Question

You are provided with photographs of specimen M and N. Examine them.

1. Identify the bones. 
2. Name the parts labeled X and Y. 
3. State three significance of the part labelled Y. 
4. Calculate the actual size of specimen labelled M. (Show your working). 
5. Name the part of the mammalian body from where the specimens were obtained. 
6. State with reasons the type of joint formed at the proximal and distal end of M 
    

Answer 1

1.   
   • M Humerus;
   • N Ulna & radius;
2.    
   • X Olecranon process;
   • Y Sigmoid notch;
3.    
   • Attachment of muscles/tendons;
   • Formation of hinge joint ;( with adjacent bone)
   • prevents overstretching of the forearm backwards
4.   
   • Actual length = 22.6 ± 0.1cm
   • Drawing length = 11.3 ± 0.1cm
   • Magnification= 
     ^{Drawing length}/_{actual length}=^11.3/_22.6;=^11cm/_actual =22cm;
5. Forelimb/arm/legs; acc humerus –upper arm; Ulna and radius lower arm;
6.   
   • Proximal end - Ball and socket;
     Reason - Head shaped like a ball/rounded head/round head/Allows movement in all planes/360°;
     Distal end - Hinge joint;
     Reason - Allows movement in only one plane/presence of a groove/presence of condyles/troches which articulates with the sigmoid notch;