Gamete reproduction

Question 1

Spermatogenesis

Answer 1

Formation of spermatozoa in the seminiferous tubules of each testis

Question 2

What are seminiferous tubules lined with

Answer 2

Spermatogonia which are stem cells (meaning they can undergo unlimited cell cycles) that have a diploid number of chromosomes

Question 3

What happens during puberty in spermatogenesis

Answer 3

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

Question 4

What happens to the primary and secondary spermatocytes

Answer 4

Primary spermatocytes undergo meiosis I to form secondary spermatocytes which are haploid, secondary spermatids then undergo meiosis II forming 4 haploid spermatids

Question 5

Final stage of spermatogenesis

Answer 5

When the spermatids mature into spermatozoa- most of the cytoplasm is lost and a tail containing contractile material forms

Question 6

Spermatozoa

Answer 6

Stored in the epididymis where they become motile and are transported through the vas deferens into the urethra

Question 7

How long does it take for spermatogium to mature into spermatozoa

Answer 7

72 days

Question 8

Life span of sperm after ejaculation

Answer 8

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

Question 9

Glands that produce fluid that makes up the semen

Answer 9

Prostate gland, seminal vesicles, cowper’s/bulbourethral gland

Question 10

What does the prostate gland produce

Answer 10

Produces a milky alkaline fluid that neutralises the acidic conditions in the vagina

Question 11

What do the seminal vesicles produce

Answer 11

produces a thick sugar rich fluid that provides nutrients (glucose) for the sperm

Question 12

What does the cowper’s/bulbourethral gland produce

Answer 12

produces a clear alkaline lubricating fluid to protect sperm in the urethra from traces of urine

Question 13

Oogenesis

Answer 13

Formation of the ova

Question 14

What are the 4 stages of oogenesis

Answer 14

In the foetus, during puberty, during ovulation, at fertilisation

Question 15

What happens during oogenesis in the foetus

Answer 15

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

Question 16

Around how many oogonia does a female baby have

Answer 16

around 400,000 in each ovary

Question 17

What happens during puberty in females

Answer 17

Ovarian cycle commences, follicle stimulation hormone is released

Question 18

What happens during oogenesis during puberty

Answer 18

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

Question 19

What happens during oogenesis at ovulation

Answer 19

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

Question 20

What happens during oogenesis at fertilisation

Answer 20

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