Phrenic nerve

Question 1

What is the starting trajectory of the phrenic nerve?

Answer 1

• anterior rami of C3, C4, C5
  formed at upper part of lateral border of scalenus anterior
  descends almost vertically across its anterior surface behind prevertebral fascia
  descends posterior to sternocleidomastoid and internal jugular vein
  In neck, each nerve receives variable filaments from cervical sympathetic ganglia or their branches + may also connect with internal thoracic sympathetic plexuses
  At root of neck :runs anterior to second part of subclavian artery and posterior to the subclavian vein
  enters thorax by crossing medially in front of internal thoracic artery
  in thorax descends anterior to pulmonary hilum, between fibrous pericardium and mediastinal pleura
  to diaphragm accompanied by pericardiophrenic vessels.

Question 2

The phrenic nerve divides into 2 portions, what are they called?

Answer 2

left

right

Question 3

What is the trajectory of the left phrenic nerve?

Answer 3

passes anteromedially, superficial to the left vagus nerve just above the aortic arch
then passes superficial to the aortic arch and the left superior intercostal vein, anterior to the left pulmonary hilum, to lie between the fibrous pericardium covering the surface of the left ventricle and the mediastinal pleura
crosses anterior to left internal thoracic artery
descending across medial aspect of apex of left lung + its pleura to first part of subclavian artery
crosses it obliquely to reach groove between the left common carotid + subclavian arteries.

Question 4

What is the trajectory of the right phrenic nerve?

Answer 4

shorter and more vertical than left, separated at root of neck from 2nd part of right subclavian artery by scalenus anterior
descends lateral to right brachiocephalic vein, superior vena cava, fibrous pericardium that covering right surface of right atrium + inferior vena cava
divides just above or at level of diaphragm

Question 5

What is motor function of the phrenic nerve?

Answer 5

innervates diaphragm,

Question 6

What are the sensory functions of the phrenic nerve?

Answer 6

innervates central part of diaphragm, pericardium, mediastinal part of parietal pleura