Week 6: Female Endocrinology
Week 6: Female Endocrinology Biol360
Cal State Fullerton
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This 6 page Class Notes was uploaded by Monique Magpayo on Sunday March 6, 2016. The Class Notes belongs to Biol360 at California State University - Fullerton taught by Maryanne Menvielle in Spring 2016. Since its upload, it has received 29 views. For similar materials see Biology of Human Sex in Biology at California State University - Fullerton.
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Date Created: 03/06/16
CH 2. Pg 4759 Female Endocrinology BOOK NOTES The OVARIES – a woman’s GONADS are paired organs located on either side of the uterus OVARIES are egg shaped structures measuring about 1 to 1.5 inches long. o OVARY the female gonad; the organ that produces the ova and secretes sex hormones o GONAD an organ that produces ova or sperm and secretes sex hormones Under the microscope, an adult woman’s ovary can be seen to contain a large number of follicles at various stages of development o FOLLICLE a fluid filled sac that contains an egg (ovum), with its supporting cells, within the ovary. Each FOLLICLE consists of an ovum, or egg cell, surrounded by fluids and supporting cells. o OVUM a female gamete or egg THE OVARIES 2 DISTINCT FUNCTIONS o 1) first is to release the ova in a process called OVULATION OVULATION: the release of an ovum from an ovary. A new born female has about a million undeveloped ovum in each ovary, but the numbers decline throughout life By puberty, a woman has about 200,000 ova in each ovary. During her reproductive life she typically releases only one mature ovum per menstrual cycle. so only a few ova are actually ovulated over time. Much greater numbers die and are reabsorbed in the body OVULATION occurs when an ovary’s wall ruptures and releases an ovum and its surrounding cells. The FIMBRIA of the nearby oviduct catches the ovum, and the CILIA propel it into the OVIDUCT, where fertilization may occur if sperm are present o 2) the second function of the ovaries is the PRODUCTION AND SECRETION OF SEX HORMONES These sex hormones regulate the monthly menstrual cycle. The ovarian hormones are mostly SEX STEROIDS, which are fatty compounds derived from cholesterol. SEX STEROID any of the steroid hormones that are active in sexual and reproductive processes o SEX STEROIDS come in 3 classes 1 ESTROGENS (of which the main representative is ESTRADIOL) o ESTROGENS any of a class of steroidsmost important being estradiol that promote the development of female secondary sexual characteristics at puberty and that have many other functions in both sexes. ESTRADIOL the principal estrogen, secreted by ovarian follicles. ESTRADIOL is produced in the GONADS MAIN TARGET: widespread in body and brain MAIN HORMONAL ACTIONS o Feminizes body at puberty; o contributes to menstrual cycle; o increases density of bone; o ends growth of limb bones at puberty; o feedback inhibition of gonadotropins; o maintains sex drive. 2PROGESTINS (main rep: PROGESTERONE) o PROGESTINS any class of steroids, the most important being progesterone, that cause the endometrium to proliferate and help maintain pregnancy PROGESTERONE a steroid hormone secreted by the ovary and the PLACENTA; it is necessary for the establishment and maintenance of pregnancy. PROGESTERONE is produced in the OVARY (corpus luteum), placenta MAIN TARGETS the uterus MAIN HORMONAL ACTIONS contributes to menstrual cycle; maintains pregnancy 3 ANDROGENS (main rep: TESTOSTERONE) o ANDROGENS any class of steroids most important being testosterone that promote male sexual development and that have a variety of other functions in both sexes TESTOSTERONE the principal androgen, synthesized in the testicles and in lesser amounts, in the ovaries and adrenal glands. T is produced in the Gonads, adrenal cortex MAIN TARGET widespread in body and brain MAIN HORMONAL ACTIONS Masculinizes body and brain during fetal development and at puberty. Anabolic effects maintains sex drive; feedback inhibition of gonadotropins 5 (ax) DIHYDRO TESTOSTERONE is produced in the external genitalia, prostate gland, skin (converted from testosterone) MAIN TARGET: external genitalia, prostate gland, skin MAIN HORMONAL ACTIONS Development and maintenance of male external genitalia and prostate gland; adult male patterns of hair distribution Both male and female gonads (ovaries and testes) make all three classes of sex steroids, but in differing amounts. OVARIES secretes large quantities of ESTROGEN AND PROGESTINS and a small amount of ANDROGENS which are supplied by the adrenal glands o