Human Evolution by Rusty Huddle

Author:Rusty Huddle
Language: eng
Format: epub
Publisher: Britannica Educational Publishing
Published: 2016-12-09T00:00:00+00:00

The human hand has a fully opposable thumb, which means it is capable of being placed against one or more of the remaining digits of the hand. An opposable thumb gives the hand a unique power grip (left) and a precision grip (right).

The features of human hands are easily distinguishable from those of the great apes, and they underpin our refined manipulatory abilities. The most complex adaptations of the human hand involve the thumb, powered by the unique and fully independent flexor pollicis longus muscle. It is this muscle that gives the thumb its remarkable strength in pinch and power grips. The fingertips are broad and equipped with highly sensitive pads of skin. The proportional lengths of the thumb and other fingers give us an opposable thumb with precise, firm contact between its tip and the ends of each of the other fingers. A special saddle joint and associated ligaments at the base of the thumb facilitate refined rotation. Special configurations of joints at the bases of the fifth, fourth, and second fingers facilitate tip-to-tip precision grips with the thumb. Asymmetry of the heads of the second and fifth palm bones induces rotation of the articulated fingers during opposition with the thumb. Finally, numerous modifications of the small muscles in the hand are associated with fine control of the thumb and fingers.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.