Topic 1 Human Biology Unit 4

Front 1

3 stages of gametogenesis?

Back 1

1. Multiplication where primordial germ cells divide by mitosis

2. Growth this is where the cells grow in size

3. Maturation this is where the cells divide by meiosis to produce haploid cells (there are two meiotic divisions) they then differentiate into gametes (Spermatozoa and Ova)

Front 2

Differences between spermatogenesis and oogenesis?

Back 2

1. Spermatogenesis happens at puberty whereas oogenesis multiplication phase starts in fetal life

2. the stages in Spermatogenesis pass through uninterupted wheras oogenesis pauses at mitosis 2 until fertilization.

3. oogenesis stops at menopause wheras Spermatogenesis goes on until old age

4. Number of daughter cells are different. cytoplasm in Spermatogenesis divides equally so 4 daughter sperm cells produced from primary spermatocyte. wheras in oogenesiscytoplasm does not divide equally so only one ovum produced and 3 polar bodies from primary oocyte

5. In females this process is cyclic but in men non cyclic (menstruatal cycle)

Front 3

What happens in spermatogenosis

Back 3

primordial germ cells divide by mitosis in the multiplication phase, this is done in the germinal epithelium, as cells divide they form spermatogonia and move towards the centre of the tubule. here the growth stage occours and the spermatogonia develop into primary spermatocytes. now begins the maturation stage where meiosis occours, where secondary spermaotocytes are produced. in the second meiosis spermatids are formed which embed themselves into sertoli cells in the tubules this protects them from the immune system as they are genetically different from body cells and here nutrients are provided for the spermatids.

Front 4

What happens in oogenesis

Back 4

Primordial germ cells divide by mitosis in the multiplication phase to produce oogonia.then growth phase occours to produce primary ooctytes. these oocytes then undergo the first meoitic division to produce secondary oocyte. and a polar body the process then pauses until fertilisation where a second meitic division occours to produce 2 polar bodies, another polar body and an ovum.

Front 5

Reading menstrual cycle graphs

Back 5

- body temperature goes up at time of ovulation

- where oestrogen is high so is LH - ovulation

- menstruation is where the enodmetrium is at its thinnest,

Front 6

role of fsh

Back 6

fsh travels in blood to ovary causing primary folicule to grow, as folicule grows it releases oestrogen

Front 7

role of oestrogen

Back 7

inhibits fsh and strimulates growth of blood vessels in the endometrium and stimulates the production of LH

Front 9

a

Back 9

A