Reproductive System Part 2 PDF

Reproductive System Marie A. Román Martínez, PhD Department of Biology Office hours: by appointment Email: [email protected] Copyright-This presentation is intended for educational purpose only. No part of this presentation may be reproduced or transmitted in any form without written permission. O...

Reproductive System Marie A. Román Martínez, PhD Department of Biology Office hours: by appointment Email: [email protected] Copyright-This presentation is intended for educational purpose only. No part of this presentation may be reproduced or transmitted in any form without written permission. Objectives 1. Define the key terms of reproduction. 2. Describe the locations and functions of the male reproductive organs. 3. Describe spermatogenesis. 4. Describe the actions of testosterone. 5. Describe the location and functions of the organs of the female reproductive system. 6. Describe oogenesis and the development of the corresponding ovarian follicles. 7. Describe the ovarian and menstrual cycles and their regulation by hormones. 8. Describe the structure of mammary glands and breasts. 9. Describe how various methods of birth control work. 10. Describe the common disorders of the reproductive system. 2 Female Reproductive System Produces female sex hormones. Produces secondary oocytes. Transports secondary oocytes to site where they can unite with sperm. Provides a suitable environment for development of the embryo and fetus. Actively involved in birthing process. 3 Female Reproductive System Structures Paired ovaries produce female sex hormone. Paired uterine tubes which transports secondary oocytes. Uterus where development of the embryo and fetus occurs. Vagina serves as the female copulatory organ and birth canal. External genitalia. Female reproductive tract: uterine tubes, uterus, vagina. 4 Ovaries Located near the upper side walls of pelvic cavity. Same size and shape as almonds. Structure: Outer surface is covered by the ovarian mesothelium. Under the mesothelium are ovarian follicles. Consists of an oocyte enveloped by supporting cells. The inner region has areolar connective tissue with nerves and blood vessels. 5 Oogenesis Process of producing oocytes. Similar to spermatogenesis, with a few notable exceptions. Tied closely to the ovarian cycle. By 5th month of fetal development, ovaries contain several million oogonia the stem cells of the ovaries (46 chromosomes). 6 Steps of Oogenesis Most of the oogonia mature into primary oocytes (46 chromosomes) prior to birth. Each is surrounded by a single layer of follicular epithelial cells, forming a primordial ovarian follicle. Females are born with their total number of primary oocytes (approximately 2 million). No oogonia exist at birth. Beginning at puberty, a few primordial follicles are activated monthly and require nearly a year to mature. 7 Steps of Oogenesis One primary oocyte will complete meiosis I each month. Prior to meiosis I, chromosomes in primary oocyte replicate. In metaphase of meiosis I, homologous pairs line up. Random alignment and crossover occurs. At the end of meiosis I, primary oocyte divides into two distinct cells each with 23 chromosomes. Polar body (no function). Secondary oocyte (has nearly all of the cytoplasm). Secondary oocyte is released each month during a female’s reproductive life from the ovary at ovulation. 8 Steps of Oogenesis Meiosis II only occurs if secondary oocyte is penetrated by a sperm. Meiosis II yields two distinct cells, each with 23 chromosomes. Polar body (no function) Ovum (has nearly all of the cytoplasm). Fusion of ovum nucleus and sperm nucleus forms a zygote, the first cell of the preembryo. 