Lecture 2- Human Reproduction Flashcards
When does gamete formation occur in humans?
-Starts in males at puberty and theoretically can go on until death (sperm) (may be other problems e.g. erectile dysfunction)
What was the youngest mother on record?
-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)
What does the male reproductive system look like?
-on the way the liquid is taken from prostate gland + bulborethral= nourishes the sperm, if issues then problems with reproduction
How many chromosomes etc. do humans have?
-46 -22 autosomes -2 sex chromosomes = X and Y -female= XX -male= XY
What does homologous mean?
-one pair from mother, other from father
What is spermatogenesis like?
- meiosis once puberty reached
- spermatids (immature) 8.3 weeks from start to end
- so having sex every day not good to get pregnant
Where does spermatogenesis take place?
-seminiferous tubules
What are the parts of a sperm?
- Acrosome – contains enzymes to penetrate zona pellucida
- Nucleus – contains compacted chromosomes
- Midpiece – mitochondria provide energy for movement
- Tail - swimming
What does spermatogenesis looke like?
-
Where is sperm collected and stored?
-collected in duct and stored in epididymis
What is the composition of semen?
-
What is classified as normal sperm?
-average 20-120 million sperm/ mL -280 000 000- 500 000 000 sperm/ejaculate
How many sperms reach the position of the egg in the oviduct?
-about 200
Below which point are men considered infertile?
-below 20 million/mL
What is the average volume of ejaculate?
2-6mL -average is 2.75 mL (5mL= 1 teaspoon)
What is the WHO definition of normal sperm count?
• 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.
What is the study suggesting that the volume of ejaculate has been in decline in society?
- study that says that male ejaculate volume is decreasing
- maybe pollutants or lifestyle
What is azospermia?
- no or low sperm count
What is necrospermia?
- dead sperm
What is oligospermia?
- sperm with defects -can have 2 heads, defects in tail, fused heads etc. -motility issues
What can the sperm insufficiencies be also a result of?
-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
What can the sperm insufficiencies be also a result of (another)?
-Antibodies in male or female -Even the male can produce antibodies to his own sperm
What are some of the solutions to male problems?
-When there are some sperm
What is ICSI (Intracytosplasmic sperm injection)?
-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
What are some of the issues with the Intracytoplasmic sperm injection?
-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?
What are the male problems?
What is the prostate enlargement male problem?
-limits the amount of seminal fluid going to the ejaculate and then not enough nutrients for their sperm
What is the varicocele?
-approximately 15% of the general population and 25% of men with infertility. -obscures the way -enlarged veins
What are some of the environmental factors affecting fertility?
• sexually transmitted infections • zinc deficiency • Alcoholism • Smoking • anabolic steroid use • ionising radiation. • toxic pollutants
What are some pollutants that may cause fertility problems?
-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
What does the female reproductive system look like?
-
When does production of gametes commence in females?
-production of the ovum starts at 3 months after conception, not mature until it is fertilised
What is Oogenesis like?
- 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
What are some of the reasons for female infertility?
What is the polycystic ovary disease?
-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
What is endometriosis?
-a condition that affects a woman’s reproductive organs. It happens when the tissue that lines the uterus grows outside of it
What are fibroids?
-fibrous growth in the uterus that prevent implantation but can be removed surgically
What are blocked fallopian tubes?
-because of mucous, can be corrected surgically
Where does fertilisation occur?
-
What are some more female causes of infertility?
1.Hostile mucus – too thick for sperm to swim
How does fertilisation occur?
- 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
What is the development of the embryo right after fertilisation?
-don’t get a positive result pregnancy test= until implantation
