Biology, Grade 12 SBI4U Female Reproductive System

Specific Expectations E2.1 Use appropriate terminology related to homeostasis, including, but not limited to: insulin, testosterone, estrogen, nephron, dialysis, pituitary, synapse, and acetylcholine. E3.2 Explain how reproductive hormones act in human feedback mechanisms to maintain homeostasis (e.g., the actions of male and female reproductive hormones on their respective body systems).

Agenda The Female Reproductive System Puberty Sex Hormones Negative Feedback Loop The Menstrual Cycle (Ovarian/Uterine) Rhythm Method Menopause Amenorrhea

The human reproductive system involves separate male and female reproductive systems. In many ways, the female system is more complicated than that of the male. Gonads are organs such as the testes (male), which produce sperm, and ovaries (females) that produce eggs(ova). These reproductive cells are known as gametes. Introduction

Uterus and Vagina The uterus is a muscular organ that holds and nurtures a developing fetus Size/shape of a pear (when not pregnant) The lining of the uterus is known as the endometrium The upper end of the uterus connects to the fallopian tubes and the lower end connects to the cervix.

Ovaries The two ovaries are involved in Oogenesis, which is the production of ova/egg cells. In general, ovaries switch, producing one egg per ovary each month

Ovaries Each ovary contains specialized structures called follicles. Follicles contain 2 types of cells: 1. Egg Cells 2. Follicular Cells Each month 1 follicle releases 1 ovum into a fallopian tube (ovulation) Any remaining follicles deteriorate and are reabsorbed within the ovary.

Puberty Puberty occurs around ages 9-13 in females, and in males where the reproductive system starts to develop maturely.

Puberty and Sex Hormones How does it begin? Puberty begins when GnRH is released from the hypothalamus and acts on the anterior pituitary causing secretion of the following protein hormones: 1. Follicle Stimulating Hormone (FSH) 2. Luteinizing Hormone (LH) FSH and LH stimulate the ovaries to secrete the steroid hormone: 1. Estrogen - activates the development of most secondary sex characteristics.

Menstrual Cycle Begins in girls at years of age Lasts about 28 days (may vary:20-45) Two separate cycles controlled by ovarian hormones (mainly estrogen and progesterone) and pituitary hormones (mainly FSH and LH) 1)Ovarian Cycle- Occurs in the ovaries 2)Uterine Cycle- Occurs in the uterus

Ovarian Cycle 1) Each follicle in the ovary contains an immature single ovum 2) In one ovarian cycle, one follicle in the ovary matures and releases a single ovum. 3) Once ovum is released, the existing follicle develops into a yellowish gland structure known as the corpus luteum, which then degenerates if fertilization does not occur Repeats every month

Uterine Cycle Essentially, after the end of menstruation, the endometrium begins to grow and thicken in cells, blood vessels, and glands.

Menstrual Cycle: Ovarian + Uterine Cycles

Negative Feedback Mechanism

DaysOvaryUterusHormones 1-5Menstruation (Menstrual Flow) Shedding of the endometrium -No particular hormonal surges 6-13Follicles develop in ovaries Endometrium is restored -Estrogen rises to maximum -FSH rises a bit 14Egg bursts from the ovary and follicular cells differentiate into the corpus luteum Endometrium gradually thickening -Estrogen drops sharply -LH surges 15-28Corpus Luteum is maintained and slowly degenerates if fertilization does not occur Endometrium thickens to maximum Estrogen/Progesterone rises then falls if fertilization does not occur -FSH/LH inhibited Menstruation Summary

Rhythm Method The rhythm method, also called the calendar method is a form of natural family planning. How it works: You track your menstrual history to predict when you'll ovulate. This will help to determine when you're most likely to conceive. Similarly, if you're hoping to avoid pregnancy, you can use the rhythm method to determine which days to avoid unprotected sex. Using the rhythm method for birth control requires careful record keeping and diligence. If you don't want to conceive, you and your partner must avoid having sex or use other forms of contraception

Menopause Number of functional follicles begins to decline with age which leads to a gradual decline in estrogen and progesterone in the blood. As these hormone levels drop, the menstrual cycle becomes irregular and then stops which is known as menopause around the age of 50 years. Can have a wide range of effects of women -hot flashes -loss of bone mass -increase risk of heart disease, breast cancer and uterine cancer Hormone replacement therapy may be considered.

Amenorrhea The term used to describe "absence of periods“. There are two types of amenorrhea: 1. Primary amenorrhea is when a young woman has not had her first period by the age of Secondary amenorrhea is when a woman who has had normal menstrual cycles stops having her monthly periods for three or more months.

Causes of Amenorrhea Possible causes of primary amenorrhea include: Failure of the ovaries Poorly formed reproductive organs Common causes of secondary amenorrhea include: Pregnancy Stopping the use of birth control Stress/depression Poor nutrition Extreme weight loss/sudden weight gain Over-exercising