#### Germinal Period (0-14 Days) 

- Zygote: The fertilized egg, the first stage of development. 

- Mitosis: The process of cell division, leading to the growth of the zygote. 

- Blastocyst: A structure formed in early development, containing pluripotent stem cells. 

- Pluripotent: Cells that can differentiate into various tissue types. 

- Implantation: The attachment of the blastocyst to the uterine wall. 

#### Embryonic Period (Weeks 2-8) 

- Embryo: The early stage of human development. 

- Chorion: The outer membrane, which becomes the placenta. 

- Amnion: The inner membrane filled with fluid, protecting the embryo. 

- Placenta: A temporary organ that provides nutrients and removes waste from the fetus. 

- Organogenesis: The formation of organs and major body systems. 

- Cephalocaudal: Development pattern from head to tail. 

- Proximodistal: Development pattern from the center outward. 

#### Fetal Period (Week 9-Birth) 

- Sexual Differentiation: The process by which male or female genitalia form. 

- Fetal Movement: Movements begin between 12-16 weeks, allowing muscle development. 

- Sensory Systems: Development of touch, hearing, vision, balance, and pain systems. 

- Fetal Learning: The ability of the fetus to recognize and respond to external stimuli by 32 weeks. 

### Teratogens and Environmental Influences 

- Teratogens: Environmental agents that can cause harm during prenatal development (e.g., drugs, alcohol, stress). 

- Fetal Alcohol Spectrum Disorders (FASDs): Caused by maternal alcohol consumption, leading to physical and cognitive deficits. 

- Chronic Stress: Associated with premature birth, low birth weight, and behavioral dysregulation. 

- Nutrition: Malnutrition, particularly in the 1st and 3rd trimesters, can lead to brain abnormalities and low birth weight.