CH 28 Reproductive System
Reproductive system includes the following components
-*Gonads*: reproductive organs that produce gametes and hormones. -*Ducts* that receive and transport gametes -*Accessory glands and organs* that secrete fluids into the reproductive system ducts or into other excretory ducts -*External genitalia* (perineal structures) ▪*In males*: testes produce sperm expelled from semen during ejaculation. ▪*In females*: the ovaries produce *oocytes* that travel along uterine tubes toward the uterus, which is connected to the exterior body by the vagina.
Spermatogenesis (Step by Step)
1) *Mitosis*: Each division of a diploid spermatogonium produces 2 daughter cells; 1 is a spermatogonium that remains in the basement membrane of the seminiferous tubule, and the other is a primary spermatocyte that moves toward the lumen. These events take 16 days. 2) *Meiosis I*: Each primary spermatocyte contains 46 individual chromosomes. At the end of meiosis I, the daughter cells are called secondary spermatocytes, each containing 23 chromosomes, each with a pair of duplicate chromatids. This phase takes about 24 days. 3) *Meiosis II*: The secondary spermatocytes soon enter meiosis II, which yield 4 haploid *spermatids*, each containing 23 chromosomes. For each primary spermatocyte that enters meiosis II, 4 spermatids are produced. This phase lasts a few hours. 4) *Spermiogenesis*: Each spermatid matures into a single sperm. This process -from spermatid to perm- takes 24 days.
Three estrogens circulate in the bloodstream
1) estradiol 2) estrone 3) estriol Estradiol is the most abundant estrogen, the dominant hormone of the follicular phase prior to ovulation.
Functions of Estrogens
1) stimulating bone and muscle growth 2) maintaining female secondary sex characteristics, such as body hair distribution and the location of adipose tissue deposits 3) affecting CNS activity, especially in the hypothalamus, where estrogens increase the sexual drive 4) maintaining functional accessory reproductive glands and organs 5) initiating the repair and growth of the endometrium
Secondary spermatocytes each contain
23 chromosomes
A typical ejaculation releases approximately ________ sperm
250 million
What event in the uterine cycle occurs when the levels of estrogens and progesterone decrease?
A decrease in the levels of estrogens and progesterone signals the beginning of menstruation, the end of the uterine cycle.
Meiosis II (Oogenesis)
After the ovarian cycle begins each month, 1 or more secondary oocytes leaves the ocary suspended in metaphase of meiosis II. At time of fertilization, a second polar body forms and the fertilized oocyte is then called a mature ovum. *The secondary oocyte is released (during ovulation) in metaphase of meiosis II. If fertilized (by a haploid sperm, the second polar body forms. The nucleus of the oocyte, second polar body, and the first two polar bodies are all haploid (n) with 3 single chromosomes*
LH surge
At day 14, estrogen levels have peaked, gonadotropes are at max sensitivity, and the GnRH pulses are arriving every 30 mins. This results in a massive release of LH from the anterior lobe of pituitary gland. This sudden surge in LH concentration triggers 1) the completion of meiosis I by the primary oocyte 2) the forceful rupture of the follicular wall 3) ovulation. Typically, ovulation occurs 34-38 hours after the LH surge begins, 9 hours after the LH peak.
Why does the level of FSH increase and remain high during menopause?
At menopause, circulating estrogen levels begin to decrease. Estrogen has an inhibitory effect on FSH (and on GnRH). As the level of estrogen decreases, the levels of FSH increase and remain high.
Would the blockage of a single lactiferous sinus interfere with the delivery of milk to the nipple? Explain.
Blockage of a single lactiferous sinus would not interfere with the delivery of milk to the nipple because the mammary gland of each breast generally has 15-20 lactiferous sinuses.
What effect would a blockage of progesterone receptors in the uterus have on the endometrium?
Blockage of progesterone receptors in the uterus would inhibit the development of the endometrium, making the uterus unprepared for pregnancy.
What is the precursor for all steroid hormones in both males and females?
Cholesterol is the precursor for all steroid hormones in both males and females.
