The Female Reproductive System

Flashcards about the female reproductive system, covering puberty, oogenesis, folliculogenesis, and the menstrual cycle.

What triggers puberty in girls?

Rising levels of GnRH from the hypothalamus, stimulating the anterior pituitary to secrete FSH and LH.

What are the feminizing hormones secreted by ovarian follicles?

Estrogen (estradiol, estriol, estrone), progesterone, inhibin, and a small amount of androgen.

How do estrogen and progesterone affect FSH and LH secretion?

They suppress FSH and LH secretion through negative feedback.

How does inhibin affect FSH secretion?

Inhibin selectively suppresses FSH secretion.

What is Thelarche?

The onset of breast development, triggered by estrogen, progesterone, and prolactin.

What is Pubarche?

The appearance of pubic and axillary hair, sebaceous glands, and axillary glands stimulated by androgens.

What is Menarche?

The first menstrual period, requiring at least 17% body fat.

What happens when body fat and leptin levels drop too low?

Gonadotropin secretion declines, and the menstrual cycle might cease.

What is the primary action of progesterone?

To prepare the uterus for possible pregnancy in the second half of the menstrual cycle.

What is Climacteric?

Midlife change in hormone secretion, accompanied by menopause (cessation of menstruation).

What happens to the ovaries during climacteric?

Follicles become less responsive to gonadotropins and secrete less estrogen and progesterone.

What is Menopause?

Cessation of menstrual cycles, usually between ages 45 and 55.

What is the reproductive cycle?

Sequence of events from fertilization to giving birth and returning to fertility.

What is the sexual cycle?

Events that recur every month when pregnancy does not intervene, consisting of the ovarian and menstrual cycles.

What is oogenesis?

Egg production, which produces haploid gametes by meiosis.

When do female germ cells colonize gonadal ridges?

The first 5 to 6 weeks of development.

What are oogonia?

The cells that female germ cells differentiate into.

What is atresia?

The degeneration of primary oocytes before birth.

Define Ovum.

Any stage from the primary oocyte to the time of fertilization.

How many times will a woman likely ovulate?

Probably only 480 times.

How is the secondary oocyte produced?

The primary oocyte divides into two haploid daughter cells. The larger daughter cell is the secondary oocyte.

What happens to the secondary oocyte if it is not fertilized?

If not fertilized, it dies and never finishes meiosis.

What is Folliculogenesis?

Development of the follicles around the egg that undergoes oogenesis.

What are primordial follicles?

A single layer of squamous or cuboidal follicular cells surrounding a primary oocyte in early meiosis.

What happens to primordial follicles in the adult ovary?

Adult ovary has 90% to 95% primordial follicles.

How long is the monthly recruitment that about 24 follicles begins toward maturity?

290-day path to maturity that only one will finish (about 23 die).

What are primary follicles?

Recruited primordial follicles that contain larger, primary oocytes and a surrounding layer of cuboidal follicular cells that are developed about 140 days into the cycle.

When do secondary follicles appear?

Appear about 170 days into cycle. The primary oocytes are even larger and follicular cells are now in two or more layers (granulosa cells).

What is the zona pellucida?

Layer of glycoprotein gel secreted by the primary oocyte (will surround itself).

What is the theca folliculi?

Connective tissue around the granulosa cells condenses to form a fibrous husk.

What is the difference between the theca externa and theca interna?

Theca externa: outer fibrous capsule rich in blood vessels. Theca interna: inner cellular, hormone-secreting layer producing androgens, and granulosa cells convert them to estradiol.

When do tertiary follicles appear?

Appear about 230 days into cycle.

What are antral follicles?

Tertiary and mature follicles where granulosa cells begin secreting follicular fluid into small pools; as pools enlarge, they merge, forming a single antrum.

What is the cumulus oophorus?

A mound of granulosa cells on one side of the antrum that covers the primary oocyte and secures it to the follicular wall.

What is the corona radiata?

Innermost layer of cells in the cumulus surrounding zona pellucida and primary oocyte, that forms a protective barrier around egg with function similar to blood–testis barrier.

How long before ovulation does one follicle mature while the others degenerate?

About 10 days before ovulation, one follicle becomes dominant.

What is considered a preovulatory (graafian) follicle?

The dominant follicle about 5 days before ovulation.

What happens due to the LH surge?

Triggers completion of Meiosis I (generating 2nd ary oocyte and polar body) then ovulation happens.

What is the average length of the sexual cycle?

Averages 28 days, but varies from 20 to 45 days.

What is the hierarchy of hormonal control in the sexual cycle?

Hypothalamus -> pituitary -> ovaries -> uterus.

