Reproductive system handout3

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Bio 102: Fundamentals in Animal Biology. This is a handout about the reproductive system.

Bio 102: Fundamentals in Animal Biology. This is a handout about the reproductive system.

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  • 1. ldl 1 REPRODUCTIVE SYSTEMS 1. Plants and Animals produce NEW Individuals through a process of REPRODUCTION. 2. Reproduction involves Special Structures that make up the REPRODUCTIVE SYSTEM. 3. The Reproductive System, unlike other systems we have studied, IS NOT ESSENTIAL to the survival of an INDIVIDUAL. 4. Organisms can survive and lead healthy lives WITHOUT REPRODUCING. 5. What the Reproductive System is important to is the Survival of the SPECIES. Reproduction is absolutely essential to the continuation of the SPECIES…SOME OF US MUST REPRODUCE! 6. IN HUMANS THE REPRODUCTIVE SYSTEM PRODUCES, STORES, NOURISHES, AND RELEASES SPECIALIZED SEX CELLS KNOWN AS GAMETES. 7. The ways in which the Gametes are released make possible the fusion of Sperm (Male Gametes) and Egg (Female Gametes) in the process of FERTILIZATION. From a Fertilized Egg, or ZYGOTE, come all the cells in a human body. SEXUAL DEVELOPMENT 1. For the First SIX Weeks after fertilization, human male and female Embryos are Identical in appearance. 2. During the SEVENTH Week of development, major changes occur: A. The TESTES, which are the PRIMARY Reproductive Organs of a MALE, begin to produce Steroid Hormones (Sex) known as ANDROGENS. The tissue of the Embryo responds to these hormones by developing into the MALE REPRODUCTIVE ORGANS. B. The OVARIES, or the PRIMARY Reproductive Organs of a FEMALE Embryo, produce Steroid Hormones (Sex) known as ESTROGENS. The tissue of the Embryo responds to these hormones by developing into the FEMALE REPRODUCTIVE ORGANS. 3. THE MALE AND FEMALE REPRODUCTIVE ORGANS DEVELOP FROM EXACTLY THE SAME TISSUES IN THE EMBRYO. 4. After birth the Testes and the Ovaries continue to produce small amounts of Sex Hormones. These Sex Hormones continue to influence the development of the Reproductive Organs. 5. Neither Testes or Ovaries are capable of producing Active Reproductive Cells (GAMETES) until PUBERTY. 6. PUBERTY IS A PERIOD OF RAPID GROWTH AND SEXUAL MATURATION DURING WHICH THE REPRODUCTIVE SYSTEM BECOMES FULLY FUNCTIONAL. 7. AT THE COMPLETION OF PUBERTY, THE MALE AND FEMALE GONADS, OR REPRODUCTIVE ORGANS, ARE FULLY DEVELOPED. 8. THE ONSET OF PUBERTY VARIES AMONG INDIVIDUALS. IT MAY OCCUR ANYTIME FROM AGE 9 TO 15. GENERALLY, PUBERTY BEGINS ABOUT A YEAR EARLIER IN FEMALES THAN IN MALES. 9. Puberty begins with a change in the Hypothalamus, the part of the Brain that regulates the secretions of the Pituitary Gland (GONADOTROPIN RELEASING HORMONE, GnRH). This changes causes the Pituitary Gland to produce Increased Levels of TWO Hormones that affect the Gonads: A. Follicle Stimulating Hormone (FSH) B. Luteinizing Hormone (LH) THE MALE REPRODUCTIVE SYSTEM 1. Males begin to produce Sperm during Puberty, the adolescent stage of development when changes in the body make reproduction possible. 2. At this time, the concentration of the hormone Testosterone is high enough to stimulate sperm production. Testosterone is the Main Androgen (Male Sex Hormone) produced by the Testes. 3. The TESTES (PRIMARY MALE REPRODUCTIVE ORGANS) develop within the Abdominal Cavity, just before birth the Testes descend through a canal into an EXTERNAL SAC called the SCROTUM.
