Sexual Reproduction in the Human

Depth of treatment (1/2) General structure of the reproductive system – male and female Functions of the main parts Role of meiosis in the production of sperm cells and egg (ova) Definition of “secondary sexual characteristics” Role of oestrogen, progesterone and testosterone The menstrual cycle: the events and outlined role of oestrogen and progesterone

Depth of treatment (1/2) Copulation Location of fertilisation Implantation, placenta formation and function Birth – outline of process Milk production and breastfeeding

Contemporary Issues and Technology Birth control – natural, mechanical, chemical and surgical methods of contraception Infertility One cause of male infertility from the following disorders: low sperm count, low sperm mobility, endocrine gland failure Availability of corrective measures

Contemporary Issues and Technology One cause of female infertility from the following disorders: blockage of the Fallopian tube, endocrine gland failure Availability of corrective measures In-vitro fertilisation and implantation Biological benefits of breastfeeding

Main topics to learn about... Male reproductive system Female reproductive system The menstrual cycle Sexual intercourse Human embryo development ( higher level) Placenta, birth and lactation Birth control Infertility

Part 1: Male reproductive system Objectives: Outline the general structure of the male reproductive system State the functions of the main parts of the reproductive system Outline the role of meiosis to produce sperm cells Define the term secondary sexual characteristics Outline the role of testosterone in males

Structure of the male reproductive system

Testis Epididymis Sperm duct Seminal Vesicle Prostate gland Bladder Urethra Scrotum Cowper’s Gland Penis

Male gonads are called testes and they are held in the scrotum. This means they are kept at slightly lower than body temperature (35°) which is the ideal temperature for sperm production. Testes A gonad is an organ that produces sex cell in animals.

Internal structure of testes Seminiferous tubule Sperm producing cells (2n) Sertoli cell – nourishes sperm Sperm Blood capillary Interstitial cells – produce testosterone Seminiferous tubules inside the testes are lined with sperm producing cells. Cells between the tubules produce the hormone testosterone.

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

Sperm duct and urethra The sperm duct brings sperm from the epdidymis to the urethra.

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

Urethra The urethra carries semen and urine out of the body Facts about sperm The volume of semen in a single ejaculation may vary from 1.5 to 6.0 ml. There are usually between 50 to 150 million sperm per milliliter of semen

Produces 1.Sperm 2Testosterone 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

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

Produces Seminal Fluid - For sperm to swim in - Nourishment for 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

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

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

Places sperm in the females body 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

Summary of functions of main parts of male reproductive system PartFunction TestisProduces sperm and testosterone EpididymisMatures and stores sperm Sperm ductCarries 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. UrethraAllows the passage of either urine or sperm. PenisPlaces 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 Head Middle Tail Acrosome (contains digestive enzymes) Nucleus (contains 23 chromosomes) Collar (contains mitochondria) Flagellum (allows sperm to swim) Diploid sperm producing cells (46 chromosomes) divide by meiosis to form haploid sperm cells (23 chromosomes )

Male Hormone - Testosterone Testosterone is the hormone responsible for 1.Development of male sex organs 2.Sperm production 3.development of the secondary male sexual characteristics

The growth of pubic, facial and body hair The enlargement of larynx and ‘breaking’ of the voice Increased muscular development and bone development A growth spurt at puberty An increased secretion of sebum in the skin Male Secondary Sexual characteristics Secondary sexual characteristics refer to features that distinguish males from females, apart from the sex organs themselves

Part 1: Male reproductive system Can you.. Outline the general structure of the male reproductive system? State the functions of the main parts of the reproductive system? Outline how sperm cells are produced? Define the term secondary sexual characteristics and give examples? Outline the role of testosterone in males

Part 2: Female reproductive system Outline the general structure of the female reproductive system State the functions of the main parts of the reproductive system Outline the role of meiosis to produce egg cells Define the term secondary sexual characteristics

Objectives for today Outline the general structure of the female reproductive system State the functions of the main parts of the reproductive system Outline the role of meiosis to produce egg cells

Structure of the female reproductive system

The Ovary These produce the eggs and some female hormones. Diploid egg producing cells (46 chromosomes) divide by meiosis to form haploid egg cells (23 chromosomes )

Catch the egg after it is released from the ovary. The egg is moved along the tube by cilia and muscular peristalsis The Fallopian tube

The Uterus (womb) Inner lining of the womb 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. The cervix separates the uterus from the vagina.

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

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 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.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 1.Implantation 2.Hold foetus 3.Forms placenta 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 1.Allows entry of sperm into female system 2.Birth canal to allow exit of baby Fallopian tube (Oviduct)

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 A combination of oestrogen and progesterone hormones at puberty causes the development of the secondary female sex 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.

