Flashcards in Reproduction Deck (50)
Up to what week of foetal development are humans indifferent?
Indifferent until week 7
What is the default gender pathway?
What the factors involved in producing a male foetus?
SRY - transcription factor expressed by the Y chromosome
Androgens and AMH are important signals in males
Where do the primordial germ cells migrate to ?
migrate to the genital ridge
What is the flow of cells produced during oogenesis?
Primordial germ cell
What is significant about meiosis and what is the purpose of producing polar bodies during oogenesis?
Discontinuous - primary oocytes are all ready and waiting before a foetus is born and the cells are arrested in
prophase I, and then by puberty the secondary oocytes are arrested in metaphase II until a sperm fertilises them
-finite number of egg cells - born with all the eggs we will ever have
- up to week 20 there is massive proliferation of oogonia but in the second half of pregnancy there is significant atresia
Help the egg to get rid of excess genetic material
What are the different stages of follicles?
Primordial follicle (formed in utero), primary follicle (pre-antral), secondary follicle (pre-antral), tertiary follicle (antral/graafian follicle)
When and why does the blood-testis barrier form?
Develops during puberty to protect the sperm from the immune system and controls what enters and exits the seminiferous tubules
Forms between the sertoli cells
What is the flow of cells produced during spermatogenesis?
Primordial germ cells
Prospermatogonia - at genital ridges
Spermatogonial stem cells
What is the purpose of the centrioles in the sperm?
eggs don't have centrioles so these centrioles are essential for the first cell division
Why does the sperm shed its cytoplasm?
Sheds it to make them more streamline
What does LH stimulate in the male HPG axis?
leydig cells to produce androgens (testosterone)
What does LH stimulate in the female HPG axis?
Theca cells - androgens which are aromatised in the granulosa cells by aromatase to produce oestrogens
What does the corpus luteum produce?
Oestrogen and progesterone
What are the 3 main families of steroids?
What do high levels and low levels of oestrogen do to the HPG axis?
High levels stimulate the anterior pituitary to release FSH/LH
Low levels inhibit the hypothalamus and anterior pituitary from releasing GnRH and LH/FSH respectively
Normal menstrual cycle
Normal menstrual cycle = bleed every 28 days (26-32days)
Oligomenorrhoea =<9 cycles in the last 12 months
Amenhorrhoea = no bleed in the last 6 months - before puberty = primary whereas periods stopping = secondary
Which phase varies and subsequently affects the length of a female menstrual cycle?
variations in the follicular phase length (pre-ovulatory phase)
What are some causes of amenorrhoea?
ALWAYS exclude pregnancy
Central causes: hypothalamic (low leptin, Kallman syndrome), pituitary (hyperprolactinaemia, tumour ) (Low FSH/LH) = suppresses the HPG axis
Ovarian causes: Turners (X -), premature ovarian failure (elevated FSH/LH- brain is functioning but ovaries are not)
What is polycystic ovary syndrome?
Commonest endocrine condition (>10% of pre-menopausal women)
Symptoms: hyperandrogenic, insulin resistance, PCO
Rotterdam criteria- diagnosis criteria requiring you to have 2 out of 3 symptoms:
1) poly cystic ovaries
3) oligomenoorhoea (80%)
Other common symptoms
- hirsuitism (30%)- excess body hair due to high levels of androgens
- obesity (40%)
- infertility (30%)
What are examples of male endocrine disorders?
Reduced shaving frequency
Reduced testicular volume
What are the primary causes of gonadal failure?
High FSH, LH
Trauma, chemo, surgery, cryptochidism (testes fail to descend), infections/inflammation, genetic (Klinefelter's - sometimes not picked up until infertility clinic)
What are the secondary causes of gonadal failure?
Low FSH, LH
Hypothalamic disorders (Kallman), hyperprolactinaemia
Pituitary tumours, androgen abuse
What are some other endocrine disorders affecting reproduction?
Congenital adrenal hyperplasia (21-OHD)- decreased cortisol and aldosterone and increased testosterone
Androgen insensitivity syndrome - androgen receptor
What are the prerequisites for fertilisation?
Sperm and oocyte in ampulla in the correct state
- oocytes - 24 hours its completed meiosis I and has started meiosis II but is arrested in metaphase II
- Capacitation of the sperm = final maturation process which takes place in the female tract - only once this has occurred can it fertilise the ovum
How long can sperm remain in the female tract?
Sperm can remain there for about 5 days but the egg of only viable for about 24 hours so there is a relatively small window for fertilisation to take place
What happens when the sperm fuses with the egg?
Sperm fusions triggers calcium increase = releases meiotic block, block to polyspermy (egg has evolved special mechanisms to prevent more than one sperm fusing with the egg)
Fast reaction = membrane depolarisation
Slow reaction = cortical reaction
Only about 10-100 sperm actually reach the ampulla
What defines the end of fertilisation?
Male and female pronuclei migrate towards each other and combine forming a zygote nucleus
- then cleavage commences
- implantation occurs at around day 7
How many couples have infertility problems ?
1 in 6 couples
15% unexplained - could be due to minor problems in both partners