9 Uterine Tubes Each extends from laterally from upper side of the uterus to an ovary. Receive and transport secondary oocyte. Site of fertilization. Transport preembryo if fertilization occurs. The infundibulum partially envelops the ovary. Possesses fimbriae. Inner lining consists of simple ciliated columnar epithelium and secretory cells. Beating cilia create a current to draw the secondary oocyte into the infundibulum. Cilia and peristalsis move oocyte toward uterus. Epithelial lining of the uterine tube. Secretory cells are shown in red and green and ciliated cells in yellow (SEM). Image obtained from Figure 28.4 from Saladin Anatomy & Physiology 9th edition 10 Uterus Behind the urinary bladder in pelvic cavity. Above the vagina and bent forward over the urinary bladder. Hollow organ with thick muscular walls. Provides an appropriate internal environment for developing embryo and fetus. Has three major regions: Fundus Body Cervix 11 Pap Smears and Cervical Cancer Cervical cancer usually occurs between the ages of 30 and 50. Higher risk in women who smoke, who began sexual activity at an early age, and who have histories of frequent sexually transmitted diseases or cervical inflammation. Cervical cancer it is almost always caused by the human papilloma virus (HPV). Pap smear—a procedure in which loose cells are removed from the cervix and vagina then microscopically examined. The pathologist looks for cells with signs of dysplasia (abnormal development) or carcinoma. From age 21 to 65, women are advised to have a Pap smear every 3 years. Pap smear. Image obtained from Figure 28.5 from Saladin Anatomy & Physiology 9th edition 12 Uterus Wall is composed of three layers: Endometrium Inner mucosal layer. Myometrium Middle muscular layer-thicker layer of smooth muscle that forms most of the wall thickness. Perimetrium Outer serous layer. 13 Vagina Collapsible tube extending from uterus to the external environment. Behind the urethra and in front of the rectum. Functions: Copulatory organ Birth canal 14 Female External Genitalia Also called the vulva. Surrounds the orifices of the urethra and vagina. Perineum: Area between the mons pubis and the anus. Obstetrical perineum is between vaginal orifice and anus. It is so named because this tissue is often torn during childbirth. 15 Female External Genitalia Labia majora: Paired, longitudinal folds of hair-covered skin covering adipose and smooth muscle. Formed from the same embryonic tissue as scrotum. Labia minora: Paired, thinner longitudinal folds. 16 Female External Genitalia Vestibule: Narrow space between the labia minora. Urethra opens into the front portion, while vagina opens behind it. Bulbs of the vestibule: Composed of corpus spongiosum. Beneath the labia minora surrounding the beginning of the vagina. Engorged with blood during the female sexual response. 17 Female External Genitalia Vestibular glands: Lie behind the bulbs on each side of vaginal orifice. Release secretions into vestibule. Clitoris: Formed of two columns of corpora cavernosa near the pubis. Glans of the clitoris: Union of the two columns of the clitoris. The only portion of the female erectile tissues that is visible in the perineum. Located behind the mons pubis where the labia minora meet. Abundant sensory receptors. 18 Female Sexual Response In absence of sexual stimulation: Erectile tissues of bulb of the vestibule and clitoris have a small amount of blood. In the presence of sexual stimulation: Parasympathetic action potentials Cause dilation of the arterioles and constriction of the venules supplying the erectile tissues to become engorged with blood and produce erection. Lead to erection of the clitoris (same mechanism as in males). Cause enlargement of vaginal mucosa and breast and erection of nipples due to increase in blood flow in these areas. Stimulate vestibular gland secretion to lubricate the vestibule. Sexual response culminates in orgasm, as in males. 19 Female Sexual Response In the presence of sexual stimulation: Sympathetic action potentials and prostaglandins in semen trigger reverse peristalsis (cause the muscles to contract rhythmically) in pelvic floor muscles uterine wall, and uterine tubes. Aids in moving sperm through the uterus to the upper uterine tubes. 20 Female Sex Hormones Estrogens: Group of female sex hormones produced primarily by the ovaries. Produced by ovarian follicles exposed to FSH. Stimulate maturation of female reproductive organs. Stimulate development and maintenance of female secondary sex characteristics: Development of mammary glands and breasts. Broad pelvis. Increased subcutaneous tissue deposition. Increased blood supply to skin. Development of axillary and pubic hair (due to androgens). 