the common carotid artery. Common carotid will then divide into external and internal carotid arteries via a bifurcation.

Question 3

What branches does the common carotid artery give off in the neck?

Answer 3

None.

Question 4

What arteries does the thyrocervical divide into?

Answer 4

Ascending cervical and transverse cervical arteries to supply the neck. Suprascapular to supply the shoulder. Inferior thyroid artery as well.

Question 5

What does the inferior thyroid artery supply?

Answer 5

The lower pole of the thyroid gland.

Question 6

Give the route of the vertebral arteries.

Answer 6

Arise from the subclavian arteries on both the left and right. It will then ascend in the neck through the transverse foramina in cervical vertebrae from C6 to C1. (Not C7). It then passes through the foramen magnum to enter the cranial cavity. It will then curve around the medulla to join the vertebral artery fromthe other side to form the basilar artery.

Question 7

Route of the internal carotid artery.

Answer 7

Arise from the common carotid artery at the bifurcation. It will not give any branches off in the neck and will ascend to enter the skull through the carotid canal. (External branch does give off branches).

Question 8

Where does the internal carotid artery enter the skull?

Answer 8

Through the carotid canal in the petrous of the temporal bone.

Question 9

At around which level does the bifurcation of common carotid artery occur?

Answer 9

At around C4 at around the level of the superior border of the thyroid cartilage.

Question 10

Borders of the carotid triangle.

Answer 10

Superior: Posterior belly of digastric muscle Inferolaterally: Medial border of sternocleidomastoid. Medially: Superior belly of omohyoid muscle.

Question 11

Contents of the carotid triangle.

Answer 11

Laterally to medially: Internal jugular vein Vagus nerve Common carotid artery

Question 12

What is a pathological complication of the bifurcation of the carotid artery?

Answer 12

At the bifurcation it is common for atheromas to form. This will cause narrowing (stenosis) of the artery and the rupture of the atheroma can cause embolus to travel to brain and cause a TIA or stroke.

Question 13

What else can be found at the bifurcation of the common carotid artery?

Answer 13

The carotid body and the carotid sinus. The carotid sinus can technically be found as a curvature of the internal carotid artery.

Question 14

What can be found in the carotid sinus?

Answer 14

Baroreceptors responsible for quick response in change of arterial BP.

Question 15

What can be found in the carotid body?

Answer 15

Peripheral chemoreceptors which detect arterial O2. Also glossopharyngeal nerve.

Question 16

Clinical relevance of the carotid triangle.

Answer 16

It is important for surgical approach to the carotid arteries or internal jugular veins. (Carotid endarterectomy) Access to vagus and hypoglossal nerves. Carotid pulse can be felt just below the bifurcation. Carotid sinus massage.

Question 17

Briefly explain carotid endarterectomy.

Answer 17

Restricted blood flow due to stenosis of the bifurcation. A surgeon uses the carotid triangle to locate the bifurcation and then cuts it open to remove a plaques to restore normal blood flow.

Question 18

Explain carotid sinus massage.

Answer 18

It is used to resolve supraventricular tachycardia. By massaging the carotid sinus the baroreceptors are tricked into thinking BP has increased. This sends parasympathetic signals to counter the ‘increased’ BP and so decreases heart rate.

Question 19

Route of internal carotid artery as it enters the skull.

Answer 19

Enters the skull through carotid canal in petrous part of the temporal bone. It then turns medially and horizontally. It will then enter the cranial cavity to make an S-shaped bend. It then goes on to course through the cavernous sinus.

Question 20

What is the cavernous sinus?

Answer 20

A plexus of extremely thin-walled veins on upper surface of sphenoid.

Question 21

What else can be found in the cavernous sinus?

Answer 21

Internal carotid artery CNIII oculomotor nerve CNIV trochlear nerve CNVI abducent nerve 2 branches of trigeminal (CNV) which are opthalmic (CNV1) and maxillary (CNV2)

Question 22

Important branches of the internal carotid artery.

Answer 22

Opthalmic artery branching into the central retinal artery, the anterior and posterior ethmoidal arteries in canals in ehtmoid bone. Supratrochlear artery and supra-orbital artery.

Question 23

What do the ethmoidal arteries supply?

Answer 23

The ethmoid bone of the nose.

Question 24

Important branches of the external carotid artery.

Answer 24

Superior thyroid Linguial Facial Ascending pharyngeal Occipital Posterior auricular 2 terminal branches: Superficial temporal Maxillary (become middle meningeal branch later on)

Question 25

Blood supply of the scalp posteriorly and anteriorly.

Answer 25

Mainly anteriorly the supply is from supra-orbital and supratrochlear aka internal carotid supply. Mainly posteriorly the supply is from superficial temporal artery, posterior auricular artery and occipital artery aka external carotid.

Question 26

Layers of the scalp.

Answer 26

SCALP Skin Connective tissue (dense) Aponeurosis Loose connective tissue Periosteum

Question 27

Where can you find the vessels of the scalp?

Answer 27

They are found in the subcutaneous connective tissue layer.

Question 28

Clincal relevance of the blood supply to the scalp.

Answer 28

You can get profuse bleeding if you damage it.

Question 29

Why might you get profuse bleeding from trauma to scalp?

Answer 29

The walls of arteries are closely attached to connective tissue and limits constriction of the arteries -> profuse bleeding. Numerous anastomoses. Deep lacerations involving the epicranial aponeurosis cause profuse bleeding because of opposing pull of occipitofrontalis.

