Arteries of the Head and Neck

Question 1

Via which 2 arteries does the head and neck receive the majority of its blood supply through?

Answer 1

Vertebral and carotid arteries

Question 2

Where does each common carotid artery originate from?

Answer 2

• Left common carotid arises directly from the arch of the aorta
• Right common carotid arises from the brachiocephalic trunk (the right subclavian artery is the other branch)

Question 3

After arising, the left and right common carotid arteries ascend up the neck, lateral to the trachea and the oesophagus. Do they give off any branches in the neck?

Answer 3

No

Question 4

Where does each common carotid artery bifurcate? What does it bifurcate into?

Answer 4

• Bifurcates at the level of the superior margin of the thyroid cartilage (C4) –> carotid triangle
• The carotid arteries split into the external and internal carotid arteries.

Question 5

The bifurcation of the common carotid occurs in an anatomical area known as the carotid triangle. What is important to note about the common carotid and internal carotid here? What is this area called?

Answer 5

• They are slightly dilated –> this area is known as the carotid sinus
  
  • ​Important in detecting and regulating blood pressure

Question 6

What is the carotid sinus important for?

Answer 6

detecting and regulating blood pressure

Question 7

What is the carotid sinus? What is it important for? How does it carry out this function?

Answer 7

• The carotid sinus is a dilated portion of the common carotid artery and proximal internal carotid artery.
• It contains baroreceptors: specialised sensory cells.
  
  • The baroreceptors detect stretch as a measure of blood pressure.
  • The glossopharyngeal nerve feeds this information to the brain, and this is used to regulate blood pressure.

Question 8

In some individuals, the baroreceptors are hypersensitive to stretch. What is Carotid Sinus Hypersensitivity?

Answer 8

• When external pressure is placed on the carotid sinus it automatically reduces your heart rate, normally this is only by a small amount.
• External pressure on the carotid sinus in these cases (e.g. even wearing tight clothes around the neck) can cause their heart rate to slow down or their blood pressure to drop a significant amount.
  
  • The brain becomes under-perfused and syncope results.

Question 9

What should be noted about checking pulses in patients with Carotid Sinus Hypersensitivity?

Answer 9

checking the pulse at the carotid triangle is not advised.

Question 10

External to the carotid sinus, there is a cluster of nervous cells known as the carotid body. What is this?

Answer 10

These cluster of nerve cells act as peripheral chemoreceptors -> these detect the O2 content of the blood and relaying this information to the brain to regulate breathing rate.

Question 11

Carotid body vs carotid sinus

Answer 11

• Carotid body –> chemoreceptor
  
  • Monitors the blood’s pH, pCO2, and pO2
  • Innervation: a branch of the glossopharyngeal (CN IX)
• Carotid sinus –> baroreceptor
  
  • Senses changes in systemic blood pressure
  • Innervation: a branch of the glossopharyngeal (CN IX)

Question 12

What does the external carotid artery supply?

Answer 12

• The areas of the head and neck external to the cranium.
• After arising from the common carotid artery, it travels up the neck, passing posteriorly to the mandibular neck and anteriorly to the lobule of the ear.

Question 13

Where and how does the external carotid artery end?

Answer 13

The artery ends within the parotid gland by dividing into the superficial temporal artery and the maxillary artery.

Question 14

What branches does the external carotid give off?

Answer 14

1. Superior thyroid
2. Lingual
3. Facial
4. Ascending pharyngeal artery
5. Occipital artery
6. Posterior auricular artery
7. Maxillary
8. Superifical temporal

Question 15

The facial, maxillary and superficial temporal arteries are the major branches of note. What do these supply?

Answer 15

Maxillary - deep structures of the face

Facial & superficial temporal - generally supply superficial areas of the face.

Question 16

What is the middle meningeal artery a branch of? How is this artery unique?

Answer 16

• The maxillary artery (a branch of the external carotid)
• Unique as it supplies some intracranial structures (remember, the external carotid artery and its branches usually supply extra-cranial structures).

Question 17

What does the middle meningeal artery supply?

Answer 17

The skull and dura mater

Question 18

A fracture of the skull at its weakest point, the pterion, can injure or completely lacerate the MMA. What can this lead to?

Answer 18

An extradural/epidural haematoma –> causing a dangerous increase in intra-cranial pressure

Question 19

An increase in intra-cranial pressure causes a variety of symptoms. What are these? How is it treated?

Answer 19

• Symptoms: nausea, vomiting, seizures, bradycardia and limb weakness.
• Treated: diuretics in minor cases, and drilling burr holes into the skull the more extreme haemorrhages.

Question 20

Describe the route of the internal carotid artery. How does it enter the cranium?

Answer 20

The internal carotid arteries do not supply any structures in the neck, entering the cranial cavity via the carotid canal in the petrous part of the temporal bone.

Question 21

Within the cranial cavity, what does the internal carotid artery supply?

Answer 21

The brain

Eyes

Forehead

Question 22

How is the carotid sinus and atherosclerosis related? What can this result in?

Answer 22

• The swelling at the bifurcation of the common carotid arteries, the carotid sinus, produces turbulent blood flow.
• This increases the risk of atheroma formation in this area, with the internal carotid most susceptible.
• Atherosclerotic thickening of the tunica intima of these arteries will reduce blood flow to the brain
  
  • Resulting in the variety of neurological symptoms: headache, dizziness, muscular weakness.
  • If blood flow is completely occluded, a cerebral ischaemia (stroke) results.

Question 23

The vertebral arteries are paired vessels. Where do they arise from?

Answer 23

Arise from the subclavian arteries.

Question 24

How do the vertebral arteries ascend up the neck?

Answer 24

They ascend the posterior aspect of the neck, passing through holes in the transverse processes of the cervical vertebrae (known as foramen transversarium).

Question 25

How do the vertebral arteries enter the cranium?

Answer 25

Via the foramen magnum

Question 26

After entering the cranium, what do the vertebral arteries converge to form?

Answer 26

The basilar artery - this continues to supply the brain

Question 27

The neck is supplied by arteries other than the carotids. The right and left subclavian arteries give rise to the thyrocervical trunk. What vessels arise from this trunk?

Answer 27

• Inferior thyroid artery
• Ascending cervical artery
• Transverse cervical artery
• Suprascapular artery

Question 28

Describe the arterial supply of the thyroid gland

Answer 28

• Superior thyroid artery: arises from the external carotid artery
• Inferior thyroid artery: arises from the thyrocervical trunk from the subclavian artery

Question 29

What does the suprascapular artery supply?

Answer 29

This is a branch of the thyrocervical trunk –> goes to supply the supra- and infraspinatus muscles