21 Female Sex Hormones Progesterone: Produced by the corpus luteum (also releases estrogen) after ovulation under stimulation by LH. Major role is development and maintenance of endometrium in pregnancy. Also inhibits uterine contractions and dilation of the cervix during pregnancy. Both estrogen and progesterone play major roles in the regulation of the female reproductive cycle. 22 Female Reproductive Cycles There are two cycles that are hormonally controlled and occur simultaneously starting at puberty. Ovarian cycle Monthly formation and release of a secondary oocyte and the ovarian events that occur in anticipation of pregnancy. Menstrual cycle Repetitive changes in the endometrium that causes monthly menstruation if pregnancy does not occur. 23 Female Reproductive Cycles Cycle lengths range from 24 to 35 days. 28 days is about average. Cycles continue from puberty (approx. 11 years of age) until menopause (between ages of 45 to 55). Cessation of reproductive cycles Periods of pregnancy and nursing. 24 Ovarian Cycle First menstruation at approx. age 13. Cycle begins when the hypothalamus secretes GnRH. Release FSH and LH. During the follicular phase, FSH promotes development of approx. 20 primordial ovarian follicles into primary ovarian follicles. Some primary ovarian follicles develop into secondary ovarian follicles. 25 Ovarian Cycle Secondary ovarian follicles transition into tertiary ovarian follicles with small fluid-filled spaces. Each with a primary oocyte surrounded by granulosa cells. Granulosa cells secrete estrogens and pass nutrients to developing oocyte. One dominant tertiary ovarian follicle continues to develop. 26 Ovarian Cycle Dominant tertiary ovarian follicle secretes low levels of estrogens and inhibin into the blood. Initiates a negative-feedback mechanism on GnRH and FSH. Inhibition of FSH prevents development of additional ovarian follicles. 27 Ovarian Cycle Due to increased FSH sensitivity, granulosa cells increase estrogen production. Begins on day 7 and peaks on day 12. High blood estrogen levels, stimulate GnRH production in a positive-feedback mechanism. GnRH leads to production of LH. The rapid increase in blood LH: Causes maturation of tertiary ovarian follicle into mature ovarian follicle. Stimulate the completion of meiosis I to form a secondary oocyte. Stimulates ovulation of secondary oocyte. Occurs 14 days prior to onset of next menstruation. 28 Ovarian Cycle After ovulation, the luteal phase begins. LH stimulates remaining granulosa cells in ovary to become the corpus luteum. The corpus luteum secretes progesterone (some estrogens) for approx. 10 days after ovulation. Elevated blood progesterone level. Loss of GnRH inhibits the release of LH and FSH. 29 Ovarian Cycle If fertilization does not occur: Corpus luteum degenerates into the nonfunctional corpus albicans. Rapid decline in blood estrogens and progesterone during the last few days of the cycle. Loss of negative-feedback control allows GnRH secretion to begin the next cycle. If fertilization occurs: Corpus luteum enlarges: Produces increasing amounts of progesterone and estrogens. Degenerates by 16 to 20 weeks of development. 30 Menstrual Cycle Refers to monthly changes in the endometrium, unless pregnancy occurs. Occurs in response to changes in estrogen and progesterone. Has four phases: Menstruation Proliferative phase Secretory phase Premenstrual phase 31 Menstrual Cycle Menstruation: Menstruation begins on the first day and lasts 3 to 5 days. Proliferative phase: Characterized by a buildup of the endometrium. Stimulated by estrogens produced by the developing ovarian follicles. Begins at the end of menstruation and ends at ovulation. 32 Menstrual cycle Secretory phase: Begins at ovulation and last approx. 10 days. Controlled by hormones from the corpus luteum: Estrogens continue to stimulate endometrial thickening. Progesterone stimulates the formation of blood vessels and glands in the endometrium. Prepares endometrium for a pre-embryo. 33 Menstrual cycle Premenstrual phase: Occurs during the last few days of the cycle if fertilization does not occur. Breakdown of the endometrium occurs: Due to rapid decrease in blood levels of estrogens and progesterone. Leads to menstruation (start of a new cycle). 