Reproduction 2

Hormonal Controland

Fertilisation

Dr Viv Rolfe

Lecture Outline

• To investigate the control of the female and male reproductive systems.

• The main hormones and hypothalamo-pituitary axis.

• Control of the menstrual cycle.

• Control of the testes.

• Fertilization and infertility.

Hormonal Controlof Reproduction

Hormones

• What are the main female and male reproduction hormones?

OestrogenProgesteroneTestosterone

Follicle stimulating hormoneLutenizing hormone

SIMPSON, H.

Source: Aha! Jokes, http://www.AhaJokes.com/ © www.nlm.nih.gov (National Library of Medicine)

Hypothalamus

Pituitary

Pituitary Gland

HYPOTHALAMUSGnRH - gonadotrophin-releasing hormone

PITUITARYFSH - follicle stimulating hormone

LH - luteinising hormone

Hypothalamo-pituitary Axis

FEMALE OVARIESP - progesterone

O - oestrogen

MALE TESTEST - testosterone

Male

Testes

Spermatid

FSHworks with

testosterone tostimulate

spermatogenesis

LHstimulates

testosterone secretion in the

testes.

What does testosterone do?

• It drives the development of the male reproductive system in the uterus.

• Controls the descent of the testes.• Stimulates all the secondary sex

characteristics at puberty.• Stimulate protein synthesis (anabolic

hormones).• With FSH, controls sperm production.

Female reproductive cycles

Uterine cycle+

Ovarian cycle

FEMALE OVARIESP - progesterone

O - oestrogen

HYPOTHALAMUSGnRH - gonadotrophin-releasing hormone

ANTERIOR PITUITARYFSH - follicle stimulating hormone

LH - luteinising hormone

Hypothalamo-pituitary Axis

Ovary

Fallopian Tube

Uterine cavity

Anatomy - front view

Uterine wallENDOMETRIUM

DAYS

1 5 14 28

1st day of menstrual cycleUterine contractions (cramps) push egg out

DAYS

1 5 14 28

DAYS

1 5 14 28

Day 6Bleeding stopsNew egg is maturingEndometrium starts to rebuild & prepare for pregnancy!

DAYS

1 5 14 28

Day 14Ovulation - egg is released from ovary andgrabbed by the fibria (fringe)

DAYS

1 5 14 28

15-18Egg wafted by fallopian tube contractionsand cillia on the tube’s surface

DAYS

1 5 14 28

19-20Uterus prepares for pregnancy!Blood builds up in the walls to nourish the egg.

DAYS

1 5 14 28

1st day of menstrual cycle

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Summary

Hormones LH

O

FSH

O - rise in oestrogen stimulates brain to release FSH and LH.

FSH - stimulates growth of several follicles in the ovary until one dominates(Graafian follicle).

LH - causes ovulation - one follicle ruptures releasing the egg.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Progesterone

Hormones LH

O

FSH

PP

P - stimulates the rebuilding of the uterus wall anticipating the presenceof an egg for implantation.

O and P - rapid drop at day 28 triggers menstrual bleeding again.

PMS

Fertilisation

Fertilisation

The egg is viable for 12 to 24 hours after ovulation.

Sperm are viable for 12 to 48 hours after ejaculation.

There is a 3 day fertility window when sperm must make their way to the egg.

Fertilization occurs in the fallopian tube.

Ovary

Fallopian Tube

Fertilisation

• Of the millions of sperm in the ejaculate, only 200 reach the egg and only 1 penetrates it.

• Sperm mature en route called CAPACITATION which helps prepare for the penetration and makes the tail swim faster.

The Egg at Fertilisation

Cytoplasm

Zona pellucida

Corona radiata

DNA isstopped half waythough meiosis

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Corona Radiata

Membrane receptors on the egg attaches the first sperm.

The acrosome reaction occurs -digestive enzymes are released from the ACROSOME

This digests a path as the sperm swims onwards.

Hey guys, I’m in!

Fertilisation

Fertilisation occurs when the genetic material of a sperm combines with the egg to form a ZYGOTE.

Blocking Polyspermy

Polyspermy - multiple fertilisation - is blocked by

1)Sperm’s swimming is inactivated2) The egg coat (zona pellucida) hardens

Exchanging DNA

• The sperm head swells and bursts and the DNA is released into the cytoplasm.

Pro-nuclei

23 male chromosomes

+

23 female chromosomes

=

23 pairs (diploid)

Pronucleui

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Hardened Zona Pellucida

Sperm + ovum = zygote

•The zygote travels to the uterus dividing intoclusters of cells called the MORULA (by day 3).

•The morula develops a cavity and the cell numbers increase to form the BLASTOCYST, which will eventually become the EMBRYO.

The final steps...

Stem Cells

• The ZYGOTE is a STEM CELL meaning this single cell can form an entire organism.

• These cells are used for CLONING.

Infertility

_

Definition

• Primary infertility - inability to conceive after 12 months of unprotected sex.

• Secondary infertility – inability to achieve another pregnancy.

Causes?

• Half the class – list some fertility causes for males.

• Other half – list some fertility causes for females.

Males

Male factors

• Impotency• Low sperm count• Scarring from sexually transmitted disease.

• These are often associated with– Diseases and conditions - diabetes, poor

circulation, neurological disorders– Some medication.– Nicotine, alcohol, or cocaine use.– Stress, fear, anxiety, or anger.– Emotional and psychological problems.

Females

Female factors

• STD• Endometriosis• Hormone imbalance• Cysts• Poor nutrition

Endometriosis

• Endometrium is not lost per vaginum but moves into the pelvic cavity via fallopian tubes

• The rogue endometrium respond to hormones and continue to grow (and bleed)

• Causes irritation, inflammation and scarring

• Causes fallopian tube blockage preventing eggs being released or transferred to the uterus.

Ovarian Endometrioma

Ovary

Endometriosis (“powder burn” effect)

Haemorrhagic region

© Edward C. Klatt, Health Educations Assets Library (www.healcentral.org)

Polycystic Ovary Syndrome

• Ovarian follicles fail to mature each month.

• Eggs are trapped - follicles swell to form cysts.

• Progesterone production is low but oestrogen is normal.

• Symptoms include facial hair, acne and obesity.

Polycystic Ovary Scan

Bladder

Ovary

Cysts - in classic “pearl necklace” appearance

© Paula Woodward, Health Educations Assets Library (www.healcentral.org)

Pelvic Inflammatory Disease

• Caused by STDs (sexually transmitted diseases) Chlamydia trachomatis and Gonorrhoea.

• Infects reproductive organs, appendix and intestines.

• Results in inflammation and damage.

• Increases risk of ectopic pregnancy.

http://www.nlm.nih.gov/medlineplus/ency/article/

001191.htm

MedlinePlus Medical Health Encyclopedia