Lecture 3: Female Reproductive Physiology: Terminology and basic concepts Flashcards
What is the most external surface of the ovary
Germinal epithelium
What is internal to the germinal epithelium of the ovary
Tunica albuginea
What region of the ovary contains follicles
Cortex
What region of the of the ovary with blood supply and lymphatics
Medulla
What are the two functions of the ovary
- Secrete hormones- estrogen and progesterone
- Produce oocytes
What is the order of events from primordial follicle to ovulating follicle or corpus albicans
- Primordial follicle
- Primary follicle (oocytes)
- Secondary follicle
- Tertiary follicle (developing antrum)
- Antral follicle
- Ovulating follicle exits ovary
OR - Corpus luteum forms
- Corpus albicans
When does the first mitotic division of the oogonium occur
Prior to birth
When are the stages of oogenesis
- Mitotic proliferation prior to birth to primary oocytes
- Arrested in first meiotic division
- After puberty, one primary oocytes reaches maturity and is ovulated for about once a month until menopause ensues-> enlarged primary oocytes
- First meiotic division completed just prior to ovulation—> creates first polar body and secondary oocytes
- Develop into second polar bodies
- Second meiotic division is completed after fertilization into mature ovum
Between birth and puberty follicles do not develop, what keeps follicles in arrest during this time
Oocytes inhibiting factor and luteinizing inhibiting factor
What factor keeps the oocyte in prophase I
Oocyte inhibiting factor
What factor prevents granulosa cells from becoming luteal tissue
Luteinizing inhibiting factor
What cells multiply by mitosis during gestation
Primordial germ cells
What cells develop 8-9 weeks gestation to after birth
Oogonia
What cells enter prophase I of meiosis and become primary oocytes
Oogonia
What cells arrest in prophase I of meiosis and then meiosis occurs before ovulation
Primary oocytes
Each oocyte is surrounded by a layer of ___ cells to make a follicle
Granulosa cells
What is the ovarian reserve
Stock of healthy follicles and oocytes. Number is established prior to birth and constantly decline from birth
How many follicles do female cows have at birth
100,000
How many follicles do female cows have at 12 months
75,000
How many follicles do female cows have at 4-6 years
21,000
How many follicles does an aged cow have
2,500
Follicles consist of what 3 types of cells
Oocyte, granulosa cells, theca cells
What is the zona pellucida
Layer of glycoproteins that occur between the oocyte and granulosa cells
The ___ membrane surrounds the outer layer of granulosa cells and the spindle-shaped theca cells
Basement
As follicles mature a fluid fluid ___ develops within the granulosa cells
Antrum
What is the interval between successive ovulations
Ovarian cycle
What are the two phases of the ovarian cycle
- Follicular phase
- Luteal phase
What dominates the follicular phase
Maturing follicles
The luteal phase is characterized by ___
Corpus luteum
What are the 3 cell types of the maturing follicle
- Primary oocyte
- Inner layer of granulosa cells
- Outer layer of thecal cells
What phase does the antrum form in
Follicular phase
What does the antrum secrete
Estrogen
When the antrum forms and starts secreting estrogen it becomes sensitive to what hormone
FSH
When does the dominant follicle (Graafian follicle) form
When first meiotic division completes
Rapid growth of the dominant follicle is driving by what hormone
FSH
What is the dominant follicle largely composed of
Largely antrum, oocyte encased in zona pellucida
In order for the dominant follicle to development what must it have
Receptors for FSH
What occurs when follicular cells release enzymes that weaken the follicular wall
Ovulation
What hormone drives differentiation into corpus luteum
LH
Ovulation is enhanced by increased ___ receptors
LH
What 3 things facilitate ovulation
- Hyperemia
- Collagenease synthesis by thecal cells
- Prostaglandin release by ovary stimulate smooth muscle contraction
Rupture if the follicular wall signals the end of the ___ phase and beginning of the ___ phase
End of follicular phase and beginning of the luteal phase
What does the corpus luteum produce large amounts of
Steroids due to cholesterol storage
If no fertilization occurs at the corpus luteum phase what happens
Corpus albicans develops due to formation of fibrous tissue
If fertilization occurs what happens to corpus luteum
Uterus releases hormones to notify body that you are pregnant and corpus luteum lifespan increases and maintains pregnancy
What regulates spontaneous ovulations
Internal hormonal cycles
___signals the release of gonadotropins
Estrogen
Which species have complete separation of luteal and follicular phase and what does that result in
Primates, results in rapid decline in hormones resulting in menstruation
How many days is ovarian cycle in primates
28 days
What animals have follicular growth at the end of luteal phase and what does it result in
Cows and horses- why they don’t get menstrual cycles
How many days id the ovarian cycle for cows and horses
17-21
What are induced ovulations
Animals that require copulation for ovulation
___ replaces estrogen as the signal that releases gonadotropins for induced ovulators
Copulation
What are some examples of induced ovulators
Rabbits, cats, and mustelids
What hormone stimulates cholesterol desmolase in thecal cells of corpus luteum in luteal phase
LH
FSH stimulates ___ in the granulosa cells
Aromatase
Enzymes for ___ synthesis become active only during luteal phase
Progesterone synthesis
What enzyme is used for progesterone synthesis
3B-hydroxysteroid dehydrogenase
What hormone stimulates the thecal cells in the ovarian follicle
LH
When thecal cells are stimulated they convert cholesterol to what
Androgen
Androgen diffuses from the thecal cells into adjacent ___ cells
Granulosa
What hormone stimulates granulosa cells in the ovarian follicle
FSH
Upon stimulation of granulosa cells androgen is converted to ___
Estrogen
Where are the two places estrogen can go after synthesized