What are the three principal steps within the Ovarian Cycle?

Follicular phase, ovulation, and luteal phase.

What occurs during the first 3 to 5 days of the follicular phase?

Menstruation occurs during first 3 to 5 days of cycle; uterus replaces lost tissue by mitosis and cohort of follicles grow.

When does ovulation occur?

Ovulation around day 14: remainder of that follicle becomes corpus luteum.

What happens during the luteal phase?

Corpus luteum stimulates endometrial secretion and thickening; if pregnancy does not occur, endometrium breaks down in the last 2 days; menstruation begins and the cycle starts over.

When does the follicular phase extend to?

From beginning of menstruation until ovulation (Days 1-14).

What stimulates follicles to grow and secrete estradiol?

FSH.

When does ovulation typically occur?

Typically around day 14.

What does estradiol stimulate?

A surge of LH and a lesser spike of FSH by anterior pituitary.

What does LH induce?

Several events including, primary oocyte completes meiosis I, Follicular fluid builds rapidly and follicle swells, Macrophages and leukocytes secrete enzymes that weaken follicle wall, and a nipple-like stigma appears on surface.

Describe how ovulation takes place?

Stigma seeps follicular fluid for 1 to 2 minutes. Follicle bursts and remaining fluid oozes out carrying the secondary oocyte and cumulus oophorus. Normally swept up by ciliary current and taken into uterine tube.

What happens with the uterine tube to prepare to catch oocyte?

It swells with edema, its fimbriae envelop and caress the ovary in synchrony with the woman’s heartbeat, and cilia create gentle current in nearby peritoneal fluid.

Signs of ovulation

Cervical mucus becomes thinner and more stretchy and resting body temperature rises 0.4° to 0.6°F.

What is Mittelschmerz?

Twinges of pain at time of ovulation.

What is the best time for conception?

Within 24 hours after the cervical mucus changes and the basal temperature rises.

What are the key events in the luteal phase?

When follicle ruptures it collapses and bleeds into antrum, clotted blood is slowly absorbed, granulosa and theca interna cells multiply and fill antrum, and a dense bed of capillaries grows amid them.

What are lutein cells?

Cells within the corpus luteum with yellow lipid that accumulates in theca interna cells.

What regulates transformation from ruptured follicle to corpus luteum?

LH stimulates corpus luteum to grow and secrete rising levels of estradiol and progesterone.

Why is it crucial for progesterone to be secreted during the luteal phase?

Progesterone has a crucial role in preparing the uterus for possibility of pregnancy.

What is the process of involution?

Corpus luteum begins process of involution (shrinkage) beginning about day 22 (8 days after ovulation); by day 26 involution is complete and what was corpus luteum becomes corpus albicans—small scar.

What happens with diminishing ovarian steroid secretion?

FSH levels rise, ripening a new cohort of follicles.

What happens to the ovaries during monthly ovulation?

Ovulation occurs in one ovary per cycle with the two ovaries usually alternating from month to month.

What is the menstrual cycle?

A buildup of endometrium during most of the sexual cycle, followed by its breakdown and vaginal discharge.

What are the four phases of the menstrual cycle?

Proliferative phase, secretory phase, premenstrual phase, and menstrual phase.

What is the first day of the sexual cycle?

First day of noticeable vaginal discharge is defined as day 1 of the sexual cycle.

What occurs during the proliferative phase?

Rebuilding of functional layer of endometrium that was lost in last menstruation; estrogen stimulates mitosis in basal layer and regrowth of blood vessels to regenerate the functional layer; Estrogen also stimulates endometrial cells to produce progesterone receptors.

How thick is the endometrium by Day 14 in the proliferative phase?

2 to 3 mm thick.

What occurs during the secretory phase?

Endometrium thickens more in response to progesterone from corpus luteum; thickening due to secretion and fluid accumulation rather than mitosis; endometrial glands secrete glycogen, become wider, longer, and more coiled creating a soft, wet, nutritious bed available for embryonic development.

How thick is the endometrium during the secretory phase?

5 to 6 mm thick.

What occurs during the premenstrual phase?

Corpus luteum atrophies and progesterone levels fall, triggers spasmodic contractions of spiral arteries causing endometrial ischemia, tissue necrosis and menstrual cramps, and pools of blood accumulate in the functional layer as necrotic endometrium mixes with blood and serous fluid (menstrual fluid).

What occurs during the menstrual phase?

Discharge of menstrual fluid from the vagina.

How much blood and serous fluid does an average woman expel during menstruation?

About 40 mL of blood and 35 mL of serous fluid over a 5-day period, containing fibrinolysin so it does not clot.