Female Reproductive System
Summarize hormonal regulation of the uterine cycle
(1) GnRH stimulates the anterior pituitary to release FSH and LH, which stimulates follicle maturation and estrogen production. (2) When blood estrogens reach a certain level, positive feedback exerted on the hypothalamic-pituitary-gonadal axis causes a sudden release of LH that stimulates the primary oocyte to continue meiosis and trigger ovulation. LH then causes conversion of the ruptured follicle to a corpus luteum and stimulates its secretory activity. (3) Rising levels of progesterone and estrogens inhibit the hypothalamic-pituitary- gonadal (HPG) axis, the corpus luteum deterioirates, ovarian hormones drop to their lowest levels, and the cycle begins anew. While the ovarian cycle is about 28 days, maturation of a primordial follicle from its recruitment until it is ready to be ovulated takes about 290 days
Summarize hormonal regulation of the ovarian cycle
1. GnRH stimulates FS and LH secretion 2. FSH and LH stimulate follicles to grow, mature, and secrete sex hormones. FSH exerts its main effects on the granulosa cells of vesicular follicles, causing them to release estrogens, whereas LH prods the thecal cells to release androgens, which the granulosa cells convert to estrogens. Only tiny amounts of ovarian androgens enter the blood, because they are almost completely converted to estrogens within the ovaries. 3. Negative feedback inhibits gonadotropin release. As estrogen levels in the plasma rise, they exert negative feedback on the hypothalamus and anterior pituitary, inhibiting release of FSH. Inhibin, released by the granulosa cells, also exerts negative feedback controls on FSH release during this period. Only the dominant follicles fail to develop further. 4. Positive feedback stimulates gonadotropin release. Although the initial small rise in bloodborne estrogens inhibits the hypothalamic-pituitary-gonadal axis, once the dominant follicle becomes a mature vesicular follicle just before ovulation, the follicles produce high levels of estrogen. When estrogens reach a critical blood concentration, they briefly exert positive feedback on the hypothalamus and anterior pituitary. 5. LH surge triggers ovulation and formation of the corpus luteum. This LH surge rouses the primary oocyte of the mature vesicular follcile from its resting state and it completes its first meiotic division. 6. Negative feedback inhibits LH and FSH release
Of what does a primordial follicle consist?
A primary oocyte enveloped by a single layer of flattened squamous follicular cells; the primary oocyte is arrested in prophase I
List the external genitalia of the female and relate that to the homologous structures of the male reproductive system
Clitoris contains erectile tissue, homologous to the penis of the male Mons pubis fourchette labia majora: fatty skin folds homologous to male scrotum labia minora: two thin, hair-free skin folds homologous to the spongy urethra of the penis greater vestibular glands: release mucus into the vestibule and help to keep it moist and lubricated facilitating intercourse, homologous to bulbourethral glands bulbs of the vestibule: lie along each side of the vagina orifice and deep to the bulbospongiosus muscles are homologous of the single penile bulb and corpus spongiosum of the male
Summarize the events of the follicular and luteal phases of the ovarian cycle
During the follicular phase (day 1-14), several vesicular follicles are rescued from atresia and continue to grow. Generally, only one follicle per month is selected to become the dominant follicle and complete the maturation process. Late in this phase, the oocyte in the dominant follicle completes meiosis 1. Ovulation occurs about day 14, releasing the secondary oocyte into the peritoneal cavity. Other developing follicles deteriorate In the luteal phase (days 15-28), the ruptured follicle is converted to a corpus luteum, which produces progesterone and estrogens for the remainder of the cycle. If fertilization does not occur, the corpus luteum degenerates after about 10 days
List the extrauterine effects (effects that are revealed in structures outside the uterus) of estrogen and progesterone on the female body
Estrogen: Stimulate growth and maturation of reproductive organs and breasts at puberty and maintains their adult size and function. Promote long bone growth followed by epiphyseal closure, and feminization of the skeleton; inhibit bone reabsorption. Promote female pattern of fat deposit. Partially responsible for female libido. Progesterone: Cooperates with estrogen in stimulating growth of breasts. Promotes the secretory phase of the uterine cycle. During pregnancy, quiets the myometrium and acts with estrogens to cause mammary glands to achieve their mature milk-producing state. Metabolic effects-promotes diuresis (antiestrogenic effect). Increases body temperature
Compare and contrast oogenesis and spermatogenesis
Oogenesis: In females, oogenesis occurs prior to birth and at birth 2 1/2 million primary oocytes are made which is the greatest # of oocytes the female will have. b/c of the unequal divisions during meiosis we get a bigger and bigger cell. Most of the cytoplasm goes to the 2nd oocyte females invest more in the gametes at are produces. 3 cells are lost in female reproduction and only one female gamete is produced Spermatogenesis: gamete formation occurs relatively late to establishment of immune system
When in the ovarian cycle does ovulation typically occur?
