Major arteries of head & neck: clinical Flashcards
what is the carotid sinus?
dilated portion of the common carotid and internal carotid arteries
what does the carotid sinus contain?
specific sensory cells: called baroreceptors
what do baroreceptors do?
detect stretch as a measure of blood pressure
what feeds the information from baroreceptors to the brain?
glossopharyngeal nerve
to regulate blood pressure
what can the baroreceptors be like in some patients?
hypersensitive to stretch
what happens to patients who have baroreceptors hypersensitive to stretch? leading to?
external pressure on the carotid sinus can cause slowing of heart rate and a decrease in blood pressure - brain then becomes underperfused = syncope
what should be advised against in patients with baroreceptors hypersensitive to stretch?
checking the pulse at the carotid triangle is not advised
what is present external to the carotid sinus?
cluster of nervous cells called the carotid body
what do the nervous cells (carotid body) do?
act as peripheral chemoreceptors - detecting the O2 content of the blood, and relaying this information to the brain to regulate breathing rate
which arteries b=provide a dense blood supply to the scalp?
posterior auricular
occipital
superficial temporal arteries
(along with 2 branches of the internal carotid artery: supra-orbital and supratrochlear)
what can injuries to the scalp result in?
excessive bleeding
what do injuries to the scalp result in excessive bleeding?
- walls of arteries are tightly and closely bound to the underlying CT of the scalp
- numerous anastomoses
- deep lacerations can involve epicranial aponeurosis
why does ‘walls of arteries are tightly and closely bound to the underlying CT of the scalp’ result in excessive bleeding in injuries to the scalp?
this prevents the arteries from constricting to limit blood loss following injury or laceration
why does ‘numerous anastomoses’ cause excessive bleeding in injuries to the scalp?
numerous anastomoses formed by the arteries produce a very densely vascularised area
why do ‘deep lacerations can involve the epicranial aponeurosis’ result in excessive bleeding in injuries to the scalp?
involve the epicranial aponeurosis - which is worsened by the opposing pulls of the OCCIPITAL and FRONTALIS muscles
how is bleeding to the scalp prevented from progressing to avascular necrosis?
the bony skull gets its blood from an alternative source (middle meningeal artery), so will not undergo avascular necrosis
what is the middle meningeal artery a branch of?
maxillary artery
what does the middle meningeal artery supply?
intracranial structures:
skull and dura mater
what supplies extra-cranial structures?
external carotid artery and its branches
what is dura mater?
the outer membranous layer covering the brain
what is the weakest point of the skull?
pterion
what does a fracture at the pterion result in?
injure / complete lacerate the middle meningeal artery
what does fracture at the pterion injuring the middle meningeal artery result in?
blood to collect in between the dura mater and the skull, causing a dangerous increase in intra-cranial pressure
what is an increase in intra-cranial pressure from blood collecting between the dura mater and skull called?
extradural haematoma
what are the symptoms caused by an increase in intra-cranial pressure?
a variety of symptoms:
nausea, vomiting, seizures, bradycardia, limb weakness
how do you treat minor increase in intra-cranial pressure?
treated by diuretics in minor cases
how do you treat extreme haemorrhage causing intra-cranial pressure?
drilling burr holes into the skull
what is the carotid sinus?
swelling at the bifurcation of the common carotid arteries
what does swelling of the carotid sinus produce?
turbulent blood flow
what does turbulent blood flow from swelling of the carotid sinus result in?
increases risk of atheroma formation in this area
within the tunica intima
which artery is more susceptible to increase risk of atheroma formation?
internal carotid artery
what does atherosclerotic thickening of the tunica intima of the internal carotid artery (/carotid sinus) result in?
reduce blood flow to the brain, resulting in neurological symptoms
what are the neurological symptoms resulting from atherosclerotic thickening of the tunic intima?
headache, dizziness, muscular weakness
if the blood flow to the brain is completely occluded, what will result?
a cerebral ischaemia (stroke)
if atherosclerosis of the carotid arteries is suspected, what should be used to assess the severity of any thickening?
a Doppler study
in severe cases, how should an atherosclerosis of the carotid artery be treated?
the artery can be opened, and the atheromatous tunica intima removed
what is the process of artery being opened and atheromatous tunica intima removed called?
carotid endarterectomy
