2. the corpus luteum Flashcards
what is the corpus luteum
- highly vascularised, transient endocrine gland
- solid
- progesterone production
what is luteinisation
- the formation of the CL
- process where granulosa and theca cells are transformed into luteal cells
which hormone causes ovulation and subsequent development and maintenance of the CL
LH
what is a luteotroph
a hormone that stimulates the CL
what is luteolysis
process whereby luteal tissue undergoes regression and cell death
how does the CL form
- after ovulation (follicle bursts
- basement membrane breaks down –> mixing of granulosa and theca cells
- luteinisation and migration: granulsa becomes large luteal cell, theca = small
- rapid ptoliferation and hypertrophy
- intense angiogenesis
- steroidogenesis switch and increase (oestradiol –> progesterone)
which hormones support the growth and function of the CL in different species
- LH in ruminants, sows and mares
- prolactin in rodents
- IGF-1, growth hormone and PGE2 also play a role
how does the CL produce progesterone
- both large and small luteal cells produce progesterone (but differ in their capacity and regulation)
- large luteal cells: make the majority of the progesterone
- stimulated by LH (small luteal cells only)
- key regulatory step transfers cholesterol into mitochondria (critical factor = StAR)
what are the target organs for progesterone
- uterus
- hypothalamus
- mammary
what are the function of progesterone
- progesterone is of major importance in the endocrine control of reproduction
- negative feedback of progesterone on hypothalamus
- reduces GnRH, LH and FSH pulsatility
- limits preovulatory follicle development and oestradiol production
- prevents oestrus behaviour
- prevents the LH surge
- promotes alveolar development in mammary gland prior to partuition
- growth of uterine glands and their secretions to support early embryo
- inhibits myometrial contractility
when does the CL regress and what does this process enable
- in the absence of fertilisation, luteolysis is induced
- luteolysis is the structural and functional degradation of the CL
- enables release from negative feedback on GnRH
- enables pre-ovulatory follicular development –> ovulation
- return to oestrus
what happens structurally in the regression of the CL
- reduced blood flow
- increase in macrophages and lymphocytes
- apoptosis and tissue resorption
- corpus albicans (remnant) forms
how does the CL regression functionally during lutolysis
- down regulation of steroidogenic enzymes
- rapid fall in progesterone
what is the key luteolytic hormone
prostaglandin F2alpha
in ruminants, pigs and horses which additional hormonal communication occurs during luteolysis
CL produces oxytocin
- receptors present in the uterine endometrium for oxytocin
- oxytocin binds
- PGF2a released by the uterine endometrium
- PGF2a = luteolysis
