Flashcards in Lecture 2 - Major Blood Vessels Of The Head And Neck Deck (79)
Arterial supply to the head and neck arise form branches of which arteries?
Right and left common carotid and vertebral arteries
Which artery is the vertebral artery a branch of?
What structures to the vertebral arteries supply?
Posterior neck posterior aspects of the brain like the brainstem and cerebellum
What is the route of the vertebral arteries and what do they form when joined?
The vertebral arteries travel through the transverse foramina of the cervical vertebrae, except for C7. Then they enter the subarachnoid space between the atlas and occipital bone. Then pass through the foramen magnum where they curve around the medulla of the brainstem and join together to form the basilar artery.
The basilar artery runs along the anterior aspect of the brainstem (namely the pons)
What do the common carotid arteries arise form and what is the significance of their origin and route?
The right common carotid artery originates from the brachiocephalic artery behind the right sternoclavicular joint, whilst the left common carotid arises directly from the arch of the aorta.
Consequently, the left common carotid artery is slightly longer as it courses for about 2 cm in the superior mediastinum before entering the neck.
What is the mediastinum?
The mediastinum is the area in the chest between the lungs that contains the heart, part of the trachea, the oesophagus, and the great vessels including the ascending aorta
It is the central part of the thoracic cavity and separates the two lateral pleural cavities
It is divided into anterior, posterior, middle and superior regions
What are the CCAs enclosed within as they ascend the neck and were is this structure found?
Deep to the SCM muscle
What is the carotid sheath derived from?
a) the prevertebral layer of cervical fascia (posteriorly)
b) the pretracheal layer (anteromedially) and
c) the investing layer of cervical fascia (anterolaterally)
What structures are fond within the sheath and what is associated with it?
The sheath is thin over the vein but thicker around the artery.
The artery lies medially within the sheath whilst the vein is lateral and the nerve behind and in between the vessels.
The sympathetic chain lies outside of the sheath, medially and behind it.
Where do the CCAs bifurcate/terminate into the terminal branches?
The common carotids most commonly terminate at the level of the upper border of the thyroid cartilage (C4 level), and divide into internal and external carotid arteries.
What is significant about the ICA at the site of bifurcation from the ECA and what is the clinical significance of this feature?
Internal carotid artery is more bulbous due to the carotid sinus (and carotid body).
The site of the carotid sinus is clinically important as rubbing this area firmly can alleviate supra-ventricular tachycardias (SVTs) i.e. carotid massage.
What distinguishes the ICA from the ECA as it ascends through the neck?
The internal carotid artery is distinguished by a lack of branches in the neck.
What is the route of the ICA through the neck?
It ascends then enters the base of the skull, through a bony canal called the carotid canal which is found in the petrous part of the temporal bone.
Its course intracranially involves passage through a structure called the cavernous sinus.
Once it exits the cavernous sinus, it gives its terminal branches which supply the brain and the eye (i.e. intercranial structures)
What structures do the ECAs supply and why is their ascent through the neck different to the ICAs?
The external carotid artery, is the major source of blood supply to extra- cranial structures of the head and neck region, and gives rise to eight branches, some arising in the neck
What are the 8 branches of the ECA and which two are the terminal branches?
The last two are terminal branches
‘Some Anatomists Like Freaking Out Poor Medical Students’
What does the facial artery supply?
Man arterial supply to the tissues of the face
Where do the maxillary and superficial temporal arteries arise and where do they travel?
The maxillary and superficial temporal arteries are considered the terminal branches of the external carotid artery, arising at a level behind the neck of the mandible.
They arise within and travel through the substance of the parotid gland (along with the facial nerve and its branches) and provide the gland its major source of blood.
What structures does the maxillary artery supply and what branch does it give off?
The maxillary artery also supplies deep tissue and bone structures of the face e.g. paranasal air sinuses and nasal cavity.
It gives a branch called the middle meningeal artery, which runs through the base of the skull to supply the meninges and skull bones.
What structure does the superficial temporal artery supply?
The superficial temporal artery supplies the tissues of the scalp, joining with other branches of the external carotid artery (and
branches of the internal carotid artery (supratrochlear and supraorbital) that exit the skull through the orbit).
A number of veins drain the scalp, face and neck. Most of the structures of the face drain via the _________ vein, which runs from the __________ angle of the eye towards the inferior border of the mandible, with the facial artery. The facial vein then joins the _______________ ______________ vein.
Which veins does the facial vein connect to and what doe these veins then connect to?
The facial veins are connected to the superior and inferior opthalmic veins which have a direct connection with the cavernous sinus and pterygoid venous plexus
Where does the cavernous sinus lie?
