Reproduction (Yr 1) Flashcards
what is oogenesis?
formation of gametes (oocytes) in the ovaries
what does the mature graafian follicle (dominant follicle) form after ovulation?
corpus luteum
how long does the corpus luteum last before undergoing luteolysis?
14 days
what hormones does the anterior pituitary release?
FSH
LH
ACTH
TSH (thyroid stimulating hormone)
growth hormone
prolactin
what hormone involved in the oestrus cycle is released by the hypothalamus?
GnRH (gonadotrophin releasing hormone)
what is FSH responsible for?
stimulating growth and recruitment of immature ovarian follicles
what is LH responsible for?
stimulation maturation of follicle, ovulation and luteinisation
what hormone is produced by the corpus luteum?
progesterone
what effect does progesterone have on GnRH and the anterior pituitary?
negative feedback to prevent GnRH, LH and FSH production
what triggers the LH surge?
positive feedback from oestradiol being released from the dominant follicle
what controls seasonality?
the effect of melatonin on GnRH production
how long is the oestrus cycle of the sheep?
17 days
how long does oestrus last in sheep?
30 hours
when do sheep ovulate in relation to oestrus?
20-25 hours after the start of oestrus
how long is the oestrus cycle of cows?
21 days
how long is oestrus in cows?
18 hours
when does ovulation occur in relation to oestrus in cows?
20-30 hours from the start of oestrus
what effect does progesterone always have of GnRH?
inhibits it
what determines the length of the oestrus cycle?
lifespan of the corpus luteum
what causes luteolysis?
prostaglandin F2 alpha
what is reproductive function controlled by?
GnRH pulse generator in the brain
what is puberty?
the acquisition of reproductive competence
what signals sexual maturity in animals?
the increased pulsatility of GnRH
what factors can influence when puberty occurs?
weight
age
metabolic status
photoperiod
social conditions (group/male presence)
how is seasonality governed in sheep?
decreased periods of light is detected in the eye and passed through to the superior cervical ganglion and then pineal gland
pineal gland releases higher levels of melatonin which increased the GnRH pulsitility and hence FSH/LH leading to cycling
what hormones have a role in the development of mammary glands?
oestrogen
progesterone
prolactin
growth hormone
what is lactogenesis?
the onset of milk secretion
what hormones synchronise the onset of milk secretion?
increased cortisol, prolactin and oestrogen couples with decreased progesterone
how does decreased progesterone at the end of pregnancy aid the secretion of milk?
as it decreases it allows synthesis of prolactin receptors meaning prolactin and bind and up regulate enzymes involved in lactose synthesis
what is galactopoesis?
the maintenance of milk secretion
what governs galactopoesis?
hormones - prolactin and oxytocin
removal of milk
what is the function of prolactin in galatopoesis?
maintain alveolar cell metabolism and upregulate lactose producing enzymes
what are some important factors affecting milk yield?
number of secretory cells in mammary gland
blood supply to mammary gland
water intake
lactose (blood glucose concentration)
milk removal
where does spermatogenesis occur?
Sertoli cells of the seminiferous tubules
what is the function of the sperm-testis barrier?
prevents immunological destruction of foreign haploid cells
what is the sperm-testis barrier between?
blood vessels and seminiferous tubules
what cells synthesise testosterone?
ledig cells
where do spermatids end up?
in the lumen of the seminiferous tubules
what is the route sperm take?
seminiferous tubules
rete testis
efferent tubules
epididymis
ductus deferens
urethra
where do spermatozoa mature?
epididymal duct
how long does it take sperm to mature?
8-15 days in the epididymis
what hormone is required for spermatogenesis?
testosterone (and FSH)
what hormone do the leydig cells respond to?
LH
what cells secrete testosterone?
leydig
what hormone do Sertoli cells respond to?
FSH
what hormone do Sertoli cells secrete?
inhibin
what structure is similar between all the sex hormones?
cholesterol ring (steroid)
what factors control scrotal temperature?
profuse sweat glands
tunica dartos (contracts to pull testes towards body)
cremaster muscle (pulls testes towards body for short time periods)
pampiniform plexus
what are the main receptors involved in erections?
parasympathetic (NANC - nonadrenergic noncholinergic) neurones
what are the parts of the oviduct (fallopian tube)?
ampulla - wide portion attached to infundibulum on ovary
isthmus - narrow attached to uterotubal junction
where is semen deposited in natural service?
vagina
(cervix in pigs)
what happens in the female reproductive tract for sperm to become fertile?
capacitation (seminal plasma proteins removed from membrane)
what must happen when the sperm reaches the egg for successful fertilisation?
bind to zona pellucida
undergo acrosome reaction (digest zona pellucida)
penetrate zona pellucida and fuse with oocyte membrane
zona block to prevent further sperm penetrating
what does capacitation do?
remove protein coating so sperm can bind with egg and gives them hyperactive motility
what is the process called when male and female pronuclei fuse to form a zygote?
syngamy
what does syngamy produce?
zygote
what is cleavage?
rapid mitotic division of zygote starting the first week of development
what is the luteolytic signal in cattle?
oxytocin is secreted by the CL, receptors for this appear in the late luteal phase
binding of oxytocin then stimulates prostaglandin release
how does maternal recognition of pregnancy occur in cattle and sheep?
blastocyst produce interferon which blocks the synthesis of oxytocin receptors and hence blocking prostaglandin synthesis
how does maternal recognition of pregnancy occur in pigs?
prostaglandin release is rerouted to the uterine lumen when it can’t cause luteolysis but at least 2 conceptuses per horn is needed for this
how many days after ovulation will attachment of placenta occur?
18-22 days
what does the endoderm form?
digestive system
lungs
endocrine system
what does the mesoderm form?
muscle
skeleton
cardiovascular
reproductive system
what does the ectoderm form?
nervous system
skin
hair
what is the inner sac of the placenta called?
amnion
what is the outer day of the placenta called?
chorioallantois
what is the function exchange apparatus of the placenta called?
allantochorion
why do freemartins develop?
testis develop before ovariess and secrete AMH and testosterone which reaches both foetuses meaning the females tract cannot develop normally
what vessels are found in the umbilical cord?
two umbilical arteries
umbilical vein
urachus
what does the umbilical arteries become?
round and lateral ligaments of bladder
what does the umbilical vein become?
round ligament of liver
what does the urachus become?
median ligament of bladder
how long do cows rely on the CL for to produce progesterone in pregnancy?
around 6-8 months
how long do sheep rely of the CL for to produce progesterone in pregnancy?
about 50 days
what triggers parturition?
the lack of foetal space causes stress and release of ACTH causing corticoids to be released
what are the effects of foetal cortisol on initiation of parturition?
removes the myometrial progesterone block allow myometrial contractions (and stimulate prostaglandin release by placenta)
increase reproductive tract secretions for parturition
what is the function of prostaglandin release around parturition?
synthesis of relaxin causing softening of tissues and increased elasticity of pelvic ligaments
luteolysis of any remaining CL
what are the stages of parturition?
1 - initiation of contractions and cervical dilation
2 - expulsion of foetus
3 - expulsion of foetal membranes
what is the name of the reflex responsible for increasing contractions during parturition?
Fergusons reflex (stretch receptors produce more oxytocin - positive feedback)
what is lochia?
remnants of foetal tissue expelled out the vagina as brown discharge
