MUSCLES OF THUMB 33 



attached to the tubercles on the sides of the heads ot the 

 metacarpal bones and the bases of the phalanges. 



The Palmar ligaments are plates of fibre-cartilage attached 

 firmly to the phalanges, but only loosely to the metacarpals, so 

 that during movements of the joints they can glide up ancL 

 down. In this plate two sesamoid bones are developed in the 

 thumb, and one on the radial side of the forefinger. 



Synovial membrane lines the capsule of each joint. 



Transverse Metacarpal ligament consists of bands of transverse 

 fibres, which connect the palmar ligaments of the four inner 

 metacarpo-phalangeal joints. This binds together the distal 

 -extremities of the bones. 



Interphalang-eal Joints. These joints are all hinge-joints, 

 .allowing movements round one axis only : 



Transverse flexion and extension. 



Their ligaments and synovial membrane are similar to those 

 of the metacarpo-phalangeal joints. 



MUSCLES ACTING ON THE JOINTS. 



FIRST METACARPO-PHALAXGEAL AXD INTERPHALANGEAL JOINT. 



