Higher Human Biology
Unit 2: The continuation of life
Reproduction revision!
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Mrs Smith Ch15 Sex organs and
hormonal control
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Lesson Aims:
• To revise the structure and function of the
male reproductive system.
• To revise the structure and function of the
female reproductive system.
Fertilisation video clip
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Reproduction Revision
• All living things reproduce and produce
offspring similar to themselves.
• If they did not then eventually the species
would become extinct.
Sex cells – sperm
In males, the sex cells are called sperm.
tail
middle piece
cell membrane
head
nucleus containing
DNA
Sperm are produced in sex organs called testes.
Sex cells – egg
In females, the sex cells are called eggs.
nucleus containing
DNA
cytoplasm
membrane
jelly coat
Eggs are produced in sex organs called ovaries.
Sexual Reproduction
• This is when 2 types of sex cells or gametes
are produced which then joins together at
fertilisation to produce the new individual.
• In animals the gametes are egg and sperm.
An egg is so big that this is how
big a sperm looks next to it.
The egg is much larger because it has a food supply.
fertilisation
Zygote - Sperm enters the egg. The
sperm nucleus fuses with
egg nucleus to create a single
cell.
Fertilisation
http://www.youtube.com/wa
tch?v=vyWuMo3bzRU&feat
ure=relmfu
After fertilisation….
1 cell –
fertilised
egg
Cell division
2 Cells
4 cells…
8 cells…leading to a ball of cells
Revision. The female reproductive system
Revision: The male reproductive system
Male or female?
Roles of the reproductive
system
Fertilisation and implantation
The placenta
How does an embryo receive food and oxygen and how
does it get rid of waste?
An embryo forms a structure called the placenta, which
attaches to the uterus wall.
umbilical
The umbilical cord joins
cord
the fetus to the placenta.
In the placenta, food and oxygen
diffuse from the mother’s blood
into the blood of the foetus.
Carbon dioxide and waste
products diffuse from the blood of
the foetus into the mother’s blood.
How does the placenta work?
Placenta
Maternal and foetal blood separated by a thin barrier
Summary: Role of the Placenta
1. Nourishment
•
Food from the mother
2. Gaseous exchange
•
•
Oxygen from mother
Carbon Dioxide from embryo to mother
3. Excretion
•
Waste materials from embryo to mother
Higher Human Biology
Unit 2: The continuation of life
Chapter 15: Sex organs
and hormonal control!
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Mrs Smith Ch15 Sex organs and
hormonal control
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What you need to know: The
arrangements
Reproduction
Fertility and its control:
i Structure and function of reproductive organs.
Structure of testes and ovaries and their function.
The contribution to fertilisation of the secretions of the prostate gland and the
seminal vesicles.
ii Hormonal control.
The influence of the pituitary hormones, follicle stimulating hormone (FSH) and
luteinising hormone (LH) on the testes and the ovaries.
The influence of testosterone on the testes.
The influence of the ovarian hormones, oestrogen and progesterone, on the
uterus and the pituitary.
Changes during the menstrual cycle and control of these changes through
interaction of hormones.
Continuous fertility in the male compared with cyclical fertility in the female.
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The words you need to know:
boys and girls!
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The boy words you need to know!
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The girl words you need to know!
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Lesson Aims:
• Expand on the structure and function of the
male reproductive system
• To learn about sperm production and hormonal
control
• Expand on the structure and function of the
female reproductive system
• To learn about egg production and hormonal
control
Fertilisation video clip
13/04/2015
Mrs Smith Ch15 Sex organs and
hormonal control
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Learning
Intentions
Understanding
The Continuation
of Life
Success
Criteria
1. Describe the structure &
function of the testes
2. Explain the contribution to
fertilisation of the
secretions of the prostate
gland and the seminal
vesicle
Male Reproductive System
Made up of testicles, duct
system, accessory glands
and penis.
Functions:
• produce hormones
• produce sperm
• store sperm
• deposits sperm inside
vagina during sexual
intercourse
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FYI - sperm
• The average man
produces roughly 525
billion sperm cells
over his lifetime and
releases, in one way
or another, more than
one billion of them per
month and anywhere
from 40 million to
1.2 billion in a single
ejaculation.
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Sperm (spermatozoa) production
•Testosterone produced in interstitial cells stimulates sperm
production. Testosterone passes directly into the bloodstream.
