Discover the incredible journey of fetal development and anatomy, unraveling the mysteries of life within the womb.
2023-04-06
USMLE Guide: Fetal Development and Anatomy
Introduction
This USMLE guide aims to provide a comprehensive overview of fetal development and anatomy. Understanding fetal development is crucial for medical professionals, especially those specializing in obstetrics and pediatrics. This guide will cover the major stages of fetal development and highlight key anatomical structures that can be tested on the USMLE.
The embryonic period spans from conception until the end of the 8th week of gestation. During this period, the three germ layers (ectoderm, mesoderm, and endoderm) differentiate and form the basis for all major organ systems.
Ectoderm gives rise to the nervous system, skin, hair, and nails.
Mesoderm forms the musculoskeletal system, cardiovascular system, kidneys, and reproductive system.
Endoderm develops into the gastrointestinal tract, respiratory system, liver, and pancreas.
Fetal Period
The fetal period begins at the start of the 9th week and continues until birth. During this phase, the major organs are already formed, and the fetus undergoes rapid growth and maturation.
Week 9 to 12: Fetal movements are observed, and the sex of the fetus can be determined through ultrasound.
Week 13 to 16: The fetus grows rapidly, and skeletal development progresses.
Week 17 to 20: Vernix caseosa (a protective substance) forms on the skin, and lanugo (fine hair) covers the body.
Week 21 to 24: The fetus develops a regular sleep-wake cycle, and the lungs continue to mature.
Week 25 to 28: Rapid brain development occurs, and the eyes can open.
Week 29 to 32: The fetus gains significant weight, and the bones are fully developed.
Week 33 to 36: Subcutaneous fat is deposited, and the fetus assumes a head-down position.
Major Organ Systems
Central Nervous System (CNS)
The CNS begins to form during the embryonic period and continues to develop throughout the fetal period.