✅ INTRODUCCIÓN A LA EMBRIOLOGÍA HUMANA | Conceptos Básicos 📚
Introduction to Embryology
What is Embryology?
- Embryology is defined as the study of the embryo, encompassing all changes from fertilization to birth.
- It includes the examination of the placenta and extra-embryonic structures such as the amnion, yolk sac, chorion, allantois, and umbilical cord.
- Human prenatal development is divided into three periods: pre-embryonic, embryonic, and fetal.
Stages of Prenatal Development
- Development begins on day 0 with fertilization, forming a zygote (egg cell).
- The zygote undergoes segmentation in the fallopian tube during its first week and becomes a blastocyst.
- By the second week, implantation occurs; the embryo is now bilaminar.
- The third week introduces a trilaminar embryo through gastrulation; this marks the end of the pre-embryonic period.
Organogenesis and Fetal Development
- Between weeks four to eight, organogenesis occurs where outlines for future organs are formed; this phase is known as the embryonic period.
- From week nine onward, development transitions into a fetal stage characterized by functional organ development and body growth.
Factors Influencing Development
- Two major factors influence normal development: genetic regulation (DNA influence) and epigenetic regulation (external factors).
Morphogenetic Mechanisms
- Five key morphogenetic mechanisms guide embryonic development: induction, cell differentiation, growth, migration, and programmed cell death (apoptosis).
- Induction encourages tissue changes among embryonic cells.
- Cell differentiation leads to diverse cell types through increased complexity.
- Growth refers to size increase in parts/organs.
- Migration involves cells moving from their origin site to new locations.
Position Terminology in Embryology
- Understanding relative positions within an embryo requires specific terminology related to orientation planes: sagittal (right/left), coronal (ventral/dorsal), and transverse (cranial/caudal).