Question

What is the difference between the internal and external urethral sphincter?

Answer 1

Hint: Urinary sphincter is one of the important muscular structures that helps in the regulation of the rate of the flow of urine in the body. They are of two types that help in regulating the involuntary and voluntary flow of urine in the body. They are not just the passage for urine but also for the ejaculation of sperms out of the body of males.

Complete answer:
The urinary sphincter is a muscular structure that helps in the regulation of the outflow of urine from the bladder into the urethra. When these muscles contract, the urethra becomes narrow and it will lead to stoppage or will slow the process of urination. This sphincter is used for the maintenance of the urinary flow and for the ejaculation of the semen of the males. It is generally located inside the deep perineal pouch.

In the ninth week of the fetal period of a child, mesenchyme is generally undifferentiated that is present inside the anterior part of the urethra which helps in the development of the external urethral sphincter which is also known as rhabdosphincter. Later, in the 12th week, striated muscle fibres will start to develop. While the internal urethral sphincter will rise from the Wolffian duct into the bladder and the urethra. It can be damaged during childbirth which may occur due to stretching of the ligaments and dysfunction of the pelvic floor muscle.

DIFFERENCE:

Internal sphincter	External sphincter
The internal urinary sphincter regulates the involuntary flow of urine that take place from the bladder to the urethra.	External urinary sphincter voluntary control of urine from the bladder to the urethra.
It is made up of smooth muscle.	It is made up of striated muscle.
They are passage for urine in females but in ejaculation of sperms in males.	They are passage for urine in both males and females.

Note: Urinary inconsistency can occur after the pelvic surgeries that can cause excretion of urine out of the body at any time. Urinary sphincter being an important contributing factor for post-radical prostatectomy can cause urinary incontinence. In some cases, bladder dysfunction at times also plays a role in incontinence. Rates of postoperative urinary incontinence usually vary through surgeon experience, and the result is between 4 - 8%.