The Carotid Triangle |
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Boundaries: |
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Superomedially |
Posterior belly of the digastric |
Laterally: |
Anterior border of the .sternocleidomastoid muscle |
Inferomedially: |
superior belly of omohyoid |
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Contents: |
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The carotid sheath:
Location: Longitudinal interval between cervical viscera (pharynx, esophagus, larynx, trachea and thyroid gland) medially, and prevertebral muscles posteriorly
Formation:
- Prevertebral fascia behind
- Pretracheal fascia medially
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Contents of carotid sheath
- Common and Internal Carotid arteries medially.
- Internal jugular vein laterally.
- Vagus nerve posteriorly and between the above two.
- Ansa cervicalis embedded in the carotid sheath(anteriorly).
- Deep cervical lymph nodes.
Note:
1) Common carotid artery divides at superior border of thyroid gland (C3,4).
2) The carotid sinus (the baroreceptor) is a slight dilatation at the proximal part of the internal carotid artery. It is innervated by:
- Carotid sinus nerve, a branch of glossopharyngeal.
- A branch of vagus nerve.
- Sympathetic division of ANS.
3) The carotid body, is a small reddish brown, ovoid mass of tissue located at the carotid bifurcation. The same nerves that go to the carotid sinus innervate it. |
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Common carotid artery |
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Origin
Right:
Brachio cephalic trunk- behind right sternoclavicular joint
Left:
Aortic arch – behind manubrium sterni
Course
- Extends from sternoclavicular joint to upper border of thyroid gland c3/ c4
- Anterolateral neck in the carotid sheath lateral to trachea/ esophagus and larynx/ pharynx
- Palpable between sternocleidomastoid and angle of the mandible
- Divides in the carotid triangle into internal and external carotid arteries
Innervation
- Parasympathetic: Submandibular ganglion
- Sympathetic: superior cervical ganglion
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Branches
From the ventral side: |
From the dorsal side: |
Terminates by dividing into:
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- Superior thyroid artery. [5]
- Lingual artery. [4]
- Facial artery. [3]
- Ascending pharyngeal (may form from medial side).
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- Occipital artery. [7]
- Posterior auricular. [6]
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- Superficial temporal artery [1]
- Maxillary artery. [2]
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Internal jugular vein |
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Origin
- Union of sigmoid and inferior petrosal sinuses
Extent
- Base of skull to sternoclavicular joint
Landmark
- Between sternal and clavicular heads of sterno cleido mastoid muscles
Tributaries
- Pharyngeal veins
- Lingual
- Common facial
- Superior thyroid
- Middle thyroid
Termination:
Joins subclavian vein to form brachio-cephalic vein |
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Vagus Nerve
Course
- Emerges through jugular foramen
- Two ganglia- superior and inferior cervical ganglia
- Runs straight down in the carotid sheath
- Between and behind carotid artery and internal jugular veins
- At the root of the neck, it passes infront of the subclavian artery to enter mediastinum
- Branches and distribution
Branch |
Distribution |
Meningeal |
- Dura of posterior cranial fossa
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Auricular |
- Postero inferior quadrant of external surface of tympanic membrane
- Floor of external auditory meatus
- Skin on the cranial auricular canal
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Carotid body branch |
- Carotid body
- Carotid sinus
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Pharyngeal branch |
- Muscles of pharynx except stylopharyngeus
- Muscles of soft palate except tensor palate
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Superior laryngeal |
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External Laryngeal |
- Cricothyroid muscle
- Inferior pharyngeal constrictors
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Internal Laryngeal |
- Pharyngeal mucosa
- Laryngeal mucosa above vocal folds
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Recurrent Laryngeal |
- Trachea and Esophagus
- Cricopharyngeus
- Laryngeal muscles except cricothyroid
- Laryngeal mucosa below vocal folds
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Cardiac branches |
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