Chapter 9- Luteal Phase

luteinization

After ovulation the theca interna and the graulosal cells of the follicle undergo a dramatic transformation whereby cells of the ovulatory follicle are transformed into luteal tissue. Governed by LH.

Prostaglandin F2a

Causes luteolysis, secreted by the uterine endometrium. During the first half of the luteal phase- no secretion by uterus. However, during the late luteal phase secretion begins to pulse. Likely, controlled by levels of progesterone, ovarian oxytocin, and number of progesterone receptors in the endometrium.

vascular countercurrent transport

Prostaglandin F2a is transported from the uterus to the ipsilateral ovary involving two closely associated blood vessels in which blood from one vessel flows in the opposite direction to that of the adjacent vessel. Moves from high concentration to low concentration

Luteal tissue

Steriodogenic- prossessing the ability to produce steroids- progesterone. consists of large and small luteal cells -large cells originate from granulosal cells (hypertrophy=increase in size as CL develops) -small cell originate from theca interna (hyperplasia=increase in numbers as CL develops)

luteolysis

degradation of the corpus luteum. A regressed corpus luteum will become a corpus albicans. Induced by the hormone PGF2a secreted by the uterine endometrium. Results 1)cessation of progesterone secretion 2)structural regression to form a corpus albicans 3) removal of negative feedback by progesterone upon GnRH secretion resulting in a new follicular phase.

luteal phase

lasts from the time of ovulation until luteolysis of the corpus luteum (CL). Dominant follicle is progesterone consist of 1)luteinization (formation of the CL) 2)synthesis and secretion of large quantities of progesterone 3)luteolysis

cytokines

non-antibody proteins secreted by a variety of immune cells that activate macrophages that then phagocytize damaged dead luteal cells and cellular debris. Inhibit progesterone synthesis by luteal cells Ex. interferons, interleukins, and tumor necrosis factors (TNF)

corpus luteum

originates from the ovulatory follicle- secretes progesterone. The 'vigor' depends on number of luteal cells and degree of vascularization. Insufficient function leads to reproductive failure within animals

Progesterone

primary target organs is the hypothalamus, the uterus, and the mammary gland. Exerts negative feedback on the hypothalamus. elevated progesterone reduces the pulse frequency of GnRH , however, LH remains high with basal FSH to stimulate follicle growth during luteal phase. Will not reach preovulatory status until progesterone. High progesterone prevents development of steroidogenic preovulatory follicles, secretion of estradiol, behavioral estrus and the preovulatory surge of GnRH and LH. Uterus 1)glandular endometrium- secretory products to support conceptus after it enters uterine lumen. 2)muscular myometrium- reduces contraction creating a calm environment for conceptus

contralateral

uterine horn on the opposite side of corpus luteum, there is little affect on the life-span of the corpus luteum.

ipsilateral

uterine horn on the same side as the corpus luteum is removed, the life-span of the corpus luteum is twice as long

corpus hemorrhagicum

when the follicle ruptures at ovulation, blood vessels within the follicular wall also rupture. THis vascular breakage results in a structure with a 'bloody' clot-like appearance.