  • 2. ldl 2 4. The Testes (two egg-shaped structures) remain in the Scrotum, outside the body, where the temperature is about 3 degrees C Cooler than the body internal temperature (27 degrees C). 5. Sperm development in the Testes Requires the Lower Temperature. 6. The Testes are clusters of hundreds of Tiny Tubules called SEMINIFEROUS TUBULES, which means "SEED BEARING". Sperm Form through Meiosis in the specialized lining of this extensive network of tubules. 7. As the Pituitary Gland begins to release FSH and LH, these Hormones stimulate the Testes to make the PRINCIPAL MALE SEX HORMONE TESTOSTERONE. 8. Cells that respond to Testosterone are found all over the body. 9. Testosterone produces a number of SECONDARY SEX CHARACTERISTICS that appear in Males at Puberty – Voice Deepens, Beard Grows, and Body Hair. 10. FSH and Testosterone stimulate the development of Sperm. When large numbers of sperm have been produced in the Testes, the development process of Puberty is completed - THE REPRODUCTIVE SYSTEM IS NOW FUNCTIONAL. SPERM DEVELOPMENT 1. Sperm are derived from Special Cells within the Testes that go through the process of MEIOSIS to form HAPLOID NUCLEI found in Mature Sperm. The Chromosome number drops from 46 to 23, Four sperm cells result from each cell that begins meiosis. 2. A Mature Sperm consists of THREE Regions: A. HEAD - which contains the Nucleus (The 23 Chromosomes) and enzymes that help the sperm penetrate the protective layers that surround and Egg Cell. B. MID PIECE - packed with energy releasing Mitochondria (Energy Source). The Mitochondria supply the energy that is required for sperm to reach an Egg. C. TAIL – Consists of a Single, Powerful FLAGELLUM that propels the Sperm. 3. Developed Sperm travel from the Seminiferous Tubules into the EPIDIDYMIS. Within each Epididymis, a Sperm MATURES AND GAINS THE ABILITY TO SWIM AS ITS FLAGELLUM COMPLETES DEVELOPMENT. 4. Although most Sperm remain stored in each Epididymis, some leave the Epididymis and pass into through the VAS DEFERENS, a duct that extends from the Epididymis. 5. Each Vas Deferens enters the Abdominal Cavity, where it loops around the Urinary Bladder and merges with the Urethra. In a Male, both Urine and Sperm exit the body through the Urethra. 6. In the Urethra, Sperm Mix with Fluids that are secreted by Three Exocrine Glands- the Seminal Vesicles, Bulbourethral Glands, and the Prostate Gland- to produce SEMINAL FLUID -which Protects and Nourishes the Sperm. 7. THE COMBINATION OF SPERM AND SEMINAL FLUID IS KNOWN AS SEMEN. 8. Semen has a high concentration of Fructose to be used by Sperm as an Energy Source. 9. To increase sperm survival, semen also contains Alkaline Fluids that help to Neutralize the Acidic Environment of the Female's Vagina. 10. To help sperm move through the Female Reproductive system, Semen also contains Prostaglandins that Stimulate contractions of Smooth Muscles that line the Female Reproductive Track. 11. BETWEEN 100 AND 200 MILLION SPERM ARE PRESENT IN 1 milliliter OF SEMEN OR ABOUT 5 MILLION SPERM PER DROP! 12. The Vas Deferens merges with the URETHRA, the Tube that leads to the outside of the body through the PENIS. 13. The Penis is the Male Reproductive Organ that makes it possible for Sperm to be delivered to the body of the Female. 14. When the Male is Sexually Excited, the Autonomic Nervous System prepares the Male Organs to deliver Sperm (Erect). 15. Sperm are Ejected from the Penis by Contractions of Smooth Muscles Lining the Vas Deferens. THIS PROCESS IS CALLED EJACULATION.
