Summary Introduction to General Embrology

GENERAL EMBROLOGY 1 INTRODUCTION . OBJECTIVES • Introduction/Definition of Human Embryology • Terminologies Used in Embryology • To Understand Normal Human Development from Conception to Birth. • To Understand the Principle of Teratogenesis and the Basis of Birth Defects • To Understand the Developmental Basis in the Study and Practice of Medicine/Importance Embryology is a branch of Anatomy that studies; a) The development of gametes (sperm and ovum)/gametogenesis, b) Fertilization. c) Development of embryos and fetuses. d) Teratology Fertilization is followed by continuous cell division, cell migration, programmed cell death, cell differentiation, cell growth, and cell rearrangement that transform the zygote, into a multicellular human being. Most developmental changes occur during the intra-uterine life, though important changes occur during later periods of development including infancy, childhood, adolescence, and early adulthood e.g., development of teeth and female breasts). Sub-divisions of Embryology 1. Developmental anatomy is the field of embryology concerned with the changes that cells, tissues, organs, and the body as a whole undergo from a germ cell of each parent to the resulting adult. 2. Teratology- is the division of embryology and pathology that deals with abnormal development (birth defects). • It is concerned with various genetic and/or environmental factors that disturb normal development giving rise to birth defects Why study Embryology? • It develops knowledge concerning the beginnings of human life and the changes occurring during prenatal development. • It helps in understanding the causes of variations in human structure. • It also helps in understanding gross anatomy and explaining how normal and abnormal relations develop. Developmental Periods Human development is usually divided into two broad periods: 1. Prenatal development- (before birth): -Prenatal period is further divided into three stages; Stage 1; Pre-Embryonic period -First 2 weeks; Fertilization to formation of the bilaminar germ disc Stage 2:- Embryonic stage; -From Week 3 - day 56 (8 weeks) - Most visible advances occur during the third to eighth weeks. - Is the most susceptible period to teratogenic factors because intensive differentiation occurs in this period. Stage 3:- the fetal stage: The fetal period; -Begins on day 57(8 weeks) and ends when the fetus is completely outside the mother. -After 8th weeks the fetal period, is characterized with differentiation and growth of tissues and organs occur. -The rate of body growth increases during this period 2. Postnatal development- (after birth): • This period is characterized by further differentiation of organs and specializations of body tissues