Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
CHAPTER 23: PREGNANCY, GROWTH, AND DEVELOPMENT BIO 139 ANATOMY AND PHYSIOLOGY II MARY CATHERINE FLATH, Ph.D. Copyright 2010 Dr. Mary Cat Flath FERTILIZATION Fertilization is the fusion of genetic material from the sperm and ovum into a single nucleus Occurs in fallopian tube Sperm becomes capacitated Secondary oocyte surrounded by zona pellucida and corona radiata Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Path of sperm cells Fig. 23.1 Body of uterus Ovary Infundibulum Path of egg cell Egg cell Sperm cells Cervix Vagina Semen deposited in vagina during sexual intercourse Copyright 2010 Dr. Mary Cat Flath Steps in Fertilization • sperm cell reaches corona radiata of oocyte • acrosome releases enzymes to digest corona radiata • one sperm cell penetrates zona pellucida (syngamy) Copyright 2010 Dr. Mary Cat Flath 23-4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Corona radiata First polar body Fig. 23.3 Second meiotic spindle Cytoplasm of secondary oocyte Zona pellucidav Cell membrane of secondary oocyte Acrosome containing enzymes Nucleus containing chromosomes 3 1 4 5 2 Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 23.3a Corona radiata First polar body Second meiotic spindle Cytoplasm of secondary oocyte Zona pellucidav Cell membrane of secondary oocyte Copyright 2010 Dr. Mary Cat Flath Fertilization Once the sperm has penetrated the secondary oocyte: Meiosis II occurs forming female pronucleus 23 chromosomes Sperm’s flagellum is shed forming male pronucleus 23 chromosomes Pronuclei fuse forming segmentation nucleus 23 pairs of chromosomes ZYGOTE = segmentation nucleus and cytoplasm surrounded by the zona pellucida Copyright 2010 Dr. Mary Cat Flath Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acrosome Fig. 23.3b containing enzymes Nucleus containing chromosomes 3 1 4 5 2 Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 23.2 From M. Tegner and D. Epel. 16 February 1973. "Sea Urchin Sperm." Science, 179:685-688. © 1973 American Association for the Advancement of Science Copyright 2010 Dr. Mary Cat Flath Formation of the Morula CLEAVAGE Early mitotic divisions of the zygote Occur rapidly so growth of cells does not take place between divisions Mass of cells, blastomeres, are held within the zona pellucida First division = 36 hours = 2 cells Second division = 48 hours = 4 cells MORULA Solid ball of 32 cells; about 4 days Copyright 2010 Dr. Mary Cat Flath Copyright 2010 Dr. Mary Cat Flath Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 23.4 (a) (b) (c) a: © A. Tsiara/Photo Researchers, Inc.; b: © Omikron/Photo Researchers, Inc.; c: © Petit Format/Nestle/Photo Researchers, Inc. Copyright 2010 Dr. Mary Cat Flath Formation of Blastocyst Blastocyst is a hollow ball of cells surrounding a central cavity; 5 days Trophoblast Inner cell mass (ICM) Outer covering of the blastocyst, beneath zona pellucida Will become chorion, fetal portion of placenta Cells concentrated in one portion of cavity Will become the embryonic body Blastocoel Fluid-filled cavity Copyright 2010 Dr. Mary Cat Flath Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sperm nucleus Egg nucleus Polar bodies Zona pellucida Cleavages (first cleavage completed about 30 hours after fertilization) Stem cells EaEarly Human DevelopmentrlyEarly Human Development Human Development Day 0 Pronucleus formation begins Zygote First cleavage division Day 1 2-cell stage Day 2 4-cell stage Day 3 Early morula Day 4 Late morula Stem cells Fertilization occurs about 12-24 hours after ovulation Day 6-7 Blastocyst implantation Endometrium Ovulation Uterus Copyright 2010 Dr. Mary Cat Flath Implantation The zona pellucida surrounding the blastocyst disintegrates while in uterine cavity (Day 5) At about day 6, implantation occurs. The blastocyst adheres to the endometrial wall through the ICM. Copyright 2010 Dr. Mary Cat Flath Implantation The trophoblast forms two layers Cytotrophoblast Boundary cells Syncytiotrophoblast Closest to endometrium Invades endometrium (decidua basalis) by secretion of digestive enzymes Endometrial cells nourish burrowing embryo for one more week Decidua capsularis is the portion of the endometrium that surrounds the burrowed blastocyst. Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Trophoblast Fig. 23.6a Blastocyst Inner cell mass Uterine wall (a) Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 23.6b Invading trophoblast (b) Copyright 2010 Dr. Mary Cat Flath Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Trophoblast Blastocyst Trophoblast Fig. 23.6 Inner cell mass Inner cell mass Uterine wall (a) (c) Invading trophoblast (b) c: Courtesy of Ronan O'Rahilly, M.D. Carnegie Institute of Washington Copyright 2010 Dr. Mary Cat Flath Endometrium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lumen Fig. 23.7 Endometrium Copyright 2010 Dr. Mary Cat Flath Courtesy of Ronan O'Rahilly, M.D. Carnegie Institute of Washington Summary of Stages and Events of Early Human Prenatal Development • fertilized ovum • 12-24 hours after ovulation • zygote forms • cleavage • 30 hours to third day • mitosis increases cell number • morula • third to fourth day • solid ball of cells • blastocyst • fifth day through second week • trophoblast and inner cell mass form • gastrula • end of second week • primary germ layers form Copyright 2010 Dr. Mary Cat Flath 23-8 Let’s shift to what’s happening during pregnancy. HORMONES MATERNAL CHANGES Copyright 2010 Dr. Mary Cat Flath HORMONES OF PREGNANCY ESTROGENS AND PROGESTERONES HUMAN CHORIONIC GONADOTROPIN HUMAN PLACENTAL LACTOGEN RELAXIN INHIBIN ALDOSTERONE PARATHYROID HORMONE Copyright 2010 Dr. Mary Cat Flath HORMONES OF PREGNANCY ESTROGENS AND PROGESTERONES From corpus luteum through month 3 Relatively low levels to maintain uterine lining during pregnancy From chorion of placenta from month 3 through birth Extremely high levels to maintain pregnancy Develop mammary glands for lactation Inhibit secretion of FSH and LH Inhibit uterine contractions Enlarge reproductive organs Copyright 2010 Dr. Mary Cat Flath HORMONES OF PREGNANCY hCG HUMAN CHORIONIC GONADOTROPIN is secreted from the chorion of the placenta Stimulates the corpus luteum’s continued secretion of estrogens and progesterones Can be detected by day 8, peaks at week 9, decreases sharply during month 4-5 May cause “morning sickness” Copyright 2010 Dr. Mary Cat Flath Hormonal Changes During Pregnancy Mechanism that preserves uterine lining during early pregnancy Copyright 2010 Dr. Mary Cat Flath 23-9 Hormonal Changes During Pregnancy Relative concentrations of three hormones in maternal blood during pregnancy Copyright 2010 Dr. Mary Cat Flath 23-10 HORMONES OF PREGNANCY HUMAN PLACENTAL LACTOGEN (hPL) Secretion starts about day 8 Levels increase as placenta enlarges and peak at week 32 Effects include: Breast development for lactation Protein deposition in tissues Regulation of metabolism Copyright 2010 Dr. Mary Cat Flath HORMONES OF PREGNANCY RELAXIN Secreted by corpus luteum of ovary Relaxes symphysis pubis and pelvic ligaments Dilates uterine cervix INHIBIN Secreted by ovaries Inhibits secretion of FSH Copyright 2010 Dr. Mary Cat Flath HORMONES OF PREGNANCY ALDOSTERONE Secreted by adrenal cortex Promotes sodium and fluid retention PARATHYROID HORMONE Maintains high calcium concentrations in maternal blood Fetal demand may cause hypocalcemia Leading to cramping Copyright 2010 Dr. Mary Cat Flath GESTATION The length of time that the zygote, embryo and fetus is carried in the female reproductive tract About 266 days Obstetrics is the special branch of medicine that deals with this period Copyright 2010 Dr. Mary Cat Flath PREGNANCY: Anatomical changes Fetus occupies pelvic cavity by end of month 3 At full term, fetus occupies most of abdominal cavity Diaphragm pushed upward by liver, intestine and stomach Thoracic cavity is widened Ureters and bladder are compressed Copyright 2010 Dr. Mary Cat Flath PREGNANCY: Physiological Changes General Cardiovascular changes Pulmonary