Part 3: The menstrual cycle Be able to outline the events in the menstrual cycle with reference to oestrogen and progesterone. Menstrual disorders –one example of a menstrual disorder from the following: endometriosis and fibroids –one possible cause, prevention and treatment Ordinary level

The Menstrual Cycle The menstrual cycle is a 28 day sequence of events when the body prepares the uterus lining so that it is able to receive a fertilized egg Summary of events in the menstrual cycle Ordinary level

Events in the menstrual cycle Days 1 – 5 i.Menstruation (period).The old lining of the uterus (endometrium) breaks down and leaves the body. ii.A new egg is produced in the ovary by meiosis. This new egg is surrounded by the Graafian follicle. Ordinary level

The Menstrual Cycle Days The hormone oestrogen is produced by the developing Graafian follicle: -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. Ordinary level

Days The Graafian follicle now develops into the Corpus Luteum : -It causes the endometrium to thicken even further. -It also prevents new eggs from forming. If fertilisation does not take place The egg that was released will die by day 16 if it is not fertilised. the Corpus Luteum starts to degenerate at 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. Ordinary level

The fertile period This is the time in the cycle when the woman could get pregnant after having sex. Between days 11 and days 16 of the menstrual cycle Ordinary level

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. Ordinary level

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) Ordinary level

Days Graafian follicleCorpus Luteum Oestrogen________ Progesterone _____ Endometrium Hormones

Learning Check. 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

Learning objectives Outline the stages in the menstrual cycle Discuss the role of hormones in the menstrual cycle Discuss the Cause/Prevention/Treatment for fibroids What is fertilization?

The Menstrual Cycle DAY 1-5 : Blood from the womb lining is shed from the body (Menstruation). Eggs are made in the ovary. Each egg is surrounded by a Graffian follicle. Fertile period

The Menstrual Cycle Days The hormone oestrogen is produced by the developing Graafian follicle: 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.

The Menstrual Cycle Day 14: Ovulation occurs – the Graffian follicle bursts and releases the egg from the ovaries

The Menstrual Cycle DAY 14 – 28 The corpus luteum develops from the Graffian follicle in the ovary. The corpus luteum makes the hormone progesterone. Implantation may happen If fertilisation does not occur : Egg breaks down (day 16) the corpus letuem breaks down ( day 22) Endometrium breaks down (day 1)

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) Ordinary level

Survival times sperm and ova Sperm can survive for a maximum of 72 hours inside the body before dying An egg can survive for 24 hours after ovulation

The fertile period This is the time in the cycle when the woman could get pregnant after having sex. Between days 11 and days 16 of the menstrual cycle

Today’s objectives Today you should learn about.. Hormonal control of the menstrual cycle (HL) A menstrual disorder – cause and treatment Copulation Fertilisation Implantation

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 Higher level

FSH – Follicle Stimulating Hormone Produced by pituitary gland (days 1-5) Stimulates a few potential eggs to develop, surrounded by graafian follicles (Only one usually survives) Stimulates the release of oestrogen by the graafian follicle Higher level

Oestrogen Produced from days 5 – 14 by the graafian follicle in the ovary Causes the endometrium to develop Inhibits FSH so no further eggs develop High levels of oestrogen just before day 14 stimulate release of LH Higher level

LH - Luteinising Hormone Produced on day 14 by the pituitary gland Causes: 1.Ovulation 2.Causes the remains of graafian follicle to develop into corpus luteum Stimulates release of progesterone from corpus luteum Inhibits The release of oestrogen Higher level

Progesterone Produced from days by the Corpus Luteum in the ovary 1.Maintains structure of endometrium 2.Prevents contractions of the uterus 3.Inhibits FSH (stops further eggs developing) 4.Inhibits LH (stops further ovulation) Higher level

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) Ordinary levelHigher level

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

Menstrual disorder (Fibroids) Fibroids are tumours of the uterus They do not invade other tissues and do not spread (benign) As they enlarge they produce heavy and prolonged menstrual bleeding (this can lead to anaemia, pain, miscarriage or infertility)

Menstrual disorder (Fibroids) Treatment Large fibroids can be removed by surgery A Hysterectomy may be necessary (uterus is removed) Cause is uncertain.. May be an abnormal response to oestrogen Can occur in women taking the contraceptive pill

Part 4: Sexual intercourse Explain copulation State the location of fertilisation Explain implantation How the zygote develops before pregnancy

Copulation – Sexual intercourse Sexual arousal –The penis becomes erect –The vagina becomes lubricated Copulation –The penis is inserted into and moved inside the vagina Orgasm –Sperm is released from the penis (Ejaculation) –Contraction of vagina and uterus

Fertilisation

. Fertilisation is the fusion of the egg and sperm nuclei to form a diploid zygote. Fertilisation usually occurs in the fallopian tube.