What is the name of the cell at each stage of sperm development, from mitosis to spermiogenesis?
During mitosis, the *spermatogonium* divides, forming another spermatogonium and a primary spermatocyte. During meiosis I, the *primary spermatocyte* divides into two secondary spermatocytes. During meiosis II, each *secondary spermatocytes* divides into two *spermatids*. During spermiogenesis (the physical maturation), the four spermatids develop into four *sperm*.
At what stage of development is the oocyte during ovulation?
During ovulation, the oocyte is a secondary oocyte.
What changes would you expect to observe in the ovarian cycle if the LH surge did not occur?
If the LH surge did not occur during an ovarian cycle, ovulation and corpus luteum formation would not occur.
What effect would a low FSH level have on sperm production?
Low FSH levels would lead to low levels of testosterone in the seminiferous tubules, decreasing both the sperm production rate and sperm count.
menopause
Menopause is the time when ovulation and menstruation cease, typically around ages 45-55.
On a warm day, would the cremaster be contracted or relaxed? Why?
On a warm day, the cremaster (as well as the dartos muscle) would be relaxed so that the scrotum could descend away from the warmth of the body, thereby cooling the testes.
Mitosis of Ooginium
Oogonia complete their mitotic divisions before birth. An oogonium divides into 2 daughter cells: an oogonium and a primary oocyte (diploid, 2n). All of the cells drawn have 3 pairs of chromosomes (6 total)
What changes occur in females during sexual arousal as the result of increased parasympathetic stimulation?
Parasympathetic stimulation in females during sexual arousal causes (a) engorgement of the erectile tissue of the clitoris and vestibular bulbs, (b) increased secretion of cervical and greater vestibular glands, (c) increased blood flow to the wall of the vagina, and (d) engorgement of the blood vessels in the nipples.
In a condition known as endometriosis, endometrial cells are believed to migrate from the body of the uterus into the uterine tubes into the peritoneal cavity, where they becomes established. A major symptom of endometriosis is periodic pain. Why does such pain occur?
Regardless of their location, endometrial cells have receptors that respond to estrogen & progesterone. Under the influence of estrogen at the beginning of the menstrual cycle, any endometrial cells in the peritoneal cavity proliferate & begin to develop glands and blood vessels, which then further develop under the control of progesterone. The dramatic increase in the size of this tissue presses on neighboring abdominal tissues and organs, causing periodic painful sensations.
Name the male reproductive structures.
Scrotum, testes, epididymides, ductus deferentia, ejaculatory duct, urethra, seminal glands, prostate, bulbo-urethral glands, and penis.
Contraceptive pills contain estradiol and progesterone, or progesterone alone, administered at programmed doses during the ovarian cycle to prevent tertiary ovarian follicle maturation & ovulation. Explain how such pills are effective.
Slightly elevated levels of estradiol & progesterone inhibit both GnRH release at the hypothalamus & the release of FSH & LH from the anterior lobe of the pituitary gland. Without FSH, primordial follicles do not begin to develop, and the levels of estrogen remain low. An LH surge, triggered by the peaking of estradiol, is necessary for ovulation to occur. If the level of estradiol is not allowed to rise above the critical level, the LH surge will not occur, & thus ovulation will not occur, even if a follicle managed to develop to a stage at which it could ovulate.Any mature follicles would ultimately degenerate, and no new follicles would mature to take their place. Although the ovarian cycle is interrupted, the level of hormones is still adequate to regulate a normal menstrual cycle.
Name the structures of the female reproductive system.
Structures of the female reproductive system include the ovaries, uterine tubes, uterus, vagina, and external genitalia (mons pubis, the clitoris and the labia majora and labia minora).
What benefit does the acidic pH of the vagina provide?
The acidic pH of the vagina helps prevent bacterial, fungal, and parasitic infections in this region.
Proliferative phase
The basal layer survives menstruation intact. The epithelial cells of the uterine glands multiply and spread across the endometrial surface, restoring uterine epithelium. Growth and vascularization restore the functional layer, and the endometrium is in the proliferative phase during this reorganization. By the time ovulation occurs, the functional layer is several mL thick, and the uterine glands are manufacturing mucus rich in glycogen, which is essential for the survival of the fertilized ovum.
