breifly mention the changes in the human ovary which takes place under the influence of FSH and LH.
Answers
FSH stimulates the growth and maturation of immature oocytes into mature (Graafian) follicles before ovulation. ... However, once estrogen levels reach a critical level as oocytes mature within the ovary in preparation for ovulation, estrogen begins to exert positive feedback on LH production, leading to the LH surge.
Answer:
Explanation:
The typical female pelvis has two ovaries, one on either side of the uterus. Each ovary is attached to the uterus by its Utero ovarian ligament, and to the pelvic sidewall by the infundibulopelvic ligament, which carries the ovarian vessels. Ovaries contain oocytes, or eggs, which are female gametes. Females are born with a lifetime supply of immature oocytes, each ovary containing one million to two million eggs. While the number of eggs declines with time, within a typical female lifespan, about 300 to 500 eggs mature and progress through ovulation, the process of mature egg releaseD from the ovary into the adjacent fallopian tube, through which the egg is carried into the uterus. The ovaries are not directly attached to the fallopian tubes, and either fallopian tube may pick up an egg from either ovary.
Hormones involved in ovulation include:
Gonadotropin-releasing hormone (GnRH) is a tropic peptide hormone made and secreted by the hypothalamus. It is a releasing hormone that stimulates the release of FSH and LH from the anterior pituitary gland. Low-frequency GnRH pulses are responsible for FSH secretion whereas high-frequency pulses are responsible for LH secretion.
Follicle-Stimulating Hormone (FSH) is a gonadotropin synthesized and secreted from the anterior pituitary gland in response to GnRH. It is involved in THE reproductive processes of both males and females. FSH stimulates the growth and maturation of immature oocytes into mature (Graafian) follicles before ovulation.
Luteinizing Hormone (LH) is a gonadotropin synthesized and secreted by the anterior pituitary gland in response to GnRH. Like FSH, LH is involved in reproductive processes in both males and females. When follicle maturation is complete, an LH surge triggers ovulation.
Progesterone is a steroid hormone that is responsible for preparing the endometrium for uterine implantation of the fertilized egg. If a fertilized egg implants, the corpus luteum secretes progesterone in early pregnancy until the placenta develops and takes over progesterone production for the remainder of the pregnancy.
Estrogen is a steroid hormone that is responsible for the growth and regulation of the female reproductive system and secondary sex characteristics. Estrogen is produced by the granulosa cells of the developing follicle and exerts negative feedback on LH production in the early part of the menstrual cycle. However, once estrogen levels reach a critical level as oocytes mature within the ovary in preparation for ovulation, estrogen begins to exert positive feedback on LH production, leading to the LH surge. Estrogen also has many other effects which are important for bone health and cardiovascular health in premenopausal patients, which will be discussed in another article.
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Issues of Concern
The most common cause of female infertility in the United States is ovulatory dysfunction, in which a variety of hormonal factors interfere with the complex sequence of hormonal events required to trigger ovulation. Problems can occur at any point in this pathway (hypothalamus, pituitary, ovary) and can lead to failure to ovulate. The most common cause of chronic ovulatory dysfunction in the United States is Polycystic Ovarian Syndrome, or PCOS, which interferes with ovulation at multiple points.[4]
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Cellular
Granulosa cells surround the oocyte. They respond to follicle-stimulating hormone (FSH) released by the anterior pituitary by converting androgens to estrogen.
Theca cells appear as the follicle matures, and produce androgens which are subsequently converted to estrogens by the granulosa cells.
Development
The prepubertal ovary contains primordial follicles, which consists of an oocyte surrounded by a single layer of granulosa cells. Following puberty, the anterior pituitary begins to secrete FSH and LH in response to GnRH release from the hypothalamus, and the dormant cells in the ovary begin to secrete steroid hormones in response.
Organ Systems Involved
The hypothalamus secretes GnRH in a pulsatile fashion, which triggers FSH and LH release from the anterior pituitary. These, in turn, act on the granulosa and theca cells in the ovary to stimulate follicle maturation and trigger ovulation.
Mechanism
Follicular Development
A large number of primordial follicles begin the process of maturation into primary follicles. When this happens, the granulosa cells which surround the oocyte "plump up" and become active. The zona pellucida develops at this stage as well, and separates the oocyte from the granulosa cells. The zona pellucida in the protective casing through which sperm must penetrate in order to fertilize the egg following ovulation.