Superficial Back Muscles Flashcards
`How are the superficial and intermediate muscles different from the deep muscle in terms of embryological origin?
The deep muscles originate in the back embyrologically and thus are described as intrinsic muscles.
The superficial and intermediate muscles do not develop in the back and are classified as extrinsic muscles.
What are the superficial muscles of the back?
1) Trapezius
2) Latissimus dorsi
3) Levator scapulae
4) Rhomboids (major and minor)
Trapezius?
This is the most superficial of all the muscles of the back.
Origin - skull, nuchal ligament, spinous process C7-T12
Insertion - clavicle, acromion, spine of scapula
Innervation - motor innervation - accessory nerve. Proprioceptor fibres from C3 and C4 spinal nerves.
Actions -
- upper fibres elevates the scapula and rotates it during abduction of the arm
- middle fibres retract the scapula
- lower fibres pulls the scapula inferiorly
Clinical relevance - testing the accesory nerve (CN XI)?
The most common cause of damage of this nerve is iatrogenic (i.e. due to a medical procedure). In particular, operations such as cervical lymph node biopsy or cannulation of the internal jugular vein can cause trauma to the nerve.
To test the accessory nerve, trapezius function can be assessed. This can be done by asking the patient to shrug his/her shoulders. Other clinical features of the accessory nerve damage include muscle wasting, partial paralysis of the sternocleidomastoid, and an assymetrical neckline.
Latissimus dorsi?
The latissimus dorsi originates from the lower part of the back, where is covers a wide area.
Origin - has a broad origin.
- Arises from the spinous processes T6-T12
- Iliac crest
- Inferior three ribs
Insertion - these fibres converge into a tendo that attaches to the intertubercular sulcus of the humerus.
Innervation - thoracodorsal nerve
Actions - extends, abducts, and medially rotates the upper limb.
Levator scapulae?
The levator scapulae is a small strap-like muscle. It begins in the neck, and descends to attach to the scapula.
Origin - transverse processes of C1-C4
Insertion - medial border of the scapula.
Innervation - dorsal scapular nerve
Actions - elevates the scapula
Rhomboid major?
Located inferiorly to the rhomboid minor.
Origin - spinous procresses of T2-T5 vertebrae.
Insertion - medial border of scapula, between the scapula spine and the inferior angle.
Innervation - dorsal scapular nerve.
Actions - retracts and rotates the scapula.
Rhomboids minor?
Origin - spinous processes of C7-T1 vertebrae.
Insertion - medial border of scapula, at the level of the spine of scapula.
Innervation - dorsal scapular nerve.
Actions - retracts and rotates the scapula.
