A&P Reproduction, Fetal Development, and Heredity (Abridged) PDF

26: Reproduction, Fetal Development and Heredity Anatomy and Physiology in Context Chapter 26 Abridged Version Objectives  26.1 The Sexual Response Cycle Chapter 26: Reproduction, Fetal Development and Heredity  Sexual Arousal reflexogenic or psychogenic can incorpora...

26: Reproduction, Fetal Development and Heredity Anatomy and Physiology in Context Chapter 26 Abridged Version Objectives  26.1 The Sexual Response Cycle Chapter 26: Reproduction, Fetal Development and Heredity  Sexual Arousal reflexogenic or psychogenic can incorporate all the senses Four stages 1. Excitement 2. Plateau 3. Orgasm Urethra open widens, scrotum skin thickens, 4. Resolution cremaster muscle elevates testes increased heart rate, blood pressure breathing rate and depth, erect  26.1.1 The Male Sexual Response Cycle Originates in Requires continual erection reflex erotic stimulation center of sacral spinal cord Erection can be reflexogenic or psychogenic Loss of Reproductive voluntary tissue return to muscle their resting control state Emission and expulsion Followed by refractory period  26.1.2 The Female Sexual Response Cycle Vaginal External lubrication indicators of Uterine sexual arousal fibrillations continue to increase Reproductive Strong muscle tissues return to contractions their resting state apply greater External cervical pressure on the os dilates to aid penis sperm migration Vaginal dilation to receive ejaculate No refractory  26.1.3 Components of the Male Ejaculate COMPONENT FUNCTION Seminogelin Coagulant produced in seminal vesicle Holds the sperm against the vaginal wall after Motility ejaculation Prevents sperm from struggling in the coagulant, inhibitor PSA wasting energy Breaks down seminogelin within 20-40 minutes, Prostaglandins freeing sperm peristalsis in uterus to draw sperm Induce reverse inwards Reduce viscosity of cervical mucus hCAP-18 Anti-microbial protein that prevents bacterial growth in female reproductive tract Factor III Coagulation and abrasion healing PSAP Potent anti-nociceptive; prevents painful stimuli from detection + many  26.2 The Pre-Embryonic Period Chapter 26: Reproduction, Fetal Development and Heredity 26.2.1 VIDEO: Steps to Fertilization General Embryology – Detailed Animation on Fertilization 30 min to 2 hours 26.2.2 Capacitation Is a Last Step Maturation Process Required for Fertilization 1 Insemination; introduction of sperm 2 Initial capacitation; last step of maturation of sperm 3 Sperm reservoir 4 Hyperactivation; activity of sperm 5 Sperm penetrates cumulus mass 6 Zona penetration 26.2.3 Fertilization Is the Fusion of a Sperm and an Oocyte Zona pellucida (ZP): species- specific barrier Acrosome reaction: rupture of acrosome and release of proteases that digest ZP Hyperactive sperm have their plasma membranes rearranged and penetrate into the perivitelline space (PVS) 26.2.4 The Precise Fusion of Egg and Sperm Oocyte has microvilli all over its surface, except for overlying the oocyte’s pronucleus Microvilli serve as docking site for sperm, ensuring they dock away from pronucleus Oocyte is activated after sperm-egg Image courtesy of PDImages in the Public Domain fusion PLCz (a component of the sperm’s plasma membrane) triggers release of Ca2+ from oocyte’s ER 26.2.5 Pre-Embryonic Events Following Oocyte Activation BLOCKING POLYSPERMY SECOND MEIOTIC DIVISION, Cortical reaction occurs Meiosis II and extrusion of polar SYNGAMY directly after oocyte body in the oocyte activation Packaging material in sperm Cortical granules migrate pronucleus replaced with towards the oocyte plasma maternal histones membrane and release their contents into the PVS Paternal mitochondria destroyed; maternal These materials form a new mitochondria activated barrier against further sperm fusion Maternal RNA destroyed Ensures against euploidy Pronuclei fusion and generation 26.3 Early Embryogenesis Chapter 26: Reproduction, Fetal Development and Heredity 26.3.1 The Four Stages of Early Embryogenesis  26.4 Uterine Receptivity and Implantation Chapter 26: Reproduction, Fetal Development and Heredity 26.4.1 The Three Stages of Preparation for Uterine Implantation 1. Apposition General stromal edema brings the uterine walls into close proximity Helps incoming blastocyst find attachment point 2. Attachment Polarity is important (blastocyst’s inner cell mass must be next to uterine lining) Development of cytotrophoblast and syncytiotrophoblast 3. Penetration Blastocyst burrows into endometrial stroma for access to uterine nutrients A barrier is generated between the blastocyst and maternal  