1. Vasculature Flashcards
Where does the arterial supply of the head and neck arise from?
- Right and left common carotid arteries
- Vertebral arteries
What do the vertebral arteries branch from?
Subclavian arteries
What do the vertebral arteries supply?
Posterior neck and posterior parts of the brain e.g. brainstem and cerebellum
Where do the vertebral arteries pass through?
Route:
- Ascends through the transverse foramina of the cervical vertebrae (apart from C7)
- Subarachnoid space between the atlas and occipital bone.
- Foramen magnum
It then curves around the medulla to join the other vertebral artery (from the other side) to form the basilar artery.
Where does the basilar artery run?
Along the anterior (ventral) aspect of the brainstem, more specifically the pons.
Where does the right common carotid artery originate from?
Brachiocephalic artery behind the right sternoclavicular joint.
Where does the left common carotid artery originate from?
Directly out of the branch of aorta
Is the left or right common carotid artery longer?
Left, as it arises out of the aorta. It courses for about 2 cm in the superior mediastinum before entering the neck.
What structure is the common carotid artery found in?
Carotid sheath
What is the carotid sheath?
Fascial envelope of fused cervical fascia
What are the contents of the carotid sheath?
- Carotid artery
- Internal jugular vein
- Vagus nerve
Where is the carotid sheath located?
Deep to the sternocleidomastoid muscle
What is the carotid sheath derived from?
Fusion of three cervical fascia:
- prevertebral layer (posteriorly)
- pretracheal layer (anteromedially)
- investing layer (anterolaterally)
Where does the carotid sheath lie thickest and thinest?
Thinnest = over the vein
Thickest = over the artery
Where do the contents of the carotid sheath lie within it?
- Carotid artery lies medially
- Internal jugular vein lies laterally
- Vagus nerve runs posteriorly and in between the two vessels
Where is the sympathetic chain located?
Posterior and medial to the carotid sheath
Where do the common carotids most commonly terminate?
At the level of the upper border of the thyroid cartilage (C4 level) where they divide into internal and external carotid arteries.
What is the carotid sinus?
A dilated portion of the common carotid and internal common carotid arteries that contain baroreceptors. The baroreceptors detect stretch of the vessel as blood pressure.
What is the carotid body?
Cluster of nervous cells that lie external to the carotid sinus. These act as peripheral chemoreceptors than detect the content of O2 in the blood.
Why is the site of the carotid sinus clinically relevant?
Rubbing this area firmly can alleviate supra-ventricular tachycardias (SVTs) . This is known as a carotid massage.
How does a carotid sinus massage work?
Tricks baroreceptors into thinking that blood pressure is high by applying pressure to the area. This signal is relayed to the brain which orchestrates bradycardia and hypotension.
How can the internal carotid artery be distinguished?
Does not have branches in the neck. Ascends then enters the base of the skull through a bony canal called the carotid canal.
Where does the internal carotid artery pass through intracranially?
Cavernous sinus
Which structure does the internal carotid artery pass through before it branches?
Cavernous sinus
What does the internal carotid artery supply?
Brain and eye
What does the external carotid artery supply?
Extracranial structures
How many branches of the external carotid artery are there?
Eight
What are the branches of the external carotid artery?
- Superior thyroid artery
- Ascending pharyngeal artery
- Lingual artery
- Facial artery
- Occipital artery
- Posterior auricular artery
- Maxillary artery
- Superficial temporal artery
“Some Anatomists Like Freaking Out Poor Medical Students”
What are the terminal branches of the external carotid artery?
Maxillary and Superifical Temporal arteries
Where do the terminal branches of the external carotid artery arise?
Through the parotid gland (superfical temporal artery and maxillary artery)
What is the blood supply of the parotid gland?
Superfical temporal and maxillary artery
What does the maxillary artery supply?
Deep tissues and bone structures of the face:
- Paranasal air sinises
- Nasal cavity
- Parotid gland
What is the origin of the middle meningeal artery?
Maxillary artery
Where does the middle meningeal artery run?
Through the base of the skull
What does the middle meningeal artery supply?
Meninges and skull bones
What does the superficial temporal artery supply?
Tissues of the scalp
*** Why do many of the branches of the external carotid artery make a loop at their origin?
Where do most of the structures of the head and neck drain into?
Facial Vein
Where does the facial vein run?
From the medial angle of the eye towards the inferior border of the mandible with the facial artery
What does the facial vein drain into?
Internal jugular vein
Which veins connect to the facial vein?
Superior and inferior opthalmic veins
What do the superior and inferior opthalmic veins have a connection to?
Cavernous sinus and pterygoid venous plexus
Where does the cavernous sinus lie?
Intra-cranially forming part of the intra-cranial venous system
Where can the facial vein drain into and what clinical implications does this have?
Intracranially via the superior and inferior opthalmic veins. An infection in the ‘danger triangle’ of the superfical face can spread to intracranial structures.
