REPRODUCTIVE SYSTEM PDF
Male Reproductive System. • Male gonads, testes, are suspended in scrotum. – Sperm are produced in testes and mature in epididymis. • Travel to vas deferens . Human Anatomy & Physiology: Reproductive System; Ziser Lecture Notes, 1. Reproductive System. Function: producing offspring propagation of the . women! ppti.info reproductive processes, functions and systems at all stages of human life.
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accessory ducts, glands and the external genitalia. CHAPTER 3. HUMAN REPRODUCTION. The Male Reproductive. System. The Female Reproductive. The male reproductive system produces, sustains, and delivers sperm cells ( spermatozoa) to the female reproductive tract. ▫ The female reproductive system . Human reproduction. Male Reproductive System. Organs: 2 Testes – produce sperm and sex hormones. Hormones influence sperm production and secondary .
If fertilization has occurred, this fluid will nourish the ball of cells now developing from the zygote. At the same time, the spiral arteries develop to provide blood to the thickened stratum functionalis. If no pregnancy occurs within approximately 10 to 12 days, the corpus luteum will degrade into the corpus albicans. Levels of both estrogen and progesterone will fall, and the endometrium will grow thinner. Prostaglandins will be secreted that cause constriction of the spiral arteries, reducing oxygen supply.
The endometrial tissue will die, resulting in menses—or the first day of the next cycle. Female Reproductive System Research over many years has confirmed that cervical cancer is most often caused by a sexually transmitted infection with human papillomavirus HPV. There are over related viruses in the HPV family, and the characteristics of each strain determine the outcome of the infection. HPV infections are common in both men and women.
Indeed, a recent study determined that These women ranged in age from 14 to 59 years and differed in race, ethnicity, and number of sexual partners. Of note, the prevalence of HPV infection was HPV strains are classified as high or low risk according to their potential to cause cancer. Though most HPV infections do not cause disease, the disruption of normal cellular functions in the low-risk forms of HPV can cause the male or female human host to develop genital warts.
Often, the body is able to clear an HPV infection by normal immune responses within 2 years. However, the more serious, high-risk infection by certain types of HPV can result in cancer of the cervix Figure 8. Infection with either of the cancer-causing variants HPV 16 or HPV 18 has been linked to more than 70 percent of all cervical cancer diagnoses.
Although even these high-risk HPV strains can be cleared from the body over time, infections persist in some individuals. If this happens, the HPV infection can influence the cells of the cervix to develop precancerous changes.
Risk factors for cervical cancer include having unprotected sex; having multiple sexual partners; a first sexual experience at a younger age, when the cells of the cervix are not fully mature; failure to receive the HPV vaccine; a compromised immune system; and smoking. The risk of developing cervical cancer is doubled with cigarette smoking. When the high-risk types of HPV enter a cell, two viral proteins are used to neutralize proteins that the host cells use as checkpoints in the cell cycle.
The best studied of these proteins is p High-risk HPV can neutralize p53, keeping the cell in a state in which fast growth is possible and impairing apoptosis, allowing mutations to accumulate in the cellular DNA. The prevalence of cervical cancer in the United States is very low because of regular screening exams called pap smears.
Pap smears sample cells of the cervix, allowing the detection of abnormal cells. If pre-cancerous cells are detected, there are several highly effective techniques that are currently in use to remove them before they pose a danger. However, women in developing countries often do not have access to regular pap smears. As a result, these women account for as many as 80 percent of the cases of cervical cancer worldwide.
In , the first vaccine against the high-risk types of HPV was approved. There are now two HPV vaccines available: Whereas these vaccines were initially only targeted for women, because HPV is sexually transmitted, both men and women require vaccination for this approach to achieve its maximum efficacy.
A recent study suggests that the HPV vaccine has cut the rates of HPV infection by the four targeted strains at least in half. Unfortunately, the high cost of manufacturing the vaccine is currently limiting access to many women worldwide. Whereas the breasts are located far from the other female reproductive organs, they are considered accessory organs of the female reproductive system.
The function of the breasts is to supply milk to an infant in a process called lactation. The external features of the breast include a nipple surrounded by a pigmented areola Figure 9 , whose coloration may deepen during pregnancy. The areola is typically circular and can vary in size from 25 to mm in diameter. The areolar region is characterized by small, raised areolar glands that secrete lubricating fluid during lactation to protect the nipple from chafing. When a baby nurses, or draws milk from the breast, the entire areolar region is taken into the mouth.
