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BIO 1414 Human A & P II Unit 9 - Reproductive System & Development Robert F. Allen - Professor of Biology Functions: Urination and Copulation Penis Functions: Transport urine & semen Bladder Urethra Function: Maintain temperature of testes approx. 30 C below normal body temp. Scrotum Function: Produce sperm and testosterone Testis Function: Produce Sperm Seminiferous Tubules Testis Testis Cross Section Interstitial Cells Produce Testosterone Function: Sperm storage and maturation Epididymis Function: Transport sperm to urethra Vas Deferens Function: Produce 60% of alkaline semen including fructose to provide energy for sperm. Seminal Vesicles Ejaculatory Duct Function: Produces up to 1/3 of the semen & includes nutrients & enzymes to activate sperm. Prostate Function: Secretes mucous & alkaline buffers to neutralize acidic conditions of urethra. Cowper’s Gland Function: Receives penis & semen and serves as birth canal & passage for menstrual flow. Vagina Function: Provides passageway for sperm, receives blastocyst, retains & nourishes fetus & expells fetus at term. Uterus Function: Cervical mucosa secretes mucous blocking cervical canal entrance to uterus. Cervix Function: Uterine lining in which implantation occurs. Endometrium Function: Muscular contractions. Myometrium Function: Passageway for oocyte and site of fertilization. Uterine Tubes Function: Produce oocytes & the hormones estrogen and progesterone. Ovaries Function: Sweep ovarian surface to draw oocyte into ovarian tube. Fimbriae Mechanisms of Hormonal Action • Direct Gene Activation – – – – lipid soluble, steroid hormones diffuse through cell membranes bind to intracellular receptor activated hormone receptor/complex binds with gene, turning it on – gene transcribes mRNA – ribosomes use mRNA to synthesize enzymes to stimulate cell activity or synthesize structural proteins to be excreted or used within the cell Direct Gene Activation Steroid Hormone Receptor/hormone Complex Direct Gene Activation Receptor/hormone Complex Protein mRNA Aldosterone Cortisol Testosterone Estrogen Progesterone Thyroxine Mechanisms of Hormonal Action • Second Messenger Systems – – – – amino acid & protein based cannot pass through cell membranes bind to cell membrane receptors activate G proteins in membrane to produce cyclic AMP in cytoplasm – cyclic AMP acts as second messenger inside cell activating protein kinases – protein kinases trigger cellular responses Second Messenger Systems Hormone Sources & Functions • Gonadotropin-releasing Hormone (GnRH) : – Source: Hypothalamus – Targets & Functions: • Females & Males - Anterior Pituitary – Stimulates the production of Follicle Stimulating Hormone (FSH) & Leutinizing Hormone (LH) – Regulates the release of FSH & LH by the anterior pituitary gland Hormone Sources & Functions • Follicle Stimulating Hormone: – Source: Anterior Pituitary – Targets & Functions: • Females - Ovaries – Stimulates follicle growth & maturation – Stimulates estrogen production • Males - Seminiferous Tubules – Promotes sperm production (Spermatogenesis) by establishing testosterone receptors on tubules Leutenizing Hormone: • Source: Anterior Pituitary – Targets & Functions: • Females - Ovaries – Stimulates primary oocyte to complete first meiotic division to become secondary oocyte – Triggers ovulation of secondary oocyte – Transforms ruptured follicle into corpus luteum – Stimulates production of progesterone by corpus luteum Corpus luteum • Males - Seminiferous Tubules – Stimulates sperm production (Spermatogenesis) by causing interstitial cells in testes to secrete testosterone Estrogen: • Sources: Maturing Follicles & Corpus Luteum – Targets & Functions: • Body in general – Stimulates the development of female secondary sexual characteristics • Uterus – Stimulates proliferative phase of uterine cycle • Ovaries – Promotes oogenesis • Breasts – Stimulates development of milk ducts and sinuses (ampullae) • Anterior Pituitary – Stimulates burst-like release of LH Progesterone: • Source: Corpus Luteum & Placenta – Targets & Functions: • Females - Uterus – Maintains thickened endometrium – Stimulates nutrient release – Quiets myometrium • Females - Breasts Corpus luteum – Stimulates development of alveoli for milk production • Females - Anterior Pituitary – Inhibits production & release of FSH & LH Testosterone: • Sources: Interstitial Cells in Testes – Targets & Functions: • Body in general – Stimulates the development of male secondary sexual characteristics including: » development of male genitalia » male skeleton and muscle development » male patterns