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Various Parts Of Reproductive Organs& Their Functions
- 1. Functions : Urination and Copulation Penis www.freelivedoctor.com
- 2. Functions : Transport urine & semen Urethra Bladder www.freelivedoctor.com
- 3. Function : Maintain temperature of testes approx. 3 0 C below normal body temp. Scrotum www.freelivedoctor.com
- 5. Function : Produce sperm and testosterone Testis www.freelivedoctor.com
- 6. Function : Produce Sperm Testis Seminiferous Tubules www.freelivedoctor.com
- 7. Testis Cross Section Interstitial Cells Produce Testosterone www.freelivedoctor.com
- 8. Function : Sperm storage and maturation Epididymis www.freelivedoctor.com
- 9. Function : Transport sperm to urethra Vas Deferens www.freelivedoctor.com
- 10. Function : Produce 60% of alkaline semen including fructose to provide energy for sperm. Seminal Vesicles www.freelivedoctor.com Ejaculatory Duct
- 11. Function : Produces up to 1/3 of the semen & includes nutrients & enzymes to activate sperm. Prostate www.freelivedoctor.com
- 12. Function : Secretes mucous & alkaline buffers to neutralize acidic conditions of urethra. Cowper’s Gland www.freelivedoctor.com
- 13. Function : Receives penis & semen and serves as birth canal & passage for menstrual flow. Vagina www.freelivedoctor.com
- 14. Function : Provides passageway for sperm, receives blastocyst, retains & nourishes fetus & expells fetus at term. Uterus www.freelivedoctor.com
- 15. Function : Cervical mucosa secretes mucous blocking cervical canal entrance to uterus. Cervix www.freelivedoctor.com
- 16. Function : Uterine lining in which implantation occurs. Endometrium www.freelivedoctor.com
- 17. Function : Muscular contractions. Myometrium www.freelivedoctor.com
- 18. Function : Passageway for oocyte and site of fertilization. Uterine Tubes www.freelivedoctor.com
- 19. Function : Produce oocytes & the hormones estrogen and progesterone. Ovaries www.freelivedoctor.com
- 20. Function : Sweep ovarian surface to draw oocyte into ovarian tube. Fimbriae www.freelivedoctor.com
- 22. Direct Gene Activation Steroid Hormone Receptor/hormone Complex www.freelivedoctor.com
- 23. Direct Gene Activation Receptor/hormone Complex mRNA Protein Aldosterone Cortisol Testosterone Estrogen Progesterone Thyroxine www.freelivedoctor.com
- 25. Second Messenger Systems www.freelivedoctor.com
- 35. Hormonal Regulation of Ovarian & Menstrual Cycles 1. Hypothalamus releases GnRH . 2. GnRH stimulates anterior pituitary to release FSH. FSH 3. FSH stimulates a follicle to grow & produce estrogen . Estrogen www.freelivedoctor.com
- 36. Hormonal Regulation of Menstrual & Ovarian Cycles FSH Estrogen 4. Rising levels of estrogen cause anterior pituitary to increase production & storage of LH. LH Estrogen www.freelivedoctor.com
- 37. Hormonal Regulation of Menstrual & Ovarian Cycles 5. High estrogen causes LH to be released in a burst & the endometrium to thicken (proliferative phase). 6. High LH stimulates first meiotic division of primary oocyte. FSH Estrogen Estrogen LH www.freelivedoctor.com
- 38. Hormonal Regulation of Menstrual & Ovarian Cycles 7. High LH triggers ovulation. FSH Estrogen Estrogen LH 8. High LH causes ruptured follicle to become a corpus luteum. www.freelivedoctor.com
- 39. Hormonal Regulation of Menstrual & Ovarian Cycles FSH 9. Corpus luteum produces progesterone. Estrogen Estrogen LH Progesterone 10. Progesterone inhibits the production of FHS & LH by the anterior pituitary & stimulates secretory phase . www.freelivedoctor.com X X
- 40. Hormonal Regulation of Ovarian & Menstrual Cycles 11. Diminishing levels of FSH & LH cause corpus luteum to deteriorate & produce less progesterone. 12. Dimishing levels of estrogen & progesterone cause inhibition of FSH & LH to end & thickened endometrium to slough (menses). Estrogen Progesterone X www.freelivedoctor.com FSH LH X X
- 41. Hormonal Regulation of Ovarian & Menstrual Cycles FSH 13. Increasing levels of FSH cause a new cycle to begin. www.freelivedoctor.com
- 42. Hormonal Regulation in Pregnancy Normally dimishing levels of estrogen & progesterone from deterioration of the corpus luteum would cause thickened endometrium to slough (menses) which would terminating a pregnancy. Estrogen Progesterone X www.freelivedoctor.com X X
- 43. Hormonal Regulation if Pregnancy Occurs Blastocyst produces human Chorionic Gonadotropin (hCG) hormone which maintains corpus luteum in the absence of FSH & LH for the first trimester. hCG Eventually the placenta will produce sufficient estrogen & progesterone to sustain the pregnancy. www.freelivedoctor.com
- 44. Mitosis Interphase Prophase Metaphase www.freelivedoctor.com
- 46. Meiosis 46 www.freelivedoctor.com Interphase Prophase Metaphase
- 47. Meiosis Reduction Division www.freelivedoctor.com Anaphase Telophase Interphase 23 23
- 49. Mitosis/Meiosis Comparison 46 46 www.freelivedoctor.com 46 46 23 23 23 23 23 23
- 51. Spermatogenesis Spermatogonium (46) Mitosis Daughter Cells (46) www.freelivedoctor.com
- 52. Spermatogenesis Spermatogonium (46) Mitosis Daughter Cells (46) Growth Primary Spermatocyte (46) Meiosis I Secondary Spermatocytes (23) www.freelivedoctor.com
- 53. Spermatogenesis Spermatogonium (46) Mitosis Daughter Cells (46) Growth Primary Spermatocyte (46) Meiosis I Secondary Spermatocytes (23) Spermatogonium Meiosis II Early Spermatids (23) www.freelivedoctor.com
- 54. Spermatogenesis Spermatogonium (46) Mitosis Daughter Cells (46) Growth Primary Spermatocyte (46) Meiosis I Secondary Spermatocytes (23) Spermatogonium Meiosis II Early Spermatids (23) Spermiogenesis Late Spermatids (23) www.freelivedoctor.com
- 55. Spermatogenesis Spermatogonium (46) Mitosis Daughter Cells (46) Growth Primary Spermatocyte (46) Meiosis I Secondary Spermatocytes (23) Spermatogonium Meiosis II Early Spermatids (23) Spermiogenesis Late Spermatids (23) Spermatozoa (23) (Lumen) www.freelivedoctor.com
