REPRODUCTIVE
Fertilization and Early Development
1.Egg Transport 2. Intercourse, Sperm Transport, and Capacitation- Of the several hundred million sperm in an ejaculation, only about 100 to 200 reach the fallopian tube. 3. Fertilization
In males, this usually occurs during ___ and ____ years old
12 and 16 years of age
The blastocyst implants in the uterus on about the ________ day of the 28-day menstrual cycle. At this time, the endometrium is ________ and progesterone levels are ________.
21st; thick and secretory; high
Summary of the Menstrual Cycle: Day 7
A single follicle (usually) becomes dominant.
These are statements regarding endocrine regulation of breast function in females.
A) During puberty, ductal growth is stimulated by increasing estrogen levels in plasma. B) During puberty, progesterone stimulates the growth of breast alveoli. C) During pregnancy, the main source of plasma prolactin is secretion from the maternal anterior pituitary gland. D) Breast development fluctuates with changing blood concentrations of estrogen and progesterone during each menstrual cycle.
True statements regarding the control of parturition
A) Oxytocin secretion is stimulated by cervical dilation. B) Coordinated uterine contractions cause the cervix to dilate. c) Prostaglandins stimulate myometrial contractions. d) Stretching of the myometrium is one signal that begins uterine contractions.
Shedding of the endometrial lining occurs?
As a result of a fall in plasma levels of estradiol and progesterone.
The follicular phase of the ovarian cycle coincides with which phase or phases of the uterine cycle?
Both the menstrual phase and the proliferative phase
Maternal Responses to Pregnancy: Body Weight: Circulatation
Cardiac output increases, total peripheral resistance decreases (vasodilation in uterus, skin, breasts, GI tract, and kidneys), and mean arterial pressure does not change appreciably
Summary of the Menstrual Cycle:Days 25-28
Corpus luteum degenerates (if implantation of the conceptus does not occur). Therefore: Plasma estrogen and progesterone concentrations decrease. Therefore: Endometrium begins to slough at conclusion of day 28, and a new cycle begins.
Summary of the Menstrual Cycle: Day 15 to 25
Corpus luteum forms and, under the influence of low but adequate levels of LH, secretes estrogen and progesterone, increasing plasma concentrations of these hormones. Therefore: a. Secretory endometrium develops. b. Secretion of FSH and LH from the anterior pituitary gland is inhibited, lowering their plasma concentrations. Therefore: No new follicles develop.
Ejaculation
Ejaculation is primarily a spinal reflex mediated by afferent pathways from penile mechanoreceptors.
Maternal Responses to Pregnancy: Breasts
Enlarge and develop mature glandular structure Cause: Estrogen, progesterone, prolactin, and human placental lactogen
Summary of the Menstrual Cycle: Days 1 to 5
Estrogen and progesterone are low because the previous corpus luteum is regressing. Therefore: a. Endometrial lining sloughs. b. Secretion of FSH and LH is released from inhibition, and their plasma concentrations increase. Therefore: Several growing follicles are stimulated to mature.
What is TRUE during the luteal phase of the menstrual cycle?
Estrogen concentration in the plasma is high, but progesterone concentration rises even higher.
When does estrogen peak?
Estrogen peaks in the late follicular phase and middle of the luteal phase.
Summary of Systemic Plasma Hormone Concentrations and Ovarian Events During the Menstrual Cycle
Estrogen peaks in the late follicular phase and middle of the luteal phase. Progesterone peaks in the middle of the luteal phase. FSH increases in the middle of the follicular phase and peaks just before ovulation. LH remains fairly low, except for a peak just before ovulation. During the follicular phase, ovarian follicles are maturing, and the dominant follicle is ovulated at the end of the phase. During the luteal phase, the corpus luteum is active; in the absence of fertilization, it degenerates during the last few days of this phase.
Major Feedback Effects of Estrogen, Progesterone, and Inhibin
Estrogen, in low plasma concentrations, causes the anterior pituitary gland to secrete less FSH and LH in response to GnRH and also inhibit the hypothalamic neurons that secrete GnRH. Result: Negative feedback inhibition of FSH and LH secretion during the early and middle follicular phase.
