Here is a term paper on the ‘Carotid Artery’. Find paragraphs, long and short term papers on the ‘Carotid Artery’ especially written for school and college students.

Term Paper on the Carotid Artery

Term Paper # 1. Introduction to Common Carotid Artery:

i. Chief artery supplying head and neck.

ii. There are two common carotid arteries one on right and one on left side.

ADVERTISEMENTS:

Commencement:

i. Right Common Carotid Artery:

Arises from brachiocephalic artery behind right sternocla­vicular joint.

ii. Left Common Carotid Artery:

ADVERTISEMENTS:

Arises from arch of aorta in the thorax behind the manubrium sterni. It crosses anterior to trachea, then left side of the trachea and reaches the neck.

Termination:

Both common carotid arteries terminate at the level of upper border of thyroid cartilage which lies at intervertebral disc between C3 and C4 vertebra by dividing into its 2 terminal branches, i.e.,

1. External carotid artery

ADVERTISEMENTS:

2. Internal carotid artery.

Terminal part of common carotid artery and beginning of internal carotid artery shows a dilatation called carotid sinus. It has a rich innervation from the glossopharyngeal and sympathetic nerves.

It acts as a baroreceptor (pressure receptor) and regulates the blood pressure (B.P.).

In carotid sinus – tunica media is thin and tunica adventia is thick and richly innervated by nerves.

ADVERTISEMENTS:

Carotid Body:

It is a small reddish brown oval structure situated just behind the bifurcation of common carotid artery.

It receives rich nerve supply from glossopharyn­geal, vagus and sympathetic nerves.

It acts as a chemoreceptor and responds to the changes in the oxygen, carbon dioxide and pH content of the blood.

ADVERTISEMENTS:

Other sites of chemoreceptors are:

Arch of aorta, right subclavian artery and ductus arteriosus.

All are supplied by branches of vagus nerve.

Course:

ADVERTISEMENTS:

In the neck both arteries have similar course.

Each runs upwards from sternoclavicular joint to upper border of lamina of thyroid cartilage enclosed in a carotid sheath.

Carotid Sheath:

Carotid sheath encloses common carotid artery and internal carotid artery, internal jugular vein and vagus nerve (X).

Term Paper # 2. Relations of Common Carotid Artery:

Lower part of the artery is deeply situated

Upper part is superficially situated.

Superficial Relations:

1. Sternocleido mastoid muscle

2. Sternohyoid

3. Sternothyroid

4. Superior belly of omohyoid.

Veins Crossing the Artery:

1. Superior thyroid vein

2. Middle thyroid vein

3. Anterior jugular vein.

Posterior Relations:

1. Longus colli and capitis

2. Cervical sympathetic trunk

3. Ascending cervical artery.

Lower part of artery is posteriorly related to vertebral vessels and inferior thyroid artery.

Medial Relations:

1. Larynx and pharynx

2. Trachea and oesophagus

3. Inferior thyroid artery

4. Recurrent laryngeal nerve

5. Lateral lobe of thyroid gland.

Lateral Relations:

Internal jugular vein and vagus nerve.

Term Paper # 3. Branches of Common Carotid Artery:

It gives only two terminal branches, i.e.,

1. External carotid artery

2. Internal carotid artery.

External Carotid Artery:

Origin:

It is one of the terminal branches of common carotid artery at the upper border of lamina of thyroid cartilage.

Area of Distribution:

Structures present external to the skull and those in front of the neck are supplied by it.

Termination:

It ends by dividing into its terminal branches behind the neck of mandible in the upper part of parotid gland.

Course:

External carotid artery ascends upwards in a curved manner.

At the beginning, it lies medial and anterior to the internal carotid artery.

It crosses over it anteriorly inclining backwards to lie anterolateral to internal carotid artery.

It then runs upwards in the deep part of parotid gland (posteromedial surface) and ends behind the neck of the mandible by dividing into its terminal branches, i.e., small superficial temporal artery and maxillary artery (larger branch).

Relations of External Carotid Artery:

I. Carotid Triangle:

Anterolateral – Skin:

Superficial fascia containing platysma, cutaneous nerves and vessels.

Investing layer of deep fascia.

Anterior division of retro mandibular vein.

Common facial and lingual veins.

Hypoglossal nerve.

Sternocleido mastoid overlaps artery.

