CARPO-METACARPAL ARTICULATION. 



Fig. 57.* 



Synovial membranes. There are five synovial membranes enter- 

 ing into the composition of the articulations of the carpus : 



The first is situated between the lower end of the ulna and the 

 interarticular fibro-cartilage ; it is called sacciform, from forming 

 a sacculus between the lateral articulation of the ulna with the 

 radius. 



The second is situated between the lower surface of the radius 

 and interarticular fibro-cartilage above, and the first range of bones 

 of the carpus below. 



The third is the most extensive of the synovial membranes of the 

 wrist ; it is situated between the two rows of carpal bones, and 

 passes between the bones of the second range, to invest the carpal 

 extremities of the four metacarpal bones of the fingers. 



The fourth is the synovial membrane of the articulation of the 

 metacarpal bone of the thumb with the trapezium. 



The fifth is situated between the pisiform and cuneiform bone. 

 Actions. Very little movement exists between the bones in each 

 range, but more is permitted between the two ranges. The motions 

 in the latter situation are those of flexion and extension. 



9. The Carpo-metacarpal Articulation. The second row of 



bones of the carpus articulates with 

 the metacarpal bones of the four fin- 

 gers by dorsal and palmar ligaments ; 

 and the metacarpal bone of the thumb 

 with the trapezium by a true capsular 

 ligament. 



The dorsal ligaments are strong fas- 

 ciculi which pass from the second 

 range of carpal to the metacarpal 

 bones. 



The palmar ligaments are thin fasci- 

 culi arranged upon the same plan on 

 the palmar surface. 



The synovial membrane is a con- 

 tinuation of the great synovial mem- 

 brane of the two rows of carpal bones. 

 The capsular ligament of the thumb 

 is one of the three true capsular liga- 

 ments of the skeleton ; the other two being the shoulder-joint and 

 hip-joint. The articulation has a proper synovial membrane. 



* 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 fibro-cartilage. S. The scaphoid bone. L. The semi- 

 lunare. 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. T 3 . The trape- 

 zoides. Af. The os magnum. U. The unciforme ; interosseous ligaments are seen 

 connecting the os magnum with the trapezoides and unciforme. 9. The base of the 

 metacarpal bone of the thumb. 10, 10. The bases of the other metacarpal bones. 



