Corpus Luteum Flashcards
(32 cards)
Where does the corpus luteum orginate from?
ovulatory follicle
describe luteinization
after ovulation, the theca interna and granulosa cells of the follicle undergo a transformation
How does the theca interna change during luteinization
small luteal cells
-mitosis after ovulation (hyperplasia): 5 fold increase
How does the granulosa cells change during luteinization
large luteal cells
-hypertrophy cells( increase in cell size): 3 fold increase
What does the luteal phase consist of
-luteinization(formation of the CL)
-synthesis and secretion of large quantities of progesterone
-luteolysis
Luteal tissue consists of what type of cells
-large cells originate from the granulosal cells
-small cells originate from the cells of the theca interna
What are the three main steps of the formation of the CL
- preovulatory follicle: granulosal and theca cells start to intermingle
2.”bloody body”: small blood vessels rupture causing a local hemprrhage - CL: mixture of small and large luteal cells
What does the vigor of the C.L depend on?
-the number of luteal cells
-degree of which the CL becomes vascularized
Progesterone is an inhibitor because it..
-reduces GnRH pulse frequency
-prevents behavioral estrus
-stops the preovulatory LH surge
-reduces myometrial tone (not in the mare)
what does a vascular countercurrent transport system ensure?
that PGF2a will reach the ovary ins sufficient quantities to cause luteolysis in the ewe, cow and sow
describe the counter current exchange system
involves two closely associated blood vessels in which blood from one vessel, flows in opposite direction to that of the adjacent vessel
What are the requirements for luteolysis
-presence of oxytocin receptors on endometrial cells
-presence of critical level of oxytocin
-PGF2a synthesis by the endometrium
what does luteolysis result in
-cessation of progesterone secretion
-structural regression to form a corpus albicans
-removal of negative feedback by progesterone by GnRH secretion resulting in a new follicular phase
What does the CL vigor depend on?
appears to depend upon numbers of cells and vascularization
What are the cells found in the CL ?
non-steroidogenic cells (fibroblasts, capillary cells, eosinophilis) increase in number
how long foes the luteal phase last till
from the time of ovulation until regression (luteolysis) of the corpus luteum
What is the importance of progesterone?
-progesterine synthesis requires cholesterol and LH
-progesterone is necessary for the maintenance of pregnancy
What are the actions of progesterone
-affects basal LH secretion
-prevents estrus
-stops the preovulatroy surge of LH
-reduces myometrial tone
what is luteolysis and what is responsible for it?
-luteal regression, cessation of function of the CL
-occurs at the end of the luteal phase
-Hormone responsible for luteolysis in domestic farm specis PGF2a from the uterus
What is the relationship of oxytocin and PGF2a
oxytocin is coming from the posterior pituitary
-affecting the uterus, releasing PGF2a (from the uterus) to the ovary
-oxtocin also affects the CL
how do you initiate luteolysis
up to luteolysis, progesterone suppresses oxytocin receptors in the uterus
What are the events leading up to luteolysis?
- progesterone loses its ability to suppress formation of uterine oxytocin receptors
2.Estrogen binds to the endometrial receptors to upregulate oxytocin receptor - oxytocin binds to receptors to stimulate PGF2a release
- Amongst other actions, PGF2a increases oxytocin release from CL
describe counter current exchange
exchange of PGF2a, uterine PGF2a is transported directly from the uterine vein into the ovarian artery
What types of hysterectomy will make the C.L lifespan longer, why
ipsilateral and total hysterectomy, CL on the left/Uterine horn removed from the left or whole structure, no counter current exchange happening