The cavernous sinus lies intra-cranially and forms part of the intra-cranial venous system.
What is the significance of the connection between veins draining the face and intercranial veins?
Blood draining the face via the facial vein can therefore potentially drain intracranially. This has implications for infections involving the face, as they then can spread to involve intracranial structures, making the infection immediately more concerning.
For example, septic thrombi within the facial vein (secondary to infection in and around the tissue it drains) can travel, via the ophthalmic veins to the cavernous sinus and cause a cavernous sinus thrombosis. This is extremely serious, though very rare.
Not only is there a connection between veins draining the face and veins draining the brain but there is also a connection between veins draining the scalp and intercranial (dural) venous sinuses. What is the name of the veins connecting the veins draining the scalp to the intercranial veins and what is the significance of this?
Emissary veins, which run through the skull, between these blood vessels provide a potential route for infection of the scalp to spread into the cranial cavity.
There is significant communication between extra-cranial and intra-cranial veins, because of the numerous anastomotic points. As a result infections occurring on the _______ and __________ can potentially track intra-cranially to involve the brain and/or its associated structures, and thus become immediately more serious.
What is the IJV a continuation of?
The internal jugular vein (IJV: right and left) arises as a continuation of a venous (dural) structure found within the skull, the sigmoid sinus.
What is the route of the IJV?
The IJV runs the length of the neck (within the carotid sheath); a straight line running from the lobule of the ear to the sternoclavicular joint represents its route. Throughout much of its course the sternocleidomastoid muscle covers it anteriorly. However, towards the inferior end of the vein, the sternocleidomastoid muscle splits into its clavicular and sternal heads forming a gap anterior to the vein.
What is the significance of the gap between the two heads of SCM in relation to the IJV?
The IJV can be readily accessed through this gap when inserting central lines (central venous catheters).
This gap is also the area where the normal jugular venous pulsation (JVP) can be seen, when patients are positioned at 45 degrees.
Doctors use the JVP to give an indication of the pressures within the venous circulation and right side of the heart.
Why is the right JVP favoured over the left JVP?
The right JVP is favoured over the left, as the right has a straight, more vertical route into the right atrium and so better reflects pressures within the right side of the heart.
The IJV receives blood from a number of other veins during its descent. These include?
This includes the facial vein, and veins draining the thyroid gland and tongue.
The IJV ends by joking which vein to form what trunk?
The IJV (right and left) ends by joining with the subclavian vein (just behind the medial end of the clavicle) to form the brachiocephalic vein, which then drains into the superior vena cava and thence the right atrium.
Which veins drain into the EJV?
The external jugular vein (EJV) is formed the joining of a number of veins that have drained the scalp and the deep structures of the face
What is the course of the EJV?
The EJV runs just beneath the skin, in the superficial cervical fascia of the neck.
While deep to the thin platysma muscle, it is superficial to the sternocleidomastoid muscle and thus more readily visible than the IJV
What does the EJV then drain into?
The EJV ultimately drains into the subclavian vein, after piercing the investing layer of deep cervical fascia (as it was superficial) at the lower end of the neck.
On the right side, which arteries arise form the braciocephalic trunk?
Subclavian and CCA
Which arteries arise form the subclavian artery?
The vertebral, internal thoracic and thyrocervical arteries all arise from the subclavian artery in the base of the neck
Does the CCA give off any arteries in the neck?
The common carotid artery does not give
off any branches in the neck
• Bifurcates to give external and
internal carotid arteries
What are the branches of the thyrocervical trunk which is a branch itself of the subclavian artery?
Ascending cervical artery
Transverse cervical artery
Inferior thoracic (or inferior mammary) - supplies lower pole of thyroid gland
Suprascapular - supplies supraspinatus and infraspinatus muscles of the scapula
Where do the vertebral arteries arise form, what is their route and what do they supply?
Vertebral arteries arise from the subclavian arteries on left & right
They ascend in the neck through transverse foramina in cervical vertebrae 6-1 and pass through the foramen magnum
The vertebral arteries supply the brain along with the (branches of) internal carotid arteries
Does the ICA give off branches in the neck?
The internal carotid artery gives no
branches off in neck
– Enter skull through carotid canal to supply intercranial structures and its branches anastomose with branches of the ECA (superficial temporal and posterior auricular) to supply the scalp
Which muscle forms the medial border of the carotid triangle?
Superior belly of omohyoid muscle
What are the borders of the carotid triangle?
