Module 12: The Reproductive System PDF

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RomanticCedar

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Central Philippine University

Cherry Grace A. Dabucon, MD

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Reproductive System Anatomy & Physiology Human Biology Medical Science

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This document is a lecture module on the reproductive system, focusing on the anatomy, physiology, and functions of the male and female reproductive systems. It includes diagrams and descriptions of the reproductive organs and processes.

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References: MLS 1104 LECTURE Module 12 The Reproductive System Reference: Seeley’s Essentials of Anatomy & Physiology 11th Edition by Vanputte, Rega...

References: MLS 1104 LECTURE Module 12 The Reproductive System Reference: Seeley’s Essentials of Anatomy & Physiology 11th Edition by Vanputte, Regan Russo Prepared by: Cherry Grace A. Dabucon, MD 1 REPRODUCTIVE SYSTEM The reproductive system performs the following functions: 1. Production of gametes. gametes: sperm cells in the testes of males oocytes (eggs) in the ovaries of females. 2. Fertilization Males: duct system in nourishes sperm until they are mature and are deposited in the female reproductive tract by the penis. Female: receives the male’s sperm and transports them to the fertilization site. 3. Development and nourishment of a new individual. Female: nurtures the development of a new individual in the uterus until birth and provides nourishment (milk) after birth. 4. Production of reproductive hormones. - control its development and the development of the sex- specific body form. -normal function of the reproductive system and for reproductive behavior. From Fertilization to Fetus Fertilization: union of sperm and oocyte Zygote: what develops after fertilization develops into an embryo 3 to 14 days after fertilization Embryo:14 to 56 days after fertilization Fetus: 56 days after fertilization MEIOSIS The testes in males and the ovaries in females produce gametes or reproductive cells. Formation of gametes in males and females occurs by a type of cell division called Meiosis occurs only in the testes of males and the ovaries of females Before meiosis begins, all the chromosomes in these cells are duplicated, creating identical copies of each chromosome, called chromatids chromosomes align as pairs in a process called synapsis chromatid of 1 chromosome breaks off and is exchanged with part of another chromatid from the other chromosome. This event, called crossing over, allows the exchange of genetic material between chromosomes. At the end of telophase II, there are 4 daughter cells, each containing 23 chromosomes MALE REPRODUCTIVE SYSTEM The male reproductive system consists of (1) the testes (2) series of ducts, which include the epididymides the ducta deferentia (sing. ductus deferens; also, vas deferens) urethra, (3) accessory glands seminal vesicles, the prostate gland, the bulbourethral glands (4) supporting structures scrotum penis Scrotum: saclike structure containing the testes cold temperatures: ▪ the dartos muscle contracts, causing the skin of the scrotum to become firm and wrinkled and reducing its overall size ▪ the cremaster muscles which are extensions of abdominal skeletal muscles into the scrotum, contract and help pull the testes nearer the body ➔ keep the testes warm ▪ sperm must develop at temp. less than body temp (permissive temperature of about 34°C ) Cryptorchidism is the failure of one or both of the testes to descend into the scrotum seventh or eighth month of fetal development Inguinal hernia - weak spot in the abdominal muscles Testes: or male gonads primary male reproductive organ produces sperm in scrotum 4–5 cm long each testis into about 250 cone-shaped lobules which contain Seminiferous tubules: where sperm is produced a. contain germ cells/ each Spermatogonia are near the testis periphery, and mature sperm cells into are near the lumen of the about seminiferous tubules.