34 Menopause The cessation of regular menstrual cycles. Usually begins around ages 45-55 and can last up to 10 years. Caused by aging of the ovaries. Fewer primary ovarian follicles exist to respond to FSH and LH. No ovulation Secretion of estrogens and progesterone is reduced. Symptoms of menopause: Headaches Insomnia Depression Hot flashes Hormone replacement therapy can treat symptoms. But increases the risk of breast cancer, strokes, and heart disease. 35 Mammary glands Both males and females possess mammary glands. At puberty, estrogens and progesterone stimulate the development of female mammary glands. Estrogens: Start breast and mammary gland development. Progesterone: Stimulates mammary gland maturation so that they can secrete milk. Prolactin: Third hormone also required for milk production. 36 Mammary Gland Structure Located in subcutaneous tissue, on top of the pectoralis major. Breast contains large amounts of areolar and adipose tissues. Areola: Pigmented circle of skin near apex of each breast. Nipple: Erectile tissue in center of each areola. 37 Mammary Gland Structure Each gland consists of 15 to 25 lobes containing lobules. Lobules contain glandular alveoli that produce milk under stimulation by prolactin after the birth of an infant. Lactiferous ducts carry milk from lobules to lactiferous sinuses. The sinuses lead to the nipple and the external environment. 38 Birth control Birth control methods may be categorized into several groups based on mode of action: Hormonal Chemical Behavioral contraceptive methods Anti-implantation devices Sterilization Induced abortion 39 Contraception Contraception is the prevention of conception, which is the union of a sperm nucleus and ovum nucleus. Several types of contraception: Hormonal methods Barriers to sperm Spermicides Behavioral methods 40 Hormonal Methods Drugs that possess high synthetic progesterone and low synthetic estrogens to prevent ovulation. Inhibit production of GnRH, which reduces the secretion of FSH and LH production. Prevent maturation of ovarian follicles so ovulation does not occur. Effective but has side effects: Headache, irregular menstruation, nausea, bloating. Products should not be used with a history of: Smoking, blood clots, stroke, heart disease, liver disease and uncontrolled diabetes. 41 Hormonal Methods Oral contraceptives: “The pill” was the first available method of delivery, and it is still widely used. One pill is taken daily for 3 weeks. Combination pill, which contains both progesterone and estrogens, is most commonly used. Morning after pills for postcoital emergency contraception. Birth control patch: Adhesive skin patch containing hormones. Hormones are absorbed through skin. New patch is used each week for 3 weeks. Vaginal ring Soft plastic ring that is placed into the upper part of the vagina. Releases synthetic hormones for 3 weeks. It is removed at the start of the 4th week. 42 Male Contraceptive Both hormonal and non-hormonal approaches to stop sperm have been in development. Two months to become effective and require continuous treatment to remain fully effective. Reversing their effects takes a similarly long time. Following ejaculation, sperm begin to vigorously beat their tails. An enzyme called soluble adenylyl cyclase (sAC) is needed to https://www.nih.gov/news-events/nih-research- trigger this behavior. matters/male-contraceptive-disables-sperm Natalia Rivera Sánchez, estudiante doctoral, Cornell University An NIH-funded team of researchers, led by Drs. Jochen Buck and Lonny Levin at Weill Cornell Medicine, developed a compound called TDI-11861 that binds and inhibits sAC. When male mice treated with TDI-11861 were paired with females, none of the females became pregnant. The effect of the treatment wore off with time, and by 24 hours after treatment, fertility had recovered completely. 43 Hormonal Methods Norplant: Silicone rods containing progesterone surgically implanted under the skin. Inhibits ovulation. Effective for up to 5 years. Depo-Provera: Muscular injection of progesterone given at 3-month intervals. Prevents ovulation. Alters endometrium to inhibit pre-embryo implantation. Weight gain is a common side effect. Avoid use if there is a history of high blood pressure, asthma, kidney disease, migraine, headaches, breast cancer. 