Medial border - superior belly of omohyoid muscle
Superior border - posterior belly of digastric muscle
Lateral border - anterior border of SCM
Where does the IJV lie in relation to the CCA and where does the CCA bifurcate?
The internal jugular lies lateral to the common carotid mostly under sternocleidomastoid (scm)
The common carotid bifurcates at about the level of the superior border of the thyroid cartilage- C4 level
Why is the bifurcation of the CCA a common site for atheroma formation and what happens as a result of the atheromas?
There is turbulence at the bifurcation
The atheroma causes narrowing (stenosis) of the artery.
What happens if there is a rupture of the atheroma ta the bifurcation of the CCA?
A rupture of the clot can cause an embolus to travel to the brain and cause a TIA or (thrombotic) stroke if it lodges in a cerebral artery
Where is the carotid sinus lcoated and what is found within it?
It is a bulge in the ICA
It has baroreceptors within it that detect changes in arterial BP.
What is the carotid body and what does it contain?
It contains peripheral chemoreceptors that detect arterial O2 levels. It is found just outside the carotid sinus in the diagram in the lecture
Both the carotid sinus and carotid body work to find out how much blood is reaching the brain
What is found within the carotid triangle and what is its clinical significance?
Carotid arteries, IJV, vagus and hypoglossal nerves
- Can feel the carotid pulse within it just below the bifurcation
- important for surgical approach to the CCAs and IJV
- carotid sinus massage to relieve an SVT px.
What happens in a carotid sinus massage?
Chemicals are released from the vagus nerve - acts on the AVN to slow heart rate - stops an SVT
What is the course of the ICA?
- Enters skull through carotid canal in
petrous part of temporal bone
- Turns medially and horizontally
- Enters the cranial cavity then makes S–shaped bend
- Courses through the cavernous sinus
What is the cavernous sinus and what is found within it?
A plexus of extremely thin-walled veins on the upper surface of the sphenoid
It is one of the intracranial (dural) venous sinuses
Found within it:
- oculomotor nerve (CNIII)
- trochlear nerve (CNIV)
- abducent nerve (CNVI)
- 2 branches of the trigeminal nerve (opthalmic - CNVI and maxillary - CNV2)
What is the opthalmic artery a branch of and what branches from it?
The opthalmic artery is a branch of the ICA
• Ophthalmic artery runs with the optic nerve and gives off the central retinal artery that supplies the retina of the eye
• There are other branches that supply the orbit of the eye
• the opthalmic artery also gives off the supratrochlear and supra-orbital arteries
What do the branches of the ECA supply?
Superior thyroid - superior portion of the thyroid
Lingual - oral cavity and tongue
Facial - tissues and structures of the face
Occipital - runs up posterior aspect of the occipital bone and supplies the scalp
Posterior auricular - runs behind the ear and supplies the scalp
Maxillary - supplies structures deep to the mandible
Superficial temporal - runs along the side of the temple to anastomose with other branches of the ECA and branches of the ICA to supply the scalp
Which arteries form blood supply to the scalp?
From the ICA:
From the ECA:
- superficial temporal
- posterior auricular
What layers form the scalp?
Dense connective tissue
Aponeurosis of occipitofrontalis muscle
Loose connective tissue
Where do vessels of the scalp lie?
In the subcutaneous (dense) connective tissue (below the skin)
What is the clinical relevance of the blood supply to the scalp?
- Walls of arteries are closely attached to
connective tissue which limits their constriction - can get profuse bleeding - so if there is a cut in the connective tissue, it pulls the arteries apart - profuse bleeding
- numerous anastomoses - profuse bleeding
- deep lacerations involving epicranial aponeurosis (of occipitofrontalis) causes profuse bleeding as well due to opposing pull of the occipitofrontalis muscle
What is profuse bleeding from the scalp due to?
• The close attachment of the walls of the arteries with the dense connective tissue
• Numerous anastomoses
• Opposing pull of the occipitofrontalis muscle
Why doe scalp injuries that lead to loss of scalp not lead to loss of bone? (Note the difference between the scalp and the bone)
The blood supply to the scalp is through multiple anastomose of branches of the ICA but mainly the ECA
Blood supply to the skull is mostly from the middle meningeal artery (which is a branch of the maxillary artery which is a branch of the ECA). The middle meningeal artery runs on the inside of the cranium so is intracranial. So loss of scalp does not lead to bone necrosis.
What are some of the superficial arteries of the face and form which arteries do they arise?
- transverse facial artery
- angular artery
- lateral nasal artery
- maxillary artery
- superior and inferior labial arteries (branches of the facial artery)
- facial arteries
They all arise from the ECA except for the supra-orbital and supratrochlear which arise from the opthalmic retry which is a branch of the ICA.