Deep:

Inferior and middle constrictors of pharynx.

External and internal laryngeal nerves.

II. Parotid Region:

Superfical:

Posterior belly of digastric stylohyoid muscle, stylo mandibular ligament and parotid gland.

Branches of facial nerve and retro mandibular vein within the parotid gland.

Deep:

1. Structures which intervene between external and internal carotid artery:

(a) Styloid process

(b) Stylo glossus

(c) Stylo pharyngeus

(d) Glossopharyngeal nerve (IXth C.N.)

(e) Pharyngeal branch of vagus (Xth C.N.).

2. Internal carotid artery

3. Portion of parotid gland.

Medially:

(a) Pharyngeal wall

(b) Superior laryngeal nerve.

Laterally:

(a) Internal jugular vein

(b) Vagus nerve (X).

Branches of External Carotid Artery:

1. Ascending Pharyngeal Artery:

It is a slender branch arising from medial aspect of external carotid artery near its lower end.

Runs vertically upwards on the sidewall of pharynx upto base of skull.

It gives following branches:

(a) Pharyngeal branches to wall of pharynx.

(b) Meningeal branches which traverse through jugular foramen and foramen lacerum to supply meninges of posterior and middle cranial fossa.

(c) Inferior tympanic branch passes through inferior tympanic canaliculus situated between jugular foramen and carotid canal for supply of tympanic cavity.

(d) Palatine branches accompany levator veli palatini muscle of palate at superior border of superior constrictor of pharynx to supply soft palate and tonsil.

2. Superior Thyroid Artery:

It arises from anterior aspect of external carotid artery below the tip of greater cornu of hyoid bone.

Runs downwards and forwards parallel and superficial to external laryngeal nerve to reach the upper pole of thyroid gland.

Artery is close to external laryngeal nerve proximally and lies anterolateral to it. It diverges from the nerve near the thyroid gland, where artery lies superficial to upper pole of gland and nerve lies deep to it.

Branches are:

(a) Infrahyoid branch runs below hyoid bone and anastomoses with its fellow of opposite side.

(b) Sternocleiodmastoid branch- to supply same muscle.

(c) Superior laryngeal artery accompanies the internal laryngeal nerve, passes deep to thyrohyoid muscle and pierces the thyrohoid membrane to supply the larynx above vocal cords.

(d) Glandular branches to thyroid gland. Anterior branch anastomoses with its fellow of opposite side along the upper border of isthmus of gland. And posterior branch anastomoses with branches of inferior thyroid artery.

3. Lingual Artery:

Arises from anterior aspect of external carotid artery opposite the tip of greater cornu of hyoid bone.

It is divided into three parts by hyoglossus muscle:

(a) First Part:

Lies in carotid triangle and forms a characteristic loop with its convexity upwards. It is crossed superficially by hypoglossal nerve (XIIth C.N.). Loop permits free movement of the hyoid bone.

It gives only one branch, i.e., suprahyoid branch runs above hyoid bone and anas­tomoses with its fellow of opposite side.

(b) Second Part:

Lies deep to the hyoglossus muscle runs along the upper border of hyoid bone and gives two – dorsal lingual branches – to supply dorsum of tongue and tonsil.

(c) Third Part:

Also called arteria profunda linguae or deep lingual artery – runs upwards along the anterior border of hyog­lossus muscle and then forwards on the under surface of tongue where it anastomoses with its fellow of opposite side.

It gives sublingual branches to supply sublingual gland and floor of mouth.

4. Facial Artery (External Maxillary Artery):

Origin:

Arises from anterior aspect of external carotid artery just above the tip of the greater cornu of hyoid bone.

Termination:

It terminates at the medial end of the eye as angular artery and anastomoses with the dorsal nasal artery branch of ophthalmic artery (internal carotid artery).

Course:

It is divided into two parts:

(a) Cervical Part:

It ascends deep to posterior belly of digastric and stylohyoid muscles.

Then it passes deep to ramus of mandible and grooves the posterior border of submandi­bular gland and then passing up over the base of the mandible.

(b) Facial Part:

Facial part (course) of facial artery begins at the antero inferior angle of masseter – winds round the lower border of mandible and pierces the deep fascia of neck.

It runs upwards and forwards to reach a point half inch lateral to the angle of mouth.

