INTRODUCTION TO THE HUMAN EMBRYOLOGY.pptx

In this session, we will explore embryology—the branch of biology and medicine concerned with the development of an organism from fertilization to birth. We will also clarify important terms commonly used in this field. By the end of this lesson, learners should be able to:

Define embryology and key related terms.
Identify the primary developmental periods.
Explain the significance of embryology in understanding human growth and development.
Recognize essential embryological terminology.
Use standard anatomical nomenclature to describe body parts, positions, and relationships.
This foundational overview will equip medical students with a clear framework for studying the complex processes that shape human development.

1. INTRODUCTION TO EMBRYOLOGY BY Ini-ibehe OKOKO (Ph.D.)

2. LEARNING OUTCOME At the end of this lesson, learners should be able to: • Define Embryology and related terms • Define the developmental periods. • Define the significance of embryology. Define the different embryological terminology. • Define the nomenclature used to describe body parts, positions and relationships.

3. PRETEST 1- “Human embryology’’ is the science concerned with the origin and development of a human being from: A- birth to puberty B- sperm and ovum to zygote C- a zygote to birth of an infant D- 6th week to birth 2- When does the implantation process begin and end? A- Fertilization to 8th week B- Beginning of week 2 till the 12th day C- 12th day to birth D- Fertilization to the end of the First week

4. PRETEST 3- Epiblast layer is adjacent to ………. A- Amniotic cavity B- posterior surface of the uterus C- Yolk cavity D- Cortex of the ovary 4- Where does the spermatogenesis occur? A- Cortex of Ovary B- Endometrium C- Epididymis D- Seminiferous tubules

5. PRETEST 5- What is the term used to express the anterior direction in Embryology? A- Frontal B- Caudal C- Ventral D- Sagittal 6- Slower changes occur during which period? A- Prenatal B- Postnatal C- Embryonic D- Fetal 7- An example of a Postnatal development is? A- Development of CNS B- Formation of limbs C- Formation of teeth

6. INTRODUCTION TO EMBRYOLOGY

7. DEFINITION OF EMBRYOLOGY Embryology generally refers to the study of Prenatal development of embryos and fetuses. “Human embryology’’ is the science concerned with the origin and development of a human being from a zygote to birth of an infant.

8. DEFINITIONS What is embryology? What is an Embryo? What is a Zygote? What is a Fetus? What is Human Embryology? (Development of Human) Difference between Embryology and Developmental Biology The difference between Developmental anatomy and developmental Biology

9. ZYGOTE

10. EMBRYO

11. STUDY OF EMBRYOLOGY We can study embryology at two levels general embryology and systemic embryology. In general embryology we study the synthesis or creation of primordia of different organ systems. The bilaminar and trilaminar germ In systemic embryology we study system-wise, we study the development of different systems 

12. Why to study embryology ? to understand and realize the importance of the complex phenomena involved in development so as to realize the importance of all the precautions required for normal development. understand which is critical period in development. when / why most of the medicines should not be given to the mother during pregnancy. to determine moods of growing child. to visualize if growing fœtus is healthy or in distress. for monitoring the fœtus by ultrasound, other imaging modalities and investigations have become important tools to measure normal development.

13. Why to study embryology? with this knowledge new techniques for prenatal diagnosis of many diseases & congenital anomalies have developed. mechanisms to prevent birth defects have developed. many diseases can be treated during developmental process by medicines. foetal surgery has developed on account of understanding clinical embryology. infertile couples are being blessed with child only on account of in-depth understanding of the intricate processes involved in development. Infant mortality and morbidity have reduced. Greater realization of important for a healthy growth of the child.

14. IMPORTANCE OF EMBRYOLOGY ❖ The study of prenatal stages of development, especially those occurring during the embryonic period, help us understand the normal body structure and the cause of congenital anomalies. ❖ It is also concerned with studying various genetic and environmental factors that disturb normal development and produce birth defects.

15. DESCRIPTIVE TERMS Direction ● Cranial; the top of the embryo or the head. ● Cephalic; superior or the head. ● Caudal; inferior or the tail end. ● Dorsal; back of the embryo. ● Ventral; anterior or the belly side. ● Medial; near to the midline. ● Lateral; flank side. Planes and sections Longitudinal; median or sagittal. (cuts it to left & right) ● Coronal; frontal. ● Transverse; horizontal. (cuts it to superior & inferior)

16. DEVELOPMENTAL PERIODS Prenatal development Includes the main developmental changes occurring before birth, and is divided into 2 periods: 1. Embryonic period: Begins at fertilization and ends with the end of the 8th week. (called an embryo) 2. Fetal period : Begins at the beginning of the 9th week and ends at birth. (called a fetus) Postnatal development: Includes changes occurring after birth. e.g. teeth and breast.

17. Major events during the embryonic period • Gametogenesis → occurs at 1st week. • Fertilization → occurs at 1st week. • Implantation → begins one week after fertilization. • Development of the Central Nervous System (CNS; brain & spinal cord) → occurs at 3rd week. • Embryonic Folding → occurs at 4th week.

18. Spermatogenesis begins when the cells of the germinal epithelium become the primordial germ cells as schematically represented

19. Critical Periods of Human Development - It is the stage of development of an embryo that is susceptible to an agent, such as a drug or virus,which can lead to congenital abnormalities. - The development of the embryo is most easily disrupted when the tissues and organs are forming during the embryonic period. Note: The most critical period is the embryonic period. Note: The Bilaminar & Trilaminar discs are supposed to be present before the embryonic folding.

20. POST-TEST 1- “Human embryology’’ is the science concerned with the origin and development of a human being from: A- birth to puberty B- sperm and ovum to zygote C- a zygote to birth of an infant D- 6th week to birth 2- When does the implantation process begin and end? A- Fertilization to 8th week B- Beginning of week 2 till the 12th day C- 12th day to birth D- Fertilization to the end of the First week

21. POST-TEST 3- Epiblast layer is adjacent to ………. A- Amniotic cavity B- posterior surface of the uterus C- Yolk cavity D- Cortex of the ovary 4- Where does the spermatogenesis occur? A- Cortex of Ovary B- Endometrium C- Epididymis D- Seminiferous tubules

22. POST-TEST 5- What is the term used to express the anterior direction in Embryology? A- Frontal B- Caudal C- Ventral D- Sagittal 6- Slower changes occur during which period? A- Prenatal B- Postnatal C- Embryonic D- Fetal 7- An example of a Postnatal development is? A- Development of CNS B- Formation of limbs C- Formation of teeth

23. Answers : 1C / 2B / 3A / 4D / 5C / 6B / 7C