MEDICAL CONTITIONS that affect the ovaries. OVARIAN CANCER (asymptomatic, must be tested if you had family history of it, ) There is abdominal swelling, a constant feeling of a need to urinate or defecate, digestive problems, or pain in the pelvis, back, or leg. OVARIAN CYSTS cysts within the ovary that can arise from a number of different causes POLYCYSTIC OVARY SYNDROME (PCOS) a condition marked by excessive secretion of androgens by the ovaries MENARCHE the onset of menstruation at puberty. o THE FEEDBACK LOOK THAT CONTROLS FEMALE HORMONE PRODUCTION Ovulation and hormone secretion are regulated by a three segment control loop that involves the passage of hormones between the BRAIN, THE PITUITARY GLAND, AND THE OVARIES o 1) First a small region at the base of the brain called the HYPOTHALAMUS (a small region at the base of the brain; it contains cells involved in sexual responses and other basic functions.) secretes GONADOTROPINRELEASING HORMONE (GnRH) into local vessels that carry it to a nearby PITUITARY GLAND (a gland situated below and under the control of the hypothalamus; its anterior lobe secretes gonadotropins and other hormones) o There, it activates cells that manufacture and secrete 2 more hormones (FSH) FOLLICLE STIMULATING HORMONE stimulates the development of ovarian follicles to the point that they are capable of ovulation. FSH is one of the two major gonadotropins secreted by the pituitary gland; it promotes maturation of ova (or sperm in males) (LH) LUTENIZING HORMONE triggers ovulation itself, and it also causes the release of sex steroids by the ovaries. LH One of the two major gonadotropins secreted by the pituitary gland; it triggers ovulation and promotes the secretion of sex steroids by the ovaries (or testicles) Because these two hormones act on the gonad (in women, the ovaries) they are named GONADOTROPINS, meaning gonadinfluencing substances GONADOTROPINS hormones that regulate the functions of the gonad o 2) these two hormones enter the general blood circulation and reach their targets, the OVARIES FSH and LH target is the ovaries o 3) in the third section of the loop, ovarian hormones pass via the general circulation system to the hypothalamus and pituitary gland, where they influence the release of GnRH, FSH, and LH. This feedback influence is inhibitory of low estrogen levels, but switches to stimulation at high levels o PROTEINS/PEPTIDES RELEASING HORMONES GONADOTROPIN RELEASING HORMONE (GnRH) is produced in the hypothalamus o MAIN TARGET anterior lobe of pituitary gland o MAIN HORMONAL ACTIONS causes release of gonadotropins GONADOTROPINS FOLLICLE STUMULATING HORMONE (FSH) is produced in the anterior lobe of pituitary gland o MAIN TARGET Gonads o MAIN HORMONAL ACTION stimulates spermatogenesis; stimulates maturation of ovarian follicles. LUTEINIZING HORMONE (LH) is produced in the anterior lobe of the pituitary gland o MAIN TARGET Gonads o MAIN HORMONAL ACTIONS stimulates secretion of gonadal steroids; stimulates ovulation HUMAN CHORIONIC GONADOTROPIN (hCG) is produced in the Conceptus o MAIN TARGET: Ovary o MAIN HORMONAL ACTIONS: maintains corpus luteum OTHER PROLACTIN is produced in the anterior lobe of pituitary gland o MAIN TARGET breast o MAIN HORMONAL ACTIONS prepares breast for lactation GROWTH HORMONE is produced in the anterior lobe of pituitary gland o MAIN TARGET widespread in body o MAIN HORMONAL ACTION stimulates growth spurt at puberty. INHIBIN is produced in the Gonads o MAIN TARGET anterior lobe of pituitary gland o MAIN HORMONAL ACTION Feedback inhibition of gonadotropin secretion OXYTOCIN is produced in the Hypothalamus (transported to posterior pituitary for secretion) o MAIN TARGET Breast, Uterus o MAIN HORMONAL ACTION Milk letdown; uterine contractions during labor; role in orgasm (and other nonreproductive functions) ANTIMULLERIAN HORMONE (AMH) is produced in the testis o MAIN TARGET Mullerian duct o MAIN HORMONAL ACTIONS causes regression of Mullerian duct during male fetal development MENSTRUATION is the vaginal discharge of endometrial tissue and blood that women experience at approximately monthly intervals during their fertile years. it is brought out by an internal mechanism that involves the ovaries, the brain, the pituitary gland, and the uterus Cycle length tends to be irregular for several years after the cycles first begin at puberty and at the approach of menopause Menstrual cycle cease during pregnancy and sometimes when the mother is breast feeding Most American women who menstruate use sanitary napkins or pads , panty liners, or tampons, in order to absorb their menstrual flow Although