- 56. Oogenesis Oogonium (46) Primary Oocyte (46) (Mitosis) Primary Oocyte (46) www.freelivedoctor.com
- 57. Oogenesis Oogonium (46) (Mitosis) Secondary Oocyte (23) (Meiosis 1) Ovulation Fertilization Polar Body (23) (Meiosis 2) Primary Oocyte (46) www.freelivedoctor.com
- 64. Bone Formation Preembryonic Development www.freelivedoctor.com
- 76. Placental Function O 2 Glucose Vitamins Minerals www.freelivedoctor.com
- 77. Placental Function Alcohol www.freelivedoctor.com
- 79. Placental Function CO 2 Wastes Urea www.freelivedoctor.com
- 80. Placental Function - Smoking CO 2 O 2 CO Nicotine www.freelivedoctor.com
- 82. Drug Use Antibiotics Nicotine Crack www.freelivedoctor.com
Hinweis der Redaktion
- As you will be required to identify from diagrams of the male reproductive system, specific organs and describe their functions, this and the next series of figures will go over these. The penis * * is an organ for the discharge of urine * and for the deposition of sperm into the vagina of the female during copulation. *
- The urethra * * transports urine from the urinary bladder * and sperm and semen * produced by other organs of the male reproductive system. *
- The scrotum * * is where the testes are located. Its function is to provide an environment for the testes that is approximately 3 0 Celcius belowthe normal temperature of the body. * Thislower temperature is necessary for the production of viable sperm within the testes. *
- You may recall from your dissection of the fetal pig in your A & P I class, that often the testes had not descended completely from the pelvic cavity into the scrotum. The canal through which the testes must descend through to the scrotum is called the inguinal canal. * It not only provides a pathway for the testes but serves as a pathway through which the blood vessels, nerves, muscles and the tube which connects the testes to the urethra are found. *
- The testes * * have two primary functions. They produce sperm * and the male hormone, testosterone. *
- Each testis is filled with tiny tubules * * called seminiferous tubules. * It is within the seminiferous tubules that sperm are produced through the process of spermatogenesis which occurs from puberty on. *
- Shown here * is a cross section through a testis showing the seminiferous tubules. The white spaces * represent the central opening or lumen of each tubule. * In this more highly magnified view of seminiferous tubules, you can visualize the development of sperm cells in the walls of the seminiferous tubules. * By the time the sperm cells are fully developed, they are located in the lumen of the tubule. * Between the seminiferous tubules are groups of cells called interstitial cells. * * These are responsible for the production of the male hormone testosterone within the testes. * *
- The seminiferous tubules all eventually lead to the epididymis. * * The sperm are stored within the epididymis,* where they also complete their maturation. *
- The vas deferens * *is the duct that connects the epididymis to the urethra. * It provides the passageway for sperm to the urethra. *
- A seminal vesicle gland lies on each side of the posterior wall of the bladder. * * These glands produce approximately 60% of the semen. * The semen produced by the seminal vesicle gland is introduced into the vas deferens to form the ejaculatory duct * which connects to the urethra. Semen produced by the seminal vesicle glands is alkaline and contains the sugar fructose which supplies energy for sperm cell movement. *
- The single prostate gland encircles the urethra just below the bladder. * * The semen produced by the prostate gland contains enzymes and nutrients which are necessary to activate sperm. * Approximately 1/3 of the semen is produced by the prostate gland. *
- The Cowper’s or bulbourethral glands are located below the prostate. * * Their purpose is to produce mucous prior to ejaculation which contains alkaline buffers to neutralize the acidic conditions within the urethra. * *
- The vagina * * serves as the birth canal during the delivery of an infant, a passageway for menstrual flow and as the female organ of copulation which receives the penis and semen during sexual intercourse. * *
- The uterus * * connects the vagina with the oviduct thus providing a passageway for sperm. * It also provides an ideal environment for implantation of the blastocyst, embryonic and fetal development and contains muscular walls which contract during childbirth to expell the fetus. *
- The cervix* * is that part of the uterus that connects with the vagina. It contains glands which secrete mucous that fills the cervical canal, * isolating the uterus from the vagina and blocking the passage of sperm except during the middle portion of the ovarian cycle when the mucous becomes less viscous. *
- The uterus is composed of three layers. The innermost layer, the endometrium * * lines the uterine cavity and provides an ideal environment for implantation of a blastocyst and for embryonic and fetal development. * *
- The myometrium is the middle and thickest wall of the uterus. * * It is primarily made up of smooth muscle which produces muscular contractions during childbirth to push the fetus through the birth canal. * *
- The uterine tubes are also know as the oviducts and the fallopian tubes. * * Their function is to receive the oocyte following ovulation, provide a passageway for the oocyte to be transported to the uterus by means of peristalsis and ciliary action, and serve as an area in which fertilization of the oocyte can occur. * *
- The ovaries are the female gonads. * * The process of female gamete production (oogenesis) occurs within the ovaries, just as male gamete production (spermatogenesis) occurs in the testes. * In addition to producing the oocytes (female gametes) the ovaries also produce the hormones estrogen and progesterone. *