  • 3. ldl 3 16. Because Ejaculation is Regulated by the Autonomic Nervous System, it is NOT Completely Voluntary. 17. 300 - 400 million Sperm are released in the Reproductive Tract of a Female during a single Ejaculation; the chances of a Single Sperm Fertilizing and Ovum (Egg OR Female Gamete), if one is available, are quit GOOD. 18. Most sperm are Killed by the Acidic Environment of the Female Reproductive Track. Only a few Sperm reach the site of Fertilization. 19. Sperm make up only 10 Percent of Semen, 90 percent is the fluid secreted by the Three Glands. FEMALE REPRODUCTIVE SYSTEM 1. THE PRIMARY REPRODUCTIVE ORGANS OF THE FEMALE ARE THE OVARIES. 2. The Ovaries are located in the Lower Abdominal Cavity; the Ovaries USUALLY produce only ONE EGG or OVUM per month. (Figure 51-5) 3. In addition to producing eggs, the female reproductive system has another important job to perform - EACH TIME AN EGG IS RELEASED, THE BODY MUST BE PREPARED TO NOURISH A DEVELOPING EMBRYO. 4. Puberty in females starts with changes in the Hypothalamus that causes the release of FSH and LH from the Pituitary Gland. 5. FSH (follicle stimulating hormone) stimulates cells within the Ovaries to produce the Hormone ESTROGEN. 6. Estrogen causes the reproductive system to complete its development, and also produce SECONDARY SEX CHARACTERISTICS - Enlargement of Breast and Reproductive Organs, Widening of the Hips, and growth of Body Hair. FORMATION OF EGGS (OVA, CALLED THE OVARIAN CYCLE) 1. Each Ovary contains about 400,000 PRIMARY FOLLICLES, which are clusters of cells surrounding a single ovum (egg). 2. During her lifetime fewer than 500 Ova (Eggs) will actually be released, averaging one egg about every 28 days. 3. The FUNCTION of a Follicle is to prepare a Single Ovum for release into the part of reproductive system where it can be Fertilized. Ova mature within their follicles. The maturing eggs become large, highly complex cells, growing nearly 75,000 times Larger than Sperm. 4. When a Follicle has completely matured, the Ovum (Egg) is released. THIS PROCESS IS CALLED OVULATION. 5. If TWO Eggs mature, Fraternal, or Non Identical Twins may result. 6. Ovulation begins at Puberty and USUALLY continues until a female is in her late forties, when MENOPAUSE occurs. 7. After Menopause, Follicle Development no longer occurs and a female is no longer capable of bearing children. (Biological Clock) 8. Without Follicles, the Ovaries Cannot Secrete enough Estrogen and Progesterone to continue the Menstrual Cycle, and Menstruation ceases. 9. The Follicle literally ruptures, and the Ovum is swept from the Ovary into one of the TWO FALLOPIAN TUBES. The Fallopian Tubes provide a way for an egg to travel from the Ovary to the Uterus. 10. The Ovum is moved through the fluid filled Fallopian Tubes by Cilia attached to the cells that line the walls of the tube. 11. IT IS DURING ITS JOURNEY THROUGH THE FALLOPIAN TUBE THAT AN EGG CAN BE FERTILIZED. An Egg must be fertilized within 48 hours of its release - after that, the egg begins to break down. Unfertilized eggs dissolve in the Uterus. 12. After a FEW DAYS, the Ovum passes from the Fallopian Tube into the UTERUS. 13. The lining of the Uterus is specially designed to receive a Fertilized Ovum. 14. The lower entrance to the Uterus is called the CERVIX. A Sphincter Muscle in the Cervix controls the opening to the Uterus. 15. Leading from the Cervix to the outside of the body is a muscular tube called the VAGINA or Birth Canal.
