Bones of the Arm – Diagram and Characteristics

The Bones of the Arm are the humerus, radius, and ulna together with the muscles, ligaments, and tendons, these bones allow for mobility and offer structural support. The arm’s three bones are hard, and more than 80% of its bulk is compact bone.

Spongy bone makes up less than 20% of the arm’s mass, particularly at the tips. The bones of the arm and hand are responsible for all the functions we perform with our hands, like writing, lifting, grabbing, throwing, etc. In this article, we will discuss various bones of the arms, their function, and diagram.

Bones of the Arm

The bones in the arm consist of three primary bones: the humerus, radius, and ulna. These bones work together with the muscles, ligaments, and tendons, facilitating movement and providing structural support.

All three bones of the arm are rigid and more than 80% of its mass is made up of compact bone, while less than 20% of its mass, especially the tips have spongy bone. They also have a hollow medullary cavity in the middle that houses the bone marrow.

Bones of the Arm Anatomy

The anatomy of the bones of the arm is described not only by the bone structure but also by the joints (articulations), muscle attachments, and nerve supply.

The different joints associated with the bones of the arm and hand are:

• The shoulder joint, is formed by the articulation of the humerus and scapula.
• The elbow joint, is formed by the articulation of the humerus with the radius and ulna.
• The different muscular attachments include the deltoid, pectoralis major, and triceps brachii, each contributing to distinct movements and actions. The radius and ulna also attach muscles like the brachialis and brachioradialis, which are essential for flexion and rotation of the forearm.
• The arm bones are supplied with a rich blood flow through arteries like the brachial artery, which helps to deliver nutrients and oxygen to the bone tissue. The radial and ulnar nerves also innervate the arm muscles and skin, which are crucial for motor control.

Bones of the Arm Diagram and their Features

The bones of the arm are a complex of many bones, each with a unique function. To understand how the bones of the arm and hand function, we first need to understand their structure and location in the human body. The anatomy of the bones in the arm in humans is represented in the labeled diagram below.

Humerus

The humerus is the longest bone of the upper arm that extends from the shoulder to the elbow. The anatomy of humerus is mentioned below:

1. Proximal End: The proximal end of the humerus is divided into a rounded head that articulates with the glenoid cavity of the scapula, forming the ball and socket shoulder joint (glenohumeral joint). It also has two tubercles (bony projections) for muscle attachment and the neck.
2. Shaft: The shaft is the long body of the bone. It has the deltoid tuberosity, a rough, V-shaped area where the deltoid muscle attaches. It also has a radial groove, the site of radial nerve innervation.
3. Distal End: The distal end features the capitulum, a rounded knob-like structure that articulates with the head of the radius (radiocapitellar joint). It also has the trochlea, a spool-shaped structure articulating with the ulna (humeroulnar joint). Together, these two joints make up the elbow joint. Medial and lateral epicondyles (bony projections), fossae (depressions), and ridges are on either side of the distal end. They serve as attachment points for various muscles and ligaments, contributing to the stability and movement of the elbow joint.

Radius and Ulna

The radius and ulna are the forearm bones. The different structures associated with each of these bones are described below.

Radius

This bone is located on the thumb side of the forearm. Radius bone parts are:

• Proximal end: The proximal end has a rounded head that articulates with the humerus capitulum and the ulna’s radial notch.
• Neck: It is located just below the head and is a common fracture site.
• Shaft: The main body of the bone with the radial tuberosity is the site of attachment for the biceps brachii muscle.
• Distal End: The distal end articulates with the wrist bone with the styloid process.

Ulna

The ulna is located on the pinky side of the forearm. It is longer than the radius and runs parallel to it. The ulna bone anatomy is:

• Proximal end: The proximal end of the ulna has many bony projections with unique functions. These include the olecranon process, which forms the prominent point of the elbow, and the coronoid process, along with the olecranon, which articulates with the humerus. It has two notches, namely, the trochlear notch with the humerus’s trochlea, forming the elbow’s hinge joint and the radial notch articulating with the head of the radius.
• Shaft: This is the attachment site for muscles such as the flexor and pronator muscles.
• Distal end: Like the radius, the distal has the styloid process that forms the wrist joint.

Function of the Bones of the Arm

The functions of the bones of the arm are:

• Allowing a wide range of motion helps us reach, grasp, lift, and manipulate objects.
• The arm bones also support and stabilize the muscles and soft tissues that envelop them. This is important for overall strength for lifting heavy objects or performing weight-bearing exercises.
• To tolerate force exerted by day-to-day activities like throwing or pushing, they are distributed evenly in the bone, preventing excessive strain on any particular region.
• To do everyday tasks like writing, typing, cooking, and driving by proper coordination between bones, muscles, and joints.

Common Arm Bone Disorders or Diseases

Some common arm bone disorders or diseases are

• Fractures and Injuries
• Osteoporosis is a condition that makes the bone weak and brittle.
• Paget’s disease causes pain and changes in the shape of a bone.
• Osteopenia, which causes a loss in bone mineral density.
• Osteogenesis Imperfecta or brittle bone disease.
• Arthritis affects bone joints by reducing cartilage and synovial fluid between two bones.

Conclusion – Bone of the Arm

In conclusion, the humerus, radius, and ulna are among the most vital bones in the arms for facilitating movement and function. The bones of the arms work in tandem with blood arteries, muscles, and nerves to provide movement, sensation, and stability. These bones support your arm’s strength and ability to do a variety of jobs in addition to being necessary for fundamental actions. In general, the health and functionality of your upper limb are greatly dependent on the bones of the arm.

FAQs – Bone of the Arm

What is the Bone Joint in the Arm?

The bones of the arm form three main joints: the shoulder joint, the elbow joint, and the wrist joint.

What is the Forearm Bone?

Three prominent bones form the arm. The forearm comprises two main bones called the radius and the ulna.

Name the Different parts of the Hand and Arm.

The different bones of the arm and hand are the humerus, radius, and ulna, which form the arm, and the carpals, metacarpals, and phalanges, which form the hand.

How many Bones are there in the Arm?

The human arm comprises three bones: the humerus, radius, and ulna. The hand is composed of 8 carpals, 5 metacarpals, and 14 phalanges.

What are the Bones of the Arm?

The arm bones are the humerus (hindarm bone), which forms the elbow joint with the radius and the ulna (forearm bones).

What are the Bones in the Arm and functions?

Bones serve as a support system for muscles, blood vessels, nerves, and lymphatic vessels to function properly. In the upper arm area, there’s one bone called the humerus. The forearm is made up of two bones: the radius and the ulna.

What are the Structure and Function of the Arm?

The arm is essential, consisting of bones, muscles, nerves, and blood vessels. Muscles allow movement, nerves transmit signals, and blood vessels supply oxygen. It enables mobility, manipulation, and sensation while bones provide support and protection.