Week 2.0 - Major Blood Vessels Flashcards
Which structure is most lateral, common carotid or internal jugular?
-Internal jugular
Describe the major branches arising from the aortic arch
- On the right the brachiocephalic trunk (splits into r subclavian and common carotid)
- Left common carotid medial to that
- L subclavian on the left
What 3 arteries arise from the base of the subclavian?
- Vertebral
- Internal thoracic
- thyrocervical trunk
Which arteries arise from the thyrocervical trunk? Where does each of these supply?
- Ascending and transverse cervical supply the neck
- Suprascapular supplies the shoulder
- Inferior thyroid supplies lower pole of thyroid gland
From where do the vertebral arteries arise, and what is significant about their course?
- Base of subclavian arteries
- Ascend through transverse foramina of C6-1
How do the vertebral arteries enter the cranium? With what do they anastomose to form what structure?
- Through foramen magnum
- Basilar arteries = circle of willis
From where do the basilar arteries arise? How does this enter the skull?
- Internal carotid artery
- Through carotid foramen and then carotid canal
Where does the common carotid bifurcate?
-C3/C4
Where is the carotid sinus and carotid body?
- Carotid sinus in internal carotid artery
- Carotid body lies close to this
What is the carotid sinus?
- Swelling at the region of bifurcation which contains baroreceptors for detecting changes in BP
- Relays this information to the medulla oblongata (the greater the stretch the more signals fire)
What is the carotid body?
-A small cluster of peripheral chemoreceptors which detect arterial pO2
(most vascular tissue in the body)
Relative to the carotid arteries, what is a common site of atheroma? Why?
- The level of the bifurcation
- Area of turbulent flow
What are the possible consequences of atheroma at the carotid bifurcation?
- Stenosis of the artery causes symptoms over 70% occlusion
- Risk of embolism causing TIA/Stroke
What is the carotid sheath? What does it enclose?
-A layer of fascia within the neck which encloses the common carotid artery, internal jugular vein, vagus nerve and deep cervical lymph nodes
State the boundaries of the carotid triange
- Superior -> Posterior belly of digastric
- Lateral -> sternocleiodomastoid
- Medial -> Superior belly of omohyoid
Why is the carotid triangle clinically important? (4 reasons)
- Surgical access to carotid arteries or IJV
- Access to Vagus and Hypoglossal nerve
- Carotid pulse
- Carotid sinus massage
When is carotid sinus massage used and why?
- Supraventricular tachycardia
- Stimulate the baroreceptors to increase vagal activity and resolve SVT
State the 8 branches of the external carotid artery
- Superior thyroid
- Lingual
- Facial
- Ascending pharyngeal
- Occipital
- Posterior auricular
- Superficial temporal
- Maxillary
Which 5 arteries are the major supply to the scalp?
- Supra-orbital
- Supratrochlear
- Superficial temporal
- Posterior auricular
- Occupital
Name the 5 layers of the SCALP
- Skin
- Connective tissue (dense)
- Aponeurosis
- Loose connective tissue
- Periosteum
In which layer of the scalp do blood vessels lay?
-subcutaneous connective tissue layer (dense layer)
From where do the arteries of the scalp arise?
-All from ECA except supra-orbital and supratrochlear which are from the ophthalmic branch of internal carotid artery
Why is there profuse bleeding with a scalp laceration? (3 reasons)
- Many anastomoses
- Walls of arteries closely attached to connective tissue -> limits constriction
- Lacerations involving epicranial aponeurosis can bleed profusely due to opposing pull of occipitofrontalis
Is there usually necrosis of the skull in a scalp laceration?
-No, mostly supplied by middle meningeal artery
Describe the venous drainage of the scalp
- Most superficial veins follow arteries (eg occipital/superficial temporal veins etc)
- Supraorbital and supratrochlear do not follow the course of their arteries, instead they units at medial angle of the eye to form angular vein which drains into facial vein
- Some deep parts of the scalp in temporal region drain into pterygoid venous plexus
What is an emissary vein?
-Connection between the extracranial venous drainage of the scalp and intracranial venous drainage
What is a dural venous sinus?
- Endothelial lined Venous channels found at dural septae between the double layers of dura mater (periosteal and meningeal layers)
- Receive blood from large veins draining the brain
Why are emissiary veins clinically significant?
- They are valveless thus blood can flow in either direction
- Potential route for infection spread between scalp and cranial cavity-> can lead to meningitis
Describe the orientation of the external and internal jugular vein, relative to sternocleidomastoid
- External is anterior to SCM
- Internal is posterior to SCM
What is the pterion and why is it clinically significant?
- Site of fusion of 4 bones of the skull
- It is a weak area of the skull which overlays anterior branch of middle meningeal artery
- > Blow to pterion can cause fracture -> risk damage to mma -> extradural haemorrhage
What is the main blood supply to skull and dura mater?
-Middle meningeal artery
Why is the bone and scalp flap retracted inferiorly in a craniotomy?
-To preserve blood supply
Which major artery supplies the main blood supply to the face?
-External carotid
From where does the middle meningeal artery arise?
-Maxillary artery (from ECA)
Name 3 dural venous sinuses
- Cavernous sinus
- Superior/inferior saggital sinus
- Transverse sinus
Which sinus leaves the brain as internal jugular vein?
-Sigmoid sinus
Describe venous drainage of the face
-Follow the arteries
Which veins unite to form angular vein?
-Supraorbital and supratrochlear
What is clinically significant about facial veins?
- They are valveless and thus blood can flow in either direction
- They connect to cavernous sinus and pterygoid plexus via ophthalmic and facial veins -> potential route for infection spread to cranial cavity, especially from danger triangle
- Thrombophlebitis of facial vein can lead to infected clot entering intracranial venous system
Describe the cavernous sinus and its contents
- Plexus of extremely thin walled veins on upper surface of sphenoid bone
- Internal carotid artery
- CN III, IV, VI (all nerves to eye) and CNV1 and CNV2
Which jugular vein is used to measure JVP?
-Right Internal jugular
Describe how to measure JVP
- Sit patient at 45 degrees
- Observe pulsation under SCM
- Height from sternal angle + 5cm = mmHG