  • 4. ldl 4 16. The External Structures of the Female Reproductive System are collectively called the VULVA. The Vulva includes the LABIA, folds of Skin and Mucous Membranes that Cover and Protect the Opening to the Female Reproductive System. THE MENSTRUAL CYCLE 1. In females, the interaction of the Reproductive System and the Endocrine System takes the form of a complex series of periodic events called the Menstrual Cycle. The Cycle takes an average of about 28 days. 2. Each month, the Uterus prepares to receive and nourish an Embryo. 3. THE MENSTRUAL CYCLE IS THE SERIES OF CHANGES THAT OCCUR IN THE UTERUS EACH MONTH. 4. The Menstrual Cycle has FOUR Stages: THE FOLLICULAR PHASE, OVULATION, THE LUTEAL PHASE AND MENSTRUATION. 5. These Stages are Regulated by the Hormones of the Endocrine System. 6. During the First Stage-THE FOLLICULAR PHASE, of the Menstrual Cycle, the Egg Matures, and the Lining of the Uterus GROWS THICKER, many tiny Blood Vessels grow into the thickened lining, in preparation for receiving a Fertilized Egg. 7. The development of an Egg in this stage of the Cycle takes about 14 DAYS. 8. The Second Stage, OVULATION, the shortest phase in the Cycle (3-4 DAYS), is the release of an egg from a ruptured follicle. Following Ovulation, an egg is swept into a fallopian tube, where it travels toward the uterus awaiting fertilization. The Egg has enough stored nutrients to survive about 48 hours. 9. The Third Stage, LUTEAL PHASE, last about 14 Days, the Cells of the Ruptured Follicle grow larger and fill the cavity, forming a New Structure called a CORPUS LUTEUM. The Corpus Luteum begins to secrete large amounts of PROGESTERONE and ESTROGEN. The Increase levels cause the Pituitary Gland to stop Secreting LH and FSH. 10. Progesterone causes the lining of the Uterus to become even thicker. 11. The Lining is prepared to receive the Embryo four or five days after the Egg is released from the Ovary. 12. An Embryo that settles into the lining of the uterus, the Corpus Luteum continues to release Hormones that causes the Uterus to maintain its thickened lining. 13. Most of the time, no embryo arrives, and the Corpus Luteum begins to produce Less and Less Estrogen and Progesterone. 14. The Decrease in Levels of Estrogen and Progesterone causes the Blood Vessels in the uterine lining to begin closing and then Break. 15. The Cells of the Uterine lining DO NOT receive adequate blood supply and come loose from the inside of the uterus. 16. The mixture of Blood and the Cells that made up the lining of the uterus is called MENSTRUAL FLUID. 17. The passage of this Fluid through the Vagina and out of the body is called MENSTRUATION OR THE MENSTRUAL PERIOD THE LAST STAGE. IT USUALLY LASTS FROM THREE TO SEVEN DAYS. At the end of the Period, a NEW Cycle Begins- THE FOLLICULAR PHASE. 18. The AVERAGE Menstrual Cycle is 28 DAYS LONG. 19. Almost ALL Women START their Menstrual Period 14 DAYS AFTER Ovulation occurs. 20. The length of the First stage of the cycle, the period when the Follicle is growing, DIFFERS from women to women. GESTATION FERTILIZATION 1. IN ORDER FOR AN OVUM TO BECOME FERTILIZED, SPERM MUST BE PRESENT IN THE FEMALE REPRODUCTIVE TRACT- MORE SPECIFICALLY, IN A FALLOPIAN TUBE. 2. During Ejaculation, 150 MILLION to 350 Million Sperm are deposited just a few inches from the Fallopian Tubes, in which Fertilization CAN OCCUR. 3. Once Sperm are released, they swim through the Vagina, Cervix, and Uterus, and, finally, up the Fallopian Tubes.
