Lecture 11: Interactive Anatomy of the Upper Limb 1

Question 1

Describe the major muscles present between the medial margin of the scapula and the midline.

Answer 1

most superficially, the trapezius muscle, in part, is between the scapula and the midline, attaching to the middle and also to the spine of the scapula
deep to this, the rhomboideus major and minor muscles are attached to the midline and the medial margin of the scapula
deep to these, with fibres now oriented along the length of the vertebral column, are the erector spinae muscles
they do not attach to the scapula

Question 2

Using organisation of the brachial plexus in your answer, why are medial cord neuropathies and hand function closely associated, and not other areas of the upper limb?

Answer 2

the brachial plexus is formed by the ventral (anterior) primary rami of spinal nerves C5 to T1
the lower (inferior) trunk is formed by the convergence of the C8 and T1 ventral primary rami, and is then split into the anterior and posterior divisions
the anterior division of this lower trunk then continues as the medial cord
the brachial plexus has a hierarchical organisation, such that the nerves with a more superior source (C5, C6) primarily innervate more proximal structures, and those with more inferior sources (C8, T1) are prominent distally
as the medial cord is formed from C8 and T1 this is most likely to cause a change in hand function