What effect would blockage of both uterine tubes by scar tissue (resulting from an infection such as gonorrhea) have on a woman's ability to conceive?
The blockage of both uterine tubes would cause sterility.
Which erectile tissue is split into two cylindrical masses that surround a central artery? Which erectile tissue surrounds the urethra?
The corpora cavernosa is split into two cylindrical masses and surrounds a central artery. The corpus spongiosum surrounds the urethra.
Menstrual Phase (menses)
The endometrial functional layer degenerates and sloughs (sheds) off, leading to menstruation. Deprived of O2/nutrients, the secretory glands begin to deteriorate, causing the arterial walls to eventually rupture, and blood pours into the C.T of the functional layer. Blood cells/degenerating tissues break away and enter the uterine cavity, to be shed as they pass through the external os into the vagina.
Which layer of the endometrium is affected most during the uterine cycle?
The functional layer of the endometrium is affected most during the uterine cycle. During menstruation, the entire functional layer is sloughed off and lost.
During the proliferative phase of the menstrual cycle,
The functional zone of the endometrium is restored
What structure in a sexually indifferent embryo may develop into a penis or clitoris and what hormone is involved in that development?
The genital tubercle of a sexually indifferent embryo will develop into a penis in the presence of testosterone or a clitoris without testosterone.
Hormones and Male Reproductive Function
The major hormones of the male reproductive system are FSH, LH, GnRH, inhibin, and testosterone. ▫*FSH and Spermatogenesis*- FSH targets primarily nurse cells of the seminiferous tubules. ▫*LH and Androgen Production*- LH causes the secretion of testosterone and other androgens by the interstitial cells of the testes.
What is the male climacteric?
The male climacteric, or andropause, is a period of declining reproductive function in men, typically between the ages of 50 and 60.
List the physiological events of sexual intercourse in both sexes, and indicate those that occur in males but not in females.
The physiological events of sexual intercourse in both sexes are arousal, erection, lubrication, orgasm, and resolution. Emission and ejaculation are additional phases that occur only in males.
Meiosis I (Oogenesis)
The primary oocytes prepare for meiosis and proceed to prophase of meiosis I before coming to a halt. They remain in a state of suspended development until puberty, when rising FSH levels trigger the start of ovarian cycle. Each month after the ovarian cycle begins, some of the primary oocytes undergo further development. Meoisis I is completed yielding a secondary oocyte and a polar body. *The primary oocyte undergoes DNA replication, resulting in a primary oocyte with tetrads (3 tetrads form). Division of the primary oocyte results in 2 daughter cells: the first polar body and the secondary oocyte. Both have 3 duplicated chromatids. The first polar body may or may not complete meiosis II. If it does, 2 polar bodies will result.*
Female bodybuilders and women with eating disorders such as anorexia nervosa commonly experience amenorrhea. What does this fact suggest about the relation between body fat and menstruation? What effect would amenorrhea have on achieving a successful pregnancy?
This suggests that a certain amount of body fat is necessary for menstrual cycles to occur. The nervous system appears to respond to circulating levels of the adipose tissue hormone leptin; when leptin levels fall below a certain set point, menstruation ceases. Because a woman lacking adequate fat reserves might not be able to have a successful pregnancy, the body prevents pregnancy by shutting down the ovarian cycle, and thus the menstrual cycle. Once sufficient energy reserves become available, the cycles begin again.
secretory phase
Uterine glands enlarge, accelerating rates of secretion. The arteries that supply the uterine wall elongate/spiral through the tissues of the functional layer, stimulated by the effects of progesterone/estrogens from the corpus luteum. Secretory activities peak 12 days after ovulation followed by the glands becoming less active over the next 1-2 days. Phase begins at ovulation and persists as long as corpus luteum remains intact; usually lasts 14 days, giving the ability to identify the date of ovulation by counting back 14 days from 1st day of menses.
What happens when the arteries within the penis dilate?
