Anatomy of the Carotid Triangle

Anatomy of the Neck

• The neck is divided into two triangles: anterior triangle and posterior triangle.
• The anterior triangle is bounded by the midline of the neck, the anterior border of the sternomastoid muscle, and the lower border of the mandible.

Layers of the Neck

• The neck has five layers:
  • Skin
  • Superficial fascia
  • Deep cervical fascia
  • Muscle layers
  • Viscera or tubes

Superficial Fascia

• Contains the platysma muscle
• Contains the cervical branch of the facial nerve
• Contains the external jugular vein
• Contains the anterior jugular veins
• Contains cutaneous branches of the cervical plexus

Deep Cervical Fascia

• Has four layers:
  • Investing fascia (superficial layer)
  • Pretracheal fascia (middle layer)
  • Prevertebral fascia (deep layer)
  • Carotid sheath

Investing Fascia

• Encircles the neck completely
• Splits to enclose the sternomastoid and trapezius muscles
• Above the hyoid bone, it splits to enclose the submandibular salivary gland
• Below the hyoid bone, it covers the infrahyoid muscles and then splits to enclose the suprasternal space

Triangles of the Neck

• The anterior triangle is subdivided into four smaller triangles:
  • Submental triangle
  • Submandibular (digastric) triangle
  • Carotid triangle
  • Muscular triangle

Submental Triangle

• Boundaries:
  • Apex: symphysis menti
  • Base: the body of the hyoid bone
  • Each side: the anterior belly of the digastric muscle
  • Floor: the mylohyoid muscle
• Contents:
  • Submental artery
  • Submental vein and the beginning of the anterior jugular vein
  • Mylohyoid nerve
  • Submental lymph nodes

Submandibular (Digastric) Triangle

• Boundaries:
  • Above: the lower border of the mandible
  • Anteriorly: the anterior belly of the digastric muscle
  • Posteriorly: the posterior belly of the digastric muscle
  • Floor: the mylohyoid, the hyoglossus, and the middle constrictor
• Contents:
  • Facial artery
  • Anterior facial vein

Carotid Triangle

• Boundaries:
  • In front and above: the posterior belly of the digastric muscle
  • In front and below: the superior belly of the omohyoid
  • Behind: the anterior border of the sternomastoid muscle
  • Floor: thyrohyoid and hyoglossus (anteriorly), and the middle and inferior constrictors (posteriorly)
• Contents:
  • Common carotid artery
  • Internal carotid artery
  • External carotid artery and its five branches
  • Internal jugular vein
  • Common facial vein
  • Last four cranial nerves (9, 10, 11, 12)
  • Ansa cervicalis
  • Deep cervical lymph nodes along the internal jugular vein

Muscular Triangle

• Boundaries:
  • In front: the midline of the neck (from the hyoid bone to the sternum)
  • Behind and above: the superior belly of the omohyoid
  • Behind and below: the sternomastoid muscle
• Contents:
  • Infrahyoid muscles
  • Cricothyroid muscle (tensor of the vocal cords)
  • Thyroid gland

Learn about the boundaries and anatomical structures of the Carotid triangle, including muscles and glands.