It ascends by the side of the nose upto the medial angle of eye and terminates by anastomosing with dorsal nasal branch of ophthalmic artery.

Artery is tortuous and this allows it to move easily over facial muscles as they contract.

Important Relations of Facial Artery:

I. In the Neck:

Anterior:

Posterior belly of digastric and stylohyoid muscle.

Lower part of ramus of mandible.

Posterior:

Stylopharyngeus, middle and superior constrictor of pharynx.

II. In the Face:

Facial vein lies above and behind the artery.

Anterior:

Branches of facial nerve:

i. Facial vein

ii. Zygomaticus major and minor muscles

iii. Skin and superficial fascia.

Posterior:

Mandible in lower part:

i. Buccinator muscle

ii. Levator anguli oris muscle.

Branches of Facial Artery:

I. From Cervical Part:

1. Ascending Palatine Artery:

Arises near origin of facial artery ascends up to accompany levator palati – passes over upper border of superior constrictor and supplies soft palate.

2. Tonsillar Artery:

Is the main artery of the tonsil.

Pierces superior constrictor and ends in tonsil.

3. Glandular Branches:

To supply subman­dibular gland.

4. Submental Artery:

Runs forwards on mylohyoid muscle along with mylohyoid nerve and supplies it, submandibular and sublingual salivary glands.

II. From the Facial Part:

1. Inferior Labial Artery:

Supplies lower lip.

2. Superior Labial Artery:

Supplies upper lip.

3. Lateral Nasal Artery:

Supplies ala and dorsum of nose.

4. Angular Artery:

Terminal part of artery at medial canthus of eye anastomoses with branches of ophthalmic artery.

5. Small Unnamed Branches:

Arise from posterior aspect of facial artery and supplies muscles, fascia and skin of face.

6. Occipital Artery:

Arises from posterior aspect of external carotid artery at the same level as facial artery.

Runs backwards and upwards under cover of posterior belly of digastric crossing internal carotid artery, internal jugular vein and last four cranial nerves.

It runs deep to mastoid process by making a groove medial to mastoid notch.

Crosses apex of sub-occipital triangle to reach under trapezius muscle, pierces the muscle 2.5 cm away from midline and comes to lie just lateral to the greater occipital nerve.

Supplies most of the back of scalp.

Branches:

1. Sternomastoid branches – two

2. Mastoid artery

3. Meningeal branches – passes through jugular foramen

4. Muscular branches

5. Auricular branch

6. Descending branches

7. Occipital branches.

Important Points:

1. Hypoglossal nerve hooks under the origin of occipital artery.

2. Occipital arteries cross the apex of posterior triangle of neck.

3. Sternocleidomastoid branch – Upper one accompanies XIIth C.N.

Lower one crosses XIIth C.N.

7. Posterior Auricular Artery:

Arises from posterior aspect of external carotid artery a little above occipital artery.

It crosses superficial to stylohyoid muscle.

Runs upwards and backwards parallel to occipital artery under cover of upper border of posterior belly of digastric deep to parotid gland.

Becomes superficial and lies on the base of mastoid process behind the auricle which it supplies.

Branches:

1. Stylomastoid artery – enters the stylomastoid foramen and supply facial nerve and middle ear.

2. Auricular branch – for auricles.

3. Occipital branch – for occipital area of scalp.

8. Superficial Temporal Artery:

Is a small terminal branch of external carotid artery.

Begins behind the neck of the mandible deep to upper part of parotid gland.

Runs vertically upwards crossing the root of zygoma. (Pulsations of the artery can be felt on zygoma.)

About 5 cm above the zygoma, it divides into anterior and posterior branches, which supply temple and scalp.

Branches:

1. Transverse facial artery – runs forward below the zygomatic arch and supplies.

2. Middle temporal artery – runs on temporal fossa and supplies temporalis muscle and fascia.

3. Anterior and posterior terminal branches.

9. Maxillary Artery (Internal Maxillary Artery):

It is the larger terminal branch of external carotid artery.

Course:

Begins behind the neck of mandible.

Runs horizontally forwards deep to neck of mandible upto lower border of lower head of lateral pterygoid.

From here it turns upwards, forwards and crosses the lower head of lateral pterygoid superficially (sometimes deep).

After emerging between two heads, it enters the pterygo – palatine fossa by passing through the pterygo-maxillary fissure.