When the arteries within the penis dilate, the increased blood flow causes the erectile tissues of the corpora cavernosa and corpus spongiosum to engorge with blood, producing an erection.
Penis
a tubular organ through which conducts urine to the exterior and introduces semen into the female's vagina during sexual intercourse. -Divided into three regions: 1) *The root*: fixed portion that attaches penis to the body wall, includes the L and R crus and the bulb of penis. 2) *The body*: the tubular, movable portion; 3) *The glans*: the head/distal end that surrounds the external urethral orifice. A fold of skin called the prepuce surrounds the tip of the penis. ▫Surrounding the internal structures of the penis are three masses of erectile tissue: corpora cavernosa (2) and corpus spongiosum (surrounds urethra)
Semen
also called ejaculate, usually 2-5 mL per ejaculation, contains: ▫*Sperm*: ranges from 20-100 million sperm per mL of semen ▫*Seminal Fluid*: the liquid component of sperm; contains combined secretions of the seminal glands (60%), the prostate (30%), the nurse and epididymis (5%), and the bulbo-urethral glands (less than 5%). ▫*Enzymes*: (1) a protease to help dissolve mucus in vagina (2) seminalplasmin - a protein with antibiotic properties that helps prevent UTI (3) prostatic enzyme that convers fibrinogen to fibrin, coagulating the semen after ejaculation (4) fibrinolysin - liquifies the clotted semen after 15-30 mins.
The Vagina
an elastic muscular tube extending between the cervix and the vestibule. Has three major functions: 1) a passageway for the elimination of menstrual fluids 2) receives the penis during sexual intercourse, and holds sperm prior to their passage to the uterus 3) forms the inferior portion of the birth canal, through which the fetus passes during delivery. ▫The lining of the vagina is moistened by the secretions of the cervical glands and by water movement ▫Vagina and vestibule are separated by the *hymen*, an epithelial fold that partially or completely blocks the entrance to the vagina before the initial sexual intercourse. ▫*Bulbospongiosus* muscles extend along either side of the vaginal entrance; contractions constrict the vagina. ▫Lumen is lined by nonkeratinized stratified squamous epithelium ▫Vagina contains a normal population of bacteria that produce an acidic environment
The Ovarian Cycle
can be divided into the follicular phase and the luteal phase. Can be summarized by the following steps: 1) *Primordial ovarian follicles in egg nest*: Formed by the primary oocyte and its follicle cells; each ovary contains 200,000 primordial follicles at puberty and vanish within the next 40 years. They are continuously activated at puberty to join other follicles already in development. The activated primordial follicle will either eventually mature and release a secondary oocyte or degenerate through follicular atresia. 2) *Formation of primary ovarian follicle*: The follicular cells enlarge, divide, and form several layers of cells around the growing primary oocyte. The cells begin producing sex hormones (estrogens). 3) *Formation of secondary ovarian follicle*: Only a few of the primary ovarian follicles mature further into secondary ovarian follicles. The primary oocyte continues to grow slowly. 4) *Formation of tertiary ovarian follicle*: Follicular fluid is secreted by follicular cells and accumulates in small pockets that gradually expand between inner and outer cellular layers of the follicle. Tertiary ovarian follicles continue to grow and accumulate follicular fluid. 5) *Ovulation*: the tertiary follicle releases the secondary oocyte; the distended follicular wall ruptures releasing the follicular contents/secondary oocyte into the pelvic cavity. The oocyte moves into the uterine tube by contact with the fimbriae that extend from the tube's opening or by fluid currents produced by the cilia that line the tube. 6) *Formation of Corpus Luteum*: The empty tertiary follicle initially collapses, and ruptured vessels bleed into the antrum. Under stimulation of LH, the remaining granulosa cells invade the area and proliferate to create the corpus luteum. The corpus luteum contains cholesterol, used to manufacture progesterone. Progesterone's main fx is to prepare the uterus for pregnancy by stimulating the maturation of uterine lining/secretions of uterine glands. 7) *Formation of corpus albicans*: The corpus luteum begins to degenerate 12 days after ovulation (unless fertilization occurs). Progesterone/estrogen levels decline and fibroblasts invade the nonfunctional corpus luteum, producing a knot of pale scar tissue - the corpus albicans.
