Arm | Definition, Synonyms, Functions & Anatomy


The arm is the part of the human body. It is also known as upper extremity. In Latin, it is known as brachium. Arms have a complex network of blood vessels.

It plays a significant role in the sense of touch. This is one of the flexible parts of our body and its flexibility decreases with age. It performs various functions and is vital for our daily tasks. Its structure permits us to move and interact with the environment.


It is a functional unit of the upper body. This is among the shoulder and the elbow. It expands from the shoulder joint to the fingers. It has 30 bones and also it comprises a lot of nerves, blood vessels, and muscles.


  • Upper limb
  • Forelimb
  • Appendage
  • Limb

Functions of Arm

The muscles of the arms help us with small movements such as wiggling the fingers or binding a button. Also, they are permitted to do big movements such as straightening the elbow, raising the arms above the head, or doing push-ups. Also, it extends the hands away from the body to assist things to carry and pick up resources. Its functions include:

  • Flexion
  • Adduction
  • Extension
  • Abduction

Parts of Arm

Each of the arms has three main parts which are:

  • Upper Arm
  • Forearm
  • Hand

Upper Arm:

This part of the arm is between the shoulder and the elbow.


This arm part extends from the elbow to the wrist.


It is the end part of the arm which includes fingers. It is used for touching, moving, holding, and many more.

Anatomy of Arm


Arms are made up of three bones which are:

  • Humerus
  • Ulna
  • Radius


It is the largest bone of the upper arm. It appears nearly with the glenoid by the GH joint and at a distance with the radius and ulna at the elbow joint.


It is the bones in the forearm. It assists us in the movement of the arms, hands, and wrist. Also, it helps many of the muscles, ligaments, and blood vessels.


It is the bone found on the side forearm. It rotates over the ulna. This can alter its position depending on the hand movement. The radial nerve is responsible for several various arms movements such as elbow extension, forearm rotation, and wrist and finger movement.

Arms Muscles

The muscles in the upper and lower arm are divided into anterior and posterior compartments

Upper Arm Muscles:

The four muscles in the upper arm are:

  • Biceps brachii
  • Brachialis
  • Coracobrachialis
  • Triceps brachii

Anterior Compartment

Biceps/Biceps brachii:

This is a large muscle on the front of the superior arm. It is among the shoulder and elbow. It is a two-headed muscle. Its function is to bend the elbow. Also, it works to rotate the forearm.


It is under the biceps muscles. This is an elbow flexor that originates from the anterior humerus and includes the ulnar tuberosity. It is the largest elbow flexor. It provides a curve of the forearm at the elbow.


This muscle widens from the scapula to the humerus. It flexes and adducts the arms.

Posterior Compartment

Triceps brachii:

This muscle is used for the extension of the elbow and to stabilize the shoulder. This muscle helps us in our daily activities such as in:

  • Throwing ball
  • Lifting the objects
  • Typing on the keyboard

Forearm Muscles:

There are almost 19 muscles in the forearm which are further sub-divided into layers.

Anterior Compartment

This compartment is divided into three layers which are given:

Superficial layer:

  • Flexor carpi ulnaris
  • Palmaris longus
  • Flexor carpi radialis
  • Pronator Teres

Intermediate layer:

  • Flexor digitorum superficialis

Deep compartment:

  • Flexor pollicis longus
  • Flexor digitorum profundus
  • Pronator quadrates

Posterior Compartment:

This compartment is divided into two layers which are given:

Superficial layer:

  • Brachioradialis
  • Extensor carpi radialis longus
  • Extensor carpi radialis brevis
  • Extensor digitorum
  • Extensor carpi ulnari

Deep layer:

  • Supinator
  • Abductor pollicis longus
  • Extensor pollicis brevis
  • Extenor pollicis longus
  • Extensor indices

Arm Injuries & Disorders

  • Tendinitis and Bursitis
  • Sprains
  • Dislocations
  • Fractures (broken bones)
  • Nerve problems
  • Osteoarthritis


  • Sara has a newspaper under her arm.
  • Ahmad broke her right arm.
  • Ali put his arm around her shoulders.
  • Hamza wrapped his arms around her knees.

FAQs (Frequently Asked Questions)

Which of the arms is connected to the heart?

The left arm is connected to the heart in the human body.

Mention the name of the three veins on the arms.

  1. Basilic
  2. Cephalic
  3. Median cubital

Mention the scientific name of the arm.

Brachium is the scientific name of the human arm.

What joints are in the arms of humans?

  • Acromioclavicular
  • Shoulder
  • Radioulnar
  • Sternoclavicular
  • Elbow
  • Wrist

How does the brain control the arms?

It controls them by moving an arm requires the brain to send electrical signals to the muscles of the arm which causes them to contract.

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