Gamete reproduction Flashcards
Spermatogenesis
Formation of spermatozoa in the seminiferous tubules of each testis
What are seminiferous tubules lined with
Spermatogonia which are stem cells (meaning they can undergo unlimited cell cycles) that have a diploid number of chromosomes
What happens during puberty in spermatogenesis
Spermatogonia divide by mitosis which is a source of new cells for spermatozoa which are pushed inwards towards the centre of the tubule where they grow to become enlarged cells called primary spermatocytes which are diploid
What happens to the primary and secondary spermatocytes
Primary spermatocytes undergo meiosis I to form secondary spermatocytes which are haploid, secondary spermatids then undergo meiosis II forming 4 haploid spermatids
Final stage of spermatogenesis
When the spermatids mature into spermatozoa- most of the cytoplasm is lost and a tail containing contractile material forms
Spermatozoa
Stored in the epididymis where they become motile and are transported through the vas deferens into the urethra
How long does it take for spermatogium to mature into spermatozoa
72 days
Life span of sperm after ejaculation
In the uterus/fallopian tubes- 5 days but most only live 1-2
Vagina- a few hours due to the acidity
Outside the body- few mins as they dry out
Glands that produce fluid that makes up the semen
Prostate gland, seminal vesicles, cowper’s/bulbourethral gland
What does the prostate gland produce
Produces a milky alkaline fluid that neutralises the acidic conditions in the vagina
What do the seminal vesicles produce
produces a thick sugar rich fluid that provides nutrients (glucose) for the sperm
What does the cowper’s/bulbourethral gland produce
produces a clear alkaline lubricating fluid to protect sperm in the urethra from traces of urine
Oogenesis
Formation of the ova
What are the 4 stages of oogenesis
In the foetus, during puberty, during ovulation, at fertilisation
What happens during oogenesis in the foetus
The Oogonia are diploid and undergo mitosis becoming more mature to form a diploid primary oocyte (differentiates) in a follicle, Primary oocytes undergo meiosis I but stops in Prophase (meaning no separation, still diploid) until puberty
Around how many oogonia does a female baby have
around 400,000 in each ovary
What happens during puberty in females
Ovarian cycle commences, follicle stimulation hormone is released
What happens during oogenesis during puberty
Primary oocyte completes meiosis I (goes from prophase to the end of meiosis I) to form a haploid secondary oocyte as well as a haploid polar body, Secondary oocyte- bigger than the polar body and has most of the cytoplasm meaning it is viable to be fertilised and become a baby, Meiosis stops in metaphase II, Polar body can undergo meiosis again to make a second polar body
What happens during oogenesis at ovulation
Most mature follicle moves to the surface of the ovary which bursts/opens and releases the secondary oocyte which stays in metaphase II until it interacts with the sperm, Secondary oocyte moves into the fallopian tube which is viable for around 24 hours
What happens during oogenesis at fertilisation
Secondary oocyte rapidly finishes meiosis II to produce 1 mature ovum and another polar body, Ovum haploid nucleus fuses with the sperm haploid nucleus to form a zygote with a diploid number of chromosomes, Polar bodies (secondary nucleus) disintegrates