The vulva includes all of the following, except the A. vaginal opening B. cervix C. vestibule D. clitoris E. labia minora
cervix
External Genitalia
contained within the vulva ▫*Vestibule*: the vagina opens into the vestibule ▫*Clitoris*: small rounded tissue projection; major role in female sexual response. ▫*Prepuce of clitoris*: extension of the labia minora that surround the clitoris. ▫*Greater vestibular glands*: located oneach side of the vagina, secrete into the vestibule during sexual arousal. ▫*Mons pubis:* pad of adipose tissue covering the pubic symphysis. ▫*Labia majora*: folds of skin that encircle and conceal the labia minora and adjacent structures. ▫*Labia minora*: central space surrounded by small folds
Hormones and the Female Reproductive Cycle
coordinate the uterine cycle and the ovarian cycle to ensure proper reproductive function. ▫If these two cycles are not coordinated, infertility can result ▫GnRH from hypothalamus regulates the release of FSH and LH by changing the pulse frequency and amplitude throughout the course of the ovarian cycle. ▫Changes in the GnRH pulse frequency are controlled by circulating levels of estrogens and progestins; estrogens increase GnRH pulse frequency while progestins decrease it. ▫FSH initiates follicular development, and activated follicles and ovarian interstitial cells produce estrogens. High estrogen levels stimulate LH secretion, increase pituitary sensitive to GnRH, and increase the GnRH pulse frequency. ▫Progesterone is the main hormone of the luteal phase.
The broad ligament
encloses ovaries, uterine tubes, and uterus
Sperm travel along the
epididymis, ductus deferens, the ejaculatory duct, and the urethra before leaving the body. Accessory organs (seminal glands, prostate, and bulbo-urethral gland) secrete fluids into the ejaculatory ducts and the urethra.
In females, meiosis II is not completed until
fertilization occurs
The Uterine Tubes
hollow muscular tube, roughly 13 cm long, divided into three segments: ▫*Infundibulum*: contains fimbriae; fingerlike projections that extend into pelvic cavity and drape over the surface of ovary, although no physical contact. ▫*The Ampulla*: Middle region; thickness gradually increases as tube approaches uterus. ▫*Isthmus*: The ampulla leads to the isthmus, short region connected to uterine wall. ▫The uterine tube provides a nutrient rich environment that contains lipids/glycogen for both oocytes and sperm. If fertilization occurs, it typically takes place between the ampulla and isthmus.
Which region of the uterine tube "receives" the ovum?
infundibulum
The uterine cycle (menstrual cycle)
is a repeating series of changes in the endometrium structure; Averages 28 days in length. Begins with the onset of menstruation, a process that continues from 1-7 days. The uterine cycle ends as the corpus luteum stops producing stimulatory hormones. A new uterine cycle begins with the onset of menstruation and the disintegration of the functional layer. Can be divided into three phases: 1) Menstrual Phase 2) Proliferative Phase 3) Secretory Phase
Blood Testis Barrier
isolates seminiferous tubules from general circulation; Nurse cells produce a fluid in the lumen of the seminiferous tubule and regulate the fluids composition. Fluid is rich in androgens, estrogens, potassium and amino acids. The Blood Testis Barrier is essential in preserving the differences between the luminal and interstitial fluid.
Menarche and Menopause
menarche is the first uterine cycle. Menopause is the last uterine cycle.
The monthly process of the maturation, ovulation, and degeneration of a tertiary ovarian follicle
ovarian cycle
Organs of the female reproductive system
ovaries, uterine tubes, uterus, vagina, external genitalia
Oogenesis
ovum production begins before a woman's birth, accelerates during puberty, and ends at menopause. Occurs in ovarian follicles.
