Final answer:
The palmer grasp involves using the whole hand to grasp objects, primarily utilizing the palm and fingers, whereas the pincer grasp involves the precise opposition movement of the thumb to the fingers to pick up small objects, signifying more advanced motor control and dexterity.
Step-by-step explanation:
The difference between a palmer grasp and a pincer grasp has to do with the developmental stages of hand and finger use in infants and toddlers and involves different muscles and movements of the fingers and thumb. The palmer grasp is an early grasping movement where an object is grasped with the whole hand, utilizing a combined action of the fingers and the palm, whereas the pincer grasp is a later-developing skill where the thumb and one or more of the fingers are used to pick up small objects.
In the palmer grasp, an infant usually wraps their fingers around an object from the pinky side of the hand towards the thumb, often including contact with the palm. This movement makes use of muscles like the flexor digitorum superficialis and the flexor digitorum profundus, which flex the fingers and the hand at the wrist and contribute to a firm grip. It reflects a loosely held to firmly gripped strategy as the infant's motor skills develop.
On the other hand, the pincer grasp emerges later as the child's motor skills mature. It involves the opposition movement of the thumb—an action facilitated by the first metacarpal bone, which is free from the other metacarpal bones—to the fingers of the same hand to pick up small objects between the thumb and one or more of the fingertips. This ability is crucial for tasks involving fine motor skills, such as writing or buttoning a shirt. The opposition movement is necessary for precise finger movements.
The development of these grasps is also influenced by bones such as the phalanx bones of the fingers and thumb, with the thumb having two phalanges (the proximal and distal phalanx) and the fingers each having three. These bones are connected with joints, such as the metacarpophalangeal joint, which is the articulation between the distal end of a metacarpal bone of the hand and a proximal phalanx bone of a finger or thumb.