- The finbriae are the finger-like structures at the end of the oviducts closest to the ovaries. * * They are ciliated and sweep over the surface of each ovary to collect oocytes which have been released from the ovariesand direct them into the oviducts. * *
- Hormones are chemical messengers which regulate the activity of cells by binding with specific receptors either on cell membranes or within the cell itself. Their effects may be to increase activity or reduce activity depending on the target cell type and their mechanism of action. Direct gene activation hormones are chemical messengers which are lipid soluble * and can thus easily diffuse through the phospholipid bilayer of cell membranes * and bind with receptors inside the cell. * The activated hormone/receptor complex makes its way into the nucleus where it binds with a DNA-associated receptor protein which turns on the gene. * The affected gene than transcribes mRNA * which causes the translation of enzymes to stimulate cell activity or structural proteins to be used within the cell or excreted. * *
- The mechanism of action of a direct gene activation hormone is illustrated in the next few slides. * A steroid hormone produced elsewhere in the body * diffuses through the plasma membrane of the target cell, passing through the cytoplasm * to enter the nucleus. * The hormone binds with a receptor in the nucleus to form a receptor/hromone complex. * *
- The receptor/hormone complex * then binds with a specific receptor * stimulating the affected gene to transcribe mRNA.* The newly transcribed mRNA moves to ribosomes in the cytoplasm where it directs the translation (synthesis) of specific proteins. * Steroid hormones such as * Aldosterone, * Cortisol, * Testosterone, * Estrogen, * Progesterone and * Thyroxine are examples of direct gene activation hormones. *
- Second Messenger Hormones * are amino acid or protein based chemical messengers. * As such, they cannot pass through cell membranes, but must bind to receptors on the membranes of target cells. * The binding of the hormone with membrane receptors activates G proteins in the membrane to produce cyclic AMP in the cytoplasm. * The cyclic AMP acts as a second messenger inside the cell by activating protein kinases * which trigger cellular responses. *
- As illustrated here, a peptide homone * binds to a cell membrane receptor. * This causes the production of cyclic AMP within the cell * which acts as a second messenger within the cell * by activating protein kinase enzymes * which trigger the cellular response to the hormone. * Common second messenger hormones which function in this way include; * Follicle Stimulating Hormone (FSH), Leutenizing Hormone (LH), Glucagon, Parathormone (PTH), Thyroid Stimulating Hormone (TSH), and Calcitonin. *
- Gonadotropin-releasing Hormone (GnRH) * is produced by the hypothalamus. * * It’s target in both males and females is the anterior pituitary gland. * * which it stimulates to produce FSH and LH. * The Hypothalamus also regulates the release of FSH and LH by the anterior pituitary.* *
- Follicle stimulating hormone (FSH) * is produced by the anterior pituitary gland. * * It’s target in females * is the ovaries * in which it stimulates the growth and maturation of a follicle * and causes the maturing follicle to produce the hormone estrogen . * The target of FSH in males is the seminiferous tubules. * The effect of FHS is to cause the development of testosterone receptors on the seminiferous tubules, promoting sperm production. * *
- Leutenizing hormone (LH) * is produced by the anterior pituitary gland. * * It’s targets in the female are the ovaries. * The effect of LH within the ovaries is to stimulate a primary oocyte * to complete its first meiotic division to become a secondary oocyte. * It triggers ovulation (release) of the secondary oocyte, * the transformation of the ruptured follicle into a corpus luteum * and stimulates the production and release of the hormone progesterone from the corpus luteum. In Males, * the target of LH is the interstitial cells between the seminiferous tubules of the testes. Under the influence of LH, the interstitial cells produce and release testosterone * which binds to the receptors on the seminiferous tubules making possible sperm production (spermatogenesis). *
- Estrogen is the principle female hormone. * It is produced by maturing follicles and by the corpus luteum within the ovaries. * Estrogen has a number of targets and functions within the body. * In general, estrogen stimulates the development of female secondary sexual characteristics * which are those that distinguish females from males. These would include the development of female genital organs, breasts, bone development and growth patterns typical of females, etc. * During the uterine cycle, estrogen stimulates the proliferative phase which causes the thickening and growth of the endometrium in preparation for possible implantation of a blastocyst. * Within the ovaries, estrogen promotes oogenesis within a developing and maturing follicle. * It stimulates the development of milk ducts and sinuses (ampullae) within the breasts in preparation for milk production. * Estrogen also has an effect on the anterior part of the pituitary gland in that as estrogen levels in the blood rise to a certain level, it stimulates a burst-like release of the hormone LH from the anterior pituitary. *
- Progesterone * is produced initially by the corpus luteum. * If pregnancy occurs, progesterone is also produced by the placenta as well. * It also has several targets and functions within the body. * One of the target organs of progesterone is the uterus. It maintains the thickened condition of the endometrium, stimulates nutrient release from the blood vessels in the walls of the uterus, and decreases muscular contractions of the myometrium. * Progesterone also affects the breasts by stimulating the development of the milk producing glands (alveoli). * Progesterone has the effect on the anterior pituitary gland of inhibiting the production and release of both FSH and LH. *
