What is the humerus function?

Answer 1

The humerus bone of the upper arm (the arm in anatomy refers only to the top part of the upper limb i.e. between the elbow and the shoulder). Like all bones it gives shape to the body and acts as an attachment site for the muscles around it.

Most of the muscles that actually move the humerus are within the region called the thorax or torso. The humerus joins the thorax at the glenohumeral joint (the shoulder joint) which is a synovial joint, or freely moving joint. It is actually designeda as a ball-and-socket type of joint. At this joint there are many movements that can occur: Flexion (the arm is brought up forwards so the elbow is at shoulder height), extenstion (the reverse of flexion, so the arm is pushed backwards behing the body), Abduction (the arm is lifted up and out from the side, like flapping it); adduction (the arm is lowered back into the side of the body, like unflapping it), if all four of these are combined you get circumduction (swinging your arms around in circles, forming a cone shape); rotation (when the shoulder is turned forwards or backwards).

The muscles that are found on and around the humerus are mostly for acting on the forearm, i.e. at the elbow joint. This joint is a synnovial hinge joint and as such only two movements occur here: Flexion (bending the elbow) and Extension (straightening it).

Their biceps brachi (or biceps) muscle is also found around the humerus but it is not really very involved in flexion of the elbow as many would believe. It is in fact used for supination of the forearm bone, the radialis, which means it turns the radius over the ulna. When they lie parallel next to each other, this is when the palm is facing forwards. Only when the forearm is fully supinated can the biceps act to flex the elbow joint. Otherwise the braachialis, a synergist to the biceps, does most of the work.