From a cell to DNA

Fertilization and cell division – animation

Identical twins – animation

Non-identical twins – animation

Role of meiosis in sperm and egg production

Implantation is the embedding of the fertilised egg into the lining of the uterus Zygote Implanted embryo

Part 5 : Human Embryo Development Higher level only List the sequence of development of an embryo Explain the term fertilized egg Explain the term blastocyst Explain the term amnion Explain how the placenta is formed Explain how the embryo develops up to the third month of gestation

Sequence of development from fertilised egg The zygote contains 46 chromosomes, twenty three from the egg and 23 from the sperm Higher level only

It divides rapidly by mitosis to produce 2 cells, then 4, then 8, 16 etc. and continues to divide Higher level only

When there are 8 cells the developing individual is referred to as the morula Higher level only

Around 5 days after fertilisation the morula forms a hallow ball of cells called the blastocyst Higher level only

The inner cells of the blastocyst will eventually form the embryo. These cells are not yet specialised. They have an ability to differentiate – divide to give rise to many different types of tissue Inner cell mass Higher level only

Learning check How many chromosomes in a fertilised egg? Is a fertilised egg haploid or diploid? What is the developing individual referred to when it is made up of 8 cells? What is it referred to after a number of days? What is unusual about the cells of the inner cell mass?

Part 5 : Human Embryo Development Higher level only Explain the term blastocyst Explain the term amnion Explain how the placenta is formed Explain how the embryo develops up to the third month of gestation

The morula/blastocyst is pushed along the fallopian tube until it enters the uterus Higher level only

Here it will implant into the uterus wall. The endometrium now provides nourishment for the developing blastocyst Higher level only

This point marks the beginning of pregnancy Higher level only

Germ layers in the embryo The embryo consists of three layers called germ layers –Ectoderm (outside) –Mesoderm (middle) –Endoderm (inside) Each of these layers gives rise to specific structures in the developing embryo Endoderm – inner lining of digestive system Mesoderm – muscles, skeleton Coelom – heart, lungs Ectoderm – skin, nervous system Higher level only

See animations and videos

Four to five weeks after fertilisation Amniotic fluid begins to accumulate. This protects the embryo for its future development The heart forms and starts to beat The brain also develops The limbs have started to form Higher level only

By the 6th week Eyes are visible The mouth, nose and ears are forming The skeleton is at the early stages of development Higher level only

By the 8th week the major body organs are formed Sex glands have developed into testes or ovaries Bone is beginning to replace cartilage At this stage the embryo has taken on a recognisably human from ( called a foetus ) Higher level only

By the 12th week (3 months) The nerves and muscle become co- ordinated allowing the arms and legs to move The feotus sucks its thumb, urinates and even releases feaces into the amniotic fluid Higher level only

By the 12th week (3 months) The gender of the foetus can be seen in scans The time from fertilisation to birth (the gestation period) lasts about 38 weeks (9 months) Higher level only

Learning Check Is a fertilised egg haploid or diploid? What is the developing individual referred to when it is made up of 8 cells? What are germ layers? Name them What features have already appeared by the fifth week? At what stage is the developing individual referred to as a foetus?

Part 6: Placenta formation, Birth and Breastfeeding

Placenta Formation After implantation the embryo forms an develops projections (chorionic villi) which form the placenta along with the blood vessels of the mother in the endometrium, The placenta allows nutrients, wastes, gases, antibodies and hormones to be exchanged between the blood of the mother and the embryo

Placenta Formation The blood of the mother and embryo do not mix This is important as: -The blood groups of mother and baby might not be compatible. -The blood pressure of the mothers system may cause damage to the embryo

Placenta Formation The umbilical cord connects the placenta with the embryo. It contains blood vessels which circulate blood between the embryo and the placenta

Placenta Mother’s blood Embryo’s blood Chorion Embryo Amnion Amniotic fluid Umbilical cord Embryo Mother Nutrients, Oxygen, antibodies Wastes, Carbon Dioxide, Water The Placenta

Learning check Name the structures that move into the endometrium and eventually become part of the placenta At what point does the placenta become fully operational? Why is it important that the blood of the mother and baby do not mix?