•Sperm formed by meiosis in seminiferous tubules.
•These tubules unite to form coiled tubes which connect to the
SPERM DUCT. (Free swimming sperm leave the testes by this
duct.
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hormonal control
Sperm mother
cell
Spermatozoa
Interstitial
cell
Accessory Glands
• Fertilisation is
dependent on;
– Motility of sperm
which requires a fluid
medium.
– a source of energy
• The semen released by
the male during
ejaculation contains
sperm from the testes
and fluid secretions from
the seminal vesicles and
the prostate gland.
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The Accessory Glands con’t
Seminal vesicles: secrete viscous liquid containing:
– Fructose:
Provides energy source for motility following there release
after male ejaculation.
–Prostaglandins:
(Hormone like compounds)Stimulate contraction in the
female reproductive tract. These movements help the sperm
reach the oviduct at a much faster rate than could be
achieved by swimming alone.
Prostate Gland:
– Secretes a thin lubricating fluid containing enzymes which
maintains the fluid medium at OPTIMUM VISCOSITY for
sperm motility.
Where is your pituitary gland?–
Hormonal Control.
The Pituitary gland is located in the centre of the brain and produces many
hormones
Hormones are chemical messengers produced by an animal’s endocrine
glands and secreted directly into the bloodstream. When a hormone
reaches a certain target tissue, it brings about a specific effect.
Pituitary gland
• Pituitary gland is a gland that produces many hormones.
• Two of these are called GONADOTROPIC hormones
because their target are the gonads (reproductive
organs).
1. FSH –Follicle stimulating hormone.
2. In men - ICSH – Interstitial Cell Stimulating
hormone.
In women – LH – Luteinising hormone
• These hormones are released at puberty.
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Influence of testosterone
• Testosterone stimulates sperm production.
• It also activates the prostrate gland and seminal vesicles
to produce their secretions.
SELF REGULATION OF TESTESTORONE
• As the concentration of testosterone builds-up in the
bloodstream, it reaches a level where it INHIBITS the
secretion of FSH and ICSH by the anterior pituitary.
• This leads to a decrease in testesterone concentration,
soon followed by a resumption of the activity by the
anterior pituitary.
• This makes gonadotropic hormone again and the cycle
starts again.
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hormonal control
Influence of pituitary Hormonal
on testes – negative feedback!
This type of self-regulating mechanism is called NEGATIVE FEEDBACK
CONTROL.
ICSH
ICSH stimulates
interstitial cells to
produce male sex
hormone
TESTOSTERONE
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FSH in the bloodstream
promotes sperm
production in the
seminiferous tubules.
ICSH
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Learning
Intentions
Understanding
The Continuation
of Life
Success
Criteria
1. Describe the structure &
function of the ovaries
2. Explain the influence of
pituitary hormones on the
ovaries.
3. Explain the influence of
ovarian hormones on the
uterus and pituitary gland
Female Reproductive System
Made up of uterus, oviducts, ovaries and vagina.
Functions:
• produces ova (eggs).
• Receives sperm from
penis.
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FYI - Eggs
• Evidence suggests that eggs are formed in foetal life. About
400,000 immature eggs reside in each ovary at puberty. The
menstrual cycle, as a biologic event, allows for ovulation of one
egg typically each month. Thus over her lifetime a woman will
ovulate approximately 400 to 450 times. All the other eggs
dissolve.
• As a woman's total egg supply is formed in foetal life, to be
ovulated decades later, it has been suggested that this long
lifetime may make the chromatin of eggs more vulnerable to
division problems, breakage, and mutation than the chromatin
of sperm, which are produced continuously during a man's
reproductive life. This possibility is supported by the
observation that foetuses and infants of older mothers have
higher rates of chromosome abnormalities than those of older
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fathers.
hormonal control
The Female reproductive
system continued.
The role of the female in reproduction is not only to
produce gametes but also….
• Houses and provides nutrients (food and
oxygen) to the developing zygote (fertilized
egg) and later the embryo and foetus.
• Remove its waste products.
• Gives birth to the offspring.
– After delivering into the world, provide it with
continued supply of food for a period of time.
