Forelimb

Anatomy of the Forelimb

The forelimb is a crucial anatomical structure in many vertebrates, including humans. It is primarily involved in locomotion, manipulation of the environment, and various other functions depending on the species. In humans, the forelimb is commonly referred to as the arm, which includes the shoulder, upper arm, forearm, and hand.

Diagram of the human hand skeleton

Structure

The forelimb consists of several key components:

• Shoulder Girdle: This includes the scapula (shoulder blade) and the clavicle (collarbone). These bones connect the forelimb to the axial skeleton and provide attachment points for muscles.

• Upper Arm: The main bone of the upper arm is the humerus. It articulates with the scapula at the shoulder joint and with the bones of the forearm at the elbow joint.

• Forearm: The forearm contains two bones, the radius and the ulna. These bones allow for the rotation of the forearm, enabling pronation and supination.

• Hand: The hand is composed of the carpals (wrist bones), metacarpals (bones of the hand), and phalanges (finger bones). The intricate structure of the hand allows for a wide range of movements and dexterity.

Function

The forelimb serves several functions:

• Locomotion: In quadrupeds, the forelimbs are essential for movement. In humans, they are primarily used for balance and support during activities such as climbing.

• Manipulation: The human hand is highly specialized for grasping and manipulating objects, a key factor in the development of tool use and fine motor skills.

• Sensation: The forelimb, particularly the hand, is rich in sensory receptors, allowing for detailed perception of the environment.

Evolution

The evolution of the forelimb has been a significant factor in the adaptation of various species to their environments. In tetrapods, the forelimbs have evolved from the pectoral fins of lobe-finned fish. This transition involved changes in bone structure and function, allowing for the development of limbs capable of supporting weight on land.

In humans, the forelimb has evolved to prioritize dexterity and manipulation over locomotion, leading to the development of the opposable thumb and increased manual dexterity.

Related Pages

• Humerus
• Radius (bone)
• Ulna
• Scapula
• Clavicle
• Hand
• Shoulder joint