Reproductive Physiology 3, Ovary and Follicular Development

Follicular rupture

Ovulation, Begins with LH surge which breaks down junction between oocyte and granulosa cells. Increases in Prostaglandin 2 leads to increase in follicular pressure. PGF2a increase for contraction Shift from estrogen to progesterone promotes synthesis of Collagenase to break down follicle wall

Estrogen on behavior

Peak of estrogen leads to sexual receptivity Is needed for ovulation. Negative Feedbacks on the surge center of the hypothalamus to stop GnRH release.

Oogenesis

Production, growth, and maturation of an egg. Division, Arrestation, Cytoplasmic Growth and Activation after puberty

Progesterone action

Shift from Estrogen to Progesterone promotes synthesis of an enzyme (Collagenase) that will help in the breakdown of the follicle wall. In Metestrus, Corpus luteum is beginning to formed and there is a rise in progesterone At the end of Diestrus Corpus Luteum will break down and progesterone will go down as well starting the cycle over

Monotocous species

Single follicle is selected

Recruitment Follicular Dynamics

Small follicles are recruited High secretion of FSH with low of LH and No to little inhibin or estradiol

Selection Follicular Dynamics

Some follicles are selected to move on and become large follicles or atretic ones. Secrete Low FSH with Moderate LH and Low inhibin and estrogen

Granulosa cells

The majority of the cells surrounding an oocyte in a follicle. Secrete estrogen during the follicular phase of the ovarian cycle (before ovulation).

Polytocous species

litter bearers - multiple dominant follicles

Follicular Development

After Luteolysis, Progesterone is reduced and GnRH secretion is increased and then FSH/LH as secreted to develop follicles.

Antral follicle

Also known as Graafian follicle and tertiary follicle Contains oocyte, zona pellucida, granulosa cells, theca cells, and antrum

Ovarian follicles

Areas within the ovary in which individual eggs develop. Contain oocytes in various stages of development, follicular cells and granulosa cells

Atresia

Degeneration of Follicles

Corpus Luteum

Endocrine tissue which produces hormones, estrogen, and progesterone which prepares the uterine lining for receiving an embryo.

Theca Cells

Estrogen-producing cells in a maturing ovarian follicle

GnRH role in follicular development

GnRH from Tonic center acts on the anterior lobe to secrete FSH/LH to act on the follicle, after it releases Estrogen to feed back on the Surge center. The follicles also release inhibin and works on the anterior pituitary to inhibit FSH and LH.

Cycle of Follicular Phase

Gonadotropins from the Tonic Center act of the Ovaries to release estrogen and feed back on the surge center to stop GnRH At the end of follicular phase (Estrus) a surge of LH and have the eruption of the follicles or ovulation, egg is release.

Dominance Follicular Dynamics

Largest follicle will become the dominant, which ruptures and released oocyte. Secrets Low FSH, high LH, High Inhibin and Large amounts of estrogen.

Two cell, two gonadotropin model

In response to LH signaling in theca cells, peptide hormone signaling causes cAMP to activate Protein Kinase to convert cholesterol to testosterone. Testosterone goes to a granulosa cell and FSH (from blood) activates protein kinase. Testosterone becomes Estradiol and released into the blood and eventually to the Brain and Reproductive tract.

Estrogen's Action of Reproductive Tract

Increase blood flow, Genital swelling. Leukocytosis Increased mucosal secretion from vagina, to prepare for mating, flush foreign material. Initiation of uterine gland growth, Elevated myometrial tone.