THE BONES OF THE LOWER EXTREMITY 93 



THE BONES OF THE LOWER EXTREMITY 



Lower 



Pelvis Ossa innominate (with sacrum and coccyx) 



Thigh Femur 



T /Tibia 



Leg \Fibula 



limb (Tarsus 



Foot ] Metatarsus 



( Phalanges (toes) 



The Bones of the Pelvis. The Os Innominatum 

 (Hip Bone). This is so named from its bearing no 

 resemblance to any known object. There is one on 

 either side. It is irregular in shape, twisted, flat above, 

 expanded below, and constricted in the centre. With 

 its fellow of the opposite side it forms the lateral and 

 anterior walls of the pelvic cavity, which is completed 

 behind by the sacrum. In young subjects it consists 

 of three separate parts that meet to form the large 

 bone, and for purposes of description is divided into 

 the ilium, ischium, and pubis. 



The ilium is the upper expanded portion and forms 

 less than two-thirds of the acetabulum (this is the 

 cavity which receives the head of the thigh bone). 



The os pubis forms with its fellow of the opposite 

 side the anterior wall of the pelvic cavity, and bounds 

 the thyroid or obturator foramen above and partly 

 in front. It consists of a body and two rami; at the 

 inner extremity of the body is a roughened surface, 

 oval in shape for articulation with the opposite bone; 

 when the two bodies articulate they form the symphysis 

 pubis. The ascending and descending rami pass up- 

 ward and downward respectively from the body. 



The ischium forms the lower and back part of the 

 hip bone, bounds the thyroid foramen below, and forms 

 over two-fifths of the acetabulum. It presents a body, 

 a ramus, and a tuberosity. 



The Pelvis as a Whole. The pelvis (basin) is com- 

 posed of four bones: two ossa innominata (innominate 