44 Barriers Prevent sperm from entering the uterus. Condoms: Prevent sperm from being deposited in the vagina. Male condom Female condom is a thin polyurethane bag wit a flexible ring at each end. Condoms reduce but do not eliminate the chance of infection by sexually transmitted diseases. Diaphragm: Dome-shaped sheet of rubber supported by flexible ring. Placed in the upper vagina over the cervix prior to intercourse. Blocks sperm from entering the uterus. Used with spermicidal substances. 45 Barriers Cervical cap: Thimble-shaped latex rubber cap that fits snugly over the cervix. Used with spermicidal substances. Not recommended for females with abnormal pap smears of cervical infections. 46 Spermicides Kill sperm by destroying their plasma membranes. Examples: creams, jellies, suppositories. 47 Behavioral Methods Rhythm method: Abstinence from intercourse from 3 days before to 3 days after ovulation, for a total of seven days. It is based on the fact that the secondary oocyte may be penetrated by a sperm for only about 24 hours. Difficulty is in timing ovulation, because few women have perfectly regular cycles. Failure rate is higher in women with irregular cycles. Withdrawal or coitus interruptus: Removal of the penis from the vagina prior to ejaculation. Failures result from pre-ejaculatory emission of semen or failure to withdraw in time before ejaculation. 48 Anti-implantation devices Intrauterine device (IUD): Small plastic or copper object placed into the uterus by a doctor. Inflames the endometrium, which prevents implantation of a pre-embryo. Side effects include excessive menstrual bleeding, painful cramps, increased risk of pelvic inflammatory disease, infertility. 49 Sterilization Vasectomy: Cutting and blocking of the vas deferens within the scrotum. Sperm cannot be part of semen. Tubal ligation: Performed through a small abdominal incision. Uterine tubes are cut and blocked. Blocks transport of secondary oocyte toward uterus. Vasectomies and tubal ligations do not affect the production of sex hormones or the sexual response. 50 Induced Abortion Abortion is the premature expulsion of an embryo or fetus from the uterus. Miscarriage: Spontaneous abortion. Usually result from hormonal disorders or serious abnormalities in the embryo. Induced abortion: Used to terminate unwanted pregnancies. Involve dilation of the cervix and removal of the embryo or fetus with suction or surgical means. Side effects include prolonged bleeding, perforation of the uterus, and emotional trauma. 51 Induced Abortion Mifepristone: The so-called abortion pill, mifepristone. Progesterone antagonist: Blocks ability of the placenta to recognize progesterone. Endometrium breaks down allowing the embryo or fetus to detach and pass from the uterus. Prostaglandins are used to help cause uterine contractions. Limited to the first 5 weeks of pregnancy and requires physician care. 52 Reproductive System Disorders Reproductive system disorders are grouped into: Male disorders Female disorders Sexually transmitted disease (STDs) 53 Male Disorders Prostatitis: Acute or chronic inflammation of the prostate gland. Usually caused by bacteria associated with urinary tract infections or STDs. Symptoms include tenderness and an enlarged prostate. Benign prostatic hyperplasia (BPH): Enlargement of the prostate gland without inflammation, resulting from an increase in the number of glandular cells. Occurs in 33% of males over 60. Detected by rectal exams. May restrict urine flow and ability to control micturition. Cause unknown. Transurethral resection is a common therapy. 54 Male Disorders Prostate cancer: Most common cancer and second leading cause of cancer death in American males. Cause unknown but probably related to genetic or hormonal factors. Males over 40 should have annual exams. Testicular cancer: Most common male cancer between 15 and 35 years. Cause unknown: May be related to cryptorchidism, physical damage, environmental pollutants. Easily detected with the highest cure rate of all the cancers. Monthly testicular exams recommended over age 14. 