1. Unit 2 - Physiology and Health
Chapter Hormonal Control of Reproduction

2. 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.

3. 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).
FSH –Follicle stimulating hormone.
In men - ICSH – Interstitial Cell Stimulating hormone.
In women – LH – Luteinising hormone
These hormones are released at puberty.
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4. 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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5. Influence of pituitary Hormonal on testes – negative feedback!
This type of self-regulating mechanism is called NEGATIVE FEEDBACK CONTROL.
ICSH
FSH in the bloodstream promotes sperm production in the seminiferous tubules.
ICSH stimulates interstitial cells to produce male sex hormone TESTOSTERONE
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6. Female Reproductive System
Made up of uterus, oviducts, ovaries and vagina.
Functions:
produces ova (eggs).
Receives sperm from penis.
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7. 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 fathers.

8. 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.

9. 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

10. Corpus Luteum SEE SCHOLAR – Maturation of ova simulation
Graafian follicle developing
OVARY
egg
Immature Graafian follicle

11. Graafian Follicle
ovum
Graafian follicle
follicular liquid
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12. 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.

13. 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

14. Continual Fertility vs 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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15. 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.

16. 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.

17. 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.
FOLP

18. 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

19. 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.

20. Menstrual cycle – Changes
Two other changes which take place during the menstrual cycle are changes to the
cervix
body temperature.

21. 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.

22. Diagram of changes to the cervix during menstrual cycle.
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Mrs Smith Ch15 Sex organs and hormonal control

23. 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

24. 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).