Common carotid artery
COMMON CAROTID ARTERY & INTERNAL CAROTID ARTERY
Study notes covering the common carotid artery, its course and relations, followed by the internal carotid artery, its parts, relations, course and branches.
01
Common Carotid Artery
Common Carotid Artery
- Right common carotid artery arises from the brachiocephalic artery behind the right sternoclavicular joint.
- Left common carotid artery arises from the arch of aorta in the thoracic cavity.
- It ascends toward the left sternoclavicular joint to the neck.
- The common carotid artery is enclosed in the carotid sheath.
02
Course of Common Carotid Artery
- Common carotid artery begins in the thorax, in front of the trachea, opposite a point a little to the left of the centre of the manubrium.
- It ascends to the back of the left sternoclavicular joint and enters the neck.
- In the neck, both arteries have a similar course.
Course in the Neck
Each artery:
- Runs upwards within the carotid sheath.
- Lies under cover of the anterior border of sternocleidomastoid.
- Lies in front of the lower four cervical transverse processes.
Termination
At the level of the upper border of the thyroid cartilage, the artery ends by dividing into:
- External carotid artery
- Internal carotid artery
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Relations of the Artery in the Neck
A. Anterior Relations
- The common carotid artery is crossed by the superior belly of omohyoid at the level of the cricoid cartilage.
- Below the omohyoid, the artery is deeply situated and is covered by:
- Sternocleidomastoid
- Anterior jugular vein
- Sternohyoid
- Sternothyroid
- Middle thyroid vein
B. Posterior Relations
1. Transverse Processes of Vertebrae C4–C7
And the muscles attached to their anterior tubercles:
- Longus colli
- Longus capitis
- Scalenus anterior
2. Inferior Thyroid Artery
- Crosses medially at the level of the cricoid cartilage.
3. Vertebral Artery
4. Thoracic Duct — Left Side
- Crosses laterally behind the artery at the level of vertebra C7.
- Lies in front of the vertebral vessels.
C. Medial Relations
- Thyroid gland
- Larynx and pharynx
- Trachea
- Oesophagus
- Recurrent laryngeal nerve
D. Lateral Relation
- Internal jugular vein
E. Posterolateral Relation
- Vagus nerve
04
Clinical Anatomy — Common Carotid Artery
- The pulsation of the common carotid artery can be felt by compressing it against the carotid tubercle.
- Carotid tubercle = anterior tubercle of the transverse process of vertebra C6.
- It lies at the level of the cricoid cartilage.
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Internal Carotid Artery
- The internal carotid artery is one of the two terminal branches of the common carotid artery.
- It begins at the level of the upper border of the thyroid cartilage, opposite the disc between the 3rd and 4th cervical vertebrae.
- It ends inside the cranial cavity by supplying the brain.
- It is the principal artery of the brain and the eye.
- It also supplies the related bones and meninges.
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Parts of Internal Carotid Artery
For convenience of description, its course is divided into four parts:
1. Cervical Part
In the neck.
2. Petrous Part
Within the petrous temporal bone.
3. Cavernous Part
Within the cavernous sinus.
4. Cerebral Part
In relation to the base of the brain.
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Cervical Part
- It ascends vertically in the neck from its origin to the base of the skull to reach the lower end of the carotid canal.
- This part is enclosed in the carotid sheath with:
- Internal jugular vein
- Vagus nerve
- No branches arise from the internal carotid artery in the neck.
- Its initial part usually shows a dilatation called the carotid sinus, which acts as a baroreceptor.
- The lower part of the artery, in the carotid triangle, is comparatively superficial.
- The upper part, above the posterior belly of digastric, is deep into:
- Parotid gland
- Styloid apparatus
- Many other structures
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Relations of Cervical Part
A. Anterior or Superficial Relations
1. In the Carotid Triangle
- Anterior border of sternocleidomastoid
- External carotid artery is anteromedial to it.
2. Above the Carotid Triangle
- Posterior belly of digastric
- Stylohyoid
- Stylopharyngeus
- Styloid process
- Parotid gland with structures within it
B. Posterior Relations
- Superior cervical ganglion
- Carotid sheath
- At the base of the skull:
- Glossopharyngeal nerve
- Vagus nerve
- Accessory nerve
- Hypoglossal nerve
C. Medial Relations
- Pharynx
- The external carotid artery is anteromedial to it below the parotid.
D. Lateral Relations
- Internal jugular vein
- Temporomandibular joint — at the base of the skull.
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Petrous Part
In the carotid canal, the artery:
- First runs upwards.
- Then turns forwards and medially at right angles.
- It emerges at the apex of the petrous temporal bone, in the posterior wall of the foramen lacerum.
- Here it turns upwards and medially.
10
Cavernous and Cerebral Parts
Cavernous Part
- The cavernous part runs in the cavernous sinus.
Cerebral Part
- The cerebral part lies at the base of the skull.
- It gives:
- Ophthalmic artery
- Anterior cerebral artery
- Middle cerebral artery
- Posterior communicating artery
- Anterior choroidal artery
11
Branches of Internal Carotid Artery
A. Cervical Part
No branch.
B. Petrous Part
- Caroticotympanic branches
- Pterygoid branch
C. Cavernous Part
- Cavernous branches
- Superior hypophyseal arteries
- Inferior hypophyseal arteries
D. Cerebral Part
- Ophthalmic artery
- Anterior choroidal artery
- Posterior communicating artery
- Anterior cerebral artery
- Middle cerebral artery
12
Internal Carotid Artery — Beginning and Termination
Beginning
- Terminal branch of the common carotid artery.
- Begins at the level of the upper border of the lamina of thyroid cartilage.
Termination
- Divides into the anterior and middle cerebral arteries.
Parts and Branches
Cervical Part
No branch
Petrous Part
- Caroticotympanic branch
- Pterygoid branch
Cavernous Part
- Cavernous branches
- Superior and inferior hypophyseal arteries
Cerebral Part
- Ophthalmic
- Anterior choroidal
- Posterior communicating
- Anterior cerebral
- Middle cerebral arteries