The Ovaries
paired, small, lumpy organs located near the lateral walls of the pelvic cavity. Perform three main functions: 1) Produce immature female gametes (oocytes) 2) Secrete female sex hormones including estrogens and progesterone. 3) Secrete inhibin, involved in feedback control of pituitary FSH production. ▫Can be divided into the outer cortex and inner medulla, gametes are produced in the cortex. ▫*Mesovarium* supports and stabilizes position of each ovary. ▫Held in position by the *ovarian ligament* and *suspensory ligament*, which contains the blood vessels and nerves. ▫Each ovary is covered by a *tunica albuginea*.
Spermatogenesis
process of producing spermatozoa, involves three integrated processes: 1) *Mitosis*: Spermatogonia are stem cells in the seminiferous tubule that undergo cell divisions throughout adult life. Some of the cells differentiate into primary spermatocytes, which prepare to begin meiosis. 2) *Meiosis*: Primary spermatocytes then undergo meiotic divisions that produce spermatids, undifferentiated male gametes. 3) *Spermiogenesis*: Spermatids differentiate into physically mature sperm.
The Testes
produce physically mature spermatozoa, but they are not functionally mature. ▫Descent of the testes usually occurs in the 7th month of gestation ▫*Spermatic cords* contain nerves and blood vessels that serve the testes. ▫*Scrotum* is separated into two chambers, keeps infection or inflammation from spreading from one testis to the other. -Contains a thin layer of skin and underlying superficial fascia -The Raphe marks the boundary between the two chambers in the scrotum -Dartos muscle: smooth muscle, tightens the scrotum, giving it a wrinkled appearance as it elevates the testes. -Cremaster muscle: skeletal muscle; contracts during sexual arousal or decreased temperature moving scrotum closer to the body. ▫*Tunica albuginea*: connective tissue with collagen fibers; surrounds each testis. ▫Septa divide the testes into lobules, *seminiferous tubules* are distributed among the lobules ▫Each seminiferous tubule is about 80 cm in length, sperm production occurs in these tubules. ▫Each lobule contain several seminiferous tubules that merge into straight lobules, which form a maze of passageways called the *Rete testis*. 15-20 efferent ductules connect the rete testis to the epididymis. ▫*Interstitial cells* secrete sex hormones/androgens (androsterone/testosterone); are located between each seminiferous tubule.
The reproductive system
produces, stores, nourishes, and transports functional *gametes* (reproductive cells).
Male Accessory Glands
provide nutrients for spermatozoa, activates spermatozoa, propels spermatozoa, and produces buffers to protect against urine and vaginal acids. ▫*Seminal Vesicles*: glands embedded in CT on either side of the midline; each seminal gland is an active secretory gland that contributes to 60% of semen volume. Secretions are discharged into the ejaculatory duct and contain fructose, bicarbonate ions, prostaglandins, and fibrinogen. ▫*Prostate Gland*: small, muscular, round gland that surrounds the initial portion of the urethra. Secretes slightly acidic prostatic fluid. ▫*Bulbourethral Glands*- small gland embedded in the urogenital diaphragm; secretes alkaline mucus and has lubricating properties.
The Uterus
provides mechanical protection, nutritional support, and waste removal for the developing embryo and fetus. Also contractions of the muscular wall of the uterus is important for ejecting the fetus at the time of birth. ▫Composed of two main regions, the body and the cervix -The superior part of the body is called the fundus, body ends at the uterine isthmus -Cervix extends from uterine isthmus to the vagina. -The broad, uterosacral, round, and lateral ligaments stabilize the uterus.
A sudden surge in LH secretion causes the
rupture of the follicular wall and ovulation
Testicular nurse cells function in all of the following ways, except that they don't A. secrete Müllerian inhibiting factor B. support meiosis C. secrete progesterone-binding protein D. coordinate spermiogenesis E. serve as a blood-testis barrier
secrete progesterone-binding protein
Trace the pathway that a sperm travels from the site of its production to outside the body.
seminiferous tubule → straight tubule → rete testis → efferent ductules → epididymis → ductus deferens → ejaculatory duct → urethra.
