The Reproductive System

Review of Endocrine System

Reproductive System  Gonads (testes and ovaries) are the organs that produce reproductive cells (sperm and eggs). Also, produce sex hormones.  Sex hormones (ie, testosterone and estrogen) are the chemical compounds that control the development and function of the reproductive system.  The male and female reproductive cells are called gametes.  The fusion of a male and a female sex cell during a process called fertilization, produces a zygote.

Male Reproductive System

Seminal Fluid  These vesicles provide the energy for movement of the sperm, produce a mucus-like fluid that contains the sugar fructose.  The prostate gland and Cowper’s gland also secrete mucus-like fluids, as well as an alkaline fluid to neutralize acids from urine in the urethra.  The combination of sperm cells and fluids is called semen.

Nervous System and Hormone production  The hypothalamus and the pituitary gland control the production of sperm and male sex hormones.  Negative-feedback systems ensure that adequate numbers of sperm cells and constant levels of testosterone are maintained.  The pituitary gland produces and stores the gonadotropic hormone, male follicle- stimulating hormone (FSH), and male luteinizing hormone (LH or ICSH).  At puberty, the hypothalamus secretes the gonadotropin-releasing hormone (GnRH) which activates the pituitary gland to secrete and release FSH and LH.

Hormonal control  GnRH from the hypothalamus acts on the anterior pituitary to release FSH and LH (causing the testes to begin producing sperm and to release testosterone)  Follicle Stimulating Hormone (FSH): causes the cells in the seminiferous tubules to produce sperm and the release of inhibin (which acts on the anterior pituitary to inhibit the production of FSH).  Luteinizing Hormone: causes the testes to release testosterone (promotes secondary sex characteristics and stimulate spermatogenesis)

Female Reproductive System

Hormonal Control – Female System  Similar control as to the male system.  The beginning of GnRH production signals puberty which begins the release of FSH and LH.  Female FSH and LH regulate the control of hormones produced by the ovaries – progesterone and estrogen.  The workings of FSH and LH and estrogen and progesterone during the menstrual cycle enable it to run efficiently.

Menstruation

Hormonal production in the menstrual cycle (Day 1-5)  Hormones are involved at every stage of the menstrual cycle.  The pituitary gland produces FSH which starts the development of one egg in a follicle in one of the ovaries.

Production of estrogen – Follicular stage – Day 6-12  The ovary produces estrogen which causes the repair of the lining of the uterus after the last menstruation.  As the follicle matures, it releases estrogen and some progesterone  The increase of estrogen, inhibits the release of FSH.  Estrogen also triggers a sudden release of GnRH which leads to an increase in LH—which triggers ovulation and an ovum is released.

Ovulation – thickening of uterus membranes – end of Follicular stage – Day  In the uterus, progesterone, which is released by the newly erupted follicle, causes the lining of the uterus to get thicker ready for the fertilized egg.  The follicular cells, left within the ovary develops into the corpus luteum, which produces progesterone and some estrogen.

Development of corpus luteum – Luteal phase – Day  Once the ovum is released, LH causes the follicle to develop into a corpus luteum, which secretes progesterone and some estrogen.  As progesterone and estrogen rise in the blood, FSH and LH are inhibited in their production.  If the egg is not fertilized, the corpus luteum degenerates, causing the decrease in production of progesterone and estrogen.  This decrease in the sex hormones causes the cycle to begin again with the production and secretion of FSH and LH.  The lining of the uterus breaks down and menstruation occurs by the shedding of the uterine lining (endometrium).

Sexually Transmitted Infections (STI)  A number of infections can be transmitted through sexual intercourse. The involvement of close physical contact and the exchange of body fluids causes this.  STIs may be caused by viruses, bacteria, and parasites. The greatest concern are those caused by viruses and bacteria.  The most common viral STIs are HIV/AIDS, hepatitis, genital herpes, and humanpapilloma virus (HPV)  The most common bacterial STIs are chlamydia, gonorrhea, and syphilis.