Presentation on theme: "Human Sexual Reproduction Part 1. Learning Objectives (1/3) Outline the general structure of the reproductive system (Male & Female) State the functions."— Presentation transcript:
Human Sexual Reproduction Part 1
Learning Objectives (1/3) 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 nature of birth control to include natural, mechanical, chemical and surgical methods State the location of fertilisation
Learning Objectives (2/3) Outline the events & outline the role of oestrogen and progesterone of the menstrual cycle Explain copulation 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
Learning Objectives (3/3) Explain implantation, placenta formation & function Outline the birth process Explain In-vitro fertilisation & implantation Outline milk production & breastfeeding including biological benefits
A gonad is an organ that produces sex cell in animals. Male gonads are called testes Testes develop inside the body at first, but a few weeks before birth descend into the scrotum. This means they are kept at slightly lower than body temperature (35°) which is the ideal temperature for sperm production. Testes
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 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
Seminal fluid + Sperm = Semen 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.
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.
Role of meiosis in sperm and egg production Sperm and egg producing cells are diploid i.e. they contain 46 chromosomes. They divide by meiosis to form sperm and egg cells. Each sperm and egg cell, therefore, has a haploid number of chromosomes i.e. they have 23 each
Role of meiosis in sperm and egg production As both a sperm nucleus and an egg nucleus are haploid they combine in fertilisation to form a diploid zygote i.e. the new zygote has 46 chromosomes. 23 chromosomes + 23 chromosomes = 46 chromosomes The zygote now grows by mitosis division ensuring that each new cell has a diploid number of chromosomes.
Role of meiosis in sperm and egg production
Male Hormone - Testosterone Testosterone is the male hormone responsible for the development of the primary and secondary male sexual characteristics The primary sexual characteristics are the presence of the male and female reproductive parts Secondary sexual characteristics refer to features that distinguish males from females, apart from the sex organs themselves
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
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)
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 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)
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.
The Menstrual Cycle 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.
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
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
Insemination Insemination is the release of sperm into the female Contractions of uterus and fallopian tubes move the sperm to the fallopian tubes within 5 minutes If an egg is present it releases chemicals to attract the sperm this is called chemotaxis
Fertilisation is the fusion of the egg and sperm nuclei to form a diploid zygote. Fertilisation
Fertilisation usually occurs in the fallopian tube.
Fertilisation A number of sperm may reach the egg at the same time. The acrosome releases enzymes to digest the egg membrane The sperm loses its tail and the head enters the egg. The sperm and egg nuclei fuse to form a zygote A chemical reaction at the membrane prevents other sperm cells entering.
Implantation Implantation is the embedding of the fertilised egg into the lining of the uterus This occurs days after fertilisation. By this time the zygote has grown into an embryo. After implantation the placenta forms. During implantation a membrane called the amnion develops around the embryo. This secretes amniotic fluid which will surround the developing embryo and act as a shock absorber.
Implantation is the embedding of the fertilised egg into the lining of the uterus Zygote Implanted embryo
Placenta Formation After implantation the embryo forms an outer membrane called a chorion This chorion develops projections (chorionic villi) which, together with the blood vessels of the mother in the endometrium, form the placenta 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 placenta also makes the hormone progesterone The umbilical cord connects the placenta with the embryo. It contains blood vessels which circulate blood between the embryo and the placenta