tampons are convenient if they are in for a long time, they may have MENSTRUAL TOXIC SHOCK SYNDROME a rare but life threatening illness caused by a staphylococcal infection and associated with tampon use. This condition is caused by certain strains of bacterium STAPHYLOCOCCUS AUREUS and is marked by high fever, vomiting, diarrhea, rash, and other symptoms Tampons should be changed after 48 hours of use MENSTRUAL CUPS are an alternative to pads and tampons. And it’s a cup placed within the vagina that collects the menstrual flow. They have to be emptied and replaced two or three times a day. o THE MENSTRUAL CYCLE HAS 3 PHASES MENSTRUAL PHASE: the days of the menstrual cycle on which bleeding occurs. This phase is the obvious outward sign of the cycle and its most significant internal event is ovulation, which involves the release of an ovum from one or the other ovary about midway between one menstrual period and the next The portion of the menstrual cycle between menstruation and ovulation is called PREOVULATORY or FOLLICULAR PHASE because it is marked by the maturation of follicles in the ovaries. PREOVULATORY PHASE (the phase of the menstrual cycle during which follicles are developing in the ovaries) The portion of the cycle between ovulation and menstruation is called the POSTOVULATORY OR LUTEAL PHASE because it is marked by the presence of a CORPUS LUTEUM a hormone secreting structure formed from the single follicle that ruptured at ovulation POSTOVULATORY PHASE (the phase of the cycle between ovulation and the beginning of menstruation ) CORPUS LUTEUM a secretory structure in the ovary derived from an ovarian follicle after ovulation A typical 28 day cycle is divided up roughly as follows: o The menstrual phase occupies days 1 through 5 o The preovulatory phase occupies days 614 o The postovulatory phase occupies days 1528 Of these three phases, the postovulatory phase is the most constant It usually lasts 14 days, give or take 2 days. Most of the variation in total cycle length is accounted for by variation in the menstrual and preovulatory phases THE CYCLE IS DRIVEN BY HORMONAL CHANGES During the menstrual phase, much of the inner lining of the uterus – THE ENDOMETRIUM sloughs off, thus beginning the process of preparing the uterus for the development of a fresh endometrium whose properties facilitate the transport of sperm. o The sloughing off process is triggered primarily by a drop in the circulating level of the hormone PROGESTERONE Blood levels of estrogens also drop at this time. o At the start of the PREOVULATORY phase, rises in FSH levels promote the development of about 15 to 20 immature follicles in the ovaries. These follicles secrete ESTROGENS and ANDROGENS, so the levels of these sex steroids in the bloodstream gradually rise during the preovulatory phase o The estrogens cause the ENDOMETRIUM in the uterus to thicken. In the latter part of the preovulatory phase, the cervix secretes a type of mucus that permits the passage of sperm, greatly increasing the chances of fertilization. o By the time all but one of the 1520 immature follicles has died, and the remaining one grows larger. Toward the end of the preovulatory phase – about 36 hours before ovulation – estrogen levels rise high enough that their feedback influence on the hypothalamus switches from inhibition to stimulation. Triggering a surge in the secretion of GnRH , LH, and FSH This surge drives the final development of the one remaining follicle , which expands to a diameter of about 1 inch o The follicle creates a bulge on the wall of the ovary At the moment of ovulation, the bulge breaks, releasing the ovum and its halo of supporting cells. The nearby FIMBRIA of this oviduct catches the ovum, and the waving of cilia propels it into the oviduct If the sperm are present in the oviduct, one of them may fertilize the ovum o Otherwise the ovum simply dies after 24 hours in the oviduct For about 2 weeks after ovulation, the uterus changes its structure to prepare for a possible pregnancy, regardless of whether fertilization happened or not o This process is guided by the hormones secreted from the remnants of the ruptured follicle, which transforms itself into a secretory structure, the CORPUS LUTEUM The predominant hormone secreted by the corpus luteum is PROGESTERONE, along with some estrogens PROGESTERONE stimulates the endometrium to thicken even further and become richly supplied with blood vessels In this state it is capable of supporting an embryo Progesterone also causes the cervical mucus to change its properties
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