unit 2: the continuation of life

Unit 2: The continuation of life

Reproduction revision!

Higher Human Biology

20/04/23 1Mrs Smith Ch15 Sex organs and hormonal control

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


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

Sperm are produced in sex organs called testes.

In males, the sex cells are called sperm.

headtail middle piece

cell membrane nucleus containing DNA

Sex cells – egg

Eggs are produced in sex organs called ovaries.

In females, the sex cells are called eggs.

nucleus containing DNA

membrane jelly coat

cytoplasm

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/watch?v=vyWuMo3bzRU&feature=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 placentaHow 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.

The umbilical cord joins 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.

umbilicalcord

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

Unit 2: The continuation of life

Chapter 15: Sex organs and hormonal control!

Higher Human Biology


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.

20/04/23 Mrs Smith Ch15 Sex organs and hormonal control

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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


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


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.

20/04/2332Mrs Smith Ch15 Sex organs and

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.


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 control38

Influence of pituitary Hormonal on testes – negative feedback!

ICSH

ICSH


FSH in the bloodstream promotes sperm production in the seminiferous tubules.

ICSH stimulates interstitial cells to produce male sex hormone TESTOSTERONE

This type of self-regulating mechanism is called NEGATIVE FEEDBACK CONTROL.

Learning Intentions


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

Functions: • produces ova (eggs).• Receives sperm from

penis.


Made up of uterus, oviducts, ovaries and vagina.

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.

Mrs Smith Ch15 Sex organs and hormonal control

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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

Graafian follicle developing

OVARY

Corpus Luteum SEE SCHOLAR – Maturation of ova simulation

http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=f65bd0a3-3b06-6409-554b-934e6eb2195a

egg

Immature Graafian follicle

Graafian Follicle

ovum

Graafian follicle

follicular liquid


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 theUterus &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 Femalesfluctuating levels of FSH, LH, oestrogen and progesterone only fertile for a few days before and after ovulation20/04/23 49Mrs Smith Ch15 Sex organs and

hormonal control

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=viewContent&contentGUID=713b3f30-e1fb-1b8c-e143-c13651f07dad

– Table 1.2 - Effects of ovarian hormones http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=1f1334fa-2e17-b3fe-c450-fec3e51ea083

– Once complete copy into notes or jotters

Task: TYK -Torrance pg113

20/04/23 51Mrs Smith: Ch13: Mutations an Chromosomal Abnormalities

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

• 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 – intro.

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/

session.controller?action=viewContent&back=topic&contentGUID=650c9519-54da-d59d-6bca-011fdcf01cf2

Menstrual cycle – Changes

• Two other changes which take place during the menstrual cycle are changes to the1. 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

20/04/23 68Mrs Smith: Ch13: Mutations an Chromosomal Abnormalities

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)

20/04/23 Mrs Smith 69

unit 2: the continuation of life

Documents

types of sex cells

sex cells spermsperm

hormonal controllesson

hormonal controlwhat

egg nucleus

structure of testes

male reproductive system

mothers blood