The Ovaries
• The ovaries are the site of
ova production by meiosis
• Ova are contained in a
developing Graafian follicle
• The Graafian follicle
secretes the hormone
oestrogen
• After ovulation, the
Graafian follicle becomes
the corpus luteum which
secrete progesterone
Corpus Luteum
SEE SCHOLAR – Maturation of ova simulation
http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=f65bd0a33b06-6409-554b-934e6eb2195a
Graafian
follicle
developing
OVARY
egg
Immature
Graafian
follicle
Graafian Follicle
Graafian
follicle
follicular
liquid
ovum
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Pituitary Hormones & the Ovaries
• F.S.H (Follicle Stimulating Hormone)
– Stimulates the development of eggs (inside the structures called
follicles) and the development and maturation of Graafian Follicle
– Stimulates ovary to produce the hormone oestrogen
• L.H (Lutenising Hormone)
– Triggers ovulation
– Brings about the development of the corpus luteum from the follicle
– Stimulates corpus luteum to produce progesterone
• Gonadotrophic hormones (FSH/LH) and ovarian hormones
(Oestrogen/Progesterone) interact to control the female
menstrual cycle.
Effect of Ovarian Hormones on the
Uterus &Pituitary Gland
• Gonadotrophic hormones (FSH/LH) and ovarian hormones
(Oestrogen/Progesterone) interact to control the female menstrual
cycle.
• During puberty the anterior pituitary gland begins to secrete FSH &
LH. These hormones are transported to the ovaries in the blood
• Oestrogen and Progesterone are called the ovarian hormones since
they are produced by the ovary.
– Oestrogen
• stimulates proliferation (cell division) of the lining of the uterus - the
endometrium. And it is responsible for the repair after menstruation.
• stimulates secretion of LH by the anterior pituitary gland
– Progesterone
• Promotes the thickening of the endometrium
• Promotes vasularisation (many blood vessels), to create a spongy
layer(of the endometrium)
• Inhibits secretion of FSH and LH by the anterior pituitary gland
Continual Fertility vrs Cyclical Fertility
Continual Fertility in Males
• high level of testosterone has a negative
feedback effect on the secretion of FSH
and ICSH by the pituitary gland
• relatively constant levels of
testosterone, FSH and ICSH
Cyclic Fertility in Females
fluctuating levels of FSH, LH,
oestrogen and progesterone
only fertile for a few days before and
after ovulation
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TASK – Complete card sorts
• Also on SCHOLAR
– Table 1.1 - Effects of pituitary hormones
http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=vie
wContent&contentGUID=713b3f30-e1fb-1b8c-e143-c13651f07dad
– Table 1.2 - Effects of ovarian hormones
http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?act
ion=viewContent&contentGUID=1f1334fa-2e17-b3fe-c450fec3e51ea083
– Once complete copy into notes or
jotters
Task: TYK -Torrance pg113
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Learning
Intentions
Success
Criteria
•
State that the changes
which takes place during
the menstrual cycle are
controlled by the
interaction of hormones
•
Give a detailed account of
the changes which occur
during the menstrual cycle
Understanding
The Continuation
of Life
Menstrual cycle – intro.
• The ovarian hormones oestrogen and progesterone, and the
pituitary hormones FSH and LH interact with each other to
coordinate the menstrual cycle.
• The menstrual cycle is a repeating series of changes in the
levels of the above hormones which is accompanied by
changes in the development of the Graafian follicle and the
lining of the uterus (the endometrium).
• The average length of a cycle is 28 days, although it can vary
greatly from one individual to another.
• The first day of menstruation, that is the start of the monthly
'period', is usually regarded as day 1 of the cycle.
Menstrual cycle- Hormonal Control
(a) changes in levels of the
pituitary hormones FSH and
LH;
(b) development of the
Graafian follicle;
(c) changes in the levels
of the ovarian hormones
oestrogen and progesterone
(d) changes in the thickness
of the endometrium.
The menstrual cycle can be divided
into two parts:
– Follicular Phase
• First half - from day 1 (the start of menstruation) to
about day 14 (when ovulation occurs)
– Luteal Phase
• Second Half - from day 14 to day 28, when
menstruation begins again.
Menstrual cycle - Follicular Phase
• FSH from the pituitary gland
– stimulates the development and maturation of the
Graafian follicle
– produces oestrogen by the ovary;
• As the concentration of oestrogen increases:
– stimulates the repair of the endometrium after
menstruation
– stimulates the pituitary to secrete LH;
• Concentrations of LH gradually increase until there is a sharp
increase around day 12 or 13.