Major Feedback Effects of Estrogen, Progesterone, and Inhibin
Estrogen, when increasing dramatically, causes anterior pituitary gland cells to secrete more LH and FSH in response to GnRH. Estrogen also stimulates the hypothalamic neurons that secrete GnRH. Result: Positive feedback stimulation of the LH surge, which triggers ovulation.
Ovulation
Expulsion of the mature oocyte (ovulation)
When does FSH peak?
FSH increases in the middle of the follicular phase and peaks just before ovulation
During the early part of the menstrual cycle, ________ acts on granulosa cells, which ________. ________ acts on theca cells, which ________.
FSH; convert androgens to estrogens; LH; synthesize androgens
The onset of puberty is triggered by an increase in
GnRH secretion.
Major Feedback Effects of Estrogen, Progesterone, and Inhibin
High plasma concentrations of progesterone, in the presence of estrogen, inhibit the hypothalamic neurons that secrete GnRH. Result: Negative feedback inhibition of FSH and LH secretion and prevention of LH surges during the luteal phase and pregnancy
The corpus luteum persists in pregnancy because the implanting blastocyst secretes:
Human chorionic gonadotropin (hCG). Human chorionic gonadotropin maintains the corpus luteum!!!!
Maternal Responses to Pregnancy: Respiration
Hyperventilation occurs (arterial P_(CO_2 ) decreases) due to the effects of increased progesterone
Maternal Responses to Pregnancy: Nutritional RDAs*
Increased
Maternal Responses to Pregnancy: Bone turnover
Increased Cause: Increased parathyroid hormone and 1,25-dihydroxyvitamin D
Maternal Responses to Pregnancy: Blood Volume
Increased Cause: Total erythrocyte number increased by erythropoietin, and plasma volume by salt and water retention; however, plasma volume usually increases more than red cells, thereby leading to small decreases in hematocrit
Maternal Responses to Pregnancy: Appetite and Thirst
Increased (particularly after the first trimester)
Maternal Responses to Pregnancy: Body Weight
Increased by average of 12.5 kilograms, 60% of which is water
Maternal Responses to Pregnancy: Adrenal Cortex
Increased secretion of aldosterone and cortisol
Maternal Responses to Pregnancy: Parathyroids
Increased secretion of parathyroid hormone
Maternal Responses to Pregnancy: Posterior Pituitary Gland
Increased secretion of vasopressin
Major Feedback Effects of Estrogen, Progesterone, and Inhibin
Inhibin acts on the pituitary gland to inhibit the secretion of FSH. Result: Negative feedback inhibition of FSH secretion.
How does estradiol increase the likelihood that an egg will be fertilized?
It changes cervical mucus to a watery consistency that allows sperm to penetrate the cervix
Implantation of a blastocyst:
It normally occurs midway through the luteal phase.
LH cycle
LH remains fairly low, except for a peak just before ovulation.
Summary of the Menstrual Cycle: Days 12 to 13
LH surge is induced by increasing plasma estrogen secreted by the dominant follicle (positive feedback). Therefore: a. Oocyte is induced to complete its first meiotic division and undergo cytoplasmic maturation. b. Follicle is stimulated to secrete digestive enzymes and prostaglandins.
Events Leading to Fertilization
Many sperm attempt to penetrate the zona pellucida, via the acrosome reaction, which releases enzymes. Only 1 sperm penetrates the egg membrane. Now the egg releases enzymes that enter the zona pellucida to prevent polyspermy. As the penetrating sperm enters the egg, the egg completes meiosis II, the sperm and egg nuclei unite, and the zygote starts embryogenesis.
If the amount of progesterone in the blood remained at the level seen in the middle of the luteal phase for 6 straight months, what would the effect be on menstruation?
Menstruation would not occur.