Here it ends by giving its terminal branches.

Parts:

Maxillary artery is divided into three parts by lower head of lateral pterygoid:

(i) First Part or Mandibular Part:

From its origin to lower border of lateral pterygoid.

Lies between neck of mandible laterally and spheno-mandibular ligament medially.

Auriculo temporal nerve – lies above this part.

(ii) Pterygoid Part:

From lower border to upper border of lower head of lateral pterygoid.

(iii) Third Part or Pterygo-Palatine Part:

Lies in pterygo-palatine fossa – From upper border of lower head of lateral pterygoid, here it lies in front of pterygo palatine ganglion.

Branches of Maxillary Artery:

Ist Part- Deep auricular artery, Anterior tympanic artery, Middle meningeal artery, Accessory meningeal artery, Inferior alveolar artery.

IInd Part- Two deep temporal arteries, Pterygoid branches to muscles, Masseteric artery, Buccal artery.

IIIrd Part- Posterior superior alveolar artery, Infra orbital artery, Greater palatine artery, Pharyngeal artery, Artery of pterygoid canal, Spheno palatine artery, Internal carotid artery.

It is the upward continuation of the common carotid artery, lies in the carotid sheath.

It supplies structures lying within the skull and in the orbit.

Origin:

It begins at the upper border of the lamina of thyroid cartilage (Disc between C3 and C4) and runs upwards to reach the base of skull, where it enters the carotid canal in the petrous part of temporal bone.

Termination:

It enters the cranial cavity by passing through the upper part of the foramen lacerum.

In the cranial cavity it enters the cavernous – sinus and finally ends below the anterior perforated substance of the brain by dividing into the anterior cerebral and middle cerebral arteries.

Structures Passing between External and Internal Carotid Artery:

1. Stylopharyngeus muscle

2. Glossopharyngeal nerve

3. Pharyngeal branch of vagus nerve

4. Styloid process

5. Deep part of parotid gland.

Course and Branches of Internal Carotid Artery:

It is divided into four parts:

I. Cervical Part:

1. From its origin it ascends vertically upwards and lies infront of transverse process of upper cervical vertebrae.

2. Enclosed in the carotid sheath along with internal jugular vein and vagus nerve.

3. In the lower part it lies in carotid triangle.

4. Upper part is deeply located and lies deep to posterior belly of digastric, styloid process with the structures attached to it and the parotid gland.

5. At the upper end internal jugular vein lies posterior to internal carotid artery.

6. Last four cranial nerves (IXth, Xth, XIth and XIIth) lie between the internal jugular vein and internal carotid artery at the base of skull.

Branches:

It gives no branches in the neck.

II. Petrous Part:

1. Internal carotid artery enters the petrous part of temporal bone in the carotid canal.

2. It first runs upwards and then turns forwards and medially at a right angle.

3. It emerges in the posterior wall of foramen lacerum and passes through its upper part to enter the cranial cavity.

Branches from Petrous Part of Internal Carotid Artery:

(a) Carotico tympanic branch to middle ear.

(b) Pterygoid branch – a small and inconstant branch that enters the pterygoid canal.

III. Cavernous Part:

From the foramen lacerum the internal carotid artery ascends and enters the cavernous sinus.

In the sinus, it passes forwards along the side of sella trucica in the floor and medial wall of the sinus. It lies outside the endothelial lining of the sinus and is related to abducent nerve infero laterally.

In the anterior part of the sinus, the artery ascends up and pierces the dural roof of the sinus between the anterior and posterior clinoid processes to reach the under surface of the cerebrum.

Branches:

(a) Carvenous branch to trigeminal ganglion.

(b) Superior and inferior hypophyseal arteries to the hypophysis cerebri or pituitary gland.

IV. Cerebral Part of Internal Carotid Artery:

After emerging from the roof of cavernous sinus artery turns backwards in the subarchnoid space along the roof of the cavernous sinus and lies below the optic nerve.

Finally it turns upwards by side of the optic chiasma and reaches the anterior perforated substance of the brain.

Here it ends by dividing into anterior and middle cerebral arteries.

Branches:

(a) Ophthalmic artery

(b) Anterior choroidal artery

(c) Posterior communicating artery

(d) Anterior cerebral artery

(e) Middle cerebral artery.