The deep fascia which binds together the muscles of the shoulder is very strong and tendinous.

The deep fascia of the arm is thin over the biceps and dense over the triceps and condyles ; to the latter it is fixed. On the forearm it is strong and dense, particularly on the back and lower part ; on the back of the hand it is thin, while in the palm it is dense and serves as a protection to the nerves, blood vessels and tendons.

The superficial fascia is the tissue which lies directly over the deep fascia and immediately under the skin.

The annular ligament is a thickened band of the deep fascia which invests the forearm.

The anterior annular ligament on the front of the wrist is attached to the scaphoid and trapezium externally, and to the unciform and pisiform bones internally.

The posterior annular ligament on the back of the wrist is attached to the radius externally, and to the cuneiform and pisiform bones internally.

The extensor tendons of the muscles of the back of the forearm that have insertions into the fingers and metacarpal bones pass under the posterior annular ligament. There are six compartments for these tendons ; each compartment is lined by a synovial sheath.

The flexor tendons in the front of the forearm pass under the anterior annular ligament, and have two sheaths. One invests the tendon of the longest pollicis, the other invests the tendons of the sublimus and profundus muscles.