Maternal Responses to Pregnancy: Organic Metabolism
Metabolic rate increases Plasma glucose, gluconeogenesis, and fatty acid mobilization all increase Cause: Hyporesponsiveness to insulin due to insulin antagonism by human placental lactogen and cortisol
Sydney had an infection 10 years ago that left scarring in her fallopian tubes. Due to this scarring, the diameter of the fallopian tubes has been reduced by 75%. What effects may Sydney experience?
Oocytes may not reach the uterus.
What would be the effect of cutting the fallopian tubes at their midpoints?
Ova would not travel from the ovaries to the uterus.
Summary of the Menstrual Cycle: Day 14
Ovulation is mediated by follicular enzymes and prostaglandins.
Summary of the Menstrual Cycle: Days 7 to 12
Plasma estrogen increases because of secretion by the dominant follicle. Therefore: Endometrium is stimulated to proliferate. LH and FSH decrease due to estrogen and inhibin negative feedback. Therefore: Degeneration (atresia) of nondominant follicles occurs.
What is a TRUE statement about events occurring in the menstrual cycle?
Progesterone is low during the first half of the cycle, and rises to a peak during the second half.
When does progesterone peak?
Progesterone peaks in the middle of the luteal phase.
Puberty
Puberty is the period during which the reproductive organs mature and reproduction becomes possible.
Maternal Responses to Pregnancy: Placenta
Secretion of estrogen, progesterone, human chorionic gonadotropin, inhibin, human placental lactogen, and other hormones
Summary of Ovarian Events During a Menstrual Cycle (if Fertilization Does Not Occur) Long Description
The ovarian events of many follicles maturing (days 1 to 6), one becoming dominant (day 7), and the dominant follicle maturing (days 8 to 13) occur during uterine bleeding and the follicular phase in the uterus. Ovulation occurs on day 14. During the luteal phase, the corpus luteum functions (days 15 to 24); in the absence of fertilization, the corpus luteum degenerates (days 25 to 28).
perimenopause
The phase of life during which menstrual irregularity begins
Development of a Human Oocyte and Ovarian Follicle
The primary follicle, the oocyte grows, granulosa cells multiply, and the zona pellucida develops. In the preantral follicle, the granulosa cells proliferate even more and an early theca develops outside the follicle. In the early antral follicle, the antrum starts accumulating fluid. In the mature follicle, the oocyte is attached to one side of the follicle by the cumulus oophorus, almost surrounded by the crescent-shaped antrum; there are several layers of granulosa cells and a well-developed theca.
menopause
Ultimately, menstrual cycles cease entirely in all women; when this period exceeds 12 months
If you start at the plasma membrane of an oocyte in a mature follicle and move outward, which is the correct order in which you would encounter the three structures listed below?
Zona pellucida; granulosa cells; theca cells
The acrosome reaction is triggered by
binding of the heads of sperm to the zona pellucida.
Hormonal control during pregnancy is
by the placenta is provided with androgens by the maternal ovaries and adrenal glands, and by the fetal adrenal glands.
The placenta
is a site of diffusion and transport of wastes, oxygen, and nutrients between fetal and maternal blood.
Beginning on the first day of the menstrual cycle, the order of phases in the uterus is:
menstrual, proliferative, secretory.
Rebecca's younger sister just told her that she has begun menopause. Rebecca wonders if she has begun menopause as well. One of the symptoms to watch out for is
the cessation of menstrual cycles.
Kathryn is pregnant and very eager to breast-feed after the baby is born. Her friend gives her a supplement to encourage prolactin secretion and Kathryn starts to take it during pregnancy. The supplement works and Kathryn's blood level of prolactin increases. She does not begin lactating during pregnancy because
the high levels of estrogen and progesterone in maternal plasma inhibit the effects of prolactin.
