3 - Blood Vessels Flashcards
What is the blood supply to the posterior neck and posterior parts of the brain (e.g cerebellum and brain stem)
- Vertebral arteries - arising from subclavian arteries
- Travel through transverse foramina of C1 to C7 and enter subarachnoid betweem atlas and occipital bone
- Through foramen magnum and curves around medulla to join opposite vertebral artery making basilar artery
What is the blood supply to the brain in general?
Basilar arteries and the internal carotid arteries (entering through carotid canal) forming a Circle of Willis
What is the origins of the common carotid arteries and what are their courses?
- Right from brachiocephalic trunk
- Left from arch of aorta so slightly longer
- Run in the carotid sheath medial to IJV. Sympathetic chain outside the sheath medially and behind them
- Bifurcates at upper border of thyroid cartilage C4
What fascia make up the carotid sheath?
- Prevertebral posteriorly
- Pretracheal anteromedially
- Investing later anterolaterally
What is the clinical importance of the bifurcation of the common carotid arteries?
- Rubbing the carotid sinus signals b.p high so increases parasympathetic output lowering heart rate
- Treats SVT’s and is called a carotid massage
- Listen for bruit in case of atheromas that could rupture and cause a stroke. Atheromas mainly in internal and can cause TIAs
How would you identify the internal carotid artery in the neck dissection?
- No branches in the neck and enters skull through carotid canal.
- Passes through cavernous sinus and one it exits this it gives off it’s branches
What are the branches of the external carotid artery and label them on this diagram.
Some Anatomists Like Freaking Out Poor Medical Students
What important arteries in the head and neck originate from the subclavian arteries?
- Internal thoracic (sternum)
- Vertebral
- Thyrocervical trunk: inferior thyroid (supplies thyroid gland) and suprascapular (supplies shoulder)
What is the importance of the carotid triangle as an anatomical landmark?
- Can do carotid endarterectomy here
- Access vagus and hypoglossal nerves
- Carotid sinus massage (push and maintain pressure)
Where can you palpate the carotid pulse?
Superior part of Carotid Triangle, bifurcation of artery anterior to SCM
What does the thyrocervical trunk consist of?
What is the cavernous sinus?
Dural sinus containing plexus of veins on upper surface of sphenoid.
Also contains:
- Internal carotid artery
- CN3 occulomotor
CN4 trochlear
- CN6 abducent
- Trigeminal opthalmic and maxillary
What do the terminal branches of the external carotid arteries supply?
- Arise in parotid gland so supply this
- Maxillary* supplies deep structures like paranasal sinuses, nasal cavity, meninges
- Superficial temporal* supplies scalp by joining other arteries from internal and external carotid arteries
What is the first branch of the ICA and what does it split into?
- Opthalmic which splits into supratrochlear and supra-orbital to supply the eyes and nose, along with the anterior and posterior ethmoidal arteries
- First division to not be joining the Circle of Willis
What is the blood supply to the scalp?
Mainly superficial temporal from ECA
But note that there’s a lots of anastomoses as well
What are the layers of the scalp? And where are the vessels located?
Vessels in subcutaneous connective tissue layer
Why is there profuse bleeding when there is a scalp injury and why does losing your scalp not cause skull necrosis?
- Walls of arteries close to connective tissue limiting constriction to stop bleeding
- Numerous anastomoses
- Deep lacerations with epicranial aponerousis causes bleeding as the occipitofrontalis will pull in either direction holding vessels open
- Supply to skull is mostly middle meningeal artery not like anastomoses to the scalp
Label the superficial arteries of the face and where do they come from?
All from external carotid artery apart from supra-orbital and supratrochlear (from ICA/opthalmic)
What are the branches of the maxillary artery?
- Terminal branch of external carotid artery
- Middle meningeal supplies skull and meninges
- Sphenopalatine form anastomoses so importnant in nose bleeds
Where can you palpate the facial artery pulse?
On the mandible anterior to the masseter muscle
Where is the most common site for nosebleeds?
Kiesselbach area where the septal branch of sphenopalatine and anterior ethmoidal arteries anastomose
What is the blood supply to the dura and skull and what is the clinical relevance to the course of this blood vessel?
- Middle meningeal artery running through foramen spinosum
- Anterior branch runs past the pterion, thinnest part of the skull
- If blow to head/fracture at this point can rupture artery and cause extradural haemorrage
What are these impression on the calvaria from?
Anterior branches of middle meningeal branches supplying the dura mater
What is this CT scan displaying and why does this occur?
- Extradural haemorraghe
- Rupture of middle meningeal artery that runs between periosteum and the bone causing the periosteum to be pulled away from the bone
How can we gain access to the cranial cavity but preserve blood supply?
What is the venous drainage of the scalp?
Superficial: superficial temporal, occipital, posterior auricular, supraorbital, supratrochlear
Supraorbital and trochlear unite at medial angle of eye towards inferior border of mandible, form angular vein and drain into facial vein
Deep (temporal): drain into pterygoid venous plexus
Where do the direct veins of the scalp drain to on their course back to the heart?
- Internal jugular vein
- Facial vein recieves drainage from supratrochlear and supraorbital via the angular vein before draining into internal jugular
- Facial also has connections with the inferior and superior opthlamic veins that are connected to cavernous sinus and pterygoid venous plexus
How do veins of the scalp connect to the meninges and what is the danger with this?
Emissary veins drain the scalp to diploic veins in dural venous sinuses. Infections of the scalp can get into the cranial cavity and affect the meninges, e.g meningitis
Label the venous drainage of the face.
What can be a complication of an infection involving an external facial structure, e.g the eye?
- Facial veins valveless
- At the medial angle of the eye the superior opthalmic vein drains intra-cranially to the cavernous sinus.
- Septic thrombi from facial vein could get into opthalmic vein and cause cavernous sinus thrombosis
What is the danger triangle?
Any infections in this area can potentially track intra-cranially and involve the brain or it’s structures
Why are the medial part of the eyes in the danger triangle?
Where are all the venous sinuses intracranially and which one does the IJV arise from?
What is the anatomical course of the IJV and what is it’s clinical importance?
- From the jugular foramina to the sternoclavicular joint, mainly behind sternocleidomastoid until SCM splits into two heads forming a gap for the vein
- JVP (right side as straighter) and Central Venous Catheters
What branches drain into the internal jugular vein on its course through the neck?
And where does it go after?
- Facial vein
- Veins from tongue and thyroid
- Drains into subclavian or brachiocephalic trunk
What are the tributaries of the external jugular vein?
- Made by veins draining scalp and deep structures of the face
- Runs in superficial cervical fascia above platysma before piercing investing layer to join subclavian
How do you measure JVP?
- Can’t palpate vein so if you can you have the common carotid artery
- Might not be visible in healthy patient