Birth 1The hormones oestrogen and progesterone are produced throughout pregnancy firstly by the corpus luteum (3 months) and then by the placenta. 2Immediately before birth the placenta stops making progesterone. The walls of the uterus begin to contract as a result. 3The pituitary gland releases the hormone called oxytocin. This causes further contractions of the uterus Labour has now begun

There are three main stages: Stage 1 - (about 12 hours) The contraction of the uterus pushes the foetus towards the cervix. This causes the cervix to open (dilate). During this stage the contractions cause the amnion to break releasing the amniotic fluid through the vagina. (The ‘waters break’).

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first.

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first.

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first.

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first.

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first.

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first. The umbilical cord is tied and cut.

Stage 3 - (10 to 15 minutes) The baby is now born. The uterus now contracts again and expels the afterbirth (the umbilical cord and placenta.

Stage 3 - (10 to 15 minutes) The baby is now born. The uterus now contracts again and expels the afterbirth (the umbilical cord and placenta.

Stage 3 - (10 to 15 minutes) The baby is now born. The uterus now contracts again and expels the afterbirth (the umbilical cord and placenta.

Stage 3 - (10 to 15 minutes) The baby is now born. The uterus now contracts again and expels the afterbirth (the umbilical cord and placenta.

Umbilical cord is cut

45 seconds after birth!

Placenta formation

See caesarean section video

Breastfeeding (Lactation) The secretion of milk from the mammary glands The first days after birth colostrum produced Milk production triggered by release of prolactin by pituitary gland

Breastfeeding is better than bottle feeding because: Colostrum and breastmilk provides the baby with essential antibodies protecting it against infection Ideal balance of nutrients for baby Has little fat making it is easier to digest than milk

Infertility is the inability of a couple to achieve conception. Infertility

Female infertility disorders Blockage of the Fallopian Tube –Scarring of the fallopian tube can block the passage of the egg to the uterus –Fragments of the uterus lining may spread to the fallopian tube Treatment In-vitro fertilisation (I.V.F.)

removing eggs from an ovary and fertilising them outside the body

During the natural menstrual cycle an egg is produced by the ovary every month

During IVF fertility drugs are given to the female to stimulate the ovaries to produce more than one egg

These eggs are then taken from the females body and into the laboratory

In the meantime a sperm sample is taken from the male

The eggs and sperm are mixed together in the hope that fertilisation will occur

The sample is placed in the most ideal conditions for fertilisation to occur

The main aim of the procedure is to obtain a zygote. If successful the zygotes development will be monitored closely

If successful the zygote develops into a morula, blastocyst and eventually becomes an embryo

The developing embryo can now be placed back into the females body for implantation to take place

If analysis of a couples eggs and sperm suggests that IVF treatment is unsuitable, other methods of assisted fertility treatment are available

Birth control

Contraception is the steps we take to reduce the chance of getting pregnant or giving birth

Early forms of contraceptive

Mechanical contraception -male The use of condoms Surgical contraception –Sperm ducts are cut and tied

Mechanical contraception - female The use of diaphragms

Chemical contraception Use of ‘the pill’. The pill contains oestrogen and progesterone which prevents ovulation and hence conception. Use of spermicide

Surgical contraception The fallopian tubes and sperm ducts can be cut and tied

Natural contraception -Not having sexual intercourse during the fertile period of the menstrual cycle

Infertility is the inability of a couple to achieve conception. Infertility

Learning objectives Outline infertility State one cause of male infertility State the availability of corrective measures for male infertility State one cause female infertility State the availability of corrective measures for female infertility

Male infertility disorders Low sperm count – Refers to a low number of sperm per ml of seminal fluid. Causes: The persistent use of drugs such as alcohol, cigarettes and anabolic steroids. Treatment A change in lifestyle e.g. stopping alcohol consumption, smoking.

Female infertility disorders Blockage of the Fallopian Tube –Scarring of the fallopian tube can block the passage of the egg to the uterus –Fragments of the uterus lining may spread to the fallopian tube Treatment In-vitro fertilisation (I.V.F.)

removing eggs from an ovary and fertilising them outside the body

During the natural menstrual cycle an egg is produced by the ovary every month

During IVF fertility drugs are given to the female to stimulate the ovaries to produce more than one egg

These eggs are then taken from the females body and into the laboratory

In the meantime a sperm sample is taken from the male

The eggs and sperm are mixed together in the hope that fertilisation will occur

The sample is placed in the most ideal conditions for fertilisation to occur

The main aim of the procedure is to obtain a zygote. If successful the zygotes development will be monitored closely

If successful the zygote develops into a morula, blastocyst and eventually becomes an embryo

The developing embryo can now be placed back into the females body for implantation to take place

If analysis of a couples eggs and sperm suggests that IVF treatment is unsuitable, other methods of assisted fertility treatment are available

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