Final answer:
The 'urethra' and 'ureter' are parts of the urinary system and do not refer to chemical elements. They represent the channels through which urine are transported and expelled from the body.
Step-by-step explanation:
The elements not present in the terms "urethra" and "ureter" refer to chemical elements, which are not what these terms describe. Instead, the urethra and ureter are components of the urinary system. The ureters are two tubes that transport urine from the kidneys to the urinary bladder, while the urethra is a single tube that carries urine from the bladder to the outside of the body for excretion.
Structurally, in both males and females, the area at the base of the bladder where the urethras and ureters connect is known as the trigone, and it is shaped like a triangle. The urethra in males is notably longer than in females and has additional layers of epithelium. The process of urination, which involves the expulsion of urine from the urinary bladder via the urethra, is controlled by both the autonomic and somatic branches of the nervous system and involves two sphincters: the internal urinary sphincter and the external urinary sphincter.