MED-202 Introduction to Embryology and the 1st Week of Development PDF Fall 2024

Introduction to Embryology and the First Week of Human Development MED-202 Histology/Embryology I Fall 2024 Annita Achilleos, PhD  MED-202 Histology/Embryology I Course Lead: Annita Achilleos, PhD Contributors: Danijela Antunovič, MD (lectures and tut...

Introduction to Embryology and the First Week of Human Development MED-202 Histology/Embryology I Fall 2024 Annita Achilleos, PhD  MED-202 Histology/Embryology I Course Lead: Annita Achilleos, PhD Contributors: Danijela Antunovič, MD (lectures and tutorials) Stella Voskou, PhD (tutorials) − Lectures − Tutorials − Midterm Formative Exam − Coursework – 20% − Final Exam – 80%  Reading Material - Lecture notes - Langman’s Medical Embryology, 15th ed. Chapter 2 and 3 - Embryology – Ronald Dudek, 6th ed. Chapter 2  Learning objectives − Briefly discuss the concept of embryology. − Briefly describe oogenesis (female gametogenesis) and spermatogenesis (male gametogenesis). − Discuss the first week of development from the ovarian cycle to blastocyst formation. − Discuss examples of birth defects of the first week of development. Human Embryo Development https://youtu.be/1zpV5rzWXMA  What is Embryology? Embryology is the study of: Development of gametes Fertilization (sex cells) Development of The study of congenital disorders embryos and fetuses (birth defects)  Why Embryology? Birth defects are: - the leading cause of infant mortality - a major contributor to disabilities About 3-4% of infants are born with a birth defect The study of embryology can: - lead to understanding of the causes of birth defects - improvements to reproductive and prenatal health care - better understanding of some adult diseases (e.g. cancer)  Stages of prenatal development and risk of birth defect induction Weeks 1 – 2 Weeks 3 – 8 Weeks 9 – birth GERMINAL PERIOD EMBRYONIC FETAL PERIOD PERIOD Conception – 12 weeks Weeks 13 - 26 Weeks 27 - birth FIRST TRIMESTER SECOND TRIMESTER THIRD TRIMESTER Risk of birth Structural defect induction defects Functional defects Development of the female gametes: Oogenesis KNOW THE MAIN DIFFERNCES BETWEEON SPEROMGENISS AND OOGENESIS 2n mitosis (germ cell) Before birth 2n arrest n During cell division, this cell receives WHY? very little cytoplasm First polar body Adolescence to n Meiosis II is menopause completed only if the Second oocyte is fertilized polar body n  Oogenesis - Numbers Not IMPORTANT - 1-2 million oogonia (germ cells) are formed during development, per ovary - 60,000 – 80,000 primary oocytes remain in each ovary by puberty - About 20 secondary oocytes (follicles) proceed to maturation every month - 1 – 2 of them will further develop and proceed to ovulation each month  Clinical Correlates: Numerical Chromosomal Abnormalities KNOW THIS - WHEN CAN THIS HAPPEN - WHAT KIND OF CELLS, KNOW THE TERMS Normal Nondisjunction Nondisjunction maturation division 2nd meiotic division 1st meiotic division Chromosome # 23 23 23 23 24 22 23 23 24 24 22 22 Trisomy Monosomy Trisomy Monosomy Euploid Aneuploid Aneuploid  Chromosomal Abnormalities - Trisomies KNOW THAT NUMERICAL CHROMOSOMAL ABNORMALITIES ARE NOT TOLERATED BY THE HUMAN BODY THESE 3 ARE THE EXCEPTIONS Trisomy 21 Trisomy 18 Trisomy 13 (Down syndrome) (Edwards syndrome) (Patau syndrome) 1:2000 (maternal age