Transcript The Uterus

Sexual Reproduction
in the Human
Learning Objectives
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(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
Sexual Reproduction in Humans
In mammals male reproductive organs produce haploid
motile sperm (n)
The female non-motile egg is also haploid (n)
These fuse at fertilisation to produce a diploid zygote
(2n)
Structure of the male reproductive system
Bladder
Seminal Vesicle
Prostate gland
Cowper’s Gland
Penis
Sperm duct
Urethra
Epididymis
Testis
Scrotum
Testes
• 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.
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.
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
Bladder
Seminal Vesicle
Prostate gland
Cowper’s Gland
Penis
Sperm duct
Urethra
Epididymis
Testis
Produces
1.
2
Sperm
Testosterone
Scrotum
Functions of the main parts of the Male reproductive system
Bladder
Seminal Vesicle
Prostate gland
Cowper’s Gland
Penis
Sperm duct
Urethra
Epididymis
Testis
Stores sperm
Scrotum
Functions of the main parts of the Male reproductive system
Bladder
Seminal Vesicle
Prostate gland
Cowper’s Gland
Penis
Sperm duct
Urethra
Epididymis
Testis
Carries sperm from the
epididymis to the urethra
Scrotum
Functions of the main parts of the Male reproductive system
Bladder
Seminal Vesicle
Prostate gland
Cowper’s Gland
Penis
Sperm duct
Urethra
Epididymis
Testis
Produces Seminal Fluid
- For sperm to swim in
- Nourishment for sperm
Scrotum
Functions of the main parts of the Male reproductive system
Bladder
Seminal Vesicle
Prostate gland
Cowper’s Gland
Penis
Sperm duct
Urethra
Epididymis
Testis
Tube through which
the sperm travel
through the penis
Scrotum
Functions of the main parts of the Male reproductive system
Bladder
Seminal Vesicle
Prostate gland
Cowper’s Gland
Penis
Sperm duct
Urethra
Epididymis
Testis
Keeps testes at a lower
temperature
Scrotum
Functions of the main parts of the Male reproductive system
Bladder
Seminal Vesicle
Prostate gland
Cowper’s Gland
Penis
Sperm duct
Urethra
Epididymis
Testis
Places sperm in the
females body
Scrotum
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)
Head
Nucleus (contains 23 chromosomes)
Middle
Tail
Collar (contains mitochondria)
Flagellum (allows sperm to swim)
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
• Testosterone: 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 e.g. presence
of facial hair, deep voice
Male Secondary Sexual
characteristics
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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
Structure of the female reproductive system
The Ovary
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Produce the eggs and
female hormones.
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All the eggs in an ovary
are present at birth.
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After puberty 20 eggs
mature each month.
Only one will be
released from the
ovary – the rest will die.
The Fallopian tube (oviduct)
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The Fallopian tubes are
muscular and approx
12cm long.
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Funnels at the tip of each
tube catch the egg after it
is released from the ovary.
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The egg is moved along
the tube by cilia and
muscular peristalsis.
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The egg is either fertilised
or dies in the fallopian
tube.
The Uterus (womb)
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Muscular structure approximately the size of your
fist.
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Outer wall made of involuntary muscle.
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Inner lining is called the endometrium
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This lining thickens each month with cells and blood
vessels to nourish the embryo.
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The cervix separates the uterus from the vagina.
The vagina
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Elastic muscular tube 10cm long.
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Allows entry of sperm.
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Is the birth canal for the exit of a baby.
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Lined with cells that produce mucous. This
serves to protect against the entry of
pathogens.
Structure of the Female reproductive system
Fallopian tube
(Oviduct)
Funnel
Ovary
Ovarian Ligament
Uterus
Cervix
Lining of uterus
(endometrium)
Wall of uterus
Vagina
Vulva
Functions of the main parts of the female reproductive system
Fallopian tube
(Oviduct)
Funnel
Ovary
Ovarian Ligament
Uterus
Cervix
Lining of uterus
(endometrium)
Wall of uterus
Vagina
Vulva
Produces :
1. Egg
2. Oestrogen
3. Progesterone
Functions of the main parts of the female reproductive system
Fallopian tube
(Oviduct)
Funnel
Ovary
Ovarian Ligament
Uterus
Cervix
Lining of uterus
(endometrium)
Wall of uterus
Vagina
Vulva
1. Catches the egg after release from ovary
2. Transports egg from ovary to womb
3. Site of fertilisation
Functions of the main parts of the female reproductive system
Fallopian tube
(Oviduct)
Funnel
Ovary
Ovarian Ligament
Uterus
Cervix
Lining of uterus
(endometrium)
Wall of uterus
Vagina
Vulva
1. Implantation
2. Hold foetus
3. Forms placenta
Functions of the main parts of the female reproductive system
Fallopian tube
(Oviduct)
Funnel
Ovary
Ovarian Ligament
Uterus
Cervix
Lining of uterus
(endometrium)
Wall of uterus
Vagina
Vulva
1. Allows entry of sperm into female system
2. Birth canal to allow exit of baby
Summary of functions of main parts of female reproductive system
Part
Function
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:
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Maturing and enlargement of the breasts.
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Widening of the pelvis to allow for birth.
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The growth of pubic and underarm hair.
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A growth spurt.
The Ovary
• 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
•
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 6 - 14
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Hormone oestrogen is produced by the developing
Graafian follicle. This has two functions:
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It causes the lining of the uterus (endometrium)
to build up again in preparation for implantation.
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Oestrogen also prevents the development of any
more eggs.
