8.2 Anterior Compartment of the Forearm

Question 1

On the palmar aspect of the hand, recognize and describe the Palmar aponeurosis, Palmaris longus tendon, Flexor retinaculum, and Antebrachial fascia.

Answer 1

The extensive palmar aponeurosis (tendons across palm of hand) the tendon of the palmaris longs (that may or may not be present and anchor into it) and, below these structures, the flexor retinaculum (roof of the carpal tunnel). Note the thick antebrachial fascia covering the muscles in the anterior compartment of the forearm.

Question 2

On the dorsal aspect of the hand, recognize and describe the extensor retinaculum.

Answer 2

The broad extensor retinaculum at the base of the dorsum of the hand.

An anatomical term for the thickened part of the antebrachial fascia that holds the tendons of the extensor muscles in place. It is located on the back of the forearm, just proximal to the hand.

Question 3

Identify the 4 muscles that constitute the superficial layer of the anterior compartment of the forearm.

Answer 3

• Pronator teres
• Flexor carpi radialis
• Palmaris longus
• Flexor carpi ulnaris

Question 4

Identify the muscle that makes up the intermediate layer of the anterior compartment of the forearm.

Answer 4

Flexor digitorum superficialis

Question 5

Identify the 3 muscles that constitute the deep layer of the anterior compartment of the forearm.

Answer 5

• Flexor pollicis longus
• Flexor digitorum profundus
• Pronator quadratus

Question 6

Identify the Ulnar a.

From what proximal a. does this branch?

Answer 6

Brachial a.

Question 7

Identify the Common interoseous a.
From what proximal a. does this branch?
What are the 2 branches off of the common interoseous artery?

Answer 7

Stems from Ulnar artery.

Branches into Anterior interosseous a and Posterior interosseous artery.

Question 8

Locate the Ulnar nerve.

What is this peripheral nerve’s cord, division, trunk, and roots?

Answer 8

Medial Cord, Anterior Division, Lower Trunk, C8-T1.

Question 9

Locate the radial nerve.
What is this peripheral nerve’s cord, division, trunk, and roots?
Locate the Superficial and Deep branches of the radial nerve in the forearm.

Answer 9

Posterior Cord, Posterior Division, Middle Trunk, C5-C8.

Question 10

Be able to locate and identify all of these muscles of the anterior compartment of the forearm. Recognize commonalities in function, attachment, and innervation. (And the couple exceptions).

i. Pronator teres (two heads)
ii. Pronator quadratus
iii. Flexor carpi radialis
iv. Palmaris longus (variably present)
v. Flexor carpi ulnaris (ulnar nerve)
vi. Flexor digitorum profundus (lateral two digits by ulnar nerve)
vii. Flexor digitorum superficialis (two heads, deep)
viii. Flexor pollicis longus
ix. Flexor retinaculum –strong sheath that stretches between the hook of the hamate and hook of the trapezium. 10 things go through this tunnel, the 4 FDS, 4 FDP, flexor pollicis longus, and the median nerve.

Answer 10

-Attachments: Primarily originate off the medial epicondyle of the humerus and ulna (including the interosseous membrane between the radius and ulna).

-Innervation: Innervated by median nerve. (There are more specific roots that are generally associated with each muscle; myotomes distributed proximal-distally.)
Flexor Carpi Ulnaris is innervated by Ulnar nerve.
Lateral 2 Digits of Flexor Digitorum Profundus innervated by Ulnar Nerve.

-Function: work as flexors and pronators of the forearm and hand.