Chapter 32 Sexual Reproduction in the Human 1

Learning Objectives Draw & know the functions of the main parts of the reproductive system Outline the pathway of sperm cells from testes to the penis Draw diagrams of sperm & egg cells Name & describe the role of the male & female reproductive hormones. Describe secondary sexual characteristics Describe the menstrual cycle & the role of oestrogen and progesterone in the menstrual cycle Menstrual disorders: one example of a menstrual disorder from the following: endometriosis and fibroids; one possible cause, prevention and treatment.

The male and female reproductive systems consist of: gamete-producing structures (ovaries and testes) gamete transport tubes hormone-secreting structures

Structure of the male reproductive system Bladder Seminal Vesicle Prostate gland Cowper’s Gland Penis Sperm duct Urethra Epididymis Testis Scrotum

Structure of the male reproductive system

Diagram of male reproduction organs Diagram of female reproduction organ

Testes Seminiferous tubules inside the testes are lined with sperm producing cells. Cells between the tubules produce the hormone testosterone.

Internal structure of testes Seminiferous tubule Sperm producing cells (2n) Sperm Sertoli cell – nourishes sperm Blood capillary Interstitial cells – produce testosterone

Epididymis All the seminiferous tubules join to form the epididymis. Sperm mature and are stored here.

Sperm duct and urethra The epididymis leads to the sperm duct (vas deferens) The sperm duct brings sperm to the urethra. The urethra is responsible for carrying sperm and urine out of the body

Glands in the male reproductive system Seminal Vesicle Prostate Gland Cowper’s Gland These glands produce seminal fluid which nourishes the sperm and provides a medium in which to swim. Seminal fluid + Sperm = Semen

Functions of the main parts of the Male reproductive system Testis Epididymis Sperm duct Seminal Vesicle Prostate gland Bladder Urethra Scrotum Cowper’s Gland Penis Produces 1. Sperm 2 Testosterone

Functions of the main parts of the Male reproductive system Testis Epididymis Sperm duct Seminal Vesicle Prostate gland Bladder Urethra Scrotum Cowper’s Gland Penis Stores sperm

Functions of the main parts of the Male reproductive system Testis Epididymis Sperm duct Seminal Vesicle Prostate gland Bladder Urethra Scrotum Cowper’s Gland Penis Carries sperm from the epididymis to the urethra

Functions of the main parts of the Male reproductive system Testis Epididymis Sperm duct Seminal Vesicle Prostate gland Bladder Urethra Scrotum Cowper’s Gland Penis Produces Seminal Fluid - For sperm to swim in - Nourishment for sperm

Tube through which the sperm travel through the penis Functions of the main parts of the Male reproductive system Testis Epididymis Sperm duct Seminal Vesicle Prostate gland Bladder Urethra Scrotum Cowper’s Gland Penis Tube through which the sperm travel through the penis

Keeps testes at a lower temperature Functions of the main parts of the Male reproductive system Testis Epididymis Sperm duct Seminal Vesicle Prostate gland Bladder Urethra Scrotum Cowper’s Gland Penis Keeps testes at a lower temperature

Functions of the main parts of the Male reproductive system Testis Epididymis Sperm duct Seminal Vesicle Prostate gland Bladder Urethra Scrotum Cowper’s Gland Penis Places sperm in the females body

Seminal vesicles, Cowper’s gland and Prostate gland Summary of functions of main parts of male reproductive system Part Function Testis Produces sperm and testosterone Epididymis Matures and stores sperm Sperm duct Carries sperm from the epididymis to the urethra Seminal vesicles, Cowper’s gland and Prostate gland Produces seminal fluid which feeds the sperm and allows them to swim. Sperm and seminal fluid are collectively called semen. Urethra Allows the passage of either urine or sperm. Penis Places sperm inside the body of a female Scrotum Keeps testes at a lower temperature (35°). This is the optimum temperature for Meiosis to occur.

Sperm

Sperm Structure Acrosome (contains digestive enzymes to enter the egg) Head Nucleus (contains 23 chromosomes) Collar (contains mitochondria) Middle Flagellum (allows sperm to swim) Tail

Anatomy The sperm cell consists of a head, a midpiece and a tail. The head contains the nucleus with chromatins, surrounded by an acrosome, which contains enzymes used for penetrating the female egg. The midpiece contains mitochondria, used for ATP production for the journey to the female uterus. The tail or "flagellum” moves the sperm along.

Sperm quantity Sperm quantity and quality are the main parameters in semen quality, which is a measure of the ability of semen to accomplish fertilization. Thus, in humans, it is a measure of fertility in a man. The genetic quality of sperm, as well as its volume and motility, all typically decrease with age. Forensic Analysis Ejaculated fluids are detected by ultraviolet light, irrespective of the structure or colour of the surface

Learning Check 1 Name the main parts of the male reproductive system and give a function for each part named. Name the male hormone . Where is it produced? What is the function of seminal fluid & what glands produce it? Describe the structure of sperm.

How does the male reproductive system function? The primary hormones involved in the functioning of the male reproductive system are: follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone. The entire male reproductive system is dependent on hormones, which are chemicals that stimulate or regulate the activity of cells or organs.

Hypothalamus → Gonad Releasing Hormone → Pituitary LH →Testes →Testosterone FSH → Testes → Sperm

FSH and LH are produced by the pituitary gland. FSH stimulates cells in the testis to produce sperm. LH stimulates the production of testosterone. Testosterone causes the development of secondary sexual characteristics in the male, including muscle mass and strength, fat distribution, bone mass and sex drive.