- Testosterone is the male sex hormone. * As indicated previously, it is produced by the intersitital cells in the testes. * Like estrogen in females, testosterone in males has a number of targets and functions. It has a generalized effect on the body to stimulate the development of male secondary sexual characteristics including the development of male genital organs, stimulating male type skeleton and muscle development, male patterns for hair growth, increased red blood cell production and a higher rate of metabolism to name a few. * The seminiferous tubules of the testes also are targets for testosterone. When testosterone binds with receptors on the seminiferous tubules, the process of spermatogenesis may be completed. * The anterior pituitary gland also is affected by testosterone in the blood. It’s effect is to cause moderate inhibition of the pituitary and the hypothalamus. *
- The hormone onytocin is manufactured by the hypothalamus and is stored by the posterior pituitary. * It is involved in positive feedback mechanisms * including childbirth * and the milk letdown reflex. * The contractions associated with childbirth are triggered by stretching of the cervix and the uterus as term is reached. * Increasing amounts of oxytocin in the blood triggers the myometrium of the uterus to contract causing the lowering of the fetus and labor. * The suckling effect on the breast of a nursing baby * stimulates the release of oxytocin which when bound to the tissues of the milk ducts and sinuses of the breasts, stimulates the release of milk. *
- Prolactin is a hormone stored by the anterior pituitary. * It’s targets * are the alveoli of the breasts, which it stimulates to produce milk. The release of prolactin is regulated by the hypothalamus. * *
- Human Chorionic Gonadotropin (hCG) is a hormone that is initially produced and secreted by the trophoblast cells of the blastocyst and later the chorion. * It’s target is the corpus luteum, * which it maintains in the absence of LH. * The effect of hCG on the corpus luteum * is to cause it to continue the production of progesterone during the first four months of pregnancy. By that time, the placenta is producing sufficient estrogen and progesterone to maintain the pregnancy. *
- The ovarian cycle begins when rising levels of GnRH from the hypothalamus * * stimulate increased production and release of Follicle Stimulating Hormone (FSH) by the anterior pituitary. * * FSH stimulates one or more follicle cells within the ovaries to grow * * and begin producing estrogen. * *
- Rising estrogen levels in the blood * * inhibits further release of FHS while promoting increased production and storage of the hormone Leutinizing Hormone (LH) * within the anterior pituitary gland. *
- When estrogen levels in the blood become high enough, * * LH is released by the anterior pituitary gland in a burst. The high estrogen levels also cause the endometrium to thicken. * The sudden release of LH into the blood,* causes the primary oocyte in the mature follicle to undergo the first meiotic division. * *
- The high LH levels * also cause the mature follicle to release the primary oocyte (ovulation), * and the remains of the ruptured follicle * to become a corpus luteum. * *
- The corpus luteum * * begins to produce and release the hormone progesterone * which inhibits the production of FHS and LH by the anterior pituitary * and stimulates the secretory phase of the ovarian cycle. *
- * Diminishing levels of FSH & LH cause the corpus luteum to deteriorate & produce less progesterone. * * * Diminishing levels of estrogen and progesterone * stop the inhibition of FSH & LH by the pituitary gland. * In the absence of adequate levels of progesterone, the thickened endometrium sloughs, causing menses to occur. *
- * Increasing levels of FSH * cause a new cycle to begin. *
- * Normally diminishing levels of estrogen and progesterone * caused by the breakdown of the corpus luteum * would cause menses, terminating any pregnancy. *
- However, the blastocyst * (developing embryo) * produces the hormone human Chorionic Gonadotropin (hCG) * * maintains the corpus luteum * in the absence of FSH & LH for the first trimester of the pregnancy. * Eventually the placenta produces sufficient estrogen and progesterone to sustain the pregnancy. *
- In the cell cycle, mitosis is when the nucleus divides. * Cells spend most of their time in interphase. * * This is when the cells has a definite nucleus, the chromosomes are spread out as chromatin and the cell is actively carrying out normal metabolic activities. Mitosis begins with prophase, * when the nuclear membrane disappears, the chromosomes condense and can be seen as discrete structures, and the centrioles move to opposite sides of the cell and send out spindle fibers which attach to each chromosome.* * The centrioles begin to retract the spindle fibers causing the chromosomes to line up on the equatorial plate of the cell. * When the chromosomes are aligned in this way, the cell is in metaphase. *
- As the spindle fibers continue to tug on the chromosomes, the two chromatids making up each chromosome are pulled apart and toward opposite sides of the cell. * Anaphase is the name of this stage when the chromatids from each chromosome are moving to opposite poles of the cell. * * When the chromatids reach the opposite sides of the cell, a nucleus reforms around each cluster, nucleoli reappear and cell membrane forms between the two nuclei to form two identical cells. The division of the cytoplasm is called cytokinesis. All of this occurs in what is called telophase. When the cell membrane completely separates the two daughter cells, telophase is complete * and the daughter cells are considered to be in interphase again. * * During interphase, the DNA making up the chromatids replicates so that each chromosome is composed of two identical chromatids. In mitosis, there is no change in the number of chromosomes or genetic information. If the cell dividing started out with 46 chromosomes, * the daughter cells will have 46 chromosomes. *
