METACARPO-PHALANGEAL ARTICULATION. 157 



mctacarpal articulation a thin interosseous band which passes irom the 

 ulnar edge of the os magnum to the line of junction between the third 

 and fourth metacarpal bones. 



The dorsal ligaments are strong fasciculi which pass from the second 

 range of carpal to the metacarpal bones. 



The palmar ligaments are thin fasciculi arranged upon the same plan 

 on the palmar surface. 



The synovial membrane is a continuation Fig. 91.* 



of the great synovial membrane of the two 

 rows of carpal bones. 



The capsular ligament of the thumb is one 

 of the three true capsular ligaments of the 

 skeleton ; the other two being the shoulder 

 joint and hip joint. The articulation has a 

 proper synovial membrane. 



The metacarpal bones of the four fingers 

 are firmly connected at their bases by means 

 of dorsal and palmar ligaments, which ex- 

 tend transversely from one bone to the other, 

 and by interosseous ligaments, which pass 

 between their contiguous surfaces. Their 

 lateral articular facets are lined by a reflec- 

 tion of the great synovial membrane of the 

 two rows of carpal bones. 



Actions. The movements of the metacarpal on the carpal bones are 

 restricted to a slight degree of sliding motion, with the exception of the 

 articulation of the metacarpal bone of- the thumb with the trapezium. In 

 the latter articulation, the movements are, flexion, extension, adduction, 

 abduction, and circumduction. 



1 0. Metacarpo -phalangeal Articulation. The metacarpo-phalangeal 

 articulation is a ginglymoid joint ; its ligaments are four in number, 



Anterior, Two lateral, Transverse. 



The anterior ligaments are thick and fibre-cartilaginous, and form part 

 of the articulating surface of the joints. They are grooved externally for 

 the lodgment of the flexor tendons, and by their internal aspect form part 

 of the articular surface for the head of the metacarpal bone. 



The lateral ligaments are strong narrow fasciculi, holding the bones 

 ther at each side. 



The transverse ligaments are strong ligamentous bands, passing between 

 the anterior ligaments, and connecting together the heads of the meta- 

 carpal bones of the four ringers. 



toge 



* A diagram showing the disposition of the five synovial membranes of the wrist 

 joint. 1. The sacciform membrane. 2. The second synovial membrane. 3, 3. The 

 third, or large synovial membrane. 4. The synovial membrane between the pisiform 

 bone and the cuneiforme. 5. The synovial membrane of the metacarpal articulation of 

 the thumb. 6. The lower extremity of the radius. 7. The lower extremity of the ulna 

 8. The interarticular nbro-cartilage. S. The scaphoid bone. L. The semilunare. 

 C. The cuneiforme; the interosseous ligaments are seen passing between these three 

 bones and separating the articulation of the wrist (2) from the articulation of the carpal 

 bones (3). P. The pisiforme. T. The trapezium. 2T. The trapezoides. M. The os 

 magnum. U. The unciforme ; interosseous ligaments are seen connecting the os m?.?- 

 num with the trapezoides and unciforme. 9. The base of the metacarpal bouo of tU* 

 thumb. 10, 10. The bases of th3 other metacarpal bones. 



14 