- Part is secreted into the blood, where it exerts a systemic effect
- Part of the estrogen remains within the follicle and contributes to antral formation
Local estrogen along with FSH stimulate proliferation of ___ cells
Granulosa
How does the negative feedback work during the follicular phase
Increase estrogen and inhibin selectively inhibits FSH secretion
What hormone secretion is gradually increased over the follicular stage
LH
What hormone recruits follicles to become dominant
FSH
The effect of estrogen changes from negative feedback to positive feedback leading to the ___ surge
LH
___ of oocyte resumes under the influence of LH surge
Meiosis
___ release breaks down the follicular wall
Prostaglandin
Follicular cells with differentiate into ___ cells right before ovulation
Luteal
What hormone has a strong negative feedback suppressing second LH surge during luteal phase
Progesterone
What hormone causes regression of corpus luteum in cows, horses, goats, sheep and pigs at 14 days during absent of pregnancy
Prostaglandins (PGF2alpha)
During pregnancy what hormone is inhibited in most domestic animals
PGF2alpha
What hormone do primates release during pregnancy that rescues the corpus luteum
Chorionic gonadotropin (hCG)
Describe the follicular phase and negative feedback
- Hypothalamus releases GnRH
- GnRH stimulates anterior pituitary
- Anterior pituitary releases FSH and LH
- FSH act on ovary to release estradiol
- Negative feedback: estradiol inhibits anterior pituitary release of FSH and hypothalamus
What hormone is responsible for negative feedback in follicular phase
Estradiol
Where does estradiol act on in negative feedback in follicular phase
Anterior pituitary releasing FSH and hypothalamus
Describe the midcycle positive feedback loop
- Hypothalamus releases GnRH onto anterior pituitary
- Anterior pituitary releases FSH and LH which act on ovary
- Ovary releases estradiol
- Estradiol acts on hypothalamus to release GnRH and anterior pituitary to increase LH release from anterior pituitary and
What is the negative feedback loop in the luteal phase
- Hypothalamus releases GnRH onto anterior pituitary
- Anterior pituitary releases FSH and LH onto ovary
- Ovary releases progesterone
- Progesterone acts to inhibit release of GnRH from hypothalamus and anterior pituitary to release LH
What occurs during menstrual phase
Shedding of the previous endometrium (mostly a human trait because most species have an overlap between luteal and next follicular phase)
What happens during proliferative phase
Endometrium regenerate
What happens during secretory phase
Endometrium enriched with glycogen to nourish an incoming embryo before it implants into uterine wall
What hormone is primarily released during basal layer
Estrogen
What hormone is primarily released from secretory phase
Progesterone
What hormones stimulate oocyte development and follicle growth
FSH and LH
What hormone does FSH and LH promote release of in follicular and luteal changes in ovary
Estrogen
When does LH burst occur
To trigger ovulation
What hormone stimulates development and maintenance of corpus luteum
LH
How are estrogen and progesterone levels during menstrual cycle
Low
What hormone causes thickening of endometrium
Estrogen
What hormone increases number of blood vessels and secretory glands in endometrium
Progesterone
What phases does the ovarian cycle have
Follicular, ovulation, luteal phase
What phases do uterine cycles have
Menstrual phase, proliferative phase, secretory phase
What is estrus
Time of sexual receptivity
What occurs at end of estrus
ovulation
Metestrus
Early post ovulators phase during which CL begins development
What is diestrus
Phase of mature luteal activity which begins about 4 days after ovulation and ends with regression of CL
Is there any reproductive receptivity in diestrus cycle
No!
What hormone is present during diestrus
Progesterone
Proestrus
Phase beginning after CL regression and ending with onset of estrus. Rapid follicle development leads to ovulation and onset of sexual receptivity
In what estrous cycle do animals behaviorally start showing signs of going into estrus and could have fluid at vulva
Proestrus
What are follicular waves
Simultaneous development of multiple follicles
Which species have 1 dominant follicle while the remainder follicles become atretic
Cows, horses, human
What species can select more than one dominant follicle but also have atretic ones
Dog, cat, sheep and goats
What are the four stages of follicular waves
- Recruitment
- Selection
- Dominance
- Atresia
How are follicles recruited
Primordial follicles release FSH- causing them to increase in size
What happens during selection phase
Increase in size and receptors
What happens during dominant stage of follicular wave
Lots of estrogen
What happens during atresia follicular waves
CL producing progesterone
How many follicular waves can cows have
4
How many waves do heifer at puberty have
1
How many waves do mature cow have after calving
1
How many follicular waves do bos Taurus have
1-3
How many follicular waves do Bo’s indicus have
1-4
What causes pulsatile release of FSH during follicular waves
Decrease inhibin so not blocking FSH
What generates follicular waves
FSH
How is a single follicle selected
Dominant follicles are more sensitive to FSH because they have more FSH receptors and are selected
___ is utilized to stimulate granulosa cell growth to increase aromatase activity, to synthesize inhibin and produce estradiol
FSH
Inhibin blocks ___ synthesis and secretion
FSH
What hormone is high and inhibits final development and ovulation
Progesterone
If progesterone is low the dominant follicle can enter ___
Ovulation
Estrus occurs during a period of high ___ released from mature follicles
Estrogen
Mating induces ovulation via neural stimulation of ____ in induced ovulators
GnRH
Maximum LH surge requires ___ copulations
8-12
What are the steps in ovulation induced in the queen
- Stimulation of the vagina and cervix
- Neural signal to the hypothalamus
- GnRH release
- LH surge
- Ovulation
