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The forearm is the region of the upper limb between the elbow and the wrist. [1] The term forearm is used in anatomy to distinguish it from the arm, a word which is used to describe the entire appendage of the upper limb, but which in anatomy, technically, means only the region of the upper arm, whereas the lower "arm" is called the forearm.
The ulna or ulnar bone (pl.: ulnae or ulnas) [3] is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the radius, the forearm's other long bone. Longer and thinner than the radius, the ulna is considered to be the smaller long bone of the lower arm.
There are a total of 64 bones in the arms, 32 in each arm Upper arm bones (6 bones in total; 3 on each side) Humerus (2) Pectoral girdle (shoulder) Scapula (2) Clavicle (2) Lower arm bones (4 bones in total, 2 on each side) left bone Ulna (2) (Lined up with pinky) Radius (2) (Lined up with thumb) Hand (54 bones in total; 27 in each hand) Carpals
If you've been having trouble with any of the connections or words in Sunday's puzzle, you're not alone and these hints should definitely help you out. Plus, I'll reveal the answers further down ...
The word radius is Latin for "ray". In the context of the radius bone, a ray can be thought of rotating around an axis line extending diagonally [clarification needed] from center of capitulum to the center of distal ulna. While the ulna is the major contributor to the elbow joint, the radius primarily contributes to the wrist joint. [5]
The musculocutaneous nerve innervates all the muscles of the anterior compartment of the arm. The median nerve innervates all the muscles of the anterior compartment of the forearm except flexor carpi ulnaris and the ulnar part of the flexor digitorum profundus. It also innervates the three thenar muscles and the first and second lumbricals.
In primates, the arm is adapted for precise positioning of the hand and thus assist in the hand's manipulative tasks. The ball and socket shoulder joint allows for movement of the arms in a wide circular plane, while the structure of the two forearm bones which can rotate around each other allows for additional range of motion at that level. [16]
The olecranon is situated at the proximal end of the ulna, one of the two bones in the forearm. [1] When the hand faces forward the olecranon faces towards the back (posteriorly). It is bent forward at the summit so as to present a prominent lip which is received into the olecranon fossa of the humerus during extension of the forearm. [2] [3]