Day 14
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Ovulation. This occurs when the Graafian follicle
bursts to release the egg into the fallopian tube.
Days 14 - 28
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The Graafian follicle now develops into the Corpus
Luteum (yellow body). This has two functions:
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It causes the endometrium to thicken even
further.
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It also prevents new eggs from forming.
The released egg 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.
If fertilisation has not occurred the
cycle begins again with the breakdown
of the endometrium.
The Menstrual Cycle
28
27
1
2
3
26
4
25
DAY 1-5 : Blood from the
womb lining is shed from
the body
5
24
23
6
22
7
21
8
After day 5 the lining of
the uterus repairs and
builds up again
20
9
19
18
10
Fertile period
17
11
16
15
Implantation may happen
14 13
12
Ovulation occurs on Day 14
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
Progesterone _____
Endometrium
Hormones
Oestrogen________
5
14
Days
28
Learning Check
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Name the main parts of the male reproductive
system?
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
Fertilisation is the fusion of the egg and sperm nuclei to form a
diploid zygote.
Fertilisation
Fertilisation usually occurs in
the fallopian tube.
Fertilisation
The acrosome releases enzymes to digest the egg membrane
A number of sperm may reach the egg at the same
time.
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
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This occurs 6 - 9 days after fertilisation.
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By this time the zygote has
grown into an embryo.
•
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.
•
After implantation the placenta forms.
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
The Placenta
Placenta
Chorion
Embryo
Mother’s blood
Wastes, Carbon Dioxide, Water
Nutrients, Oxygen, antibodies
Mother
Embryo
Amnion
Amniotic fluid
Umbilical cord
Embryo’s blood
Development of Embyro
1.The diploid zygote divides by mitosis to form a Morula (a ball of
undifferentiated cells) after 3-5 days
2. Morula continues to divide by mitosis to form a blastocyst (fluid
filled sac containing an inner cell mass that gives rise to an
embryo) which moves into the uterus and implants around day
9
3. The outer layer of the blastocyst is called the trophoblast. The
inner cell mass of the blastocyst organises itself into three
distinct germ layers: ectoderm, mesoderm and endoderm
Ectoderm: Gives rise to skin and nervous system
Mesoderm: Gives rise to musuloskeletal system, kidneys, lungs,
heart etc.
Endoderm: Gives rise to liver, pancreas and inner linings of
breathing, digestive and excretory system.
Development of Foetus
1. A protective sac, the amnion, begins to form
around the embryo. It contains amniotic fluid
which protects and acts as a shock absorber
around the embryo.
2. By the end of the eighth week of pregnancy all the
major organs have formed and the embryo is now
called a foetus.
3. The skeleton is made of cartilage. From the 3rd
month onward bone begins to form.
4. Arms and legs begin to move and sex organs are
visible. The foetus urinates into the amniotic fluid.
5. The placenta forms from the trophoblast layer of
the embryo and tissue from the uterus. It is fully
formed at 3 months into pregnancy.
Birth
1
The hormones oestrogen and progesterone are produced
throughout pregnancy firstly by the corpus luteum (3
months) and then by the placenta. The placenta acts as
an endocrine gland.
2
Immediately before birth the placenta stops making
progesterone. The walls of the uterus begin to contract as
a result.
3
The 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) Labour
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) Parturition
The foetus passes through the cervix and the birth
canal head first.
Stage 2 - (20 minutes to 1 hour) After birth
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. This leaves a
scar which will eventually become the navel (belly
button).
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
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
Breastfeeding
Breastfeeding has the following advantages for the
baby:
• Colostrum and breast milk 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
Birth control
• Birth control refers to the methods employed to
limit the number of children that are born
• Removing the possibility of conception is called
contraception.
• This is achieved by preventing the egg and sperm
from meeting
• There are a number of methods:
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
- Natural methods of contraception try to identify
the time of ovulation based on:
•
monitoring the body temperature. This
rises slightly after ovulation
•
-
mucous secreted in the cervix (which
changes its texture after ovulation)
Infertility
Infertility is the inability of a couple to
achieve conception.
Male infertility disorders
• Low sperm count – Refers to a low number of
sperm per ml of seminal fluid.
• Low sperm mobility - If movement of the sperm
is slow, not in a straight line or both, the sperm
may have difficulty passing through the cervical
mucous or penetrating the shell of the egg.
• Endocrine gland failure – A failure of the testes
to produce sperm
Low sperm count
Causes:
• The persistent use of drugs such as alcohol,
cigarettes and anabolic steroids.
• Abnormalities in sperm production or
obstruction of the tubes through which
sperm travels.
• Stress
Low sperm count
Treatment
• A change in diet.
• A change in lifestyle e.g. stopping alcohol
consumption, smoking.
• A reduction in stress levels.
Female infertility disorders
• Blockage of the Fallopian Tube
– Scarring of the fallopian tube can block the
passage of the egg to the uterus
• Endocrine gland failure
– A failure of the ovaries to produce an egg
Blockage of the fallopian tubes
Causes:
• Fragments of the uterus lining may spread to the
fallopian tube
• Inflammation as a result of infection
Treatment
• In-vitro fertilisation (I.V.F.)
In-vitro fertilisation (I.V.F.)
IVF is a method of treating infertility
It involves 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
• Babies born as a result of IVF are often
incorrectly called ‘test tube’ babies.
• While fertilisation takes place in the
laboratory (‘in vitro’ – in glass) the
fertilised egg is re-inserted into the mother’s
body and develops naturally in the uterus
If analysis of a couples eggs and sperm
suggests that IVF treatment is unsuitable,
other methods of assisted fertility treatment
are available
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