Lab3 - Module 1 - Anatomy of the Arm: Page 1 of 9

READINGS:

Gray's Anatomy for Students (Fourth Edition): Pages: 740-750

CASE REPORT:

34 y/o male presented to his physician with paresthesia's in the left 4th and 5th digits 3-4 months prior with no history of trauma. He reported left forearm numbness but denied neck pain. He noted weakness in his left hand and dropping objects. He is now disabled but had worked as a bricklayer.

EXAMINATION:

• Atrophy was noted in the hypothenar eminence and first dorsal interossei.

• Significant decrease in intrinsic strength with clawing of the ring and little fingers.

• Sensation was absent in the ulnar distribution both palmar and dorsal aspects of the fourth and 5th digits and hand.

The arm extends from the shoulder to the elbow. The anterior side is also referred to as the flexor side and has three muscles. The posterior side (Discussed in Lab 4) is also referred to as the extensor side and has the triceps muscle.

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Begin with the Humerus.

Indentify the following structures of the right humerus in the 3D window:

• Close to the head of the humerus are its greater and lesser tubercles separated from one another by the intertubercular (bicipital) groove in which lies the tendon of the long head of the biceps brachii.

• The anatomical neck separates the head and the tubercles.

• Distal to the tubercles is the surgical neck, the area where the bone narrows to become the diaphysis (body). This region is called the surgical neck because it is the site of most frequent fracture of the proximal end of the humerus.

• Anterolaterally lies a roughness called the deltoid tuberosity.

• Observe the shallow radial (spiral) groove for the radial nerve that extends inferolaterally on the posterior aspect of the body.

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• The trochlea fits into the trochlear notch of the ulna.

• Just proximal to the trochlea are the coronoid fossa and the olecranon fossa for accommodating corresponding parts of the ulna.

• Adjoining the lateral part of the trochlea is the capitulum. Note the medial and lateral epicondyles; medial associated with the trochlea and lateral with the capitulum. From the epicondyles run the medial and lateral supracondylar ridges.

	You are in the Emergency Room and a patient arrives witha fractured humerus. What anatomical structures should you be concerned about?
Because they are in contact with the humerus (surgical neck – axillary nerve; radial groove – radial nerve; and medial epicondyle – ulnar nerve), the axillary, radial, and ulnar nerves may be injured in fractures of the humerus.