Question 30

Why will not these types of bleeding to the scalp result in bone necrosis of the cranium?

Answer 30

Because the blood supply to the skull is mostly from the middle meningeal artery which is not an external artery.

Question 31

Superficial arteries of the face.

Answer 31

Two internal ones: Supra orbital and supratrochlear 6 External ones: Transverse facial artery Angular artery Lateral nasal artery Maxillary artery Superior and inferior labial artery Facial artery

Question 32

Where can you palpate the facial artery pulse?

Answer 32

Can be felt at inferior border of mandible, anterior to the masseter muscle.

Question 33

The two important branches of the maxillary artery.

Answer 33

The middle meningeal branch and the sphenopalatine branch.

Question 34

Why is the sphenopalatine branch of the maxillary artery important?

Answer 34

Because it forms anastomoses by nasal septum which is important in epistaxis.

Question 35

What is the kiesselbach area?

Answer 35

An area in the nasal septum which is rich with anastomosing arteries. It is a common site for nose bleeds.

Question 36

Anastomosing arteries in kiesselbach area.

Answer 36

Septal branch of sphenopalatine artery Anterior ethmoidal arteries. Less important ones: Posterior ethmoidal arteries. Greater palatine artery Septal branch of superior labial artery.

Question 37

Blood supply to dura and skull.

Answer 37

By middle meningeal artery branching to posterior branch of middle meningeal and anterior branch of middle meningeal.

Question 38

What structure does the middle meningeal artery pass through to enter the cranial cavity?

Answer 38

Foramen spinosum.

Question 39

Site of risk of damage to anterior branch of middle meningeal artery.

Answer 39

The pterion which is a spot where the cranium is at its weakest. It is a suture intersection where frontal, temporal, spehnoid and parietal plates meet.

Question 40

What are complications of rupture of middle meningeal artery due to trauma to pterion?

Answer 40

Extradural haemorrhage which causes a biconvex haematoma. This means that the haematoma will mainly grow inwards into the brain causing increased intracranial pressure.

Question 41

How do you gain access to the cranial cavity?

Answer 41

By craniotomy by the site of the pterion.

Question 42

What do the supraorbital and supratrochlear veins drain into?

Answer 42

They unite at medial angle of the eye to form angular vein which will drain into the facial vein.

Question 43

What about the pterygoid venous plexus?

Answer 43

Some deep parts of the scalp in temporal region have veins which drain into the pterygoid venous plexus.

Question 44

Why is the connection between venous drainage of scalp and dural venous sinuses important?

Answer 44

The veins of the scalp connect to diploic veins through several emissary veins to drain into duran venous sinuses. The emissary veins are valveless which means that retrograde flow is possible.

Question 45

Why is the valveless emissary veins a problem?

Answer 45

Infections from the scalp can spread into the cranial cavity and affect the meninges which is much more serious than a scalp infection.

Question 46

What do the superior opthalmic and inferior opthalmic veins drain into?

Answer 46

The cavernous sinus.

Inferior also drains into pterygoid venous plexus.

Question 47

What do the deep facial veins drain into?

Answer 47

The pterygoid venous plexus.

Question 48

Why are both these sinuses important in drainage?

Answer 48

The veins are once again valveless. This means that infections from facial vein can spread to dural venous sinuses and cause intracranial infection. Also thrombophlebitis of facial vein can make an infected clot travel to intracranial venous system and cause a stroke or TIA.

Question 49

What is the danger triangle of the face?

Answer 49

A part of the face of which infections in the region of the face can spread through the venous system to the dural venous sinuses.

Question 50

Important dural venous sinueses.

Answer 50

Superior sagittal sinus

Inferior sagittal sinus

Cavernous sinus

Sigmoid sinus

Transverse sinus

Question 51

What do the sigmoid sinuses continue as?

Answer 51

As the internal jugular veins leaving the skull through the jugular foramina.

Question 52

Venous drainage of the neck from head.

Answer 52

Through internal and external jugular veins.

Question 53

Route of internal jugular vein.

Answer 53

Passes underneath sternocleidmastoid and can be seen in the carotid triangle and also palpated at the sternal angle where the two heads of SCM separate.

Question 54

Route of external jugular vein.

Answer 54

Superficial to SCM meaning it is much easier to see.

Question 55

Clinical relevance of internal jugular vein.

Answer 55

The right internal jugular vein is a common method to measure jugular venous pressure as an indication of venous pressure coming into right atrium.

Question 56

What do the vertebral arteries form?

Answer 56

They pass up through the foramen magnum and curve around the medulla to join to its respective vertebral artery to form basilar artery.

Question 57

What is the carotid sheath mainly derived from?

Answer 57

Fusion of the prevertebral layer of cervical fascia posteriorly and pretracheal layer anteromedially.

Also the investing layer of cervical fascia anterolaterally.

Question 58

Which vessels provide a potential route for infection of the salp to the spread into the cranial cavity?

Answer 58

The emissary vessels which are valveless.

Question 59

What does the internal jugular vein receive blood from?

Answer 59

Facialvein and veins draining the thyroid gland and tongue along with numerous other veins during its descent.

It joins with the subclavian vein behind the medial end of the clavicle to form the braciocephalic vein. This then drains into SVC.