92 



TIBIA. 



Fig. 36.* 



cular. Between the two articular surfaces is a spinous process ; 

 and in front and behind the spinous process a rough depression, 

 giving attachment to the anterior and posterior 

 crucial ligaments. Between the two tuberosities on 

 the front aspect of the bone is a prominent eleva- 

 tion, the tubercle, for the insertion of the ligamen- 

 tum patella?, and immediately above the tubercle, a 

 smooth surface corresponding with a bursa. Upon 

 the outer side of the external tuberosity is an articu- 

 lar surface, for the head of the fibula ; and upon the 

 posterior part of the internal tuberosity a depression, 

 for the insertion of the tendon of the semi-membra- 

 nosus muscle. 



The shaft of the tibia presents three surfaces; 

 internal, which is subcutaneous and superficial; 

 external, which is concave and marked by a sharp 

 ridge, for the insertion of the interosseous membrane ; 

 and posterior, grooved, for the attachment of muscles. 

 Near the upper extremity of the posterior surface, 

 is an oblique ridge, the popliteal line, for the attach- 

 ment of the fascia of the popliteus muscle ; and im- 

 mediately below the oblique line, the nutritious canal, 

 which is directed downwards. 



The inferior extremity of the bone is somewhat 

 quadrilateral, and prolonged on its inner side into a 

 large process, the internal malleolus. Behind the in- 

 ternal malleolus, is a broad and shallow groove, for 

 lodging the tendons of the tibialis posticus and flexor longus digito- 

 rum ; and farther outwards another groove, for the tendon of the 

 flexor longus pollicis. Upon the outer side the surface is concave 

 and triangular, rough above, for the attachment of the interosseous 

 ligament ; and smooth below, to articulate with the fibula. Upon 

 the extremity of the bone is a triangular smooth surface, for articu- 

 lating with the astragalus. 



Developement. By three centres ; one for the shaft, and one for 

 each extremity. 



Articulations. With three bones ; femur, fibula, and astragalus. 

 Attachment of Muscles. To ten ; by the internal tuberosity, to 

 the sartorius, gracilis, semitendinosus, and semimembranosus ; by the 

 external tuberosity, to the tibialis anticus and extensor longus digi- 

 torum ; by the tubercle, to the ligamentum patellse ; by the external 

 surface of the shaft, to the tibialis anticus ; and by the posterior 

 surface, to the popliteus, soleus, flexor longus digitorum, and tibialis 

 posticus. 



* The tibia and fibula of the right leg, articulated and seen from the front. 1. The 

 shaft of the tibia. 2. The inner tuberosity. 3. The outer tuberosity. 4. The spinous 

 process. 5. The tubercle. 6. The internal subcutaneous surface of the shaft. 7. The 

 lower extremity of the tibia. 8. The internal malleolus. 9. The shaft of the fibula. 10. 

 Its upper extremity. 11. Its lower extremity, the external malleolus. 



