Lecture 2- Human Reproduction

Question 1

When does gamete formation occur in humans?

Answer 1

-Starts in males at puberty and theoretically can go on until death (sperm) (may be other problems e.g. erectile dysfunction)

Question 2

What was the youngest mother on record?

Answer 2

-Lina Vanessa Medina, became a mother to a baby boy at 5 years and 7 months of age (1939) - A Mexican girl gave birth when she was 9 years old (2013)

Question 3

What does the male reproductive system look like?

Answer 3

-on the way the liquid is taken from prostate gland + bulborethral= nourishes the sperm, if issues then problems with reproduction

Question 4

How many chromosomes etc. do humans have?

Answer 4

-46 -22 autosomes -2 sex chromosomes = X and Y -female= XX -male= XY

Question 5

What does homologous mean?

Answer 5

-one pair from mother, other from father

Question 6

What is spermatogenesis like?

Answer 6

• meiosis once puberty reached
• spermatids (immature) 8.3 weeks from start to end
• so having sex every day not good to get pregnant

Question 7

Where does spermatogenesis take place?

Answer 7

-seminiferous tubules

Question 8

What are the parts of a sperm?

Answer 8

1. Acrosome – contains enzymes to penetrate zona pellucida
2. Nucleus – contains compacted chromosomes
3. Midpiece – mitochondria provide energy for movement
4. Tail - swimming

Question 9

What does spermatogenesis looke like?

Answer 9

-

Question 10

Where is sperm collected and stored?

Answer 10

-collected in duct and stored in epididymis

Question 11

What is the composition of semen?

Answer 11

-

Question 12

What is classified as normal sperm?

Answer 12

-average 20-120 million sperm/ mL -280 000 000- 500 000 000 sperm/ejaculate

Question 13

How many sperms reach the position of the egg in the oviduct?

Answer 13

-about 200

Question 14

Below which point are men considered infertile?

Answer 14

-below 20 million/mL

Question 15

What is the average volume of ejaculate?

Answer 15

2-6mL -average is 2.75 mL (5mL= 1 teaspoon)

Question 16

What is the WHO definition of normal sperm count?

Answer 16

• the concentration of spermatozoa should be at least 20 million per ml. • the total volume of semen should be at least 2ml. • the total number of spermatozoa in the ejaculate should be at least 40 million. • at least 75 per cent of the spermatozoa should be alive (it is normal for up to 25 per cent to be dead). • at least 30 per cent of the spermatozoa should be of normal shape and form. • at least 25 per cent of the spermatozoa should be swimming with rapid forward movement. • at least 50 per cent of the spermatozoa should be swimming forward, even if only sluggishly.

Question 17

What is the study suggesting that the volume of ejaculate has been in decline in society?

Answer 17

• study that says that male ejaculate volume is decreasing
• maybe pollutants or lifestyle

Question 18

What is azospermia?

Answer 18

• no or low sperm count

Question 19

What is necrospermia?

Answer 19

• dead sperm

Question 20

What is oligospermia?

Answer 20

• sperm with defects -can have 2 heads, defects in tail, fused heads etc. -motility issues

Question 21

What can the sperm insufficiencies be also a result of?

Answer 21

-Mutation: 10 gene loci on Y chromosome that are expressed in the testis and important for male fertility eg DAZ gene

-on the Y chromosome

-it can be a micro deletion or a mutation

Question 22

What can the sperm insufficiencies be also a result of (another)?

Answer 22

-Antibodies in male or female -Even the male can produce antibodies to his own sperm

Question 23

What are some of the solutions to male problems?

Answer 23

-When there are some sperm

Question 24

What is ICSI (Intracytosplasmic sperm injection)?

Answer 24

-can inject a sperm into the egg -one sperm is enough -select a viable one A: If: low sperm count or motility poor sperm morphology (oligospermia) antibodies in male or female Then: viable sperm selected from ejaculate B: If: azospermia (no sperm) and necrospermia (dead or immobile sperm Then: viable sperm from epididymis and/or testis

Question 25

What are some of the issues with the Intracytoplasmic sperm injection?

Answer 25

-More chromosome aneuploidies (+ or – a chromosome) in sperm of men with fertility problems in particular the sex chromosomes -Infertility often related to microdeletions or mutations in Yq (long arm of Y chromosome -offspring of this technique= more aneuploidy (addition or subtraction of a sex chromosome or autosome, here it is for sex chromosome) -you will pass on the infertility on the male offspring, so should fathers with microdeletion father sons via this technique?

Question 26

What are the male problems?

Question 27

What is the prostate enlargement male problem?

Answer 27

-limits the amount of seminal fluid going to the ejaculate and then not enough nutrients for their sperm

Question 28

What is the varicocele?

Answer 28

-approximately 15% of the general population and 25% of men with infertility. -obscures the way -enlarged veins

Question 29

What are some of the environmental factors affecting fertility?

Answer 29

• sexually transmitted infections • zinc deficiency • Alcoholism • Smoking • anabolic steroid use • ionising radiation. • toxic pollutants

Question 30

What are some pollutants that may cause fertility problems?

Answer 30

-Thalates=Plastics industry -Alkylphenols=Industrial and domestic detergents -Bisphenol A=Lacquers to coat foods, Dental treatments -Organochlorine pesticides (Lindane, DDT, etc)=Lindane used on cereals, soft fruits, cabbage -Dioxins=Paper production Transformer disposal -Vinclozolin=Fungicide used on foods -Phytoestrogens=Soya products -wearing tight undies= too close to body= too warm vasectomy= sometimes reversible, but it is difficult

Question 31

What does the female reproductive system look like?

Answer 31

-

Question 32

When does production of gametes commence in females?

Answer 32

-production of the ovum starts at 3 months after conception, not mature until it is fertilised

Question 33

What is Oogenesis like?

Answer 33

• 2 000 000 primary oocytes at birth
• 300 000 by age 7 (resorbed)
• per oocyte you get one ovum (the 3 rest are polar bodies) in males get 4 sperms per spermatocyte

Question 34

What are some of the reasons for female infertility?

Question 35

What is the polycystic ovary disease?

Answer 35

-Polycystic ovary disease PCOS – cysts in ovary and overproduction of androgens -associated with weight gain, excessive hair growth in the face and body, irregular and infrequent periods or absent periods, infrequent or absent ovulation, miscarriage and infertility. -cysts in the ovary and can lead to infertility

Question 36

What is endometriosis?

Answer 36

-a condition that affects a woman’s reproductive organs. It happens when the tissue that lines the uterus grows outside of it

Question 37

What are fibroids?

Answer 37

-fibrous growth in the uterus that prevent implantation but can be removed surgically

Question 38

What are blocked fallopian tubes?

Answer 38

-because of mucous, can be corrected surgically

Question 39

Where does fertilisation occur?

Answer 39

-

Question 40

What are some more female causes of infertility?

Answer 40

1.Hostile mucus – too thick for sperm to swim

Question 41

How does fertilisation occur?

Answer 41

• sperm has to go through
• only about 200 make it to the opening of the fallopian tube
• the sperm dissolves the region of the egg and the nuclei fuse

Question 42

What is the development of the embryo right after fertilisation?

Answer 42

-don’t get a positive result pregnancy test= until implantation