Breast milk is produced by the mammary glands , which are modified sweat glands. The milk itself exits the breast through the nipple via 15 to 20 lactiferous ducts that open on the surface of the nipple.
These lactiferous ducts each extend to a lactiferous sinus that connects to a glandular lobe within the breast itself that contains groups of milk-secreting cells in clusters called alveoli see Figure 9. The clusters can change in size depending on the amount of milk in the alveolar lumen. Once milk is made in the alveoli, stimulated myoepithelial cells that surround the alveoli contract to push the milk to the lactiferous sinuses.
From here, the baby can draw milk through the lactiferous ducts by suckling. The lobes themselves are surrounded by fat tissue, which determines the size of the breast; breast size differs between individuals and does not affect the amount of milk produced.
Supporting the breasts are multiple bands of connective tissue called suspensory ligaments that connect the breast tissue to the dermis of the overlying skin. During the normal hormonal fluctuations in the menstrual cycle, breast tissue responds to changing levels of estrogen and progesterone, which can lead to swelling and breast tenderness in some individuals, especially during the secretory phase.
If pregnancy occurs, the increase in hormones leads to further development of the mammary tissue and enlargement of the breasts. Birth control pills take advantage of the negative feedback system that regulates the ovarian and menstrual cycles to stop ovulation and prevent pregnancy.
Typically they work by providing a constant level of both estrogen and progesterone, which negatively feeds back onto the hypothalamus and pituitary, thus preventing the release of FSH and LH. Although the estrogen in birth control pills does stimulate some thickening of the endometrial wall, it is reduced compared with a normal cycle and is less likely to support implantation.
Some birth control pills contain 21 active pills containing hormones, and 7 inactive pills placebos. The decline in hormones during the week that the woman takes the placebo pills triggers menses, although it is typically lighter than a normal menstrual flow because of the reduced endometrial thickening.
Newer types of birth control pills have been developed that deliver low-dose estrogens and progesterone for the entire cycle these are meant to be taken days a year , and menses never occurs. While some women prefer to have the proof of a lack of pregnancy that a monthly period provides, menstruation every 28 days is not required for health reasons, and there are no reported adverse effects of not having a menstrual period in an otherwise healthy individual.
Because birth control pills function by providing constant estrogen and progesterone levels and disrupting negative feedback, skipping even just one or two pills at certain points of the cycle or even being several hours late taking the pill can lead to an increase in FSH and LH and result in ovulation.
It is important, therefore, that the woman follow the directions on the birth control pill package to successfully prevent pregnancy. Female Reproductive System Female fertility the ability to conceive peaks when women are in their twenties, and is slowly reduced until a women reaches 35 years of age. After that time, fertility declines more rapidly, until it ends completely at the end of menopause. Menopause is the cessation of the menstrual cycle that occurs as a result of the loss of ovarian follicles and the hormones that they produce.
A woman is considered to have completed menopause if she has not menstruated in a full year. After that point, she is considered postmenopausal. Poor health, including smoking, can lead to earlier loss of fertility and earlier menopause. As a woman reaches the age of menopause, depletion of the number of viable follicles in the ovaries due to atresia affects the hormonal regulation of the menstrual cycle. During the years leading up to menopause, there is a decrease in the levels of the hormone inhibin, which normally participates in a negative feedback loop to the pituitary to control the production of FSH.
The menopausal decrease in inhibin leads to an increase in FSH. The presence of FSH stimulates more follicles to grow and secrete estrogen. Because small, secondary follicles also respond to increases in FSH levels, larger numbers of follicles are stimulated to grow; however, most undergo atresia and die.
Eventually, this process leads to the depletion of all follicles in the ovaries, and the production of estrogen falls off dramatically. It is primarily the lack of estrogens that leads to the symptoms of menopause. Although the levels of estrogen are still nearly the same as before the transition, the level of progesterone produced by the corpus luteum is reduced. This decline in progesterone can lead to abnormal growth, or hyperplasia, of the endometrium. This condition is a concern because it increases the risk of developing endometrial cancer.
Two harmless conditions that can develop during the transition are uterine fibroids, which are benign masses of cells, and irregular bleeding.
As estrogen levels change, other symptoms that occur are hot flashes and night sweats, trouble sleeping, vaginal dryness, mood swings, difficulty focusing, and thinning of hair on the head along with the growth of more hair on the face.