55 Male Disorders Erectile Dysfunction (ED): Inability to attain and maintain an erection. Organic and psychological causes. Treatment is available in most cases. Infertility: Inability to produce and deposit sufficient numbers of viable sperm in the vagina. Low sperm count is a common cause. 56 Female Disorders Amenorrhea—Absence of menstruation. Primary amenorrhea: Failure to begin menstruation. Endocrine disorders or abnormal development. Secondary amenorrhea: Is the absence of one or more menstrual periods without pregnancy. This may result from excessive physical exertion or excessive weight loss. Dysmenorrhea: Painful menstruation that prevents normal daily activities. Premenstrual syndrome: Severe physical or emotional distress after ovulation and prior to menstruation cause unknown, although is probably related to ovarian hormone production. 57 Female Disorders Toxic shock syndrome: Symptoms include high fever, fatigue, headache, sore throat, vaginal irritation, vomiting, and diarrhea. Due to toxin from a strain of Staphylococcus aureus bacteria whose growth is enhanced by using highly absorbent tampons. Endometriosis: Growth of endometrial tissue outside the uterus. Migrates through uterine tubes and into pelvic cavity. Causes premenstrual or menstrual pain. Due to its breakdown during menstruation. Can cause infertility from tubal obstruction. 58 Female Disorders Infertility: Inability to conceive. Caused by tubal obstruction, hypothalamus, pituitary gland, or ovarian disease, or lack of maintenance of the endometrium. Pelvic inflammatory disease (PID): Infection of the female reproductive organs and or pelvic tissues. Common causes are sexually transmitted diseases. 59 Female Disorders Cancer: Breast cancer: Most common cancer and second leading cause of cancer death in American females. Strongly related to genetic factors and estrogens. More prevalent after menopause. Monthly breast exams over age 20 and yearly mammography screens over age 40 are recommended. High fatality rate unless caught early. Cervical cancer: Slow growing cancer. Most associated with human papillomavirus (HPV) infections. Early detection is possible through annual Pap smear exams over the age 21. Vaccinations (Cervarix and Gardasil) available for preventing the HPV types that cause most cervical cancer. 60 Sexually Transmitted Diseases (STDs) Gonorrhea: Caused by bacterium Neisseria gonorrhoeae. Males: painful urethritis Females: infects urethra, reproductive organs, and pelvic cavity. May not experience symptoms until later stages. Major cause of sterility. Can cause blindness in newborn infants. Antibiotics provide effective treatment. Chlamydia: Caused by bacterium Chlamydia trachomatis. Males: painful urethritis. Females: spread through reproductive tract, causing damage that can lead to sterility. Can be transmitted to a fetus during birth. Antibiotics are effective treatment. 61 Sexually Transmitted Diseases (STDs) Syphilis: Caused by bacterium, Treponema pallidum. First stage: Formation of an open sore, a chancre, at site of bacterial entrance. Lasts approximately 1 to 5 weeks. Second stage: Muscle and joint pain, fever, and skin rash. Lasts 4 to 8 weeks. Disease enters a latent period at this point. Third stage: Bacteria destroy organs like brain and liver. Antibiotics are an effective treatment prior to the third stage. 62 Sexually Transmitted Diseases (STDs) Genital herpes: Caused by herpes simplex virus type 2. Painful blisters on reproductive organs, fever, flulike symptoms. Can be transmitted to a fetus during birth. In a newborn, mild discomfort, serious neural damage, death are possible. Treatment with anti-viral drug acyclovir inhibits viral replication. The virus cannot be eliminated from the body. Genital warts: Caused by human papillomavirus (HPV). About 1 million new cases occur each year. Patients have an increased risk of certain reproductive cancers. No treatment to eliminate the virus. Warts can be removed by electrocautery, cryosurgery, or laser surgery. Vaccinations (Cervarix and Gardasil) available for HPV types that cause most genital warts. 63