Chapter 8 Oral Embryology and Histology 2015 PDF

Introduction Embryology is the study of prenatal development in the stages before birth Learning about the development of the oral structures is the foundation for understanding developmental problems that can occur in these structures...

Introduction Embryology is the study of prenatal development in the stages before birth Learning about the development of the oral structures is the foundation for understanding developmental problems that can occur in these structures 4  Introduction (Cont.) Histology is the study of the structure and function of the tissues on a microscopic level This includes the tissues and structures of the oral mucosa, which surrounds the teeth and lines the mouth Loading… By understanding the histology of the oral tissues, the dental assistant can understand the disease processes that occur in the oral cavity 5  Oral Embryology Pregnancy begins with conception, also known as fertilization This occurs when the sperm penetrates and fertilizes the ovum Birth occurs, on average, 38 weeks after conception, or 40 weeks after the beginning of the last menstrual period (LMP) For general descriptive purposes, this is divided into three trimesters of 3 months each In embryology, developmental age is based on the date of conception, which is assumed to have occurred 2 weeks after the LMP 6  Prenatal Development The preimplantation period is the first week The embryonic period extends from the beginning of the second week to the end of the eighth week; at this time the developing life is known as an embryo The embryonic period is the most critical time in development The fetal phase begins with the ninth week and lasts until birth 10  Primary Embryonic Layers During the third week of development, the cells of the embryo form the three primary embryonic layers: Ectoderm: skin, brain, spinal cord, hair, nails, enamel, lining of oral cavity Mesoderm: bones, muscles, circulatory system, kidneys, reproductive system, lining of abdominal cavity, dentin, pulp and cementum of teeth Endoderm: lining of digestive system, lining of lungs, parts of urogenital system 12  Embryonic Development of the Face and Oral Cavity The face and its related tissues begin to form during the fifth week of prenatal development within the embryonic period (5-8 week) During this time, the rapidly growing brain of the embryo bulges over the oropharyngeal membrane, beating heart, and stomodeum 13  Early Development of the Mouth Fourth week: The stomodeum, or primitive mouth, and primitive pharynx merge, and the stomodeum develops into part of the mouth Fifth week: The embryo is approximately 5 mm long The heart is prominent and bulging Facial development is beginning 16