Arm Bones

Humans have 32 bones in each of their upper limbs, totaling 64. These bones are flexible and strong, providing support and framework to the upper extremities and enabling the manipulation of shoulders, hands, and fingers.

Additionally, they help endure significant stress and force during physical activity, sports, or unexpected incidents such as collisions or falls, where individuals tend to instinctively extend their arms forward.

These bones also feature numerous points of attachment for various muscles. The joints formed by these bones bestow our upper limbs with the range of motion and dexterity necessary for carrying out everyday tasks such as grasping objects, manipulating them, and activities like eating, writing, driving, etc.

Designations and Structure of All the Bones in the Upper Extremity

Arm Skeleton

Upper Limb Humeri

These bones establish the connection between the arm and the torso.

1. Humerus (2): Positioned at the uppermost part of the arm, this bone ranks among the longest within the human skeletal framework, spanning from the shoulder to the elbow. The lateral and medial epicondyles represent two vital landmarks.

Shoulder Girdle (Pectoral)

It shapes the shoulder region and facilitates multi-directional movement of the hands. The following two bones unite to form the shoulder girdle:

2. Scapula (2): Also referred to as the shoulder blade, this bone accommodates up to 17 muscle attachments. The acromion, coracoid process, and glenoid cavity serve as three critical landmarks.
3. Clavicle (2): Establishes the connection between the upper arm and the chest. Commonly known as the collarbone.

Upper Limb Humeri

Lower Limb Bones

The forearm comprises two elongated bones and collectively serves as the link between the upper arm and the wrist-hand complex via the elbow and wrist articulations:

1. Ulna (2): Constituting the longer and overall larger of the two bones, it resides on the side of the little finger. This bone exhibits two significant landmarks, the coronoid process and the olecranon.
2. Radius (2): The second bone in the lower arm, capable of altering its position based on arm flexion. It is positioned on the thumb side of the arm, with the radial head representing a crucial landmark.

Forearm Bones

Manual Bones

Despite the hands constituting a small area, 27 bones in each hand participate in numerous joints and articulations, allowing for hand operation. The following are the names of the hand bones:

1. Carpals: The wrist bones bridging the lower arm and fingers, forming part of the palm:

• Scaphoid bone (2)
• Lunate bone (2)
• Triquetral bone (2)
• Pisiform bone (2)
• Trapezium (2)
• Trapezoid bone (2)
• Capitate bone (2)
• Hamate bone (2)

2. Metacarpals (10): Comprising five elongated bones at the base of each finger, shaping the human hand.

3. Phalanges of the Hand: Slim bones within the fingers. Each finger possesses three phalanges, with the exception of the thumb, which only has the proximal and distal phalanges.

1. Proximal phalanges (10)
2. Middle phalanges (8)
3. Distal phalanges (10)

FAQs

Q. Do your upper limb bones intertwine?

Ans. While it may appear that the two lower arm bones, radius, and ulna, would interlace during arm movement, they do not. The radius is the sole bone that rotates around the ulna, which remains fixed in place by a hinge joint. Visualize the ulna as a door that cannot revolve due to its hinges.

The only scenario wherein both lower arm bones would rotate is if the entire arm were rotated from the shoulder.

References

1. 1. Arm Bones Anatomy, Diagram, and Function – Healthline.com
   2. Bones of the Arm and Hand – Innerbody.com
   3. Arm Bones – Mayoclinic.org
   4. Body Anatomy: Upper Extremity Bones – ASSH.org
   5. Bones of the Arm and Hand: Anatomy and Functions – Study.com