changes GI changes Urinary Changes Skin changes Reproductive Changes Copyright 2010 Dr. Mary Cat Flath PREGNANCY: Physiological Changes General Weight gain Fetus, amniotic fluid, placenta, uterus, water Increased storage of proteins, Triglycerides, and minerals Breast enlargement Preparation for lactation Lower back pain lordosis Copyright 2010 Dr. Mary Cat Flath PREGNANCY: Physiological Changes Cardiovascular changes Increased SV and CO 30% Increased HR 10-15% Increased BV 30-50% Compression of IVC decreases venous return edema Copyright 2010 Dr. Mary Cat Flath PREGNANCY: Physiological Changes Pulmonary changes TV and ERV increased 30- 40% Functional residual capacity decreased To 25% Total oxygen consumption increased 10-20% Copyright 2010 Dr. Mary Cat Flath PREGNANCY: Physiological Changes GI changes Appetite increased Motility decreased constipation Nausea, vomiting, heartburn may result Copyright 2010 Dr. Mary Cat Flath PREGNANCY: Physiological Changes Urinary Changes Increased frequency and urgency Incontinence may result Increased GFR 30-50% Copyright 2010 Dr. Mary Cat Flath PREGNANCY: Physiological Changes Skin changes Increased pigmentation Blotches may occur Dermis of abdomen is stretched Striae may result Copyright 2010 Dr. Mary Cat Flath PREGNANCY: Physiological Changes Reproductive Changes Increased vascularity Vulva and vagina swell Uterus hypertrophy From 60-80 g to 900-1200g 15x original weight Copyright 2010 Dr. Mary Cat Flath Let’s shift back to what’s happening with embryonic development Copyright 2010 Dr. Mary Cat Flath EMBRYONIC DEVELOPMENT Considered first 8-10 weeks gestation Embryo = to grow Rudiments of all principle adult organs are present by 8th week Embryonic membranes have formed Copyright 2010 Dr. Mary Cat Flath EMBRYONIC DEVELOPMENT: GASTRULATION Three germ layers develop within inner cell mass of the blastocyst (now a gastrula) These germ layers will give rise to all adult organs/organ systems Ectoderm Endoderm Mesoderm Copyright 2010 Dr. Mary Cat Flath EMBRYONIC DEVELOPMENT: GASTRULATION About day 8, the ICM cells form the amnion and the amniotic cavity The Ectoderm is the outer most layer (closest to amniotic cavity) Gives rise to epidermis and Nervous tissue Copyright 2010 Dr. Mary Cat Flath EMBRYONIC DEVELOPMENT: GASTRULATION At about day 8, the endoderm is formed (ICM cells that border blastocoel) The endoderm is the innermost germ layer Gives rise to mucous membranes The endoderm and ectoderm are called the embryonic disc Copyright 2010 Dr. Mary Cat Flath EMBRYONIC DEVELOPMENT: GASTRULATION At about day 12 The endoderm forms the yolk sac A third layer called the mesoderm develops The mesoderm is the middle germ layer Gives rise to muscles, bones, and many internal organs Copyright 2010 Dr. Mary Cat Flath Development of the Three Germ Layers: Gastrulation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 23.10 Lumen of uterus Endometrium Chorion Extraembryonic cavity Amnion Ectoderm Germ layers of Mesoderm embryonic disc Endoderm Amniotic cavity Connecting stalk Chorionic villi Yolk sac of embryo Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Neural tube (Spinal cord) Skin Tail end Amnion Fig. 23.11 Chorionic villi Amniotic fluid Connecting stalk Digestive tract Heart Yolk sac Chorion Allantois Brain Endoderm Ectoderm MesodermDr. Mary Cat Flath Copyright 2010 EMBRYONIC MEMBRANES Yolk Sac Nourishment and early blood cell formation Becomes non-functional part of umbilical cord Amnion Encases embryo Cavity is filled with amniotic fluid Protection Helps regulated fetal body temperature Chorion From trophoblast of blastocyst Embryonic/fetal portion of placenta Allantois Early blood cell formation Its blood vessels will form connections with placenta as umbilical cord Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chorion Umbilical cord Allantois Amnion Maternal blood vessels Fig. 23.15 Developing placenta Amniotic cavity Yolk sac Extraembryonic cavity Endometrium Copyright 2010 Dr. Mary Cat Flath Embryos (page 