  • 5. ldl 5 4. If Ovulation occurs anytime from 72 hours before to 48 hours after Ejaculation, sperm may encounter an egg in one of the Fallopian Tubes. 5. Only a Single Sperm is needed to Fertilize an Ovum. Fertilization occurs when a sperm and an egg fuse and form a Zygote. 6. The Ovum is surrounded by a dense protective layer that contains receptor sites to which Sperm bind. 7. This binding causes a Vesicle in the Sperm Head to rupture and release enzymes that break down the protective layer and forms a pathway through which the Sperm Nucleus (Head) can reach the Ovum. 8. Once a Sperm Nucleus (Head) enters the Ovum, the Tail is left outside, the Cell Membrane changes, preventing other sperm from entering the cell. 9. The Fertilized Ovum is properly called a ZYGOTE (2N). The Zygote will go through Cell Division (Mitosis), and the Ball of Cells (Embryo) will attached itself to the wall of the uterus (IMPLANTATION) and begin to grow into an Embryo - Pregnancy. 8. Sperm can survive in the female reproductive tract for TWO days or longer, so there are usually three or four days each month when Fertilization is possible. CLEAVAGE AND IMPLANTATION 1. When an Ovum (Egg) is fertilized, the remarkable process of human development begins. 2. During this process, a single cell no larger than a period at the end of a sentence will undergo a series of Cell Divisions that will result in the formation of a new individual. 3. The first few CLEAVAGES, or MITOTIC Cell Divisions of the Zygote, take place while the Zygote is still inside a Fallopian Tube. 4. Four Days after fertilization, the Embryo consists of a solid ball of about 50 Cells known as the MORULA (MOR- yoo-luh). 5. As the Embryo grows, a fluid-filled cavity forms in the center, transforming it into a BALL of Cells known as a BLASTOCYST. 6. The Morula becomes a Blastocyst by the time it reaches the Uterus. 7. About 6 or 7 Days after Fertilization, the Blastocyst Burrows and Embeds itself to the wall of the Uterus and begins to grow Inward in a process known as IMPLANTATION. Pregnancy begins at Implantation. PREGNANCY 1. After Implantation, the Blastocyst slowly takes on the recognizable features of the human infant. 2. This nine month period of development is called GESTATION or PREGNANCY. 3. Pregnancy is divided into Three Equal Periods, or Trimesters. 4. A cluster of Cells gradually forms within the cavity of the Blastocyst. This cluster sorts itself in to TWO Layers, which then produce a THIRD Layer, by a process of Cell Migration known as GASTRULATION 5. THE RESULTS OF GASTRULATION IS THE FORMATION OF THREE CELL LAYERS KNOWN AS THE: A. ECTODERM - THE OUTERMOST PRIMARY GERM LAYER IN AN ANIMAL EMBRYO. DEVELOPS INTO THE NERVOUS SYSTEM, EPIDERMIS, AND SWEAT GLANDS. B. MESODERM- THE MIDDLE PRIMARY GERM LAYER IN AN ANIMAL EMBRYO. DEVELOPS INTO THE REPRODUCTIVE SYSTEM, KIDNEYS, MUSCLE, BONES, SKIN, BLOOD, AND BLOOD VESSELS. C. ENDODERM- INNERMOST PRIMARY GERM LAYER IN AN ANIMAL EMBRYO. DEVELOPS INTO THE LUNGS, LIVER, THE LININGS OF THE DIGESTIVE ORGANS, AND A SOME ENDOCRINE GLANDS. 6. THESE THREE LAYERS ARE REFEREED TO AS THE PRIMARY GERM LAYERS BECAUSE ALL OF THE ORGANS AND TISSUES OF THE EMBRYO WILL BE FORMED FROM THEM. 7. During Implantation, the Outer Layer of Cells of the Blastocyst produces TWO important Membranes that surround, protect, and nourish the developing Embryo - AMNION AND THE CHORION. A. CHORION = PLACENTA - THE CONNECTION BETWEEN MOTHER AND DEVELOPING EMBRYO. THE PLACENTA IS AN ORGAN THROUGH WHICH MATERIALS ARE EXCHANGED BETWEEN THE MOTHER AND THE DEVELOPING EMBRYO.