- Meiosis is a process that occurs in the gonads. In human cells, each cell undergoing meiosis begins with 46 chromosomes. * In prophase I of meiosis, * the same general things occur that happened during prophase of mitosis. * However, homologous chromosomes (one from each parent) pair up in a process called synapsis. * As the genetic information on the corresponding chromosomes from different parents will contain different genetic information, the synapsis and exchange of chromatid parts results in some shuffling and recombination of genetic information. * The spindle fibers from the centrioles attach to each chromosome pair, rather than to each chromosome. * The synapsed chromosome pairs become aligned on the equatorial plate of the cell in metaphase I of meiosis.* Thus the chromosome pairs in metaphase form a tetrad, a cluster of four chromatids. *
- In anaphase I of meiosis * the chromosomes forming each pair are pulled apart to opposite sides of the cell. * Telophase I is when the nuclear membrane forms around each cluster of chromosomes at each pole of the cell while cytokinesis occurs. * When cytokinesis complete, each of the daughter cells only contains half of the number of chromosomes that were present in the original cell. * In humans this number would be 23. * This is why the first meiotic division is referred to as the reduction division. *
- Meiosis is different from mitosis in that there is a second division of each of the daughter cells just like in mitosis. * The two daughter cells go through the same process as in a normal mitotic division, including prophase II, * metaphase II, * anaphase II, * and finally telophase II and cytokinesis. * There is no change in the chromosome number in the cells. * Thus, as the cells in prophase II have 23 chromosomes, the four daughter cells will contain 23 chromosomes. * * Meiosis is different from mitosis in that * it involved two divisions which only occur in the gonads after puberty, * as a result of the synapsis of homologous chromosomes and the exchange of genetic information that occurs, there is the possibility of greater variation within the daughter cells, * and the number of chromosomes within each of the four daughter cells that go through the process is reduced to half of the normal number * (in humans from 46 chromosomes to 23). *
- Contrasting mitosis and meiosis, in mitosis, * the chromosomes line up in metaphase as individual chromosomes. * There is no change in the number of chromosomes within each daughter cell produced through mitosis. * If the cell started out with 46 chromosomes, the daughter cells will be identical with 46 chromosomes. * In meiosis, * chromosomes synapse to form tetrads in prophase I. * As a result, the chromosomes line up in metaphase as tetrads or pairs of homologous chromosomes. * The daughter cells produced from the first meiotic division are haploid, * or contain only half of the number of chromosomes found in the original cell. * The four daughter cells produced in the second meiotic division are haploid, in that they only contain half of the number of chromosomes that were found in the original cell.* These haploid cells become gametes for sexual reproduction. * Since the chromosomes found in the daughter cells include a random distribution of chromosomes from each parent, each of the daughter cells contains genetic information that is unique. *
- Gametogenesis * is the process through which male and female gametes are formed. * Spermatogenesis is the process through which male sperm are produced. * As indicated previously, spermatogenesis occurs in the seminiferous tubules of the testes. * It involves the process of meiosis through which the number of chromosomes is reduced by half ( from 46 to 23 ). * This process occurs throughout the life of a healthy male after puberty. * As many as 400,000,000 sperm may be produced a day through this process. * * Oogenesis * is the process through which the female gamete (oocyte) is produced. * As previously discussed, oogenesis takes place in a developing follicle within the ovaries. * It also involves meiosis, in which the number of chromosomes within the oocyte changes from 46 to 23. * Oogenesis takes place as a part of the ovarian cycle from puberty until menopause. * In humans, a single oocyte is typically produced during each ovarian cycle. * *
- Spermatogenesis takes place in the walls of the seminiferous tubules within the testes. Each of the cells forming the outermost layer of cells in the seminiferous tubules * is called a spermatogonum * and has 46 chromosomes. These cells divide by mitosis * * to form identical daughter cells * with 46 chromosomes. *
- Daughter cells go through a growth process * and are referred to as primary spermatocytes * which still have 46 chromosomes. Under the influence of the male hormone testosterone, primary spermatocytes go through the first meiotic division * in which the number of chromosomes is reduced from 46 to 23. * The cells (containing only 23 chromosomes) which are produced through this first meiotic division are referred to as secondary spermatocytes. * *
- The secondary spermatocytes produced by through the first meiotic division go through a second meiotic division * in which there is no change in the number of chromosomes (23). * The cells produced through the second meiotic division are referred to as spermatids. * Note that from a single primary spermatocyte * which goes through meiotic divisions I and II, * four spermatids are formed. * *
- The early spermatids * then go through a process called spermiogenesis * in which they change in shape and form to become late spermatids * with a flagellum * and other specialized organelles necessary for them to function as male gametes. *
