Anatomy - Shoulder

Question 1

What are the two most superficial muscles of the shoulder? State their origin, insertion, innervation, function.

Answer 1

1. Trapezius
   O: Superior Nuchal Line, External Occipital Protuberance, Medial margin of ligamentum nuchae, spinous processes of C7 to T12
   I: Superior edge of crest of spine of scapula, acromion, lateral 1/3 of clavicle
   Inn: Spinal part of CN11 (motor), anterior rami of C3 and C4 (sensory)
   F: Elevates scapula, rotates scapula during abduction
2. Deltoid
   O: Inferior edge of spine of scapula, lateral margin of acromion, anterior border of lateral 1/3 of clavicle
   I: Deltoid tuberosity of humerus
   Inn: Axillary Nerve
   F: Abduction of arm, clavicular fibres assist in flexing arm, posterior fibres assist in extending arm

Question 2

For pronator Teres,
a) Origin
b) Insertion
c) Innervation
d) Function
Bonus: where does the median nerve pass after exiting cubital fossa?

Answer 2

a) Humeral Head - medial epicondyle and adjacent supracondylar ridge; Ulnar Head - Medial Side of Coronoid Process of Ulnar
b) Roughening on lateral surface, midshaft of radius
c) Median Nerve
d) Pronation
Bonus: Passes between humeral and ulnar heads of this muscle

Question 3

Apart from pronator teres, name 3 other muscles in the superficial layer of the anterior compartment of the forearm.

Answer 3

1. Flexor Carpi Ulnaris
   O: Humeral Head - Medial Epicondyle; Ulnar Head - Olecranon & Posterior Border of Ulna
   I: Pisiform
   Inn: Ulnar Nerve
   F: Flexion and Adduction of Wrist
2. Palmaris Longus
   O: Medial Epicondyle of Humerus
   I: Palmar Aponeurosis
   Inn: Median Nerve
   F: Flexion of Wrist Joint
3. Flexor Carpi Radialis
   O: Medial Epicondyle
   I: Base of Metacarpal 2 & 3
   Inn: Median Nerve
   F: Flex and Abduct wrist

Question 4

State a muscle in the intermediate layer of the forearm.

Answer 4

Flexor Digitorum Superficialis
O: Humero-ulnar Head - Medial Epicondyle and adjacent margin of coronoid process; Radial Head: Oblique Line of Radius
I: Four tendons that attach to the middle phalanges of index, middle, ring and little fingers – near base of the proximal phalanx of each finger, the tendon of the flexor digitorum superficialis splits into two and passes posteriorly around each side of the flexor digitorum profundus to attach to the margins of middle phalanx
Inn: Median Nerve
Function: Flex PIP joints, MCP joints of index, middle, ring, little; flex wrist