Semen contains all of the following, except A. spermatogonia B. spermatozoa C. seminal fluid D. fibrinogen E. prostaglandins
spermatogonia
Follicle-stimulating hormone
stimulates spermatogenesis stimulates maturation of primordial follicles in the ovary
Nurse cells
surround spermatids and spermatocytes in the seminiferous tubules; play a key role in spermatogenesis 5 important functions: 1. *Maintenance of the Blood Testis Barrier*: Nurse cells produce a fluid in the lumen of the seminiferous tubule and regulate the fluids composition. Fluid is rich in androgens, estrogens, potassium and amino acids. The Blood Testis Barrier is essential in preserving the differences between the luminal and interstitial fluid. 2. *Support Mitosis and Meiosis*: Circulating FSH and testosterone stimulate nurse cells, which promote the division of spermatogonia and the meiotic divisions of spermatocytes. 3. *Support of Spermiogenesis*: Spermiogenesis requires nurse cells; they surround and enfold spermatids providing nutrients and chemical stimuli that promote development. Also phagocytize cytoplasm that is shed by spermatids. 4. *Secretion of Inhibin*: Inhibin depresses the pituitary production of FSH, and the hypothalamic secretion of GnRH, which helps to provide negative feedback control by spermatogenesis. The faster the rate of sperm production, the more inhibin is secreted. 5. *Secretion of Androgen-Binding Protein (ABP)*: ABP binds androgens in the luminal fluid of seminiferous tubules; important for increasing androgen concentration and stimulating spermiogenesis. FSH stimulates production of ABP.
During meiosis I, maternal and paternal chromosomes come together during the process called ________ to form a ________.
synapsis; tetrad
Fertilization
the fusion of male and female gametes
The Mammary Glands
used for nourishment of an infant, lactation occurs here. ▫*Lactation*: process of milk production ▫Mammary glands are specialized organs of the Integumentary system that are controlled mainly by hormones of the reproductive system and the placenta.
Diane has a peritonitis (an inflammation of the peritoneum), which her physician says resulted from a urinary tract infection. Why might this condition occur more readily in females than in males?
women more frequently experience peritonitis stemming from a urinary tract infection because infectious organisms exiting the urethral orifice can readily enter the nearby vagina. From there, they can then proceed to the uterus, into the uterine tubes, and finally into the peritoneal cavity. No such direct path of entry into the abdominopelvic cavity exists in men.
The uterine wall is composed of three layers
▫*Endometrium*: Thin, inner glandular layer. 10% of the mass of uterus. ▫*Myometrium*: thick middle, muscular layer. 90% if the mass of the uterus. ▫*Perimetrium*: outer layer, serous membrane continuous with the peritoneum
The Male Reproductive Tract (Epididymis, Ductus Deferens, Urethra)
▫*Epididymis*- the start of the male reproductive tract, almost 23 feet long. Contains a head, body, and tail. -Has three main functions: 1. Monitors & adjusts the composition of the fluid produced by seminiferous tubules. 2. Serves as a recycling center for damaged sperm. 3. Stores & Protects sperm and facilitates their functional maturation. ▫*Ductus Deferens*- about 16-18 inches long, begins at the tail of the epididymis and continues on to the ejaculatory duct. Enlarges near the prostate to form the ampulla of ductus deferens, where sperms can be stored for several months. ▫*Urethra*- ductus deferens empties into the urethra, made of three regions: prostatic, membranous, and spongy.
Hormonal Regulation of the Ovarian Cycle
▫*Follicular Phase*: FSH and LH are the main hormones; Follicular development begins under FSH stimulation, primordial follicles begin to develop into primary follicles. -Thecal cells begin producing androstenedione, a precursor to most sex hormones. Converted to estrogens by granulose cells. -Small quantities of estrogens are released by interstitial cells scattered throughout the ovarian stroma -Circulating estrogens are bound primarily to albumins, lesser amount carried by gonadal steroid-binding globulin (GBG) ▫*Luteal phase*: Progesterone is the main hormone. As progesterone level rises and estrogen levels fall, the GnRH pulse frequency decreases sharply, stimulating LH secretion which maintains the structure and secretory function of the corpus luteum. Progesterone's primary function is to continue the preparation of the uterus for pregnancy it enhances blood supply to the functional layer and stimulates secretion of uterine glands. 12 days after ovulation, progesterone/estrogen levels fall and the GnRH pulse frequency increases, stimulating FSH secretion by pituitary gland, and the ovarian cycle begins again.
