The Ulna
The ulna is a long bone located medially in the forearm. The upper end is hook-like and is larger than the lower end. The concavity of the hook is called the trochlear notch and it is directed anteriorly to articulate with the trochlea of the humerus. The upper end of the hook is called the olecranon process, which articulates with the olecranon fossa above the trochlea, while the coronoid process projects anteriorly below the trochlea. A notch for the head of the radius is present on the upper lateral surface of the coronoid process, with a sharp ridge below it called the supinator crest. The shaft of the ulna has a sharp interosseous border laterally. The posterior border of the ulna lies subcutaneous. The lower end articulates with the ulnar notch of the radius to form the inferior radio-ulnar joint. The styloid process projects from the lower medial end of the ulna.
Figure1: The ulna
Muscles attachment of the ulna
1) Triceps is inserted into the posterior part of the upper surface of the olecranon process, while anconeus is inserted into its lateral surface.
2) Brachialis muscle is inserted in the ulnar tuberosity.
3) Supinator muscle arises from the supinator fossa and crest.
4) Flexor pollicis longus and prontor teres arise from the coronoid process of the ulna.
5) Flexor digitorum profundus and pronator quadratus originate from the shaft of the ulna.
6) Abductor pollicis longus originates from the superolateral part of the posterior surface.
7) Extensor pollicis longus originates from the middle and extensor indicis from the lowest part of the posterior surface.
2) Brachialis muscle is inserted in the ulnar tuberosity.
3) Supinator muscle arises from the supinator fossa and crest.
4) Flexor pollicis longus and prontor teres arise from the coronoid process of the ulna.
5) Flexor digitorum profundus and pronator quadratus originate from the shaft of the ulna.
6) Abductor pollicis longus originates from the superolateral part of the posterior surface.
7) Extensor pollicis longus originates from the middle and extensor indicis from the lowest part of the posterior surface.
Figure2: The anterior attachment of the radius and ulna