➔ cells that 250 sperm cells arise from cone- b. contain sustentacular cells shape (Sertoli cells):are large and extend d lobule from the periphery to the lumen of s the seminiferous tubule -nourish germ cells and produce hormones (Inhibin) Endocrine cells (outer) contain Interstitial cells (Leydig cells): secrete testosterone Ducts (2) Seminiferous tubules of each testis converge into a tubular network called the rete testis empties into 15–20 tubules called the efferent ductules ➔ Epididymis Epididymis Sperm cells taken directly from the testes are not capable of fertilizing oocytes, but after maturing for several days in the epididymis, the sperm cells develop the capacity to function as gametes Final changes in sperm cells, called capacitation occur after ejaculation of semen into the vagina and prior to fertilization Ductus deferens:“vas deferens” 45 cm Arise from the tail of epididymis extends from epididymis and joins seminal vesicle cut during a vasectomy SPERMATIC CORD Each spermatic cord consists of (1) the ductus deferens, (2) the testicular artery and veins, (3) lymphatic vessels (4) the testicular nerve Pass through the abdominal wall by way of the inguinal canal ampulla of the ductus deferens loops behind the posterior surface of the urinary bladder Wall of ductus contains smooth muscles for propelling of sperm from epididymis to ampulla Glands Seminal Vesicles: sac-shaped gland next to ductus deferens helps form ejaculatory duct which enters the prostate gland Prostate gland: surrounds urethra size of a walnut Bulbourethral gland/ Cowper’s gland small mucus secreting glands near base of prostate gland decrease in size with age Urethra: extends from urinary bladder to end of penis passageway for urine and male reproductive fluids The urethra can be divided into three parts: (1) the prostatic urethra, which passes through the prostate gland; (2) the membranous urethra, which passes throughthe floor of the pelvis and is surrounded by the external urinary sphincter; (3) spongy urethra, which extends the length of the penis Penis: male organ of copulation a. corpus cavernosum (2 columns) loose fold of skin, called the b. corpus spongiosum (1 column) prepuce or foreskin, c. spongy urethra covers the glans penis 3 columns of erectile tissue which fill with blood for erection transfer sperm from male to female excrete urine Secretions Semen: mixture of sperm and secretions from glands provides a transport medium and nutrients that protect and activate sperm 60% of fluid is from seminal vesicles 30% of fluid is from prostate gland 5% of fluid is from bulbourethral gland 5% of fluid is from testes Seminal vesicles: 1. Nourishment of sperm cells : fructose 2. Movement of sperm cells: prostaglandins stimulate smooth muscle contractions of the female reproductive tract to propel sperm cells through the tract. 3. Coagulation of semen: coagulants coagulation proteins help thicken the semen, which keeps the sperm cells in the vagina for a longer period of time Secretions Prostate gland: 1. Regulate pH: alkaline pH of prostate secretion neutralizes: a. acidity of the male urethra b. secretions of the testes c. secretions of the seminal vesicles d. secretions of the seminal vesicles e. Vagina 2. Aid in sperm cell travel to oocyte Bulbourethral gland (Cowper’s Gland): (1) lubrication of the urethra for sperm movement, (2) neutralization of acidic fluid in the urethra, (3) Some lubrication during intercourse (4) neutralization of acidity in the vagina Testicular secretions: include sperm and small amount of fluid 2 to 5 milliliters of semen is ejaculated each time 1 milliliter of semen contains 100 million sperm Sperm can live for 72 hours once inside female Path of Sperm 1. Sperm develop in seminiferous tubules (testes) ➔ rete testis ➔ efferent ductules 2. Epididymis (mature) 3. Ductus deferens 4. Receive secretions from seminal vesicles, prostate gland, and bulbourethral gland 5. Urethra where semen (sperm) exit body Spermatogenesis formation of sperm cells begins at puberty (12–14) years of age, the Interstitial cells (Leydig cells) (produces Testosterone) increase in number and size, a lumen develops in each seminiferous tubule, and sperm cell production begins 74 days for sperm cells to be produced Occurs in seminiferous tubules ➔ enlarge Seminiferous tubules produce 2 types of cells: a. germ cells (spermatogonium) - divide and differentiate to form sperm cells b. sustentacular cells (Sertoli cells) - are large and extend from the periphery to the lumen of the seminiferous tubule. They nourish the germ cells and produce a number of hormones Production of Sperm Cells Germ cells (Spermatogonium) (Mitosis)➔ Primary spermatocyte (1st meiotic division)➔ Secondary spermatocyte (2nd Meiotic division)➔ spermatids ➔ sperm cells End of spermatogenesis, the developing sperm cells are located around the lumen of the seminiferous tubules, with their heads directed toward the surrounding sustentacular cells and their tails