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Learning Check 2 Name the primary hormones involved in the functioning of the male reproductive system. Give a function for each one named. Give 3 examples of secondary sexual characteristics in males.

Structure of the female reproductive system

The Ovary Produce eggs by meiosis and female hormones – oestrogen & progesterone. 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 tube (oviduct) Funnel shaped tubes designed to catch the egg after it is released from the ovary. The egg is moved along the tube by cilia and muscular peristalsis.

The Uterus (womb) Muscular structure that holds the embryo during pregnancy Inner lining is called the endometrium This lining thickens each month with cells and blood vessels to nourish the embryo.

The vagina Allows entry of sperm. Is the birth canal for the exit of a baby. Lined with cells that produce mucus - protects against the entry of pathogens.

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

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

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

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

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

Summary of functions of main parts of female reproductive system 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 cause 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.

Learning Check 3 Name the main parts of the female reproductive system and give a function for each part named. Name the female hormones. Where are they produced? Give 3 examples of secondary sexual characteristics in females?

a mature liquid-filled cavity in a mammalian ovary that ruptures during ovulation to release an egg. The Graafian follicle represents the final stage of follicular development before ovulation.

The Ovary A number of eggs are produced by meiosis each month. Once meiosis is complete the egg is surrounded within a structure called the Graafian follicle. When mature the follicle forms a swelling on the outside of the ovary.

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.

What does the corpus luteum do? Produces progesterone until the placenta begins to - 10 weeks after gestation. Progesterone thickens the lining of the uterus for implantation. The corpus luteum dies if the egg is not fertilized, and progesterone production stops. When progesterone levels drop, the uterus lining stops thickening and is shed during menstruation.

What is corpus luteum deficiency? Corpus luteum deficiency, means the corpus luteum is not producing enough progesterone to allow pregnancy to develop. Without sufficient progesterone levels, the lining of the uterus will begin to shed. If a woman is pregnant and has low progesterone levels this may result in miscarriage.

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).

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 6 – 14 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. Ovulation

Days 14 – 28 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

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If fertilisation has not occurred the cycle begins again with the breakdown of the endometrium. The Menstrual Cycle 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 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

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

Graafian follicle Corpus Luteum Hormones Endometrium 5 14 Days 28 Oestrogen________ Progesterone _____ Endometrium 5 14 Days 28

Learning Check 4 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.

Events when pregnancy does not occur Doctors - problems with cycle

Menstrual disorder (Fibroids) Fibroids are benign non malginant tumours that grow in the wall of the uterus. As they grow they produce excessive menstrual bleeding, can lead to anaemia, pain, miscarriage or infertility.

Slow growing and range from the size of a pea to the size of a melon Common between ages of 35 and 45 Small fibroids often produce no symptoms

Cause May be an abnormal response to oestrogen Can occur in women taking the contraceptive pill

Prevention and treatment Small fibroids require no treatment just monitoring to check their growth. Large fibroids can be removed by surgery. If many large fibroids are present a hysterectomy may be necessary. This is where the uterus is removed. Fibroids that are attached to the outside of the uterus by a stalk (pedunculated myomas)  are the easiest to remove laparoscopically.

Menstrual Cycle

Hormonal control in the menstrual cycle Four hormones involved: FSH (Follicle Stimulating Hormone) Oestrogen LH (Luteinising Hormone) Progesterone Each hormone causes the production of the hormone following it and inhibits the hormone preceding it.

1. FSH – Follicle Stimulating Hormone Produced by pituitary gland During days 1-5 Stimulates a few potential eggs to develop, surrounded by graafian follicles.

Only one usually survives Sometimes used in fertility treatments to stimulate ovaries to produce eggs – often lots of eggs develop. This explains some multiple births Each graafian follicle then produces oestrogen

Multiple-Birth Pregnancy Under natural conditions, your chance of having a pregnancy with more than one baby is 1.5% chance. However, the number of multiple births has increased dramatically over the past 15 years, because of: the use of fertility drugs and in vitro fertilization(IVF). the increase of pregnancies in older moms, who have an increased likelihood of multiple birth pregnancy.

Fraternal Or Identical Twins There are two types of twins, fraternal and identical. Fraternal twins are more common because each baby develops from a separate egg and sperm. Generally, the ovaries release one egg a month, but sometimes more than one egg is released and fertilized. Fraternal twins will have individual placentas and amniotic sacs. Since each has a different egg and a different sperm, it is like siblings being born at the same time.

Identical twins come from one fertilized egg that splits early in the pregnancy and develops into more than one fetus. This is different because not only do the fetuses share the same placenta, but they also share the same genetic material. That is why they are identical (they have the same hair color, eye color, sex, and blood type). Identical twins video

Oestrogen Produced by the graafian follicle in the ovary Produced from days 5 -14 Causes the endometrium to develop Inhibits FSH ensuring no further eggs develop (useful in contraceptive pill) High levels of oestrogen just before day 14 stimulate release of LH

LH - Luteinising Hormone Produced by the pituitary gland Produced on day 14 Causes ovulation Causes the remains of graafian follicle to develop into corpus luteum Corpus luteum makes final hormone in the cycle, progesterone (along with small amounts of oestrogen)

Progesterone Produced by the Corpus Luteum in the ovary Produced from days 14-28 Maintains structure of endometrium Inhibits FSH to stop further eggs developing Inhibits LH to stop further ovulation and pregnancies Prevents contractions of the uterus Hormones in the menstrual cycle

The Ovarian Cycle

Learning Check 5 List the four hormones involved in the menstrual cycle In each case state where it is produced Give a function for each hormone