for hair growth » increased RBC production & higher metabolic rate • Seminiferous tubules – Necessary for the completion of spermatogenesis • Anterior Pituitary – Moderate inhibition of pituitary and hypothalamus Oxytocin: • Sources: Manufactured by hypothalamus. Stored & released by Posterior Pituitary Positive Feedback Mechanisms: 1. Childbirth - Stretching of uterus and cervix 2. Suckling - Milk letdown reflex – Targets & Functions: • Uterus – Stimulates contraction of uterine myometrium causing lowering of fetus & labor • Breasts – Stimulates contraction of milk ducts and sinuses, releasing milk Prolactin: • Source: Anterior Pituitary – Targets & Functions: • Breasts – Stimulates alveoli of breasts to produce milk • Regulation – Release of prolactin by anterior pituitary is regulated by hypothalamus production of Prolactin Releasing Hormone (PRH) & Prolactin Inhibiting Hormone (PIH) Human Chorionic Gonadotropin: • Source: Trophoblasts of blastocyst & Chorion – Target & Functions: • Corpus Luteum – Maintains corpus luteum & causes it to continue producing progesterone in the absence of LH through first four months of pregnancy till placenta produces sufficient estrogen & progesterone to maintain the pregnancy Hormonal Regulation of Ovarian & Menstrual Cycles 1. Hypothalamus releases GnRH. 2. GnRH stimulates anterior pituitary to release FSH. Estrogen FSH 3. FSH stimulates a follicle to grow & produce estrogen. Hormonal Regulation of Menstrual & Ovarian Cycles LH 4. Rising levels of estrogen cause anterior pituitary to increase production & storage of LH. Estrogen Estrogen FSH Hormonal Regulation of Menstrual & Ovarian Cycles 5. High estrogen causes LH to be released in a burst & the endometrium to thicken (proliferative phase). Estrogen Estrogen FSH 6. High LH stimulates first meiotic division of primary oocyte. LH Hormonal Regulation of Menstrual & Ovarian Cycles 7. High LH triggers ovulation. Estrogen 8. High LH causes ruptured follicle to become a corpus luteum. Estrogen FSH LH Hormonal Regulation of Menstrual & Ovarian Cycles 9. Corpus luteum produces progesterone. 10. Progesterone inhibits the production of FHS & LH by the anterior pituitary & stimulates secretory phase . Estrogen X FSH X LH Estrogen Progesterone 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 X FSH Progesterone X LH X Hormonal Regulation of Ovarian & Menstrual Cycles 13. Increasing levels of FSH cause a new cycle to begin. FSH 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 X Progesterone X X 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. Eventually the placenta will produce sufficient estrogen & progesterone to sustain the pregnancy. hCG Mitosis Interphase Prophase Metaphase Mitosis Anaphase Telophase Interphase 46 46 • Most cells of the body - growth, replacement, healing. • No change in the number of chromosomes within each cell. Meiosis 46 Interphase Prophase Metaphase Meiosis 23 23 Reduction Division Anaphase Telophase Interphase Meiosis 23 23 23 23 23 23 • Only in gonads. • Synapsis & shuffling of genetic information providing variation. • Results in reduction of number of chromosomes by half (haploid). Mitosis/Meiosis Comparison 46 46 23 46 46 23 23 23 23 23 Gametogenesis: Process through which gametes are formed • Spermatogenesis: – produces male gametes (sperm) – occurs in the seminiferous tubules of the testes – involves meiosis – occurs throughout life after puberty – may produce 400,000,000 per day • Oogenesis: – produces female gametes (oocytes) – occurs in the ovaries – involves meiosis – occurs after puberty until menopause – humans normally produce one oocyte during each ovarian cycle Spermatogenesis Spermatogonium (46) Mitosis Daughter Cells (46) Spermatogenesis Spermatogonium (46) Mitosis Daughter Cells (46) Growth Primary Spermatocyte (46) Secondary Spermatocytes (23) Meiosis I Spermatogenesis Spermatogonium (46) Mitosis Daughter Cells (46) Growth Primary Spermatocyte (46) Secondary Spermatocytes (23) Early Spermatids (23) Meiosis I Meiosis II Spermatogenesis Spermatogonium (46) Mitosis Daughter Cells (46) Growth Primary Spermatocyte (46) Secondary Spermatocytes (23) Early Spermatids (23) Meiosis I Meiosis II Spermiogenesis Late Spermatids (23) Spermatogenesis Spermatogonium (46) Mitosis Daughter Cells (46) Growth Primary Spermatocyte (46) Meiosis I Secondary Spermatocytes (23) Meiosis II Early Spermatids (23) Spermiogenesis Late Spermatids (23) (Lumen) Spermatozoa (23) Oogenesis Oogonium (46) (Mitosis) Primary Oocyte (46) Primary Oocyte (46) Oogenesis Oogonium (46) (Mitosis) Polar Body (23) Primary Oocyte (46) (Meiosis 1) Secondary Oocyte (23) Fertilization (Meiosis 2) Ovulation Definitions & Functions Relative to Reproduction • Hypothalamus: – Produces GnRH which stimulates the production of FSH & LH by the anterior pituitary gland initiating the ovarian cycle. – Produces Oxytocin which is stored in the posterior pituitary gland. • Posterior Pituitary: – Stores & releases hormone Oxytocin to stimulate uterine contractions (Braxton Hicks) & the milk let-down reflex. Definitions & Functions Relative to Reproduction • Anterior Pituitary: – Produces hormone FSH which stimulates the growth & maturation of a follicle, the production of estrogen in females and stimulates sperm production in males. – Produces & stores hormone LH which causes first meiotic division of primary oocyte, stimulates ovulation, causes the development of and the production of progesterone by the corpus luteum – Produces & stores hormone Prolactin which promotes lactation . Definitions & Functions Relative to Reproduction • Spermatogonium: – Primordial germ cell in seminiferous tubules of testes from which sperm are produced. • Oogonium: – Primordial germ cell in ovaries of fetus from which primary oocytes in follicles are produced. • Follicle: – Sack-like structure in ovary containing an oocyte surrounded by one or more layers of cells which produces the hormone estrogen. Definitions & Functions Relative to Reproduction • Mitosis: – Process through which the nucleus of body cells divide to produce identical daughter cells for maintenance, healing & growth. • Meiosis: – Process through which gametes are formed with half of the normal number of chromosomes for sexual reproduction. • Ovum: – Functional female gamete which has completed the first and second meiotic divisions to become haploid. Definitions & Functions Relative to Reproduction • Spermatozoan: – Haploid male gamete which has completed meiosis 1 & 2, spermiogenesis & is capable of fertilizing a female secondary oocyte. • Fertilization: – Process through which haploid male & female gametes fuse to form a diploid zygote. • Polar Bodies: – Nonfunctional haploid female cells with little to no cytoplasm produced in meiosis. Definitions & Functions Relative to Reproduction • Hormone: – Chemical messenger which is used to regulate reproductive cycles and activities. • Semen: – Mixture of sperm and fluids from male reproductive glands which supplies energy, neutralizes acidic conditions in the reproductive tracts and activates sperm. • Hyaluronidase: – Enzyme in acrosome of sperm that enables sperm nucleus to enter the female gamete. Preembryonic Development Bone Formation Definitions & Functions • Zygote: – A fertilized ovum which is diploid. • Cleavage Divisions: – Mitotic divisions of the zygote to increase the number and surface area of cells in a preembryo (2 cell, 4 cell, 8 cell, etc.) • Morula: – A berry shaped cluster of preembryonic cells produced from cleavage divisions . Definitions & Functions • Blastocyst: – A fluid filled sphere of cells formed from the morula which implants in the endometrium. • Inner Cell Mass: – A group of cells inside of the blastocyst from which the three primary germ layers will develop. • Trophoblast: – One of the cells making up the outer wall of the blastocyst which will form the chorion. Definitions & Functions • Chorionic Villi: – Finger-like growths of the trophoblasts into the endometrium to form the placenta. Definitions & Functions • Chorion: – Outermost embryonic membrane which forms the placenta & produces human chorionic gonadotropin. Definitions & Functions • Amnion: – Membrane which surrounds embryo to form the amniotic cavity & produces amniotic fluid. Definitions & Functions • Amnionic Fluid: – Protects fetus from trauma & permits free movement without adhesion. Definitions & Functions • Yolk Sack: – Provides initial nutrients, supplies earliest RBCs and seeds the gonads with primordial germ cells. Gastrulation • Preembryo becomes embryo as three primary germ layers form. Prembryo Embryo Ectoderm Derivatives • Brain, spinal cord, nerves • Cornea & lens of eyes • Outer skin & accessory structures – hair – nails • Enamel of teeth • Linings of nasal & oral cavities & anal canal Endoderm Derivatives • Epithelial lining of digestive tract • Liver and pancreas • Epithelial lining of respiratory tract & tonsils • Epithelial lining of reproductive ducts & glands • Thyroid, parathyroid & thymus glands • Epithelial lining of bladder & urethra Mesoderm Derivatives • Muscle: skeletal, cardiac & smooth • Connective tissues: cartilage, bone, adipose • Bone marrow, blood & lymphatic tissues • Endothelial linings of blood & lymphatic vessels • Visceral