Sexual Reproduction in the Human The Female – Structure & Hormones

Learning Objectives Outline the general structure of the reproductive system (Male & Female) State the functions of the main parts of the reproductive system Outline the role of meiosis to produce sperm & ova (egg) cells Define the term secondary sexual characteristics Outline the role of oestrogen, progesterone & testosterone Outline the events & outline the role of oestrogen and progesterone of the menstrual cycle

Structure of the female reproductive system

The Ovary These produce the eggs and female hormones. All the eggs in an ovary are present at birth. After puberty 20 eggs mature each month. Only one will be released from the ovary – the rest will die.

The Fallopian tubes are muscular and approx 12cm long. Funnels at the tip of each tube catch the egg after it is released from the ovary. The egg is moved along the tube by cilia and muscular peristalsis. The egg is either fertilised or dies in the fallopian tube. The Fallopian tube (oviduct)

The Uterus (womb) Muscular structure approximately the size of your fist. Outer wall made of involuntary muscle. Inner lining is called the endometrium This lining thickens each month with cells and blood vessels to nourish the embryo. The cervix separates the uterus from the vagina.

Elastic muscular tube 10cm long. Allows entry of sperm. Is the birth canal for the exit of a baby. Lined with cells that produce mucous. This serves to protect against the entry of pathogens. The vagina

Structure of the Female reproductive system Fallopian tube (Oviduct) Funnel Ovary Ovarian Ligament Uterus Lining of uterus (endometrium) Wall of uterus Cervix Vagina Vulva

Functions of the main parts of the female reproductive system Funnel Ovary Uterus Lining of uterus (endometrium) Wall of uterus Cervix Vagina Vulva Produces : 1.Egg 2.Oestrogen 3.Progesterone Ovarian Ligament Fallopian tube (Oviduct)

Funnel Ovary Uterus Lining of uterus (endometrium) Wall of uterus Cervix Vagina Vulva 1.Catches the egg after release from ovary 2.Transports egg from ovary to womb 3.Site of fertilisation Ovarian Ligament Fallopian tube (Oviduct) Functions of the main parts of the female reproductive system

Funnel Ovary Uterus Lining of uterus (endometrium) Wall of uterus Cervix Vagina Vulva 1.Implantation 2.Hold foetus 3.Forms placenta Ovarian Ligament Fallopian tube (Oviduct) Functions of the main parts of the female reproductive system

Funnel Ovary Uterus Lining of uterus (endometrium) Wall of uterus Cervix Vagina Vulva 1.Allows entry of sperm into female system 2.Birth canal to allow exit of baby Ovarian Ligament Fallopian tube (Oviduct) Functions of the main parts of the female reproductive system

Summary of functions of main parts of female reproductive system PartFunction Ovary To produce the egg (ova). To produce the hormones oestrogen and progesterone Fallopian tube (oviduct) Catches the egg from the ovary and transports it to uterus. Site of fertilisation. Uterus Site of implantation. Holds the developing embryo. Has a lining (endometrium) enriched with blood vessels to nourish the embryo. Forms the placenta. Vagina Allows entry of sperm and exit of baby at birth.

Female Hormones Oestrogen and progesterone are the female hormones A combination of oestrogen and progesterone at puberty causes the development of the secondary female characteristics: The maturing and enlargement of the breasts. The widening of the pelvis to allow for birth. The growth of pubic and underarm hair. A growth spurt.

The Ovary The ovaries produce the eggs and the female hormones oestrogen and progesterone. The ovaries of a female foetus contains all the potential eggs at birth. These eggs have not yet divided by meiosis and as a result are diploid After puberty a number of eggs are produced by meiosis each month. Usually only one egg continues to grow … the rest die

The Ovary Once meiosis is complete the egg is surrounded within a structure called the Graafian follicle. This structure produces the female hormone oestrogen When mature the follicle forms a swelling on the outside of the ovary. It bursts at ovulation to release the egg After ovulation the follicle fills with yellow cells and becomes the Corpus luteum (yellow body). This secretes the hormone progesterone

The Menstrual Cycle The menstrual cycle is a 28 day sequence of events that produces an egg and prepares the body for pregnancy. This cycle begins at puberty and continues until the menopause (the end of the woman’s reproductive life). Summary of events in the menstrual cycle Days 1 – 5 The old lining of the uterus (endometrium) breaks down and is shed from the body. The loss of this blood and tissue is called menstruation (period). A new egg is produced in the ovary by meiosis. This new egg is surrounded by the Graafian follicle.

Days The hormone oestrogen is produced by the developing Graafian follicle. This has two functions: It causes the lining of the uterus (endometrium) to build up again in preparation for implantation. Oestrogen also prevents the development of any more eggs. Day 14 Ovulation. This occurs when the Graafian follicle bursts to release the egg into the fallopian tube. The Menstrual Cycle

Days The Graafian follicle now develops into the Corpus Luteum (yellow body). This has two functions: It causes the endometrium to thicken even further. It also prevents new eggs from forming. The egg that was released will die by day 16 if it is not fertilised. Thus days 12 – 16 of the menstrual cycle are referred to as the Fertile Period. (Even though the egg is not released until day 14, sperm, which can survive for a period of time in the female body, may already be present. Thus the fertile period begins on day 12).

If fertilisation does not take place the Corpus Luteum starts to degenerate around day 22. This results in a reduction in progesterone levels. As a result the lining of the uterus breaks down again on day 28. The menstrual cycle begins again with day 1.

The Menstrual Cycle DAY 1-5 : Blood from the womb lining is shed from the body After day 5 the lining of the uterus repairs and builds up again Fertile period Ovulation occurs on Day 14 Implantation may happen If fertilisation has not occurred the cycle begins again with the breakdown of the endometrium.

Inside the Ovary Potential egg Developing Graafian follicle – secretes oestrogen Graafian follicle now changes to the Corpus luteum which secretes progesterone Egg is released from ovary (ovulation)

Days Graafian follicleCorpus Luteum Oestrogen________ Progesterone _____ Endometrium Hormones

Learning Check Name the main parts of the male reproductive system and give a function for each part named. Name the main parts of the female reproductive system and give a function for each part named. Outline what is happening on each of the following days of the menstrual cycle: 1, 5, 12, 14, 26. Outline the role played by oestrogen and progesterone in the cycle.

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