Final answer:
Urinary retention is not common in teenagers aged 13-17; it tends to occur more in older populations. Nonetheless, any case in a teenager should be medically evaluated. Urination is the process from urine formation to elimination and involves active transport, not just gravity.Correct option is b.
Step-by-step explanation:
Urinary retention is not commonly seen in healthy teenagers aged 13-17. The condition, where someone is unable to empty their bladder completely, tends to be more prevalent in older adults due to various health issues. However, if a teenager is experiencing urinary retention, it's important to seek medical advice as it could be a sign of an underlying medical condition or a side effect of medication.
In terms of the urinary system, urination refers to the entire process from the formation of urine in the kidneys to the elimination of urine from the body. The bladder muscle contracts during urination, and the urethra's smooth muscle responds to this action. Moreover, it's false that urine travels only due to the force of gravity; the muscular systems involved actively transport urine. Transitional epithelium, indeed, lines the bladder and helps it stretch as it fills.