Urethral internal sphincter present between urinary bladder and urethra is made up of _________ muscles and is _________ in nature.

The urethral internal sphincter is located at the junction of the urinary bladder and the urethra. It is formed by the thickening of the detrusor muscle, which is a smooth muscle. Since it is composed of smooth muscle fibers, its functioning is not under conscious control, making it involuntary in nature.

In contrast, the external urethral sphincter is made up of skeletal muscles and is voluntary in nature.

Answer: smooth and involuntary