Final answer:
The human female menstrual cycle, with an average length of 28 days, is an example of an infradian rhythm. It starts on the first day of menstruation and varies from 21 to 45 days among individuals. Cycle variations are normal, but significant irregularities may require medical consultation.
Step-by-step explanation:
The biological rhythm displayed by the human female menstrual cycle, which has an average length of 28 days, is called an infradian rhythm. This type of rhythm refers to cycles with a duration longer than a day, contrasting with the circadian rhythm of body temperature, which cycles over a 24-hour period. The menstrual cycle starts on the first day of menses and continues until the onset of the next period. While the average cycle length is about 28 days, variations from 21 to 45 days are considered normal.
Comprised of the ovarian cycle and the menstrual cycle, a woman's reproductive cycle involves the preparation of endocrine tissues, release of eggs, and maintenance of the uterine lining. Menstrual cycle length, which can vary significantly between individuals and even within the same individual from month to month, is influenced by a complex interaction of hormones.
In the case of Gabrielle, an 18-year-old with irregular menstrual cycles, this variation is a real-world example of how these biological rhythms can differ from the average cycle. For individuals who experience significant deviations from the average cycle length or irregular cycles, a visit to a healthcare professional, like Gabrielle deciding to go to a student health center, is often a prudent choice to rule out any underlying health issues.