Where can the facial artery pulse be felt?
Facial artery pulse can be felt at inferior border of mandible, anterior to the masseter muscle
What are the branches of the maxillary artery and what do they supply?
Middle meningeal - supplies blood to the kill and dura
Sphenopalatine - supplies the anastomoses to the nasal septum
What does the blood supply to the nasal septum consist of?
It is an anastomosis of arteries in the Kiesselbach area.
The most important branches are:
– Septal branch of sphenopalatine artery (from maxillary artery - from ECA)
Anterior ethmoidal arteries (from ophthalmic artery - from ICA)
What does the blood supply to dura and skull consist of?
Middle meningeal travels deep to the zygomatic arch/process of the temporal bone and then travels deep into the skull to give off posterior and anterior branches of middle meningeal
What is significant about the anterior branch of the middle meningeal artery?
It is found near the pterion - a particularly thin area of the skull where are a number of bones join together
Trauma to this area can cause damage to the anterior branch of the middle meningeal artery.
Middle meningeal artery supplies skull and dura. Fracture of skull at ____________ can rupture the middle
meningeal artery. This can lead to what?
An extradural haemorrhage - blood can cause the dura to peel away from skull because the blood fills the gap between the dura and skull
Would see a crescent shaped bulge on the inside of the skull in a CT scan - shape is caused by the extradural haemorrhage where the blood is limited by the dura so can’t push against the dura too much
What is done in a craniotomy?
Gain access to cranial cavity
Bone and scalp flap reflected inferiorly to preserve blood supply
Superficial veins generally accompany arteries. Give some examples.
- Superficial temporal veins
– Occipital veins
– Posterior auricular veins
Which veins drain the scalp?
Supraorbital and supratrochlear veins which unite at the medial angle of eye to form the angular vein which drains into the facial vein
Some deep parts of scalp in temporal region have veins which drain into the pterygoid venous plexus
(Which we know can communicate with the cavernous sinus via the opthalmic veins and emissary veins)
How do veins of the scalp connect to dural venous sinuses and what is different about the connecting veins and what are the implications of this?
• Veins of scalp connect to diploic veins of skull through several emissary veins andthus to dural venous sinuses
• Emissary veins are valveless - so blood can move in either direction through these veins
• Infection from scalp can spread to the cranial cavity and affect meninges
Can lead to meningitis - inflammation of the meninges - infection can spread into the cranial cavity
What are dural venous sinuses?
• Dural venous sinuses are venous channels covered in dura
They are intracranial veins
Which veins drain the face?
- supra-orbital vein and supratrochlear vein form the angular vein which drains into the facial vein
- Superior & inferior labial veins - drain into facial vein
- Facial vein - drains into IJV
- Common facial vein
What is important to note about veins of the face?
How is the facial vein connected to the cavernous sinus and pterygoid plexus?
- Veins of the face are valveless
At medial angle of eye, facial vein communicates with superior ophthalmic which drains into cavernous sinus
Deep facial veins drain into pterygoid
Pterygoid plexus is connected to cavernous sinus by emissary veins and also by the superior and inferior opthalmic veins which drain into both the cavernous sinus and pterygoid plexus
What is the comical implication of the connection of facial veins with the cavernous sinus and pterygoid venous plexus?
- Infection from facial vein can spread to dural venous sinuses –
- Thrombophlebitis of facial vein –
infected clot can travel to
intracranial (dural) venous system
Thrombophlebitis is inflammation of the wall of a vein with associated thrombosis, often occurring in the legs during pregnancy
What is the danger triangle of the face?
Infections in this region of the face can spread through the venous system to the dural venous sinuses
• Angular vein and facial vein would be in this area
• Supratrochlear and supraorbital veins drain into the angular vein which then drains into the facial vein
This further emphasises how infections can spread from superficial veins to deep intracranial venous plexuses because of how the veins are connected and the fact that veins in the face are valveless
Where is the danger triangle of the face?
Its apex is above the nose between the eyebrows and its base sits between the lips. The two sides join the apex and base together
What are the dural venous sinuses?
Superior sagittal sinus Inferior sagittal sinus Cavernous sinus
Cerebral veins drain into the sagittal sinuses
• Sigmoid sinus exits through the jugular foramen to become the IJV
Why do we use the IJV to assess JVP and on which side?
Although the EJV vein is much easier to see because the IJV is under the SCM (in carotid sheath), the IJV gives a better indication of pressure in right atrium
• IJV drains into the brachiocephalic vein
• The subclavian vein drains into the brachiocephalic vein too