Where can sceptic thrombi of the facial vein drain embolise to?
The cavernous sinus through the opthalmic veins causing a cavernous sinus thrombosis. This is serious but extremely rare.
What do emissary veins connect?
Veins of the scalp and intra-cranial (dural) venous sinuses
How could an infection spread from the scalp into the cranial cavity?
Passes through veins of the scalp to emissary veins into the intra-cranial (dural) venous sinuses
What does the left and right internal jugular vein arise out of?
Sigmoid sinus
Where does the internal juglar vein run?
The length of the neck within the carotid sheath; from the lobule of the sternoclavicular joint.
Why do many of branches of the external carotid artery make a loop at their origin?
To allow for flexion and extension of the head
What is the interal jugular vein covered by anteriorly?
Sternocleidomastoid
How does the sternocleidmastoid muscle split to to form an opening to the internal jugular vein?
At the inferior end of the vein SCM splits into clavicular and sternal heads
Where can the internal jugular vein be accessed?
At the inferior end inbetween the clavicular and sternal heads of the SCM
Why would you need access to the internal jugular vein?
- To insert a central venous catheter (central line)
- To measure jugular venous pulsation
When are central lines used in patients?
- Monitoring central venous pressure
- Administration of drugs
- Repeated blood sampling
- Temporary haemodialysis
Often used in patients who are very unwell
How do you measure jugular venous pulsation?
- Position patients at 45 degrees
- View right side
Why is the right IJV favoured over the left to view jugular venous pulsations?
Right has a more direct route into the right atrium so better reflects pressures within the right side of the heart.
Which veins drain into the internal jugular vein?
- Facial vein
- Veins draining thyroid gland and the tongue
What is the route of drainage of the IJV to the right atrium?
- Brachiocephalic vein (joins with subclavian vein)
- Superior vena cava
- Right atrium
What drains into the external jugular vein?
Veins draining the scalp and deep structures of the face
Where does the external juglar vein lie?
Beneath the skin in the superficial cervical fascia of the neck. Lies deep to platysma and superfical to SCM
Where does the external jugular vein drain into?
Subclavian vein, after travelling through the investing layer of deep cervical fascia
Where do the common carotids arise from?
- Left carotid artery arises directly from the arch of aorta
- Right carotid artery arises from the brachiocephalic trunk
Where do the vertebral, internal thoracic and thyrocervical arteries arise from?
Subclavian artery at the base of the neck
Does the common carotid artery give off branches in the neck?
No, it bifurcates to give the internal and external carotid arteries
Which blood vessel supply the neck?
Ascending cervical artery and transverse cervical artery
What is the blood supply to the shoulder?
Suprascapular artery
What is the blood supply to the lower pole of the thyroid gland?
Inferior thyroid artery
Which arteries come off of the thyrocervical trunk?
- ascending cervical artery
- tranverse cervical artery
- suprascapular artery
- inferior thyroid artery
Where do the vertebral arteries arise from?
Subclavain arteries
Where do the vertebral arteries pass through?
Transverse foramina in C6 - C1 (that order) and then pass through the foramen magnum
What is the blood supply to the brain?
Vertebral arteries and internal carotid arteries
How does the internal cartoid artery enter to skull?
Through the carotid canal
Where does the common carotid artery bifurcate?
At the level of the superior border of the thyroid cartilage
Where in the neck is a common site for atheroma?
At the bifurcation of the carotid artery
What can the rupture of a carotid artery atheroma cause?
Brain embolism; transient ischaemic attack or stroke
What is an atheroma?
A fatty deposit in the inner lining (intima) of an artery resulting from atherosclerosis
What is the carotid sinus?
A swelling at the region of bifurcation where baroreceptors for detecting changes in arterial blood pressure are located.
What is the carotid body?
Peripheral chemoreceptors detecting arterial O2, lying outside of the cartoid artery at the level of bifurcation.
What nerves can be accessed through the carotid triangle?
Vagus and hypoglossal
Where is the carotid triangle located?
Subdivision of the anterior triangle of the neck.
Boundaries:
- Superior - posterior belly of digastric muscle
- Lateral - medial border of the sternocleidomastoid muscle
- Inferior - superior belly of the omohyoid muscle
What are the contents of the carotid triangle?
- Carotid artery (bifurcates within the triangle)
- Hypoglossal nerve
- Vagus nerve
- Internal jugular vein
Where is the carotid pulse felt?
Below bifurcation of the carotid artery, can be palpated more inferiorly
Where does the internal carotid artery enter the skull?
Through the carotid canal in petrous part of temporal bone. Turns medially and horizontally.
What is the route of the internal carotid artery?
- Enters skull through carotid canal in petrous part of temporal bone
- Turns medially and horizontally
- Enters the cranial cavity and then makes S-shaped bend
- Courses through the cavernous sinus intracranially
