This large follicle is known as the dominant follicle. The other follicle stop growing and become atretic and eventually die out. Oestrogen realeased by the follicle acts on the uterine endometrium making it to proliferate. This signifies the start of the uterine cycle. The dominant follicle reaches 18-20mm in size and ruptures on the 14th -- 16th day of the menstrual cycle. This process is known as ovulation and its signals the end of the follicular phase and the beginning of the luteal phase.
The Luteal phase
Once the ovum is released certain changes take place within the follicle. The follicular cells grow, fat is deposited in them and they assume a yellowish colour. They become known as luteal cells and the whole follicle is known as corpus luteum. These cells of the corpus luteum produce the hormone progesterone which in similarity to oestrogen acts on the uterine endometrium. The levels of these hormones peak around the 24th day of the menstrual cycle. If pregnancy occurs the corpus luteum enlarges in size and produces more progesterone that is used to maintain pregnancy. If pregnancy fails to occur the corpus luteum decreases in size and becomes atretic. Consequently progesterone levels fall. If progesterone is below a certain threshold level it is unable to maintain the proliferated uterine endometrium with resultant shedding and bleeding. This shedding of the uterine endometrium is what is known as menstruation.
The hormonal regulation of the menstrual cycle
The hormone regulation of the menstrual cycle is under control of what is known as the hypothalamic pituitary ovarian axis. The hypothalamus releases a decapeptide known as Gonadotropin releasing hormone or GnRH. This is released into the hypophyseal portal system where it acts on the anterior pituitary (Sherman et al.,1979). GnRH is a neurohoermone and its released in pulsatile nature. The action of GnRH is low during childhood but its activity increases during puberty The anterior pituitary the releases two hormones. The Luteinizing hormone and the follicle stimulating hormone. The LH and FSH are released into the systemic circulation where they act on the target organs. These Hormones are known as gonadotropins because they act on the testes and the ovaries. They are glycoproteins and they are comprised of an alpha and a beta subunit. Its is the beta subunit that is unique to each of these hormones. Luteinizing hormone stimulates the secretion of sex steroids from both the testes and the ovaries. In the testes LH stimulates the synthesis of testosterone. The theca cells of the ovary also produce the production of testosterone but this testosterone is eventually converted into estrogen by the granulosa cells. FSH is important for the maturation of ovarian follicles its is also important for sperm production and maturation by its action on the sertoli cells.
Effects on other body organs
The endocrine glands oestrogen and progestron that are produced by the action of LH and FSH also act on other systems of the body. On the cardiovascular system oestrogen decreases the production of antithrombin III and increases platelet aggregation. This causes a pro-thrombotic...
Essay Topic Examples 1. The Evolution of Human Reproductive Systems and its Impact on Society Explore the biological evolution of human reproductive systems from ancient ancestors to modern humans. Discuss how changes in reproductive anatomy and physiology have influenced societal structures, family planning, and gender roles over time. Analyze the implications of these evolutionary changes on current debates around reproductive health and rights. 2. Comparative Anatomy of Mammalian Reproductive Systems Compare and contrast the
Anatomy of the UterusThe uterus is a female reproductive system organ where the growth of the baby takes place. It is also referred to as the womb. The uterus is structurally hollow and pear-shaped with almost a fist size. The uterus is connected to the fallopian tube assisting in the translocation of eggs from the ovary into the uterus. On the other hand, the uterus� lower parts form the cervix
Biology An Inconvenient Truth In Al Gore's documentary an Inconvenient Truth, he makes some very pertinent points about the issue of global warming. Included in the documentary are the following topics. a) Effects of Global Warming: Gore uses graphs to clearly illustrate some of the dangerous ramifications of global warming. One chart shows the increasing amounts of carbon dioxide in the atmosphere and data which indicates a rise in temperature is the result of
Abnormal Uterine Bleeding and Issues Reproductive Tract Diseases for human females are typically focused in the upper reproductive tract or the lower reproductive tract. The upper tract includes the fallopian tubes, ovary and uterus, while the lower reproductive tract focuses on the vagina, cervix and vulva. There are three major types of infections: endogenous, iatrogenic and sexually transmitted diseases. Endogenous diseases arise from internal cellular structures and may be bacterial, viral
Lower Abdominal Pain Patient: Patient is a 30-year-old female presenting with lower abdominal pain, beginning approximately 48-hour previous to her exam. Over the last few days, her pain has increased, and she reports vaginal bleeding that is scanty. She did have a normal menstrual period that ending two-weeks prior, and she indicates this was normal and lasted about 4 days. She is Gravida 2, Para -0, Miscarriage -- 2, and has
However, proper treatment may restore fertility. During pregnancy, existing fibroids may grow at a greater pace due to the increased blood flow and estrogen levels but they usually return to their original size after delivery. Pelvic Inflammatory Disease Definition & Cause: Pelvic inflammatory disease (PID) is a general term for infection of the lining of the uterus, the fallopian tubes. It is a very common disease and in the United States
Our semester plans gives you unlimited, unrestricted access to our entire library of resources —writing tools, guides, example essays, tutorials, class notes, and more.
Get Started Now