Anatomy of a Sperm
▫*Head*: a flattened ellipse containing a nucleus with densely packed chromosomes; the tip of the head is the *acrosome*: a membranous compartment containing enzymes essential to fertilization. ▫*Middlepiece*: connected to the head via the neck, which contains both centrioles of the original spermatid. Contains Mitochondria that provide the ATP required to move the tail. ▫*Tail*: the only flagellum in the human body; a whiplike organelle that moves a cell from place to place. ▫Mature sperm lacks ER, Golgi, Lysosomes, and Peroxisomes, must absorb nutrients from surrounding fluid
The endometrium can be divided into a
▫*The functional zone*: closest to the uterine cavity; contains most of the uterine glands and contributes to most of the endometrial thickness. ▫*The basilar zone*: attaches the endometrium to the myometrium and contains the terminal branches of the tubular uterine glands. ▫The structure of the basilar zone remains consistent over time, while that of the functional zone changes during the uterine cycle in response to sex hormone levels. -This is mostly due to the types of blood vessels found in the zones.
Contraception and Infertility
▫BBT (basal body temperature) decreases at the time of ovulation. Urine tests can detect LH surge. Monitoring these to avoid pregnancy is the rhythm method. ▫Abstinence, barrier methods, intrauterine devices, oral contraception, and surgical methods also exist to prevent pregnancy. ▫*Infertility*: the inability to conceive or carry a pregnancy to term after 1 year of unprotected sex.
Male Sexual Function
▫During sexual *arousal* in males, erotic thoughts, sensory stimulation, or both lead to parasympathetic activity that produces erection. Subsequent stimulation can initiate the secretion of the bulbo-urethral glands, providing lubrication for the spongy urethra and the surface of the glans penis. ▫*Emission* occurs under sympathetic stimulation; peristaltic contractions of the ampullae of the vas deferens push seminal fluid into the prostatic urethra. The seminal glands then contract and peristaltic contractions appear in the walls of the prostate, moving the seminal mixture into the membranous and penile urethra. ▫*Ejaculation* occurs as powerful, rhythmic contractions appear in the ischiocavernosus and bulbospongiosus muscles. Ejaculation is associated with intensely pleasurable sensations associated with perineal muscle contraction - male *orgasm*. Increase in HR and BP occurs during this time. ▫After orgasm, *resolution* phase occurs as HR and BP decrease and blood begins to leave the erectile tissue and the erection subsides. ▫Detumescence: mediated by sympathetic NS; process of losing an erection. ▫*Erectile dysfunction*: an inability to achieve of maintain an erection.
Female Sexual Function
▫During sexual arousal, parasympathetic activation leads to engorgement of the erectile tissues of the clitoris and vestibular bulbs, and increased secretion from cervical mucous glands and greater vestibular glands. ▫Clitoral erection increases the receptors' sensitivity to stimulation, and the cervical and vestibular glans lubricate the vaginal walls. ▫Parasympathetic stimulation also causes contraction of the smooth muscle of the nipples, making them more sensitive to touch and pressure. ▫Female orgasm is accompanied by peristaltic contractions of the uterine/vaginal walls.
Hormonal Regulation of the Uterine Cycle
▫Progesterone/Estrogen levels decrease as the corpus luteum degenerates, resulting in menstruation. ▫The shedding of endometrial tissue continues for several days until rising levels of estrogens stimulate repair/regeneration of functional layer of the endometrium. ▫The proliferative phase continues until a rising progesterone level marks the arrival of the secretory phase. The combination of estrogen and progesterone causes the uterine glands to enlarge and increase their secretions
The ANS influences male & female sexual function
▫Sexual intercourse introduces semen into the female reproductive tract; can lead to pregnancy and STI's. ▫*Human sexual function*: how the body reacts during the sexual response.