Oogenesis
the production of gametes during the fetal period
When the level of stimulation is high enough, a patterned sequence of discharge of the efferent neurons ensues. This sequence can be divided into two phases:
•(1) The smooth muscles of the epididymis, vas deferens, ejaculatory ducts, prostate, and seminal vesicles contract as a result of sympathetic nerve stimulation, emptying the sperm and glandular secretions into the urethra (emission); and •(2) the semen, with an average volume of 3 milliliters and containing 300 million sperm, is then expelled from the urethra by a series of rapid contractions of the urethral smooth muscle as well as the skeletal muscle at the base of the penis.
Some Effects of Female Sex Steroids: Estrogen
•Stimulates growth of ovary and follicles (local effects) •Stimulates growth of smooth muscle and proliferation of epithelial linings of reproductive tract; in addition: •Fallopian tubes: increases contractions and ciliary activity •Uterus: increases myometrial contractions and responsiveness to oxytocin; stimulates secretion of abundant, watery cervical mucus; prepares endometrium for progesterone's actions by inducing progesterone receptors •Vagina: increases layering of epithelial cells •Stimulates external genitalia growth, particularly during puberty •Stimulates breast growth, particularly ducts and fat deposition during puberty •Stimulates female body configuration development during puberty: narrow shoulders, broad hips, female fat distribution (deposition on hips and breasts) •Stimulates fluid secretion from lipid (sebum)-producing skin glands (sebaceous glands); (This "anti-acne" effect opposes the acne-producing effects of androgen.) •Stimulates bone growth and ultimate cessation of bone growth (closure of epiphyseal plates); protects against osteoporosis; does not have an anabolic effect on skeletal muscle •Vascular effects (deficiency produces "hot flashes") •Has feedback effects on hypothalamus and anterior pituitary gland (see Table 17.4) •Stimulates prolactin secretion but inhibits prolactin's milk-inducing action on the breasts •Protects against atherosclerosis by effects on plasma cholesterol (Chapter 16), blood vessels, and blood clotting (Chapter 12)
On day 14 of a typical 28-day menstrual cycle, LH concentration in the blood will be ________. The endometrium will be ________. Estrogen concentration in the blood is ________.
(at or near a peak; near the end of the proliferative phase; relatively high)
On day 1 of the menstrual cycle, FSH levels will be ________. The follicle that will become dominant is in the ________ stage of maturation. Progesterone levels in blood are ________.
(rising; preantral to antral; low)
True statements about estrogen in females!!!!!!!!!!!!!!!!
* In low plasma concentration, estrogen inhibits pituitary secretion of LH and FSH. * In high plasma concentration, estrogen stimulates pituitary sensitivity to GnRH. * Estrogen secretion is required for the LH surge. * Estrogen stimulates follicular growth.
Maternal Responses to Pregnancy: Anterior Pituitary Gland
* Increased secretion of prolactin * Secretes very little FSH and LH
Maternal Responses to Pregnancy: Kidneys
* Increased secretion of renin, erythropoietin, and 1,25-dihydroxyvitamin D * Retention of salt and water Cause: Increased aldosterone, vasopressin, and estrogen
Some Effects of Female Sex Steroids: Progesterone
* It induces thick, sticky mucus in the cervix. * It inhibits the milk-inducing effects of prolactin. * It increases body temperature. * It exerts negative feedback on the hypothalamus and anterior pituitary.
Menopause
* Menopause and the irregular function leading to it are caused primarily by ovarian failure. The ovaries lose their ability to respond to the gonadotropins, mainly because most, if not all, ovarian follicles and eggs have disappeared by this time through atresia. * The hypothalamus and anterior pituitary gland continue to function relatively normally as demonstrated by the fact that the gonadotropins are secreted in greater amounts. The main reason for this is that the decrease in plasma concentrations of estrogen and inhibin result in less negative feedback inhibition of gonadotropin secretion.
Ovarian functions
* Oogenesis * Expulsion of the mature oocyte (ovulation) * Secretion of the female sex steroid hormones (estrogen and progesterone), as well as the protein hormone inhibin
The function of estrogen during pregnancy is
* Stimulation of myometrial growth * Maintenance of the endometrium * Stimulation of prolactin secretion * Stimulationof breast development