directed toward the center of the lumen Sperm Cell Structure 1. Head: contain a nucleus and DNA Acrosome: have enzymes that are released during the process of fertilization and are necessary for the sperm cell to penetrate the oocyte(eggcell) 2. Midpiece: contain mitochondria 3. Tail: flagellum for movement Male reproductive system depends on both hormonal and neural mechanisms to function normally. produced by Hormones control: (1) the development of reproductive structures (2) the development of secondary sexual characteristics, (3) Spermatogenesis (4) some aspects of sexual behavior Travels to to produce Male Sex Hormones gonadotropins 1. Gonadotropin-releasing hormone (GnRH) is produced in the hypothalamus and stimulates secretion of LH and FSH. negative-feedback 2. Luteinizing Hormone (LH) is produced in the anterior pituitary bind and stimulates secretion of testosterone. negative-feedback 3. Follicle-stimulating hormone (FSH) is produced in the anterior pituitary and prompts spermatogenesis. 4. Testosterone is produced in the interstitial cells in the testes and is involved in development and maintenance of reproductive organs. 5. Inhibin secreted by cells of the seminiferous tubules and inhibits FSH secretion. Male Sexual Behavior and the Male Sex Act Testosterone is required for normal sexual behavior. Testosterone enters the brain, especially within the hypothalamus, and influences their functions. The blood levels of testosterone remain relatively constant throughout the lifetime of a male, from puberty until about 40 years of age. Thereafter, the levels slowly decline to approximately 20% of this value by 80 years of age, causing a slow decrease in sex drive and fertility The male sex act is a complex series of reflexes Failure to achieve erections, or erectile that result in erection of the penis, secretion of mucus dysfunction (ED), sometimes called impotence, into the urethra, emission, and ejaculation can be a major source of frustration Treatment: sildenafil (Viagra), tadalafil a. Emission is the movement of sperm cells, mucus, (Cialis), or vardenafil (Levitra), or by having specific prostatic secretions, and seminal vesicle secretions into drugs injected into the the prostatic, membranous, and spongy urethra. base of the penis. b. Ejaculation is the forceful expulsion of the secretions These drugs increase blood flow into the erectile that have accumulated in the urethra to the exterior. tissue of the penis, resulting in erection for many Orgasm/Climax minutes. -pleasurable sensations, occur during the male sex act and result in an intense sensation Resolution- after ejaculation penis becomes flaccid, an overall feeling of satisfaction exists, and the male is unable to Infertility is the inability or the reduced ability to achieve erection and a second ejaculation produce offspring. The most common cause of Erection occurs, the penis becomes enlarged and rigid. infertility in males is a low sperm cell count. -the first major component of the male sex act -sight, sound, odor, or thoughts Artificial insemination infertility due to low sperm Neural stimuli cause the penis to enlarge and become firm count or reduced motility, fertility can sometimes -parasympathetic → causes arteries to dilate → be achieved by collecting several ejaculations Blood then fills small venous sinuses called sinusoids → in the and concentrating the sperm cells before inserting erectile tissue and compresses the veins, which reduces blood flow them into the female from the penis ➔ ERECTION reproductive tract FEMALE REPRODUCTIVE SYSTEM The female reproductive organs consist of (1) the ovaries, (2) the uterine tubes (or fallopian tubes) (3) the uterus, (4) the vagina, (5) the external genitalia (6) the mammary glands Internal reproductive organs are held in place within the pelvis by a group of ligaments: Internal reproductive organs are held in place within the pelvis by a group of ligaments: 1. broad ligament -attaches to the ovaries and uterine tubes 2. Suspensory ligament extends from each ovary to the lateral body wall. - contains ovarian arteries, veins, and nerves 3. The ovarian ligament attaches the ovary to the superior margin of the uterus 4. Round ligament – supports the uterus Ovaries primary female reproductive organ produces oocytes and sex hormones one on either side of uterus ovarian ligaments: anchor ovaries to uterus suspensory ligaments: anchor ovaries to pelvic cavity ovarian follicle: cells in ovaries that contain oocytes Oocyte: female reproductive cell Mesovarium: folds of peritoneum which attaches ovaries to the posterior surface of the broad ligament by Uterine Tubes/Fallopian Tube/Oviduct from the area of the ovaries to the uterus. open directly into the peritoneal cavity near each ovary and receive the secondary oocyte. opening of each uterine tube is surrounded by long, thin processes called fimbriae secondary oocyte is ovulated, it comes into contact with the surface of the fimbriae Ampulla: fertilization occurs fertilized oocyte then travels to the uterus, where it embeds in the uterine wall in a process called implantation Uterus/Womb as big as a medium-sized pear Uterine wall is composed of three layers: larger,rounded part directed superiorly. 1. an outer serous layer, called the perimetrium, from The parts: visceral peritoneum Fundus: superior to the entrance of the uterine 2. a middle, muscular layer called the myometrium, tubes bulk of uterus Body: main part of the uterus 3. an inner layer called the endometrium - simple Cervix and the narrower part, is directed inferiorly columnar epithelial Internally: Round ligament- supports uterus uterine cavity Prolapsed uterus- weakening round ligament→ uterus cervical canal ➔opens into vagina extends out of the vagina Vagina female organ of copulation; it receives the penis during intercourse. allows menstrual flow and childbirth. extends from the uterus to the outside of the body very acidic to keep bacteria out stratified squamous epithelium young females, the vaginal opening is covered by a thin mucous membrane called the hymen greatly enlarged during the first sexual intercourse perforated or torn earlier in a young female’s life during a variety of activities unreliable indicator of virginity Lateral to the labia minora are two prominent, External Genitalia/Vulva/Pudendum rounded folds of skin called labia majora vestibule is the space into which both the vagina and the Unite anteriorly at an elevation of tissue over urethra open the pubic symphysis called the mons pubis urethra opens into the vestibule just anterior to the vagina space between the labia majora is called the bordered by a pair of thin, longitudinal skin folds pudendal cleft called the labia minora Clinical is the region between the vagina and the anus A small, erectile structure called the clitoris two labia minora unite over the clitoris to form a fold to prevent such tearing during delivery , an incision of skin called the prepuce called an episiotomy Mammary Glands Organs of milk production in breasts Modified sweat glands Female breasts begin to enlarge during puberty Consists of lobes covered by adipose Lobes, ducts, lobules are altered during lactation to expel milk glandular lobes covered by adipose tissue milk-producing, or lactating, mammary gland, the ends of these small ducts expand to form secretory sacs called alveoli Each lobe possesses a single lactiferous duct that opens independently to the surface of the nipple nipples are very sensitive to tactile stimulation become erect in response to stimulation Male can become permanently enlarged, a condition called gynecomastia Hormonal imbalance (more estrogen than testosterone) Abuse use of anabolic steroids (builds muscle) Oogenesis, Follicle Development, and Fertilization Oogenesis- process of gamete production in females begins even before a female is born 4th month of development, the ovaries contain 5 million oogonia (cells from which oocytes develop) (2 million) only about 400 will complete development and be released from the ovaries fluid-filled chamber If an egg is fertilized, the corpus luteum enlarges in response to a hormone secreted by the placenta called human chorionic gonadotropin hormone (hCG) will continue to release progesterone for about 12 weeks of pregnancy. After that, the placenta will start to produce enough progesterone to support the fetus, and the corpus luteum will break down and eventually disappear If the egg is not fertilized, the corpus luteum will stop working and break down after a few days→ corpus albicans. This will cause the uterus to shed its inner lining, resulting in a menstrual period. PHYSIOLOGY OF FEMALE REPRODUCTION Female reproduction is controlled by both hormonal and nervous system mechanisms Menarche : In females, puberty, which typically begins between ages 11 and 13 and is largely completed by age 16, is marked by the first episode of menstrual bleeding Menstrual Cycle refers to the series of changes that occur in sexually mature, nonpregnant females and that result in menses 28 days (18-40days) depends