BSC 2086 01 Anatomy and Physiology II Spring 2013 23 Development 2012 Pearson Education Inc An Introduction to Development and Inheritance Learning Outcomes 29 1 Explain the relationship between differentiation and development and specify the various stages of development 29 2 Describe the process of fertilization and explain how developmental processes are regulated 29 3 List the three stages of prenatal development and describe the major events of each 2012 Pearson Education Inc An Introduction to Development and Inheritance Learning Outcomes 29 4 Explain how the three germ layers participate in the formation of extraembryonic membranes and discuss the importance of the placenta as an endocrine organ 29 5 Describe the interplay between the maternal organ systems and the developing fetus and discuss the structural and functional changes in the uterus during gestation 2012 Pearson Education Inc An Introduction to Development and Inheritance Learning Outcomes 29 6 List and discuss the events that occur during labor and delivery 29 7 Identify the features and physiological changes of the postnatal stages of life 2012 Pearson Education Inc An Introduction to Development Development Gradual modification of anatomical structures and physiological characteristics from fertilization to maturity 2012 Pearson Education Inc 29 1 Development Fertilization Also called conception When male and female gametes fuse and begins development Differentiation Creation of different types of cells required in development Occurs through selective changes in genetic activity As development proceeds some genes are turned off others are turned on 2012 Pearson Education Inc 29 1 Development Embryological Development Occurs during first two months after fertilization Study of these events is called embryology Fetal Development Begins at start of ninth week Continues until birth 2012 Pearson Education Inc 29 1 Development Prenatal Development Embryological and fetal development stages Postnatal Development Commences at birth Continues to maturity the state of full development or completed growth 2012 Pearson Education Inc 29 2 Fertilization Capacitation Must occur before spermatozoa can fertilize secondary oocyte Contact with secretions of seminal glands Exposure to conditions in female reproductive tract Fertilization Occurs in uterine tube within a day after ovulation Secondary oocyte travels a few centimeters Spermatozoa must cover distance between vagina and ampulla covers 5 inches hour 2012 Pearson Education Inc 29 2 Fertilization Fertilization Produces zygote containing 46 chromosomes Occurs upon fusion of two haploid gametes each containing 23 chromosomes Spermatozoon Travels relatively large distance to deliver paternal chromosomes to fertilization site Secondary oocyte Provides cellular organelles inclusions nourishment genetic programming necessary to support development of embryo for a week 2012 Pearson Education Inc 29 2 Fertilization Acrosomes of Sperm Cells Release hyaluronidase enzyme that breaks bonds between adjacent follicle cells acrosin proteolytic enzyme Penetrate corona radiata zona pellucida toward oocyte surface Sperm binds to receptor found on zona pellucida activates acrosome and releases enzymes to digest path through zona pellucida 2012 Pearson Education Inc 29 2 Fertilization Oocyte Activation changes in oocyte metabolism triggered by contact and fusion of sperm and oocyte cell membranes Causes 1 Cortical Reaction oocyte plasma membrane depolarizes and releases exocytosis of enzymes that A Inactivate sperm receptors B Harden zona pellucida Both prevent polyspermy 1 Completion of meiosis II formation of 2nd polar body 2 Activation of enzymes to increase cell s metabolic rate 2012 Pearson Education Inc 29 2 Fertilization After oocyte activation and completion of meiosis II Fusion of male and female pronuclei process called amphimixis Female Pronucleus Nuclear material remaining in ovum after oocyte activation Male Pronucleus Swollen nucleus of spermatozoon Now zygote has 46 chromosomes Fertilization is complete 2012 Pearson Education Inc 29 2 Fertilization Cleavage Series of cell divisions Produces daughter cells First cleavage occurs 30 hrs after fertilization produces 2 daughter cells each size of original zygote These daughter cells called blastomeres Differentiation Involves changes in genetic activity of some cells but not others Influenced by cytoplasmic content as the blastomeres divide each receives a portion of cytoplasm that may differ in composition oocyte receives many molecules nutrients and mRNA from granulosa cells 2012 Pearson Education Inc Figure 29 1a Fertilization A secondary oocyte and numerous sperm at the time of fertilization Notice the difference in size between the gametes 2012 Pearson Education Inc Figure 29 1b Fertilization Oocyte at Ovulation Ovulation releases a secondary oocyte and the first polar body both are surrounded by the corona radiata The oocyte is suspended in metaphase of meiosis II Corona radiata First polar body Fertilization and Oocyte Activation Acrosomal enzymes from multiple sperm create gaps in the corona radiata A single sperm then makes contact with the oocyte membrane and membrane fusion occurs triggering oocyte activation and completion of meiosis Fertilizing spermatozoon Second polar body Zona pellucida 2012 Pearson Education Inc Figure 29 1b Fertilization Pronucleus Formation Begins The sperm is absorbed into the cytoplasm and the female pronucleus develops Nucleus of fertilizing spermatozoon Female pronucleus 2012 Pearson Education Inc Figure 29 1b Fertilization Spindle Formation and Cleavage Preparation The male pronucleus develops and spindle fibers appear in preparation for the first cleavage division Male Female pronucleus pronucleus 2012 Pearson Education Inc Figure 29 1b Fertilization Amphimixis Occurs and Cleavage Begins Metaphase of first cleavage division 2012 Pearson Education Inc Figure 29 1b Fertilization Cleavage Begins The first cleavage division nears completion roughly 30 hours after fertilization Blastomeres 2012 Pearson Education Inc
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