OIAN Arm
O: Infraspinous fossa. I: Middle facet of greater tubercle. A: Laterally rotates arm; holds humeral head in glenoid cavity. N: Suprascapular nerve (C5, C6)
What is the infraspinatus?
O: External occipital protuberance, nuchal ligament, spinous processes C7–T12. I: Lateral 1/3 clavicle, acromion, scapular spine. A: Elevates, retracts, rotates scapula. N: Spinal accessory nerve (CN XI) motor; C3–C4 sensory
What is the trapezius?
This large triangular muscle forms the rounded contour of the shoulder and is the principal abductor of the arm
What is the deltoid?
This muscle's action is often summarized as "shrugging the shoulders" — it elevates, retracts, and rotates the scapula
What is the trapezius?
Name the three layers of intrinsic back muscles, superficial to deep
What are the splenii, the erector spinae complex, and the transversospinalis complex?
O: Lateral 1/3 clavicle, acromion, scapular spine. I: Deltoid tuberosity. A: Abducts arm; flexes (anterior fibers); extends (posterior fibers). N: Axillary nerve (C5, C6)
What is the deltoid?
O: Spinous processes ~T6/7–T12, thoracolumbar fascia, iliac crest, inferior angle of scapula, inferior 3 ribs. I: Floor of intertubercular groove. A: Extends, adducts, medially rotates humerus. N: Thoracodorsal nerve (C6, C7, C8)
What is the latissimus dorsi?
Name the 4 rotator cuff muscles
What are supraspinatus, infraspinatus, teres minor, and subscapularis?
Nicknamed the "climbing muscle," this one extends, adducts, and medially rotates the humerus
What is the latissimus dorsi?
This most superficial intrinsic layer, made up of the capitis and cervicis muscles, extends and rotates the head and neck
What are the splenii muscles?
O: Supraspinous fossa. I: Superior facet of greater tubercle. A: Initiates abduction; holds humeral head in glenoid cavity. N: Suprascapular nerve (C5, C6)
What is the supraspinatus?
O: External surfaces of ribs 1–8/9. I: Anterior surface of medial border of scapula. A: Rotates scapula laterally, protracts scapula, holds it against thoracic wall. N: Long thoracic nerve (C5, C6, C7)
What is the serratus anterior?
This thick, round muscle on the inferolateral scapula adducts and medially rotates the arm but is NOT part of the rotator cuff
What is teres major?
Originating on ribs 1–8/9, this muscle protracts the scapula and rotates it laterally
What is the serratus anterior?
Use the mnemonic "I Like Standing" to name these three columns, from lateral to medial
What are the iliocostalis, longissimus, and spinalis?
O: Subscapular fossa. I: Lesser tubercle of humerus. A: Medially rotates and adducts arm; holds humeral head in glenoid cavity. N: Upper & lower subscapular nerves (C5, C6, C7)
What is the subscapularis?
O: Transverse processes C1–C4. I: Superior part of medial border of scapula. A: Elevates scapula, rotates it medially, depresses glenoid cavity. N: Dorsal scapular nerve (C4–C5)
What is the levator scapulae?
This muscle initiates the first 15° of arm abduction before the deltoid takes over
What is the supraspinatus?
Arising from the transverse processes of C1–C4, this muscle elevates the scapula and depresses the glenoid cavity
What is the levator scapulae?
What 3 muscles are a part of the transversospinalis muscle complex?
What is the semispinalis, multifidi, and rotatores?
O: Dorsal surface of inferior angle of scapula. I: Medial lip of intertubercular groove. A: Adducts and medially rotates the arm. N: Lower subscapular nerve (C6, C7)
What is teres major?
O: Minor from C7, major from T1–T4/5. I: Medial border of scapula (both). A: Retract and rotate scapula medially, depress glenoid cavity. N: Dorsal scapular nerve (C5)
What are the rhomboid minor and rhomboid major?
Of the four cuff muscles, this is the only one that inserts on the lesser tubercle rather than the greater tubercle
What is the subscapularis?
These two muscles retract the scapula and rotate it medially, depressing the glenoid cavity
What are the rhomboid major and minor?
Of semispinalis, multifidi, and rotatores, this one spans the most vertebral segments (4–6), while this one spans the fewest (1–2)
What are semispinalis (most) and rotatores (fewest)?