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Muscles in Action Quiz
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In the conventional description of a skeletal muscle, which statement best describes its insertion?
- A The attachment point that is often closest to the trunk, regardless of movement You picked ✕
- B The attachment that always moves, whichever end of the muscle is held fixed You picked ✕
- C The attachment point that is more proximal and usually remains stationary during contraction You picked ✕
- D The more mobile attachment, usually distal, which moves towards the origin You picked ✓
- E The attachment point that is always located on bone You picked ✕
Correct!
Incorrect
The answer is D: The more mobile attachment, usually distal, which moves towards the origin
Explanation
Why D is correct
See Origin and Insertion. Option D is correct. A muscle has two attachments, and by convention they are named by how far they move. The origin is the less mobile attachment, usually the more proximal one (nearer the trunk). The insertion is the more mobile attachment, usually the more distal one (further from the trunk), and in the usual action it moves towards the origin. Sartorius is a worked example: its origin is the anterior superior iliac spine (a bony point at the front of the pelvis) and it inserts on the medial side of the upper tibia, so when it contracts the lower limb moves towards the pelvis. The names are fixed labels and do not change when a movement reverses. If the lower limb is fixed, sartorius can instead pull on the pelvis, and its origin and insertion keep the same names. The conventional labels describe the attachments, while the task and any outside constraints decide which one actually moves. A simple way to remember the difference: the origin is where the muscle starts and stays put, and the insertion is where it goes to work.
- Origin: the less mobile attachment, usually the proximal one
- Insertion: the more mobile attachment, usually the distal one
- Movement: in the usual action the insertion moves towards the origin
- Example: sartorius originates at the anterior superior iliac spine and inserts on the medial side of the upper tibia
Why the other options are incorrect
- A. The attachment point that is often closest to the trunk, regardless of movement: Being closest to the trunk often describes the origin, not the insertion, because insertion is defined by mobility rather than proximity alone. Your answer
- B. The attachment that always moves, whichever end of the muscle is held fixed: The attachments keep their names whichever end moves. If the limb is fixed, the muscle can pull the origin end instead, so the insertion does not always move. Your answer
- C. The attachment point that is more proximal and usually remains stationary during contraction: A proximal attachment that usually stays still describes the origin, not the insertion. It would answer a question about the origin rather than the insertion. Your answer
- E. The attachment point that is always located on bone: Muscles do not have to attach to bone at both ends. Some muscles, such as the muscles of facial expression, insert into skin instead. Your answer
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More questions from this set. Start the quiz to answer them and see each explanation.
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1
Which description best characterises a multipennate muscle?
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2
Which description best defines a unipennate muscle based on the direction of its muscle fibres?
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