lutenal phase Flashcards
give an overveiw of the luteal phase, (period of occurence, subperiods and dominante hormone)
from ovulation until regression (luteolysis) of the corpus luteum near the end of the estrous cycle. This is split into two periods, diestrus and metestrus (growing of the CL). Progesterone is the dominant hormone.
what hapens in the begining of Luteinization
The corpus hemorrhagicum is formed from the theca interna (small cells) and granulosa cells (large cells) that perviously surronded the ovum. The walls collapse and the theca internal and granola cells mix forming a gland of connective tissue. (post ovulation) this is controlled by LH
what role does Angiogenesis play in luteinization
vascularisation of the CL which allows for larger secretions of hormones into the blood.
what is a key hormonal feture of the cells that form the corpus hemorrhagicum
Small luteal cells (formed from the theca interna) and large cells (from the granulosa) are steroidogenic which means they can produce progesterone
when does the corpus luteum form and how
Day 1-3 (post ovulation). As the follicle ruptures forming a corpus hemorrhagicum. the large luteal cells undergo hypertrophy and the small undergo hyperplasia. as this occurs it become more vascularised allowing for a high hormonal output.
how does the corpus hemorrhagicum form
The corpus hemorrhagicum is formed from the theca interna and granulosa cells. Due to collagenase the basement membrane deteriorates. The walls collapse and the theca internal and granola cells mix forming a gland of connective tissue.
what does the colour of the corpus structure indicate about its function
red - hemorage, newly formed with little output
yellow - luteum, high outpul and highly vascular
white - albicans, little output and is degenerating
what is luteolysis and describe the process
Day 2-3 Near the end of the luteal phase the corpus luteum loses its function and decreases in size which is irreversible, transforming into a corpus albicans. this drops the blood progesteron levels
what hormones are needed to initatie luteolysis
oxytocin, prostaglandinF2α
Oxytocin and PGF2a work in a positive feedback loop until luteolysis
A utero-ovarian vascular countercurrent diffusion system ensures correct concentration of PGF2a.
cellular phagocytosis initiates apoptosis during Luteolysis, describe this.
PGF2α binds to plasma membrane receptors on large luteal cells. This inhibits progesterone synthesis and increases calcium influx.
how is the corpus albican formed
phagocytic cells clean-up the destroyed luteal tissue leaving the connective tissue behind (scar tissue) aka the corpus albicans
progesterone development of the corpus luteum is lenear to what
the corpus luteums size
primary target organs of progesteron are what
uterus, hypothalaums, mammary gland
what is progesterons impact on the hypothalamus during the luteal phase
Causes negative feedback (reduces GnRH pulse frequency; prevents behavioural oestrus; prevents the preovulatory LH surge
what is progesterons impact on the Mammary gland during the luteal phase
Promotes alveolar development in the mammary gland
what is progesterons impact on the unterine tissue (Glandular endometrium) gland during the luteal phase
Stimulates endometrial gland secretion (supports the development of conceptus)
what is progesterons impact on the unterine tissue (Muscular endometrium) gland during the luteal phase
Reduces myometrial tone (creates ‘uterine quiescence’ – important for attachment of the embryo) – in cow, sow and ewe
In mares – a certain level of myometrial contractions continue for the early conceptus to migrate in the uterus
Describe what is meant by the ‘utero-ovarian vascular countercurrent diffusion system’
A utero-ovarian vascular countercurrent diffusion system is how PG2a enters the ovary, it ensures the correct concentration by having two blood vessels close to another.
The low molecular weight substances can move across the membrane into the adjacent vessel.
PGF2a is made in the endometrium, secreted into the uterine vein -> this connects to the ovarian artery next to the utero ovarian vein.
‘utero-ovarian vascular countercurrent diffusion system’ how it is important to the process of luteolysis.
Important so that adequate levels of PGF2α is available to exert its lytic effects directly on the functional CL
Ischemia (reduced blood flow)
Causes the reduction of the corpus luteum and thus luteolysis.
