Reproductive Hormones

The Male Reproductive System The male reproductive hormone is testosterone – a steroid within the lipid family. Testosterone… Produced in the testes. Stimulates spermatogenesis – sperm production. Brings about the secondary sex characteristics in males during puberty. Enhances male sex drive.

Male Sex Hormones & Sperm Production The pituitary gland produces and stores gonadotropic hormones that regulate the function of the testes. These hormones are… Follicle-stimulating hormone (FSH) that stimulates the production of sperm cells. Luteinizing hormone (LH) which promotes the production of testosterone. At puberty, the hypothalamus releases gonadotropin-releasing hormone (GnRH) that stimulates the pituitary to release FSH & LH.

Female Sex Hormones & Ovulation The female reproductive system is somewhat more complex than the male reproductive system because it has to not only produce and deliver a gamete, but also house and nurture the zygote that may be formed. Once again guys…the girls are doing the bulk of the work – give them props!

Ovaries & Eggs The ovary contains follicles that are made of two cell types – the primary oocyte and the granulosa. The primary oocyte is a diploid cell that will undergo meiosis and form the eggs. The granulosa will provide nutrients for the oocyte. The female ovaries have 400,000 precursor follicles that will begin to develop further and produce eggs at the onset of puberty. Many follicles develop each cycle with only one being matured fully and released.

Ovaries & Eggs

Hormones & Ovulation Again, the hypothalamus and the pituitary gland control the function of the reproductive system. The hypothalamus stimulates the pituitary to produce FSH & LH. FSH & LH regulate the actions of the ovaries… FSH stimulates the development of the follicles into eggs. LH stimulates ovulation (egg release) and the formation and maintenance of the corpus luteum. Again, at puberty GnRH is released and FSH and LH are produced and begin their roles.

What About Estrogen??? Estrogen helps to bring about the secondary sex characteristics in females. It is also released by the ovary when follicles are developing into eggs. The estrogen aids in the preparation of the eggs and their release. Estrogen levels drop after the egg has been released by the ovary. The remaining follicular cells develop into the corpus luteum with the aid of LH.

Who is this Corpus Luteum? The corpus luteum is a mass of follicle cells that form within the ovary after ovulation. It secretes both estrogen and progesterone. Progesterone is a female sex hormone that prepares the body for a possible pregnancy by maintaining the uterine lining. Progesterone levels increase after ovulation just in case the egg is fertilized and needs a place to live for the next nine months.

The Menstrual Cycle (I) The menstrual cycle takes an average of 28 days and includes three phases – the flow phase, follicular phase and luteal phase. The flow phase is marked by the shedding of the endometrium. The endometrium is a thick lining of blood that lines the uterine wall just in case the egg is fertilized. It will supply the zygote with oxygen and nutrients until an umbilical cord can be established. If there is no fertilization, there is no need to maintain this lining so it is shed. This phase lasts about 5-6 days.

The Menstrual Cycle (II) The follicular phase occurs as the follicles develop into eggs within the ovary. Estrogen is secreted in order to aid in this process. This phase lasts 7-8 days.

The Menstrual Cycle (III) The last phase is the luteal phase which is the longest phase. The egg bursts free from the ovary and the remaining follicular cells begin to form the corpus luteum. Estrogen levels decline as the egg is released but are restored by the corpus luteum. Progesterone is also secreted to prepare the body for a possible fertilization and pregnancy. It enriches the endometrium, prevents further ovulation and inhibits uterine contractions that may loosen the egg and endometrium.

The Menstrual Cycle - overview

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