peritoneum of organs in ventral cavity • Fibrous & vascular tunics of eyes • Organs of urogenital system: kidneys, gonads & reproductive ducts Placental Function Minerals Glucose O2 Vitamins Placental Function Alcohol Fetal Alcohol Syndrome • Prenatal & postnatal growth retardation • CNS involvement: – neurological abnormalities – developmental delays • • • • Alcohol related birth defects Mental retardation Speech & hearing impairment Learning, attention & memory deficits Placental Function Urea CO2 Wastes Placental Function - Smoking CO CO2 O2 Nicotine Smoking During Pregnancy • Increases risk of ectopic pregnancy • Doubles risk of placenta previa & abruptio placenta • Slows fetal development • Doubles risk of low birthweight babies • Increases risk of preterm deliveries • Increases risk of cleft palate & lip • Doubles risk of sudden infant death syndrome (SIDS) Drug Use Antibiotics Nicotine Crack Irradiation • High-energy – X-rays – Gamma rays • Penetrate deeply into tissues causing ionization of molecules. • May directly or indirectly affect the genetic material resulting in point mutations (affecting a single base). • May break chromosomes causing deletions or translocation of genetic information. Placenta abruptio • Any amount of placental separation prior to delivery. • Causes & Risk Factors: – – – – – Abdominal trauma Hypertension during pregnancy Diabetes mellitus Cigarette smoking Alcohol use during pregnancy Placenta previa • Placental growth across or adjacent to opening of cervical canal in the uterus. • Risk Factors: – The number of prior pregnancies – Multiple pregnancies (twins/triplets) – Prior C-section where scar is close to cervix • Symptoms: – Spotting during 1st & 2nd trimesters – Sudden, painless & profuse vaginal bleeding Ectopic Pregnancy • Implantation of blastocyst anywhere other than within the uterus. • Causes & Risk Factors: – Physical blockage of uterine tube. – Scarring of uterine tube by prior tubal infection (pelvic inflamatory disease). – Pregnancy following tubal ligation reversal or despite oral contraceptive use. • Symptoms: – Lower abdominal or pelvic pain. – Mild cramping on one side of pelvis. – Abnormal vaginal bleeding (spotting). Gonorrhea • Bacterial Pathogen: Neisseria gonorrhoeae • Transmission: Sexual contact with infected person or contact with bacteria in the birth canal of an infected mother. Gonorrhea • Pathology: Inflammation of skin & mucous membranes of urinary & reproductive organs. • Females: Painful urination, abdominal pain, pelvic inflammatory disease, & sterility. • Males: Painful urination with purulent discharge & possible sterility. Gonorrhea • Babies: Contract bacteria in birth canal of infected mother. • Congenital Effects: Conjunctivitis & blindness. • Treatment: Ceftriaxone & Tetracycline – Silver Nitrate in eyes of infants Syphilis • Bacterial Pathogen: Treponema pallidum • Transmission: Sexual & transplacental contact. Primary Syphilis • Incubation period - 21 days (average) • Painless chancre (lesion) where bacteria enter mucous membranes or skin. • Spontaneously heals after 3 to 8 weeks. Secondary Syphilis • Fever, influenza-like symptoms, swollen lymph nodes & skin rash. • Without treatment, these symptoms may last several weeks & disappear or death may occur. Tertiary Syphilis • Involvement of the skin, cardiovascular and nervous systems. • Gummas develop in infected tissues. • Treatment of Choice: Penicillin. Congenital Syphilis • Transplacental transmission. • Stillborn, infective skin lesions, deafness, impaired vision, Hutchison’s teeth, & skeletal deformities . Chlamydia • Most prevalent STD in US. • Bacterial Pathogen: Chlamydia trachomatis • Pathology: Nongonococcal urethritis resulting in serious reproductive tract complications (up to 80% asymptomatic) – pelvic inflamatory disease – infertility – ectopic pregnancy • Babies infected in birth canal – chlamydial opthalmia & pneumonia • Treatment: Tetracycline Genital Herpes • Pathogen: Herpes Simplex Virus - Type 2 • Transmission by secretions from lesions. • Crops of vesicular lesions occur on & around genitalia. • Lesions are recurrent (as often as 4 weeks) & lead to painful ulcerations. • Associated with higher than normal cervical cancer with a 50% mortality rate in infected women. • Transplacental transmission to fetus. • Treatment: Acyclovire to reduce symptoms. Acknowledgements Most of the figures used in this presentation came from the Benjamin Cummings Digital Library Version 2.0 for Human Anatomy & Physiology, Fifth Edition. Other figures came from public domain internet sources and software in the possession of the author.