Muscle Review – Trapezius, Levator scapula, Latissimus Dorsi, Teres major
MBLEx Muscle Review
Introduction
The kinesiology section of each lesson in this MBLEx Review Course is followed by a Muscle Review. There are a total of 114 muscles reviewed in this course. Each review includes the Origin, Insertion, Nerve (innervation), and primary Action (OINA). It also includes notes and tips related to each muscle to help you increase retention and to help in your clinical application of this knowledge.
***Study Tip: When reviewing each muscle, try to also think about and visualize the muscles that are around the muscle in the image. Think about the muscles that are deep to the illustrated muscle, or superficial to it. Try to name the muscles that are medial, lateral, proximal, distal, etc. to the illustrated muscle. Ask yourself, “Is the muscle part of a group of muscles“, as the semitendinosus is to the hamstrings? Consider the synergists and antagonists for the muscle. Another thing that many students find useful is to buy a pack of blank index cards and create your own flashcards as you work your way through this MBLEx Prep Course. The process of writing down the information in your own words and drawing your own illustrations is a form of active learning, and will dramatically increase retention.
It is unlikely that you will see more than 1 or 2 questions about muscle innervations on the MBLEx. The innervations are included here for the sake of completeness. Understanding muscle innervations also helps when learning dermatomes and myotomes too. *It is good to know the locations of the major peripheral nerves of the body (radial, median, ulnar, axillary, sciatic, femoral, tibial, fibular, etc.).
Trapezius
Origin: medial third of the superior nuchal line, external occipital protuberance, ligamentum nuchae, spinous processes of vertebrae C7-T12
Insertion: lateral third of the clavicle, medial side of the acromion and the upper crest of the scapular spine, tubercle of the scapular spine
Innervation: motor: spinal accessory (XI), proprioception: C3-C4
Action: elevates and depresses the scapula (depending on which part of the muscle contracts); rotates the scapula superiorly; retracts scapula
Notes & Tips
The trapezius sometimes referred to as “traps”. It is divided into 3 sections: upper, middle and lower. Because of the different attachment points and lines of pull, each section of the trapezius causes a different motion at the scapula.
Levator Scapula
Origin: transverse processes of C1-4 vertebrae
Insertion: medial border of the scapula from the superior angle to the spine
Innervation: dorsal scapular nerve (C5); the upper part of the muscle receives branches of C3 & C4 spinal nerves
Action: elevates scapula
Notes & Tips
This muscle is named for its action (elevating the scapula). It can be palpated at the superior angle of the scapula, up the posterolateral aspect of the neck.
Latissimus dorsi
Origin: vertebral spines from T7 to the sacrum, posterior third of the iliac crest, lower 3 or 4 ribs, sometimes from the inferior angle of the scapula
Insertion: floor of the intertubercular groove of the humerus
Innervation: thoracodorsal nerve (C7,8) from the posterior cord of the brachial plexus
Action: extends the arm and rotates the arm medially
Notes & Tips
The latissimus dorsi can be palpated along the posterior and lateral side of the thoracic region, up to its insertion point on the proximal humerus.
Teres major
Origin: dorsal surface of the inferior angle of the scapula
Insertion: crest of the lesser tubercle of the humerus
Innervation: lower subscapular nerve (C5,6) from the posterior cord of the brachial plexus
Action: adducts the arm, medially rotates the arm, assists in arm extension
Notes & Tips
The teres major inserts beside the tendon of latissimus dorsi, and assists latissimus in its actions.