Draw a neat and well labeled diagram of T.S of ovary and describe the menstrual cycle in human females.
Hint: The ovary is a key organ within the female reproductive system responsible for producing and releasing an egg cell, or ovum. Once released, the ovum moves through the fallopian tube to the uterus, where it may be fertilized by a sperm. Typically, one ovary is located on each side of the body.
Complete answer:
The ovaries are the main female reproductive organs responsible for producing the female gamete, called the ovum or egg, along with various steroid hormones. There are two ovaries, one located on each side of the lower abdomen. Each ovary is encased in a thin epithelial layer that contains the ovarian stroma. The stroma is organized into two regions:
- An outer cortex
- An inner medulla
Female Accessory Ducts:These include the fallopian tubes, uterus, and vagina.
Menstrual Cycle:The reproductive cycle in female primates, including humans, is called the menstrual cycle. In human females, this cycle typically repeats every 28 to 29 days.
Menarche: This is the onset of the menstrual cycle.
Menopause: This marks the end of the menstrual cycle, generally occurring around age 50.
Stages of the Menstrual Cycle:
(i) Menstrual Phase: This phase spans from day 1 to day 4 of the cycle. It usually occurs when fertilization does not take place. Bleeding happens as the uterine lining, or endometrium, sheds. Following the fourth day, FSH (Follicle-Stimulating Hormone) begins to be secreted again, prompting the development of a new follicle.
(ii) Follicular Phase: Lasting from day 5 to day 13, the uterus enters a proliferative phase. During this period, a new primordial follicle in the ovary begins to mature in response to FSH, eventually developing into a Graafian follicle and initiating estrogen production. This leads to uterine proliferation as well.
(iii) Ovulatory Phase: Occurring around day 14, ovulation begins as the mature Graafian follicle ruptures, releasing an ovum. This ovum, along with follicular fluid, is collected by the fimbriae of the infundibulum, part of the fallopian tube. If no sperm is present, the ovum is not fertilized and subsequently degenerates.
(iv) Luteal Phase: This phase extends from day 15 to day 28.
Ovarian Changes:The corpus luteum forms from the empty Graafian follicle, producing progesterone. If fertilization does not take place, the corpus luteum breaks down.
Uterine Changes: Progesterone increases the thickness of the endometrial lining to prepare for potential pregnancy. If progesterone production ceases, the endometrial lining sheds, leading to menstruation.
Note: Sexually Transmitted Diseases (STDs): These are infections spread through sexual contact with an infected person.
Examples include gonorrhea, syphilis, hepatitis B, genital herpes, AIDS, and more.
Infertility: This refers to the inability to conceive despite two years of marriage without the use of any birth control methods.