Which muscle types build the internal and external urinary sphincters,…

Question

Which muscle types build the internal and external urinary sphincters, respectively?

Accepted Answer

B. Smooth, then voluntary skeletal muscle

1. Voiding is regulated by two stacked sphincters.
2. The internal urinary sphincter is involuntary smooth muscle under autonomic control.
3. Below it, voluntary skeletal muscle forms the external urinary sphincter.
4. Cardiac muscle exists only in the heart, eliminating two options at once.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 25 "The Urinary System", section Urethra_

Answer

Skeletal, then cardiac muscle

Answer

Cardiac, then smooth muscle

Answer

Skeletal muscle for both of them

Which muscle types build the internal and external urinary sphincters, respectively?

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