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Question

Difficulty: EasySupport Structures and Locomotion

Which of the following represents the correct anatomical sequence of bones in the mammalian forelimb when arranged from the proximal end (closest to the shoulder girdle) to the distal end (furthest from the shoulder girdle)?

  1. 1Humerus
  2. 2Radius and Ulna
  3. 3Carpals
  4. 4Phalanges

Answer

The correct order from proximal to distal is Humerus, Radius and Ulna, Carpals, and Phalanges.
The mammalian forelimb is organized sequentially from the body attachment outward: the single humerus forms the upper arm (proximal), followed by the paired radius and ulna in the forearm, then the carpals of the wrist, and finally the phalanges forming the digits at the terminal (distal) end.

Step-by-Step Solution

1
Identify the most proximal bone attached to the shoulder girdle.
The humerus forms the upper arm segment closest to the shoulder.
Proximal anatomical orientation refers to structures closest to the point of attachment to the trunk.
2
Identify the bones of the middle forearm segment immediately following the humerus.
The radius and ulna articulate with the humerus at the elbow joint.
These bones form the framework of the lower arm.
3
Determine the wrist region following the forearm.
The carpals form the wrist cluster distal to the forearm.
The carpals join the distal ends of the radius and ulna to the palm area.
4
Identify the most distal extremity bones.
The phalanges form the terminal digits.
Phalanges represent the furthest structures from the body trunk attachment point.

Key Concept

Mammalian Appendicular Skeleton: Forelimb Anatomical Sequence
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Topics

Support Structures and Locomotion

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