Depending on the individual, these symptoms can be entirely absent, moderate, or severe. After menopause, lower amounts of estrogens can lead to other changes. Cardiovascular disease becomes as prevalent in women as in men, possibly because estrogens reduce the amount of cholesterol in the blood vessels. When estrogen is lacking, many women find that they suddenly have problems with high cholesterol and the cardiovascular issues that accompany it. Osteoporosis is another problem because bone density decreases rapidly in the first years after menopause.
The reduction in bone density leads to a higher incidence of fractures. Hormone therapy HT , which employs medication synthetic estrogens and progestins to increase estrogen and progestin levels, can alleviate some of the symptoms of menopause.
However, the study was prematurely terminated after 5. The potential positive effects on cardiovascular disease were also not realized in the estrogen-only patients.
The results of other hormone replacement studies over the last 50 years, including a study that followed over 1, menopausal women for 10 years, have shown cardiovascular benefits from estrogen and no increased risk for cancer. Some researchers believe that the age group tested in the trial may have been too old to benefit from the therapy, thus skewing the results.
In the meantime, intense debate and study of the benefits and risks of replacement therapy is ongoing. Current guidelines approve HT for the reduction of hot flashes or flushes, but this treatment is generally only considered when women first start showing signs of menopausal changes, is used in the lowest dose possible for the shortest time possible 5 years or less , and it is suggested that women on HT have regular pelvic and breast exams.
The external female genitalia are collectively called the vulva. The vagina is the pathway into and out of the uterus. The ovaries produce oocytes, the female gametes, in a process called oogenesis. As with spermatogenesis, meiosis produces the haploid gamete in this case, an ovum ; however, it is completed only in an oocyte that has been penetrated by a sperm.
In the ovary, an oocyte surrounded by supporting cells is called a follicle. In folliculogenesis, primordial follicles develop into primary, secondary, and tertiary follicles. Early tertiary follicles with their fluid-filled antrum will be stimulated by an increase in FSH, a gonadotropin produced by the anterior pituitary, to grow in the day ovarian cycle. Supporting granulosa and theca cells in the growing follicles produce estrogens, until the level of estrogen in the bloodstream is high enough that it triggers negative feedback at the hypothalamus and pituitary.
This results in a reduction of FSH and LH, and most tertiary follicles in the ovary undergo atresia they die. One follicle, usually the one with the most FSH receptors, survives this period and is now called the dominant follicle. The dominant follicle produces more estrogen, triggering positive feedback and the LH surge that will induce ovulation. Following ovulation, the granulosa cells of the empty follicle luteinize and transform into the progesterone-producing corpus luteum.
The ovulated oocyte with its surrounding granulosa cells is picked up by the infundibulum of the uterine tube, and beating cilia help to transport it through the tube toward the uterus. Fertilization occurs within the uterine tube, and the final stage of meiosis is completed.
The uterus has three regions: It has three layers: The endometrium responds to estrogen released by the follicles during the menstrual cycle and grows thicker with an increase in blood vessels in preparation for pregnancy. If the egg is not fertilized, no signal is sent to extend the life of the corpus luteum, and it degrades, stopping progesterone production. This decline in progesterone results in the sloughing of the inner portion of the endometrium in a process called menses, or menstruation.
The breasts are accessory sexual organs that are utilized after the birth of a child to produce milk in a process called lactation. Birth control pills provide constant levels of estrogen and progesterone to negatively feed back on the hypothalamus and pituitary, and suppress the release of FSH and LH, which inhibits ovulation and prevents pregnancy.
Follow the path of ejaculated sperm from the vagina to the oocyte. Include all structures of the female reproductive tract that the sperm must swim through to reach the egg. Endometriosis is a disorder in which endometrial cells implant and proliferate outside of the uterus—in the uterine tubes, on the ovaries, or even in the pelvic cavity.
Skip to content Increase Font Size. Chapter Bedford JM. The status and the state of the human epididymis. Hum Reprod ; 9: — The epididymis and sperm maturation: a perspective. Reprod Fertil Dey ; 5: — In situ histochemical analysis of region-specific gene expression in the adult rat epididymis. Mol Reprod Dey ; 1— Specialized gene expression in the epididymis. J Androl ; — Duration of transit of spermatozoa through the human male ductular system.
Fertil Steril ; — Daily spermatozoal production and epididymal spermatozoal reserves of the human male. The role of the human epididymis in sperm maturation and sperm storage as reflected in the consequences of epididymovasostomy. Freund M, Davis JE. Disappearance rate of spermatozoa from the ejaculate following vasectomy. McNeal JE.