- The spermatids * are released into the lumen of the tubule * along which they travel to the epididymis where they complete their development into mature spermatozoa * and are stored. * Note that this entire process of spermatogenesis occurs continually in the walls of the seminiferous tubules after puberty. *
- The process of female gamete production is called oogenesis. Oogenesis starts in the ovaries during fetal development, * when the female oogonia (which have 46 chromosomes), * divide by mitosis, * go through a growth phase, and are surrounded by follicle cells to become primordial follicles. The growing oogonium inside each primordial follicle is called a primary oocyte and continues to have 46 chromosomes. * Although the primary oocytes within the primordial follicles begin meiosis, they become stalled toward the end of prophase I. When a female baby is born, she has within her ovaries all of the primordial follicles she will ever have, * and they are all arrested in prophase I of meiosis. These will remain in this state of suspended animation * during childhood * until puberty. While a small number of follicles are activated each month after puberty, under the influence of FSH, only one follicle is selected to develop. *
- When LH is released in a burst, the primary oocyte within the dominant follicle completes the first meiotic division * to produce a secondary oocyte with 23 chromosomes * and a nonfunctional polar body. * The polar body is non-functional because the secondary oocyte retains almost all of the cytoplasm from the primary oocyte cell. * Under the influence of LH, the secondary oocyte is ovulated (released) from the follicle. * As the secondary oocyte travels down the oviduct, if it encounters sperm and is fertilized * * the penetration of the secondary oocyte by the sperm cell * triggers a second meiotic division, * resulting in the development of an ovum and three non-functional polar bodies from the original primary oocyte. *
- Since you will be required to give or recognize the function(s) of various things relative to reproduction, the next few slides will review these. * The Hypothalamus * produces * the hormone GnRH which stimulates production of FSH and LH by the anterior pituitary gland to initiate the ovarian cycle. * It also is where the hormone ocytocin is produced which is stored in the posterior pituitary gland. * The posterior pituitary * stores and relases ocytocin to stimulate uterine contractions during labor and delivery and the milk let-down reflex when initiated by a suckling baby. *
- The anterior pituitary gland * produces and released the hormone FSH * to stimulate follicle growth and development and the production of estrogen in females, and stimulates sperm production (spermatogenesis) in males. * In females, it also produces and stores the hormone prolactin, * which promotes lactation. *
- A spermatogonium * (spermatogonia , pleural) is the outer-most cell in the wall of seminiferous tubules. They are the cells from which sperm cellsare produced. * An oogonium * is the germ cell in the follicles of ovaries from which oocytes are produced.* A follicle * is a sack-like structure in the ovaries made up of one or more layers of cells surrounding an oogonium or oocyte. Under the influence of FSH, * a maturing follicle produces the hormone estrogen. *
- Mitosis * is the process through which the nucleus of cells divide to produce two identical daughter cells, each having the same number of chromosomes as the original cell. * Mitosis is the process through which the body maintains grows, heals and maintains itself. * Meiosis * is the process through which gametes are formed with only half of the normal number of chromosomes (ie, in humans the number changes from 46 to 23). These haploid cells (with 23 chromosomes) develop into gametes for sexual reproduction. * Ovum * is the name of the functional female gamete which, as a result of sperm penetration, has completed the first and second meiotic divisions to become haploid. * *
- A spermatozoan * is a male gamete which has completed meiosis 1 and 2, spermiogenesis and is capable of fertilizing a female secondary oocyte. * Fertilization * is the process through which haploid male and female gametes combine to form a single cell (zygote) which has 46 chromosomes. * A human cell with 46 chromosomes (23 from the spermatozoan and 23 from the ovum) is said to be diploid. * Polar bodies * are haploid female cells with an insufficient amount of cytoplasm to be functional for reproductive purposes. * One polar body is produced during the first meiotic division while two additional polarbodies are procuced during the second meiotic division. *
- A hormone * is a chemical messenger used to regulate reproductibve cycles and activities by binding with receptors on or in target cells. * Semen * is a mixture of spermatozoa and fluid secretions from male reproductive glands which supplies energy to spermatozoa, neutralizes acidic conditions within the male and female reproductive tracts and activates the spermatozoa. * Hyaluronidase * is an enzyme within the acrosome of a sperm cell that enables the sperm nucleus to enter the female ovum. *
- Objective 9 Preembryonic development * occurs from fertilization of the ovum till the third week of development. * From the third week after fertilization through the eighth week of development, * the conceptus is referred to as an embryo . The conceptus is referred to as an fetus * from the 9th week through birth. * The main event that separates embryonic and fetal development, is the beginning of bone formation * which begins during the ninth week. *
- Objective 11 A zygote * is a fertilized ovum which is diploid due to the combination of the sperm and ovum nuclei. * Cleavage divisions * refer to divisions of the zygote to increase the number and surface area of cells making up the preembryo (ie, 2 cell stage, 4 cell, 8 cell, etc.). * A morula * is a berry shaped cluster of preembryonic cells produced from the cleavage divisions. * *
