External Carotid Artery

INTRODUCTION:
  • External carotid artery is the chief artery which supplies to structures in the front of the neck and in the face.
  • The arterial supply to the parotid gland is from the external carotid artery and its branches within and near the gland.
  • Nasal mucosa is supplied by both ECA & ICA but mainly by external carotid artery
EMBRYOLOGY OF EXTERNAL CAROTID:
  • During the fourth and fifth weeks of embryological development, when the pharyngeal arches form, the aortic sac gives rise to arteries – the aortic arches.
  • The aortic sac is the endothelial lined dilation, it is the primordial vascular channel from which the aortic arches arise.
  • In the initial stage there are pairs of aortic arches, which are numbered I, II, III, IV, and V. This system becomes altered in further development.
  • 3rd Arch : forms common carotid artery, first (cervical) part of internal carotid artery (rest of internal carotid arises from dorsal aorta), and external carotid artery.
SURFACE MARKING
  • ECA is marked by joining the following two points.
  1. Point on the anterior border of the sternocleidomastoid muscle at the level of the upper border of the thyroid cartilage.
  2. Second point on the posterior border of the neck of the mandible.
  • The artery is slightly convex forwards in its lower half and slightly concave forwards in its upper half.
COURSE
  • ECA begins in the carotid triangle at the level of upper border of thyriod cartilage opposite the disc between the third and fourth cervical vertibrae.
  • In the carotid triangle,it lies under cover of the anterior border of the sternocleidomastiod muscle
  • As the artery ascends ,it passes deep to the post. Belly of digastric and stylohyoid muscle and terminates behind the neck of the mandible by dividing into the maxillary and superficial temporal arteries.
  • Has slightly curved course,so that it is anteromedial to ICA in it lower part,andanterolateral to the ICA in its upper part.
RELATIONS
  • IN THE CAROTID TRIANGLE
  1. Superficially—Cervical branch of facial nerve, Hypoglossal nerve,Facial,lingual,and superior thyriod veins
  2. Deep to the artery— Wall of pharynx, Superior laryngeal nerve & Ascending pharyngeal artery
  • ABOVE THE CAROTID TRIANGLE
  1. Lies deep in the substance of the parotid triangle.
  2. Within the gland, it is related
  3. Superficially—Retromandibular vein, Facial nerve
  4. Deep to the artery—ICA
  5. Structures passing between ECA and ICA
  • Styloglossus
  • Stylopharyngeus
  • IXth nerve
  • Pharyngeal branch of Xth nerve
  • Styloid process
  • BRANCHES
ANTERIOR—
  1. Superior thyroid
  2. Lingual
  3. Facial
  • POSTERIOR-
  1. Occipital
  2. Posterior auricular
  •  MEDIAL—
     Ascending Pharyngeal 
  • TERMINAL—
  1.  Maxillary
  2. Superficial temporal

Exam Question
  • Branches of ECA are superior thyroid, lingual, facial, occipital, post. auricular, ascending pharyngeal, maxillary, superficial temporal
  • The arterial supply to the parotid gland is from the external carotid artery and its branches within and near the gland.
  • The only medial branch of external carotid artery is Ascending pharyngeal
  • Nasal mucosa is supplied by mainly external carotid artery
  • Superior thyroid artery originates from external carotid artery

Don't Forget to Solve all the previous Year Question asked on External Carotid Artery