The zonal anatomy of the prostate. Prostate ; 2: 35— Precise localization of the autonomic nerves from the pelvic plexus to the corpora cavernosa: a detailed anatomical study of the adult male pelvis. Studies on the structure and intrinsic innervation of the normal human prostate. Prostate Suppl ; 2: 5— Sexual function following radical prostatectomy: influence of preservation of neurovascular bundles.
Detailed anatomy of penile neurovascular structures: surgical significance. Penile venous drainage in erectile dysfunction. Anatomical, radiological and functional considerations. Br J Urol ; — Virag R. Intracavernous injection of papaverine for erectile failure. Lancet ; 2: Brindley GS. Cavernosal alpha blockage: a new technique for investigating and treating penile impotence. Br J Psychiatry ; — Evaluation of arteriogenic impotence with intracorporal injection of papaverine and the duplex ultrasound scanner.
Semin Urol ; 3: 43— Immunohistochemical localization of nitric oxide synthase in the autonomic innervation of the human penis. J Urol ; 73— Burnett AL. Recall that the release of NO induces relaxation of the smooth muscles that surround the penile arteries, leading to the vasodilation necessary to achieve an erection.
There are several different forms of this enzyme, and PDE type 5 is the type of PDE found in the tissues of the penis. Scientists discovered that inhibiting PDE5 increases blood flow, and allows vasodilation of the penis to occur. PDEs and the vasodilation signaling pathway are found in the vasculature in other parts of the body. In the s, clinical trials of a PDE5 inhibitor called sildenafil were initiated to treat hypertension and angina pectoris chest pain caused by poor blood flow through the heart.
The trial showed that the drug was not effective at treating heart conditions, but many men experienced erection and priapism erection lasting longer than 4 hours. Because of this, a clinical trial was started to investigate the ability of sildenafil to promote erections in men suffering from ED. Since approval of the drug, sildenafil and similar PDE inhibitors now generate over a billion dollars a year in sales, and are reported to be effective in treating approximately 70 to 85 percent of cases of ED.
Importantly, men with health problems—especially those with cardiac disease taking nitrates—should avoid Viagra or talk to their physician to find out if they are a candidate for the use of this drug, as deaths have been reported for at-risk users. Testosterone, an androgen, is a steroid hormone produced by Leydig cells. The alternate term for Leydig cells, interstitial cells, reflects their location between the seminiferous tubules in the testes. In male embryos, testosterone is secreted by Leydig cells by the seventh week of development, with peak concentrations reached in the second trimester.
This early release of testosterone results in the anatomical differentiation of the male sexual organs. In childhood, testosterone concentrations are low. They increase during puberty, activating characteristic physical changes and initiating spermatogenesis.
The continued presence of testosterone is necessary to keep the male reproductive system working properly, and Leydig cells produce approximately 6 to 7 mg of testosterone per day. Testicular steroidogenesis the manufacture of androgens, including testosterone results in testosterone concentrations that are times higher in the testes than in the circulation. Maintaining these normal concentrations of testosterone promotes spermatogenesis, whereas low levels of testosterone can lead to infertility.
In addition to intratesticular secretion, testosterone is also released into the systemic circulation and plays an important role in muscle development, bone growth, the development of secondary sex characteristics, and maintaining libido sex drive in both males and females.
In females, the ovaries secrete small amounts of testosterone, although most is converted to estradiol. A small amount of testosterone is also secreted by the adrenal glands in both sexes.
The regulation of testosterone concentrations throughout the body is critical for male reproductive function. The intricate interplay between the endocrine system and the reproductive system is shown in Figure 7.
The regulation of Leydig cell production of testosterone begins outside of the testes. The hypothalamus and the pituitary gland in the brain integrate external and internal signals to control testosterone synthesis and secretion. The regulation begins in the hypothalamus. Pulsatile release of a hormone called gonadotropin-releasing hormone GnRH from the hypothalamus stimulates the endocrine release of hormones from the pituitary gland.
Binding of GnRH to its receptors on the anterior pituitary gland stimulates release of the two gonadotropins: These two hormones are critical for reproductive function in both men and women. In men, FSH binds predominantly to the Sertoli cells within the seminiferous tubules to promote spermatogenesis. FSH also stimulates the Sertoli cells to produce hormones called inhibins, which function to inhibit FSH release from the pituitary, thus reducing testosterone secretion. These polypeptide hormones correlate directly with Sertoli cell function and sperm number; inhibin B can be used as a marker of spermatogenic activity.
In men, LH binds to receptors on Leydig cells in the testes and upregulates the production of testosterone. Low blood concentrations of testosterone stimulate the hypothalamic release of GnRH.