• This peak of LH concentration causes ovulation (the release
of an ovum) around day 14 in the cycle
Menstrual cycle - Luteal Phase
• LH causes:
– the Graafian follicle to develop into the corpus luteum
– stimulates the corpus luteum to secrete progesterone;
• Increasing progesterone levels promote…..
– the thickening and vascularisation (build up of blood vessels) of the
endometrium, in preparation for the implantation of a fertilised ovum;
– high levels of progesterone inhibit the secretion of FSH and LH by the
pituitary gland;
• As the levels of LH decrease the corpus luteum begins to degenerate
(around day 22).
• This causes the levels of progesterone to decrease until by around day
28 of the cycle the endometrium can no longer be maintained.
• endometrium breaks down and is passed out of the body (menstruation).
• The decrease in progesterone levels removes its inhibitory effect on the
pituitary gland, which begins to secrete more FSH again.
• As the levels of FSH rise the cycle begins again.
Online Quiz
• See SCHOLAR
– Stages in the menstrual cycle
– http://courses.scholar.hw.ac.uk/vle/scholar/se
ssion.controller?action=viewContent&back=to
pic&contentGUID=650c9519-54da-d59d6bca-011fdcf01cf2
Menstrual cycle – Changes
• Two other changes which take place during the
menstrual cycle are changes to the
1. cervix
2. body temperature.
Menstrual cycle –
Changes to the Cervix
 The changes which occur to the cervix play a role in fertility.
 The cells of the cervix secrete mucus.
 High levels of oestrogen stimulate these cells to produce a
thin and watery mucus and cervix becomes slippery and
stretchy which is easily penetrated by sperm.
 Since the highest levels of oestrogen occur just before
ovulation, the production of thin mucus at this time increases
the chances of fertilisation.
 High levels of progesterone, on the other hand, cause the
mucus secreted by the cervical cells to become thicker and, if
pregnancy occurs, change into a semi-solid 'plug', which helps
to protect the developing embryo against infection.
Diagram of changes to the
cervix during menstrual cycle.
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Menstrual cycle –
Changes to the Cervix
 The thin and watery mucus of the cervix not only make it easier for
sperm to swim.
 It also helps the sperm to point in the correct direction ready for their
passage through the reproductive tract which stops this happening.
 This is further assisted by muscular contractions of the uterus and
oviduct caused by prostaglandins present in seminal fluid
Menstrual cycle –
Changes to Body Temperature
– A woman's body temperature rises by as much as 0.5°C at
ovulation.
– These changes in body temperature and the viscosity of
cervical mucus can be used as indicators of ovulation and
forms the basis of the rhythm method of birth control (see
later).
Menstrual cycle –
Changes after fertilisation
• The menstrual cycle normally occurs regularly unless
fertilisation and pregnancy occur. If fertilisation occurs the
fertilised egg secretes a hormone called HGC (human chorionic
gonadotrophin) which has the same effect as LH.
• When this happens the corpus luteum does not degenerate and
continues to secrete progesterone.
• Since progesterone levels remain high, the endometrium is
maintained (No menstruation).
• The embryo implants into the endometrium and continues to
develop.
• Also FSH secretion continues to be inhibited and ovulation is
prevented.
Pregnancy test
• It is the presence of HCG – Human
chorionic gonadotrophin is the basis of
the pregnancy test.
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Menstrual cycle – Summary
SH stimulates development of egg and production of
Oestrogen
estorgen stimulates repair of uterus and causes sudden
flood of LH
H causes ovulation and development of Corpus Luteum
rogesterone from Corpus Luteum maintains the
uterus in readiness for embryo and inhibits production
of FSH & LH (negative feedback)
Continuous versus cyclical
fertility
• MEN: The negative feedback effect of
testosterone maintains a relatively constant level
of FSH and ICSH in the bloodstream of men.
This results in a fairly steady quantity of
testosterone being secreted and sperm being
produced. Men are therefore continuously fertile.
• WOMEN: have cyclical fertility. The balance of
gonadotrophic and ovarian hormones results in
the period of fertility being restricted to 3-4 days
immediately following ovulation.
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Task: Torrance pg 115 Qu’s 1-2
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Essay Questions:
SQA 2003
1. Describe the
influence of hormone
on the testes. (10)
2. Describe the events
that take place in the
first half of the
menstrual cycle. (10)
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