Today we’ll be talking about the hand, including the wrist, which is comprised of 8 carpal bones, 5 metacarpals, and 14 phalanges. You will notice the symmetry in the names and number of bones in your feet (see Day 1). As discussed yesterday, your true wrist joint, also known as the radiocarpal joint, is formed by the articulation of your radius with your scaphoid and lunate (see image to the right). Your metacarpals essentially form the palm of your hand and your four fingers consist of 3 phalanges each, a proximal, intermediate, and distal phalanx (see image below). The thumb is actually not considered a finger anatomically because it consists of only two phalanges, a proximal and a distal – usually we use the term digit to refer to your fingers and thumb collectively.
While our hands are similar to our primate cousins in many ways, they do differ in important ways that relate to mobility and ultimately how our hands can function to manipulate objects. Our thumbs are longer and more muscular, and our fingers are more mobile in their flexion abilities (Gargulinski 2018). Recently, researchers have determined that due to the unique pressure the activities put on our hands, nut cracking and cutting/smashing open bone to get to the marrow were most influential as evolutionary forces in shaping the modern human hand (Williams-Hatala et al. 2018).
That’s all for the hand and ends our discussion of the upper extremity. Tomorrow we will head up to the neck and discuss the hyoid bone before moving onto the skull.
REFERENCES & MORE TO EXPLORE
Bones of the Hand: Carpals, Metacarpals and Phalanges. TeachMe Anatomy Series. 2020
Eating bone marrow played a key role in the evolution of the human hand. ScienceDaily. 11 July 2018
The manual pressures of stone tool behaviors and their implications for the evolution of the human hand. Williams-Hatala et al. Journal of Human Evolution. June 2018
Human Vs. Primate Hands. Gargulinski. Sciencing. 13 March 2018