26.5 Embryogenesis and the Origin of Tissues Chapter 26: Reproduction, Fetal Development and Heredity 26.5.1 Origins of the Extraembryonic Tissues Hypoblast: layer of inner cell mass closest to blastocoel; will eventually form the extraembryonic endoderm Epiblast: layer of inner cell mass farther from blastocoel; gives rise to embryo proper Two layers together form blastodisc: gives rise to yolk blastocyte sac, amnion, chorion 26.5.2 Formation of the Three Primary Germ Layers: Gastrulation 26.5.3 VIDEO: Embryonic Folding General Embryology – Detailed Animation on Embryonic Folding 26.5.4 The Developing Embryo Simultaneously Folds Along 2 Axes END RESULTS: Embryo divided into cephalic and caudal regions Embryo divided into three distinct layers (ectoderm, endoderm, mesoderm) 26.5.5 The Fate of the Mesoderm 26.5.6 The Fates of the Ectoderm and Endoderm ECTODERM ENDODERM Nervous tissue Internal lining of respiratory, GI, urinary and reproductive Epidermis and its tracts derivatives Portions of the liver, Sense organs gallbladder, and pancreas Lens of the eye Palantine tonsils Teeth enamel Thyroid and parathyroid glands Mouth and anus Thymus Pituitary and adrenal glands 26.5.7 Structure and Function of the Placenta Structure: Chimeric organ consisting of uterine and embryonic tissue Consists of several lobes called cotyledons, fed by umbilical vessels Functions: Organ of material exchange between the mother and developing embryo/fetus Endocrine organ; produces hormones required for pregnancy  26.6 Pregnancy Chapter 26: Reproduction, Fetal Development and Heredity 26.6.1 FOCUS ON DISEASE: Complications During Pregnancy ECTOPIC Development of the embryo or fetus outside of the uterus PREGNANCY Occurs when something blocks the passage of the fertilized ovum PLACENTA The placenta implants in the inferior uterus, near PREVIA to/covering the internal os of the cervix, leading to spontaneous abortion or premature birth Sudden pregnancy-induced hypertension PREECLAMPSIA Difficult labor due to an abnormal fetal position or DYSTOCIA inadequate vaginal canal; may lead to cesarean section DELIVERY OF Classified as a baby that weighs less than 2,500 g at birth PHYSIOLOGICALL Carries substantial risk to the baby Y-IMMATURE BABY  26.6.2 Growth of the Uterus During Pregnancy Primarily due to hypertrophic and hyperplastic growth of the uterine myometrium Grows all the way to the xiphoid process of the sternum by term 26.6.3 Development of the Mammary Glands During Pregnancy Grow in response to placental hormones Areola and nipple become darker in response to melanocyte- stimulating hormone (MSH)  26.7 The Hormones of Pregnancy Chapter 26: Reproduction, Fetal Development and Heredity 26.7.1 The Hormones of Pregnancy: Estrogen, Progesterone and Human Chorionic Gonadotropin (hCG) hCG: Produced by the chorion Detectable ~10 days after ovulation (hormone detected by at-home pregnancy kits) Estrogen/Progesterone: Produced by corpus luteum, then placenta Estrogen promotes uterine contraction/parturition, while progesterone prevents uterine 26.7.2 Other Hormones Involved in Pregnancy PLACENTAL Produced by syncytiotrophoblast cells LACTOGEN (PL) Shifts fuel away from mother, towards fetus (anti-insulin properties) Produced by placenta and mother’s anterior pituitary gland PROLACTIN (PRL) Shifts fuel towards mother in periods of insult/illness Produced by syncytiotrophoblast cells RELAXIN Plays important roles in osmoregulation and cardiovascular adaptation CORTICOTROPIN Produced by syncytiotrophoblast cells RELEASING Increases DHEA production, which is used to synthesize HORMONE (CRH) estrogen Serves as initial signal for parturition  26.8 Parturition Chapter 26: Reproduction, Fetal Development and Heredity 26.8.1 The First Stage of Parturition: Cervical Effacement, Dilation Effacement Dilation of cervix Transition 26.8.2 The Next Two Stages of Parturition: Fetal and Placental Expulsion 26.8.3 Hormonal Regulation of Parturition  26.10 Sexually-Transmitted Diseases Chapter 26: Reproduction, Fetal Development and Heredity 26.10.1 Sexually-transmitted diseases Are Infections That Spread Through Sexual Contact Estimated numbers of new cases of STDs Examples across the world Nongonococcal urethritis Chlamydia Syphilis Gonorrhea Vaginitis Herpes simplex Human papilloma virus AIDS  26.11 Contraceptive Methods Chapter 26: Reproduction, Fetal Development and Heredity 26.11.1 Types of Contraceptive Devices and Their Effectiveness More Less effective effective Percentage indicates number out of every 100 women who experienced an unintended pregnancy within the first year of typical use of each