Final answer:
The saddle joint in the hand is formed between the first metacarpal bone and the trapezium bone, allowing for the thumb's versatile movements and grasping objects.
Step-by-step explanation:
The saddle joint in the hand is formed between the first metacarpal bone and the trapezium bone, which is one of the carpal bones in the distal row of the wrist. This joint allows for the opposing movement of the thumb, which is essential for grasping and manipulating objects.
The first metacarpal bone is unique among the metacarpals as it is mobile and able to move in multiple directions, unlike the other metacarpal bones that are joined together and form the palm of the hand. It has a saddle-shaped articular surface that fits into the corresponding surface of the trapezium bone, allowing for greater range of motion.
The saddle joint between the first metacarpal and the trapezium bone is an example of a biaxial joint, meaning it allows movement in two planes - flexion, extension, abduction, adduction, circumduction, and opposition. This joint enables the thumb's versatile movements, such as grasping objects of various sizes and shapes.