  • 6. ldl 6 B. AMNION = AMNIOTIC SAC - FLUID FILLED STRUCTURE THAT CUSHIONS AND PROTECTS THE DEVELOPING FETUS IN PLACENTAL MAMMALS 8. The Placenta is the Embryo's Organ of Respiration, Nourishment, and Excretion. The Blood of the Mother and Embryo do NOT MIX; they flow pass each other. 9. The Nine Months of Pregnancy are often divided into THREE MONTH PERIODS KNOWN AS TRIMESTERS. 10. Most of the Fetus's (After 8 WEEKS) development is completed by the end of the Second Trimester. During this time, a structure known as the UMBILICAL CORD forms. The umbilical cord, which contains TWO Arteries and ONE Vein, connects the fetus to the Placenta. STAGES OF EMBRYONIC AND FETAL DEVELOPMENT: 0-4 WEEKS - Fertilization occurs; embryo travels through Fallopian Tubes and implants in uterine wall; Nervous System, Brain, Digestion System, Ears, and Arms begin to form; Heart Forms and Begins to Beat at 21 Days. 5-8 WEEKS - Nostrils, Eyelids, nose, Fingers, Legs, Feet, Toes, and Bones begin to Form; Females develop Ovaries, Males develop Testes; Head is as large as body; Cardiovascular System is Fully Functional; about 22 mm (less than 1 inch) long. 9-12 WEEKS - Embryo becomes a FETUS, from eight weeks until birth, the developing child is called a Fetus. Penis in Males is distinct; growth of Chin and other Facial Structures give the Fetus a Human Face and Profile; Head is still Dominant, but body is lengthening; about 36 mm (1.5 inches) long. 13-16 WEEKS - Blinking of Eyes and Sucking of Lips occurs; body begins to outgrow Head; Mother can Feel muscular activity of Fetus; about 140 mm (5.5 inches) long. 17-20 WEEKS - Limbs achieve final proportions; Eyelashes and Eyebrows are present; about 190 mm (6.5 inches) long. 21-30 WEEKS - Substantial increase in weight; may survive if born at this stage; Skin is Wrinkled and Red; about 280 mm (13 inches) long. 30-40 WEEKS - Fingernails and Toenails are present; about 360 mm (14.5 inches) long. CHILDBIRTH 1. About 9 Months (about 270 Days) after Fertilization, at the end of a Full Term Pregnancy, the Fetus is ready for Birth. By this time, it has usually moved so that its Head is against the Cervix. 2. When it is time? A Hormone known as OXYTOCIN is released from the Pituitary Gland, that affects a group of large Involuntary Muscles that surrounds the Uterus. 3. WEAK, Irregular Contractions may occur for Several Weeks before birth. (False Labor). 4. As these Muscles are stimulated, they begin a series of Rhythmic Contractions knows as LABOR that Expands the opening of the CERVIX so that it will be large enough (about 10 cm) to allow the baby to pass through it. 5. As contractions continue, they become more Powerful (PAINFUL) and more Frequent, occurring once every minute or two. 6. Little by little, in a process (LABOR) that last from 2 to 20 hours, the baby is FORCED toward the Vagina as labor continues. 7. The Amniotic Sac Breaks (“Breaking Water”), and the fluid it contains rushes out of the Vagina. 8. The baby is finally Forced out of the Uterus and the Vagina, Head First, still attached to its mother by the Umbilical Cord. 9. The Baby will begin to cough or cry in order to rid its lungs of the fluid with which they have been filled. Breathing starts almost immediately. 10. The Umbilical Cord is clamped and cut, leaving a Scar known as Navel or Belly Button. 11. In the final contractions the Placenta, Amniotic Sac and the Uterine Lining, collectively called AFTER BIRTH are expelled from the mother's body about 10 minutes after the baby is born. 12. The process of Childbirth is complete.