- Objective 11 A blastocyst * is a hollow, fluid filled sphere of cells formed from the morlula. * The blastocyst implants in the thickened uterine wall, the endometrium. * The inner cell mass * is the mass of cells inside the blastocyst * from which the three primary germ layers develop. * A trophoblast * is the name of the single layer of cells making up the outer wall of the blastocyst. * The trophoblast cells, eventually form the chorion. * *
- Objective 11 The chorionic villi * are the finger-like extensions of the trophoblasts * which grow into the endometrium * to acquire nutrients for the preembryo. * The chorionic villi eventually form the placenta. *
- Objective 11 The chorion * is the outermost embryonic membrane * which protects the developing embryo. * The Chorion eventually produces the placenta which provides for the exchange of nutrients and wastes between the mother and the embryo. * *
- Objective 11 The amnion * is the membrane * which surrounds the embryo to form the amniotic cavity. * The amnion produces amniotic fluid which bathes the embryo to protect it. * *
- Objective 11 The amniotic fluid * bathes the embryo/fetus * protecting it from trauma * and permitting free movement without adhesions. * *
- Objective 11 The yolk sack * provides initial nutrients while the placenta is developing, * supplies the first RBC’s * and seeds the gonads with primordial germ cells.* *
- Objective 11 Gastrulation * is the process through which the preembryo * becomes an embryo * as the three primary germ layers; * the ectoderm * the endoderm * and the mesoderm * develop to allow for the beginning of organ development. *
- Objective 10 The primary germ layer called the ectoderm * produces the brain, spinal cord and nerves; * the cornea and lens of the eyes; * the outer skin and accessory structures * including the hair * and nails; * the enamel of teeth * and the linings of the nasal and oral canals. * *
- Objective 10 The endoderm * is the source of the epithelial linings of the digestive tract; * the liver and pancreas; * the tonsils and the epithelial linings of the respiratory tract; * the epithelial linings of the reproductive ducts and glands; * the thyroid, parathyroid and thymus glands, * and the epithelial linings of the bladder and urethra. * *
- Objective 10 The mesoderm * produces all types of muscle tissue; * connective tissues, including cartilage, bone and adipose; * bone marrow, blood and lymphatic tissues; * the endothelial linings of blood and lymphatic vessels; the visceral peritoneum of visceral organs; * the fibrous and vascular tunics of the eyes; * and the organs of the urogenital system, including the kidneys, gonads and reproductive ducts. * *
- Objective 12 The function of the placenta is to provide for the exchange of nutrients from the maternal blood into the fetal blood, without direct mixing of the two. Nutrients move by simple diffusion from areas of higher concentration of each nutrient into the area of lower concentration. Thus O 2 diffuses from the mother’s blood into the blood of the fetus. * The same is true of glucose,* vitamins *, minerals *, etc. *
- Objective 12 If the mother carrying the fetus consumes alcohol, * it too diffuses across the placenta from the maternal blood into the fetal blood. The abuse of other drugs and even the use of legally prescribed antibiotics can have an adverse effect on the fetus.*
- Objective 12 Fetal alcohol syndrome * is used to describe a pattern of abnormalities found in children born to mothers who reported consuming moderate to large amounts of alcohol during pregnancy. Effects on the fetus vary widely but typically may include * prenatal and postnatal growth retardation; * Central Nervous System involvement including * neurological abnormalities, * developmental delays; * alcohol related birth defects including skull and facial malformations; * mental retardation; * speech and hearing impairment; * and learning, attention and memory deficits. * Although studies indicate a strong correlation between the seriousness of defects and quantities of alcohol consumed during pregnancy, it is not known whether there is a threshold below which alcohol may be consumed during pregnancy without harming the fetus. Therefore, clinicians generally recommend complete abstinance during pregnancy. *
- In addition to supplying nutrients, the placenta also provides a mechanism for the disposal of wastes from the fetus. * Since CO 2 is a metabolic waste and the fetal lungs are not working, concentrations of CO 2 in fetal blood are higher than in the maternal blood. * As a result, excess CO 2 diffuses across the placenta into the maternal blood to be carried off and disposed of. * The same is true of other wastes * including urea. * *
- Cigarette smoke contains more than 2,500 chemicals, not the least of which are carbon monoxide (CO) and nicotine. * Because CO has such a high affinity for hemoglobin, * its effect on RBCs is to reduce the amount of O 2 in the mother’s blood and therefore the amount of O 2 available to the fetus. Because smoking introduces a higher concentration of CO 2 into the lungs, it also effects the CO 2 gradient, thus reducing the amount of CO 2 which diffuses from fetal blood across the placenta in to the maternal blood for elimination. * Smoking also subjects the fetus to the carcinogen nicotine. * *
- For reasons not completely understood, research data indicates that smoking during pregnancy * increases the risk of ectopic pregnancy, * doubles the risk of placenta previa and extopic pregnancy, * slows fetal development, * doubles the risk of low birthweight babies, * increases the risk of cleft palate and lip, and * doubles the risk of sudden infant death syndrome (SIDS).