on nutrition, stress, and level of activity controlled by the secretions of FSH and LH from the anterior pituitary gland Menopause time when ovaries secrete less hormones and number of follicles in ovaries is low menstrual cycle and ovulation are less regular hot flashes, fatigue, irritability may occur Treatment: estrogen replacement therapy may be used to decreases side effects Gonadotropin-releasing (GnRH) hormone is produced in Female Sex Hormones the hypothalamus and stimulates secretion of LH and FSH Luteinizing Hormone (LH) is produced in the anterior pituitary and causes ovulation Follicle-stimulating hormone (FSH) is produced in the anterior pituitary and prompts follicles in the ovaries to begin development Estrogen: (produced the ovarian follicles) proliferation of endometrial cells development of mammary glands (especially duct system) control of LH and FSH secretion development and maintenance of secondary sex characteristics Progesterone: (from corpus luteum after ovulation) enlargement of endometrial cells and secretion of fluid from uterine glands maintenance of pregnancy state development of mammary glands (especially alveoli) control of estrogen, FSH, and LH secretion development of secondary sex characteristics Stages of Menstrual Cycle Days 1 to 5 Menses (shedding of endometrium) menstrual bleeding (menses) estrogen and progesterone levels are low follicle begins to mature Days 6 to 13 Proliferative (between end of menses and ovulation) endometrium rebuilds estrogen levels begin to increase progesterone levels remain low follicle matures Day 14 Ovulation oocyte is released due to LH estrogen levels high progesterone levels are increasing cervical mucus thins Days 15 to 28 Secretory (between ovulation and next menses) endometrium is preparing for implantation estrogen levels decrease (low) progesterone levels high cervical mucus thickens Absence of a menstrual cycle is called amenorrhea Primary amenorrhea: pituitary gland does not function properly because of abnormal development Secondary amenorrhea: normal menstrual cycles and later stops menstruating (anorexia, female athletes and ballet dancers → lowGnRH Secondary amenorrhea can occur due to a lack of normal hormone secretion from the ovaries, which can result from autoimmune diseases that attack the ovary or occur due to Polycystic Ovarian Disease (anovulatory state - with no follicles completing maturation successfully) PCOS is a common cause of infertility in women Endometriosis is a condition in which endometrial tissue migrates from the lining of the uterus into the peritoneal cavity, where it attaches to the surface of organs Myomas, also called uterine fibroids, are smooth, noncancerous tumors that may develop in or around the uterus. Female Sexual Behavior Sexual drive in females, like sexual drive in males, is dependent on hormones. Testosterone-like hormones, and possibly estrogen, affect brain cells (especially in the area of the hypothalamus) and influence sexual behavior. Testosterone-like hormones are produced primarily in the adrenal cortex. Psychological factors also play a role in sexual behavior. The sensory and motor neural pathways involved in controlling female sexual responses are similar to those found in the male Female Sex Act During sexual excitement, erectile tissue within the clitoris and around the vaginal opening becomes engorged with blood. The mucous glands within the vestibule secrete small amounts of mucus, with larger amounts extruded into the vagina through its wall. Stimulation of the female’s genitals during sexual intercourse and psychological stimuli normally trigger an orgasm, or climax The vaginal and uterine smooth muscle, as well as the surrounding skeletal muscles, contract rhythmically, and muscle tension increases throughout much of the body. After the sex act, there is a period of resolution, which is characterized by an overall sense of satisfaction and relaxation Contraception Birth control methods, also called contraception methods, are procedures or devices used to prevent pregnancy In addition, protection from sexually transmitted infections can be achieved with some birth control methods. There are six main types of birth control. They are listed in order from the most effective methods to the least effective methods: (1) long-acting reversible contraception, (2) Sterilization (3) hormonal methods (4) barrier methods (5) fertility awareness (6) emergency contraception IUD Tubal ligation Vasectomy

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