Arm Bones and Muscles

Arm Bones and Muscles

A descriptive write-up on various bones and muscles of the human arm, and the role they play in functioning of this limb.
One of the most important constituents of the human anatomy, the arm plays a vital role in various body functions. The term 'arm' is more often used to refer to the entire limb, starting from the shoulder to the wrist. However, in the medical field, the term 'arm' is technically used to refer to the upper limb, from the shoulder to the elbow joint. The remaining part, from the elbow joint to the wrist, is referred to as the 'forearm'.

Arm Bones

A look at the anatomy of the human hand shows that the entire arm has 3 bones in each arm, one in the upper arm (arm―extending from the shoulder to the elbow joint) and two in the lower arm (forearm―extending from the elbow joint to the wrist). These bones and joints works in coordination with various muscles in the arms to execute the daily functions we perform. Now let's have a detailed look at each of these bones.

The humerus is a long bone located in the upper arm, which extends from the shoulder to the elbow joint. It technically connects the scapula (flat triangular shoulder bone) to the lower arm. The humerus is further divided into three zones ...
  • Upper extremity of humerus
  • Body of humerus
  • Lower extremity of humerus
The radius is one of the two pairs of bones in the lower arm or forearm. It basically runs from the lateral side of the elbow to the thumb side of the wrist. The long, prism-shaped bone tends to join the capitulum of the humerus in the upper arm and connects the elbow to the forearm. Like the humerus, the radius is also divided into three zones ...
  • Upper extremity of radius
  • Body of radius
  • Lower extremity of radius
The ulna is another long bone located in the forearm of the individual, precisely placed at the medial side of the forearm, running parallel to the radius, to the wrist. The ulna articulates the humerus and radius in upper and lower arms respectively.

Arm Muscles

There are various muscles in the arm which control various functions of this limb. Both, arm bones and muscles work in coordination with each other to makes various functions of the hand possible. Basically, the muscles of the arm assist the bones in executing the following functions ...
  • Bend or flex the elbow
  • Extend or straighten the elbow
  • Supinate or rotate the palm up
  • Pronate or rotate the palm down
  • Abduct or take the fingers and the wrist away from the midline of the body
  • Adduct or bring the fingers and wrist closer to the midline of the body.
The tables given below will tell you the function of each of the muscles in the arm.

Muscles in the Upper Arm

Muscle NameFunction
CoracobrachialisAdducts humerus
Biceps brachiiFlexes elbow and supinates forearm
BrachialisFlexion at elbow joint
Triceps brachiiExtends forearm
Anconeus tricepsAssists triceps in extension of the forearm

Muscles in the Lower Arm

Muscle NameFunction
Pronator teresPronation of forearm, flexes elbow
Palmaris longusWrist flexor
Flexor carpi radialisFlexion and abduction at wrist
Flexor carpi ulnarisFlexion of wrist
Flexor digitorum superficialisFlexor of fingers
Pronator quadratusPronates the forearm
Flexor digitorum profundusFlex hand, interphalangeal joints
Flexor pollicis longusFlexion of the thumb
Extensor digitorumExtension of hand and fingers
Extensor digiti minimiExtends the little finger at all joints
Extensor carpi ulnarisExtends and adducts the wrist
BrachioradialisFlexion of forearm
Extensor carpi radialis longusExtensor at the wrist joint, abducts the hand at the wrist
Extensor carpi radialis brevisExtensor and abductor of the hand at the wrist joint
SupinatorSupinates forearm
Extensor indicisExtends index finger, wrist
Abductor pollicisLongus abduction, extension of thumb
Extensor pollicis brevisExtension of thumb at metacarpophalangeal joint
Extensor pollicis longusExtension of the thumb

Although these muscles are small in shape, they have a fascinating coordination between them which helps our hands perform several intricate functions. Studies have revealed that arm bones and muscle growth is inter-related and therefore, one has to ensure that the exercises which facilitate the strengthening of arm bones and muscle building are given a priority.