Answer To: Hello,I need an expert who can do an assignment on human sexuality. There are two questions, and...
Dr Shweta answered on Mar 03 2024
Ans1: Description of menstrual cycle from an anatomical and physiological perspective, along with hormonal changes during the cycle explained as follows:
Menstruation: Menstruation is the bleeding that happens due to the shedding of the endometrium, the lining of the uterus. This happens when a reproductive cycle fails to bring about the fertilization of an egg. This marks the beginning of a sequence of biological processes that ultimately result in the maturation of an immature ovum, which is performed in preparation for ovulation and the possibility of fertilization.
Phases of Menstrual cycle:
The duration of the menstrual cycle in a human being is typically 28 days. Estrogen and progesterone are the hormones that are responsible for regulating the cycle. This can be broken down into four distinct stages. The four stages that make up the menstrual cycle are: the proliferative stage, the ovulatory stage, the secretory stage, and the menstrual stage (Figure 1).
Figure 1: The four phases of menstrual cycle
1. Proliferative Phase:
The proliferative phase, the first part of the menstrual cycle, that starts after the menstruation ends and it typically lasts for 9 to 10 days in a 28-day cycle. The levels of estrogen in the body rise during this period, which results in the maturation of approximately ten to twenty ova (egg cells) within the follicles of the ovary and the development of endometrial tissue in the uterus. The endometrium proliferates during this phase. This phase is referred to as the pre-ovulatory or follicular phase, during which specific ovarian follicles mature and the ovaries get ready for ovulation.
2. Ovulatory Phase:
It is the second phase of the menstrual cycle in which the levels of estrogen in the blood reach their highest point, and ovulation takes place. Ovulation is the process by which an ovary releases a single mature ovum, which is the lone ovum that reaches maturity. During ovulation, a Graafian follicle ruptures and discharges a mature ovum close to, but not inside, a fallopian tube. Ovulation occurs when estrogen production reaches a certain threshold. A woman's basal body temperature, measured orally or rectally, decreases slightly during ovulation and increases by around 0.5°C the day after ovulation. Many women utilize this knowledge to assist with conception or contraception.
3. Secretory Phase:
The period after ovulation is known as the post-ovulatory or secretory phase. It is the third phase of the cycle that begins immediately after ovulation and continues until the beginning of the subsequent cycle and beyond. It is commonly known as the luteal phase, named after the corpus luteum, which is the ruptured Graafian follicle. The corpus luteum functions as an endocrine gland, producing substantial amounts of progesterone and estrogen. Progesterone causes the endometrium to grow denser. Progesterone and estrogen reach their highest levels around the 20th or 21st day of a typical menstrual cycle. The hormones stimulate the glands in the endometrium to release nutrients that support a fertilized ovum implanted in the uterine wall. Without implantation, the corpus luteum disintegrates. Estrogen and progesterone levels drop sharply after decomposition. As a result of these falloffs, the fourth phase, known as the menstrual phase, is triggered, which ultimately results in the beginning of a new cycle.
4. Menstrual Phase:
During the menstrual phase, the uterine lining (endometrium) is shed and expelled as menstrual flow. When estrogen and progesterone levels decrease significantly, they are no longer able to support the uterine lining, causing it to dissolve. Menstruation...