Lecture 18 - SQ

Question 1

1. What nerve passes through the posterior triangle of the neck and is embedded in fat?

Answer 1

1. The nerve is the spinal accessory nerve (CN XI) that supplies both the sternocleidomastoid
   and the trapezius muscles.

Question 2

2. What would be the effect of cutting this nerve in the posterior triangle?

Answer 2

2. When taking a biopsy of enlarged lymph nodes in the posterior triangle of the neck the
   accessory nerve should be identified and avoid cutting it, otherwise paralysis of the trapezius
   and SCM muscles will result.

Question 3

3. What would be the effect of cutting the phrenic nerve on one side of the neck as it passes
   through the thorax?

Answer 3

3. The effect of cutting the phrenic nerve on one side of the neck as it passes into the thorax will
   be paralysis of the diaphragm on the same side with loss of sensation (or sensory innervation)
   of the parietal pleura in the mediastinal part, the diaphragmatic part and the pericardium on
   the same side as well as the parietal peritoneum that covers the diaphragm on its inferior (or
   abdominal) surface.

Question 4

4. What is the spinal segmental origin of the phrenic nerve?

Answer 4

4. The phrenic nerve arises from C3, 4, 5 cervical spinal segments.

Question 5

5. What is the function(s) of sternocleidomastoid muscle?

Answer 5

5. The functions of sternocleidomastoid muscle are: if it acts on one side it flexes the head
   laterally and turns the face upwards. If both sternocleidomastoid muscles act together, they
   flex the head and neck towards the chest. Also due to their attachments to the clavicles and
   sternum they help in deep inspiration and coughing.

Question 6

6. What visceral, vascular and neural structures might be damaged by a penetrating wound
   directed posteriorly and inferiorly, just above the mid-part of the clavicle?

Answer 6

6. Damage resulting from a penetrating wound directed posteriorly and inferiorly just above the
   midpoint of the clavicle is penetration to the cervical pleura and apex of the lung, then
   damage to the brachial plexus and section of the subclavian artery and vein and other small
   blood vessels.