Acid reflux into the esophagus ("heartburn") is the glomerular filtrate by the__________.

A. Vagina: The vagina is the canal that leads from the cervix to the outside of the body, not the structure that connects the ovary to the uterus.

B. Uterine tube: The uterine tube, also known as the fallopian tube, connects the ovary to the uterus and is where fertilization typically occurs.

C. Urethra: The urethra is the tube that carries urine from the bladder to the outside of the body. It has no role in connecting the ovary to the uterus.

D. Vas deferens: The vas deferens is a structure in the male reproductive system that transports sperm from the testes. It does not exist in the female reproductive system.

A. Esophageal glands secrete mucus to lubricate the esophagus, but they do not cause acid reflux.

B. Pharyngeal constrictors are muscles that help in the swallowing process, not in preventing acid reflux.

C. The lower esophageal sphincter (LES) is a ring of muscle that controls the passage of food from the esophagus to the stomach. If the LES is weakened or relaxes inappropriately, stomach acid can flow back into the esophagus, causing acid reflux or "heartburn."

D. The upper esophageal sphincter controls the passage of food from the pharynx into the esophagus, but it is not involved in preventing acid reflux.