889) • three weeks; dorsal view • three and a half weeks; lateral view • four weeks; lateral view Copyright 2010 Dr. Mary Cat Flath 23-14 Embryonic Development Copyright 2010 Dr. Mary Cat Flath 23-15 Changes During Embryonic Development Copyright 2010 Dr. Mary Cat Flath 23-16 DEVELOPMENT OF PLACENTA COMPLETE BY THIRD MONTH OF PREGNANCY Copyright 2010 Dr. Mary Cat Flath ANATOMY OF PLACENTA SHAPED LIKE FLAT CAKE WHEN MATURE EMBRYONIC/FETAL PORTION IS CHORION CHORIONIC VILLI (CONTAINING FETAL BLOOD VESSELS FROM ALLANTOIS) EXTEND INTO INTERVILLOUS SPACES (MATERNAL BLOOD SINUSES) EXCHANGE SITE for GASES AND NUTRIENTS AND WASTES MATERNAL PORTION IS DECIDUA BASALIS Copyright 2010 Dr. Mary Cat Flath PHYSIOLOGY OF PLACENTA MAINTAINS FETUS PROTECTS FETUS OXYGEN AND NUTRIENTS DIFFUSE FROM MATERNAL BLOOD INTO FETAL BLOOD CO2 AND WASTES DIFFUSE FROM FETAL BLOOD TO MATERNAL BLOOD NEARLY ALL DRUGS PASS THROUGH PLACENTA BARRIER AGAINST MOST MICROORGANISMS PERMEABLE TO SOME VIRUSES HIV, MEASLES, GERMAN MEASLES, CHCKEN POX, ENCEPHALITIS, POLIOMYELITIS MAINTAINS PREGANACY THROUGH SECRETION OF HORMONES Copyright 2010 Dr. Mary Cat Flath Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Amniochorionic membrane Amniotic fluid Fig. 23.18 Umbilical cord Chorion Endometrium Myometrium Copyright 2010 Dr. Mary Cat Flath Placenta UMBILICAL CORD VASCULAR CONNECTION BETWEEN MOTHER AND FETUS ONE UMBILICAL VEIN TWO UMBILICAL ARTERIES OXYGEN AND NUTRIENTS TOWARD FETUS CO2 AND WASTES AWAY FROM FETUS COMPLETELY SURROUNDED BY LAYER OF AMNION SEVERED AT DELIVERY REMNANT IS NAVEL Copyright 2010 Dr. Mary Cat Flath Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Umbilical cord Umbilical arteries Fig. 23.17 Umbilical vein Chorion Embryonic blood vessels Lacuna Villi (embryonic portion of placenta) Myometrium Decidua basalis (maternal portion of placenta) Maternal blood vessels Copyright 2010 Dr. Mary Cat Flath Embryo at Eight Weeks End of eighth week marks end of embryonic period Copyright 2010 Dr. Mary Cat Flath 23-21 Teratogens • factors that cause congenital malformations during embryonic development Drugs, viruses, radiation, large amounts of normal substances (fat- soluble vitamins) •Structures in developing embryo are sensitive to teratogens at different times • Each structure has time called “critical period” • Neural Tube defects are traced to day 28 in development •Interruption results in spina bifida or anecephaly Copyright 2010 Dr. Mary Cat Flath 23-22 Teratogens In acne medications Prescribed to prevent miscarriages Prescribed to alleviate morning sickness Copyright 2010 Dr. Mary Cat Flath Development body proportions change considerably Copyright 2010 Dr. Mary Cat Flath 23-23 Development of the Genitalia Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Genital tubercle Urogenital fold Genital tubercle Urogenital folds Embryonic tail Labioscrotal folds Fig. 23.22 (a) Glans Urogenital fold Urethral groove Labioscrotal fold Male Female (b) Developing penis Developing clitoris Urethral groove Labia minora Fused urogenital folds Labia majora Perineum Anus (c) Glans penis (e) Prepuce Glans clitoris Urethral orifice Hymen Scrotum Vaginal orifice Perineum Anus (d) (f) Copyright 2010 Dr. Mary Cat Flath Position of Full-Term Fetus Copyright 2010 Dr. Mary Cat Flath 23-25 Major Events of Fetal Development 9th –12th week • ossification centers appear • sex organs differentiate • nerves and muscles coordinate so fetal limbs begin to move • length is four inches; weight is one ounce 13th – 16th week • body grows rapidly • ossification continues • length is eight inches; weight is six ounces Copyright 2010 Dr. Mary Cat Flath 23-26 Major Events of Fetal Development 17th – 20th week • muscle movements stronger • skin is covered with fine downy hair (lanugo) • length is 12 inches; weight is one pound • skin is covered sebum mixed with dead epidermal cells vernix caseosa 21st – 38th week • body gains weight (to 6-10 pounds; 21 inches in length • subcutaneous fat deposited • eyebrows and eyelashes appear • eyelids open 23-27 Copyright 2010 Dr. Mary Cat Flath • testes descend Fetal Circulation • oxygen and nutrients diffuse into the fetal blood from the maternal blood • waste diffuses into the maternal blood from the fetal blood Copyright 2010 Dr. Mary Cat Flath 23-28 Fetal Cardiovascular Adaptations • fetal blood has greater oxygen-carrying capacity • umbilical vein carries oxygenated blood from placenta to fetus • ductus venosus conducts half the blood from umbilical vein to inferior vena cava; liver is bypassed • foramen ovale conveys blood from right atrium to left atrium; lungs are bypassed • ductus arteriosis conducts some blood from pulmonary trunk to aorta; lungs are bypassed • umbilical arteries carry blood from internal iliac arteries to placenta Copyright 2010 Dr. Mary Cat Flath 23-29 Fetal Circulation Copyright 2010 Dr. Mary Cat Flath 23-30 Copyright 2010 Dr. Mary Cat Flath Copyright 2010 Dr. Mary Cat Flath Factors Contributing to the Labor Process • as birth approaches, progesterone levels decrease • prostaglandins synthesized which may initiate labor • stretching uterine tissue stimulates release of oxytocin • oxytocin stimulates uterine contractions • fetal head stretches uterus • positive feedback results in stronger and stronger contractions and greater release of oxytocin Copyright 2010 Dr. Mary Cat Flath 23-32 Birth Process A positive feedback mechanism propels the birth process Copyright 2010 Dr. Mary Cat Flath 23-33 Stages in Birth • dilation stage • expulsion stage • placental stage Copyright 2010 Dr. Mary Cat Flath 23-34 “Fight or flight” for Newborn Hypoxia results from fetal head compression High levels of epinephrine and norepinephrine are secreted which allow infant to survive extra-uterine life Lungs are cleared for breathing Nutrients are mobilized for metabolism Blood is rushed to brain and heart Copyright 2010 Dr. Mary Cat Flath Post-Natal Circulatory Changes Copyright 2010 Dr. Mary Cat Flath Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aorta Ductus arteriosus constricts and becomes solid ligamentum arteriosum Foramen ovale closes and becomes fossa ovalis Fig. 23.32 Ductus venosus constricts and becomes solid ligamentum venosum Deoxygenated blood Liver Oxygenated blood Umbilical vein becomes solid ligamentum teres Inferior vena cava Distal portions of umbilical arteries constrict and become medial umbilical ligaments Proximal portions of umbilical arteries persist Copyright 2010 Dr. Mary Cat Flath as superior vesical arteries Postnatal Period Neonatal period • birth to end of 4th week • newborn begins to carry on respiration, obtain nutrients, digest nutrients, excrete wastes, regulate body temperature, and make cardiovascular adjustments Infancy • end of 4th week to one year • growth rate is high • teeth begin to erupt • muscular and nervous systems mature • communication begins Copyright 2010 Dr. Mary Cat Flath 23-38 Postnatal Period Adolescence Childhood • puberty to adulthood • one year to puberty • person becomes • growth rate is high reproductively functional • permanent teeth appear and emotionally more • muscular control is mature achieved • growth spurts occur • bladder and bowel • motor skills continue to controls are established develop • intellectual abilities • intellectual abilities mature continue to mature Copyright 2010 Dr. Mary Cat Flath 23-39 Postnatal Period Adulthood • adolescence to old age • person remains relatively unchanged anatomically and physiologically • degenerative changes begin Senescence • old age to death • degenerative changes continue • body becomes less able to cope with demands placed on it • death results from various conditions and diseases Copyright 2010 Dr. Mary Cat Flath 23-40 Copyright 2010 Dr. Mary Cat Flath Copyright 2010 Dr. Mary Cat Flath Causes of Death Copyright 2010 Dr. Mary Cat Flath 23-43 Clinical Application Preimplantation Genetic Diagnosis Probes diseasecausing genes in an eight-celled embryo Copyright 2010 Dr. Mary Cat Flath 23-44 Copyright 2010 Dr. Mary Cat Flath