GnRH then stimulates the anterior pituitary to secrete LH into the bloodstream. When concentrations of testosterone in the blood reach a critical threshold, testosterone itself will bind to androgen receptors on both the hypothalamus and the anterior pituitary, inhibiting the synthesis and secretion of GnRH and LH, respectively.
When the blood concentrations of testosterone once again decline, testosterone no longer interacts with the receptors to the same degree and GnRH and LH are once again secreted, stimulating more testosterone production.
This same process occurs with FSH and inhibin to control spermatogenesis. Male Reproductive System Declines in Leydig cell activity can occur in men beginning at 40 to 50 years of age. The resulting reduction in circulating testosterone concentrations can lead to symptoms of andropause, also known as male menopause. While the reduction in sex steroids in men is akin to female menopause, there is no clear sign—such as a lack of a menstrual period—to denote the initiation of andropause.
Instead, men report feelings of fatigue, reduced muscle mass, depression, anxiety, irritability, loss of libido, and insomnia. A reduction in spermatogenesis resulting in lowered fertility is also reported, and sexual dysfunction can also be associated with andropausal symptoms.
Whereas some researchers believe that certain aspects of andropause are difficult to tease apart from aging in general, testosterone replacement is sometimes prescribed to alleviate some symptoms. Recent studies have shown a benefit from androgen replacement therapy on the new onset of depression in elderly men; however, other studies caution against testosterone replacement for long-term treatment of andropause symptoms, showing that high doses can sharply increase the risk of both heart disease and prostate cancer.
Gametes are the reproductive cells that combine to form offspring. Organs called gonads produce the gametes, along with the hormones that regulate human reproduction.
The male gametes are called sperm. Spermatogenesis, the production of sperm, occurs within the seminiferous tubules that make up most of the testis. The scrotum is the muscular sac that holds the testes outside of the body cavity. Spermatogenesis begins with mitotic division of spermatogonia stem cells to produce primary spermatocytes that undergo the two divisions of meiosis to become secondary spermatocytes, then the haploid spermatids.
During spermiogenesis, spermatids are transformed into spermatozoa formed sperm. Upon release from the seminiferous tubules, sperm are moved to the epididymis where they continue to mature. During ejaculation, sperm exit the epididymis through the ductus deferens, a duct in the spermatic cord that leaves the scrotum.
The ampulla of the ductus deferens meets the seminal vesicle, a gland that contributes fructose and proteins, at the ejaculatory duct. The fluid continues through the prostatic urethra, where secretions from the prostate are added to form semen. These secretions help the sperm to travel through the urethra and into the female reproductive tract.
Secretions from the bulbourethral glands protect sperm and cleanse and lubricate the penile spongy urethra. The penis is the male organ of copulation.
Columns of erectile tissue called the corpora cavernosa and corpus spongiosum fill with blood when sexual arousal activates vasodilatation in the blood vessels of the penis. Testosterone regulates and maintains the sex organs and sex drive, and induces the physical changes of puberty. Interplay between the testes and the endocrine system precisely control the production of testosterone with a negative feedback loop. Watch this video to learn about vasectomy.
Watch this video to explore the structures of the male reproductive system and the path of sperm that starts in the testes and ends as the sperm leave the penis through the urethra. What special features are evident in sperm cells but not in somatic cells, and how do these specializations function?
While anabolic steroids synthetic testosterone bulk up muscles, they can also affect testosterone production in the testis.
Using what you know about negative feedback, describe what would happen to testosterone production in the testis if a male takes large amounts of synthetic testosterone.
Skip to content Increase Font Size. Chapter The Reproductive System.
Learning Objectives By the end of this section, you will be able to: Describe the structure and function of the organs of the male reproductive system Describe the structure and function of the sperm cell Explain the events during spermatogenesis that produce haploid sperm from diploid cells Identify the importance of testosterone in male reproductive function. Interactive Link Feature.
Sperm remain in the epididymis until they degenerate. Review Questions 1.Protective role of Tribulus terrestris.
External Female Genitals
Each of our cells contains approximately mitochondria, with each mitochondrion packed with mtDNA containing approximately 37 genes. The number of times an animal comes into season during the year varies, as does the number of oestrous cycles during each season.
Share This Book. It takes an average of 12 days for sperm to move through the coils of the epididymis, with the shortest recorded transit time in humans being one day. For a woman to conceive, certain things have to happen: However, there is a great diversity of physical adaptations as well as reproductive strategies in every group of vertebrates.
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