- Just as nicotine can cross the placenta, * other drugs may do so as well. Even antibiotics * taken by the mother may cross the placenta and have an effect on the rapidly dividing cells of the growing fetus. * Of course hard core drug use may cause the fetus to become addicted along with the mother. *
- Irradiation * including high energy X -rays * and Gamma rays * may affect a fetus by penetrating deeply into fetal tissues, causing ionization of molecules, * may directly or indirectly affect the genetic material of cells, causing point mutations which affect a single base * or break chromosomes causing deletions or translocation of genetic information which may adversely affect fetal cells and tissues. *
- Placenta abruptio is the medical term used when there is any amount of placental separation prior to delivery. * Some of the most common causes and risk factors associated with placenta abruptio include: * abdominal trauma, * hypertension during pregnancy, * diabetes mellitus, * cigarette smoking, and * alcohol use during pregnancy.
- Placenta previa * is the medical term used to refer to growth of the placenta across or adjacent to the opening of the cervical canal of the uterus. * Risk factors include: * the number of prior pregnancies, * multiple pregnancies (including twins or triplets, etc.), * and a prior C-section where the scar is close to the cervix. * Symptoms associated with placenta previa may include * spotting during the 1st and 2nd trimesters, and * sudden, painless but profuse vaginal bleeding at any time during the pregnancy. *
- The term ectopic pregnancy * is used when the blastocyst implants anywhere other than within the uterus. * Common causes and risk factors for ectopic pregnancy include: * physical blockage of a uterine tube, * scarring of uterine tubes due to prior tubal infections such as venereal diseases causing pelvic inflamatory disease, * and pregnancies following tubal ligation reversal or despite oral contraceptive use. Symptoms associated with ectopic pregnancy include: * unexplained lower abdominal or pelvic pain, * mild cramping on one side of the pelvis * and abnormal vaginal bleeding or spotting. *
- Gonorrhea * is the most commonly reported sexually transmitted disease (STD) of adults in theU.S. It is caused by the bacteria Neisseria gonorrhoeae. , * which primarily affects the skin and mucous membranes associated with the reproductive system. * * Transmission is most commonly through sexual contact with an infected person. In the case of infants, the disease is most commonly acquired as the baby passes through the birth canal of an infected mother. *
- Gonorrhea * primarily causes inflammation of the skin * and mucous membranes of the urinary and reproductive organs. * Symptoms in females most commonly include one or more of the following: painful urination, abdominal pain, pelvic inflammatory disease (where the bacteria move up the reproductive system and into the abdominal cavity), and sterility. In males, * symptoms include painful urination with purulent discharge and possible sterility if the bacteria invade the testes. *
- Babies * may acquire the disease in the birth canal of an infected mother. * The congenital effects * may include conjunctivitis and blindness. * The routine placement of silver nitrate drops in the eyes of new born babies is to prevent these effects. Treatment * is with the antibiotics Ceftriaxone or Tetracycline. *
- Syphilis is a sexually transmitted disease (STD) * caused by the bacterial spirochete Treponema pallidum . * * It is acquired through sexual and transplacental contact with an infected person. Syphilis is the third most commonly reported microbial disease in the U.S.*
- While the bacteria are not able to enter the body through the intact skin, they may through the mucous membranes of tiny breaks in the epithelium. * to cause the disease which progresses in stages. * The incubation period for syphilis averages about 21 days and brings on the initial or primary stage * which is characterized by the occurrence of one or more painless chancres (lesions) where the bacteria entered the skin or mucous membranes. *
- If untreated, secondary syphilis generally appears 9-11 weeks after the chancre. * It is characterized by fever, influenza-like symptoms, swollen lymph nodes and skin rash. * Without treatment, these symptoms may last several weeks and disappear, or the individual may become ill and die. *
- Nearly a third of those who survive the secondary stage will develop tertiary syphilis in which the spirochetes invade the skin, the cardiovascular and the nervous systems. * One of the characteristic features of tertiary syphilis is the development of lesions * on the affected organs called gummas. * These may cause weakness or degeneration of the affected organs. The treatment of choice for syphilis is Penicillin. *
- After the fourth month of pregnancy, the spirochetes causing syphilis may cross the placenta * and infect the fetus causing congenital syphilis. * Babies with congenital syphilis may have or develop infective skin lesions; * may exhibit a combination of deafness, impaired vision and notched or peg-shaped teeth; * or may be stillborn. *
- Chlamydia, * also known as Chlamydial urethritis, is one of the most prevalent sexually transmitted diseases in the U. S. The causitive organism * is the bacteria Chlamydia trachomatis . It is sometimes referred to as nongonococcal urethritis * because it causes inflammation of the urethra similar to that caused by gonorrhea. However as the symptoms tend to be milder, (up to 80% asymptomatic), it frequently goes untreated. Unfortunately, the disease leads to serious reproductive tract complications including * pelvic inflamatory disease (PID), * infertility and * ectopic pregnancies. * Babies may become infected in the birth canal * and develop chlamydial opthalmia and pneumonia. * Treatment * is with the antibiotic Tetracycline.
- The Herpes Simplex Type 2 virus * is responsible for genital herpes. * Transmission may occur by secretions from active vessicles * which primarily occur on and around the genitalia. * The disease is recurrent with vessicles reappearing sometimes as often as every four weeks. * Open vessicles lead to lesions which may be very painful.. Aside from the ordinary effects of the disease, cervical cancer with a 50% mortality rate occurs at a higher than normal rate in women infected with genital herpes. * Transplacental transmission from an infected mother to a child may occur and if there are active vessicles at the time of delivery, the disease may be transmitted to a child during child birth. * There is no cure for genital herpes. Acyclovire is sometimes used to reduce symptoms, but it does not cure the disease. *