Ovulation occurs around day 14 when the ovary wall ruptures and expels the secondary oocyte into the peritoneal cavity. There is an increased concentration of estrogen in blood prior to ovulation. Stimulus: Increased LH & FSH levels, stimulated by estrogen reaching threshold that stimulates activation
What is the major tissue found in each layer of the uterine walls?
Perimetrium: incomplete outermost serous layer Myometrium: bulky middle layer, composed of interlacing bundles of smooth muscle. The myometrium contracts rythmically during childbirth to expel the baby from the mother's body endometrium: mucosa that lines the uterine cavity consisting of simple columnar epithelium and a thick lamina propria. If fertilization occurs the young embryo burrows into the endometrium and resides there for the rest of its development
Describe primary, secondary, and vesicular (mature) follicles
Primary follice: have a single layer of cuboidal pregranulosa cells surrounding a primary oocyte Secondary follicle: have multiple layers of granulosa cells surrounding a primary oocyte Vesicular (antral) follicles: have a fluid filled cavity called an antrum. Just before ovulation, the primary oocyte inside the vesicular follicle resumes meiosis and becomes a secondary oocyte
What is the function of the corpus luteum?
Secretes estrogen and progesterone, which maintains the endometrium for the fetus and suppresses ovarian function which maintains early pregnancy.
Identify the three layers of the uterine wall
The Perimetrium is the incomplete outermost serous layer The myometrium is the bulky layer, composed of interlacing bundles of smooth muscle. The myometrium contracts rythmically during childbirth to expel the baby from the mother's body The endometrium is the mucosa that lines the uterine cavity. This mucosa consists of a simple columnar epithelium and a thick lamina propria. If fertilization occurs, the young embryo burrows into the endometrium (implants) and resides there for the rest of development
How do the roles of the functional layer and the basal layer of the endometrium differ?
The endometrium consists of a functional layer (stratum functionalis), which sloughs off periodically unless an embryo has implanted, and an underlying basal layer (stratum basalis) which rebuilds the functional layer
What is the function of the mucus secreted by the cervical glands?
The mucosa of the cervical canal contrains cervical glands that secrete a mucus that fills the cervical canal and covers the external os. This helps block the spread of bacteria from the vagina into the uterus. Cervical mucus also blocks sperm entry except at midcycle, when it becomes less viscous and allows sperm to pass through.
When during the menstrual cycle is a women most likely to become pregnant?
Uterine glands secrete nutrients, and endometrial vascularity increases further. This makes the uterus receptive to implantation about one week after ovulation.
Summarize the events of each phase of the uterine (menstrual cycle)
Varying levels of ovarian hormones in the blood trigger events of the uterine cycle During the menstrual phase of the uterine cycle (day 0-4), the functional layer sloughs off in menses. During the proliferate phase (day 5-14), rising estrogen levels stimulate its regeneration. Under the influence of both estrogens and progesterone during the secretory phase (days 15-28), the uterine glands secrete nutrients, and endometrial vascularity increases further. This makes the uterus receptive to implantation about one week after ovulation. Falling levels of ovarian hormones during the last few days of the ovarian cycle cause the spiral arteries to become spastic and cut off the blood supply of the functional layer. The uterine cycle begins again with menstruation
What is the corpus luteum? What is the corpus albicans
a estrogen /progesterone hormone-secreting structure that functions as an endocrine organ and develops in an ovary after an ovum has been discharged but degenerates after a few days unless pregnancy has begun. If fertilization doesn't occur, corpus luteum is going to degrade and is replaced by the corpus albicans which is a connective tissue and is remnants of the corpus luteum
Indicate whether each of the following cells are haploid or diploid: oogonia, primary oocyte, secondary oocyte, ovum, first polar body, second polar body
oogonia (Diploid) undergoes mitosis to form primary oocyte (Diploid) Meiosis #1 divides to form secondary oocyte (Haploid) ovum (Haploid) first polar body (Haploid) second polar body (Haploid)
Describe the structure and function of the following female reproductive structures: ovary, uterine tubes (oviduct or fallopian tubes), uterus, vagina, external genitalia
ovary: gamete formation (ova) and hormone secretion uterine tubes: receive the ovulated oocyte and are the site where fertilization generally occurs. Supported by the mesosalpinx, extends from near the ovary to the uterus. Movements of its ciliated distal projections, called fimbriae, along with peristalsis, create currents that help move an ovulated oocyte into the uterine tube uterus: The uterus has fundus, body, and cervical regions. It is supported by the broad, cardinal, uterosacral, and round ligaments. It is a Hollow, thick-walled, muscular organ that receives, retains, and nourishes a fertilized ovum. Usually inverted pear size in women who have not born children. The uterine wall is composed of the outer perimetrium, the myometrium, and the inner endometrium. vagina: provides a passageway for delivery of an infant and for menstrual flow extending from the uterus to the exterior. Because it receives the penis (and semen) during sexual intercourse, it is the female organ of copulation external genitalia (vulva): include the mons pubis, labia majora and minora, clitoris, and the urethral and vaginal orifices.
