Embryo Development Process Stages Model

Embryo Development Process Stages Model consists of several stages, beginning with fertilization and progressing to a fully formed fetus. Below is a general model outlining the key stages:

1. Fertilization

• Sperm meets egg in the fallopian tube, forming a zygote (single-cell embryo).
• The zygote contains genetic material from both parents.

2. Cleavage (1-3 Days Post-Fertilization)

• The zygote undergoes mitotic divisions without increasing in size.
• Forms a morula (solid ball of cells).

3. Blastulation (4-6 Days Post-Fertilization)

• Morula transforms into a blastocyst (hollow ball of cells).
• Blastocyst consists of:
  • Trophoblast (outer layer) – develops into the placenta.
  • Inner Cell Mass (ICM) – forms the embryo.

4. Implantation (6-10 Days Post-Fertilization)

• The blastocyst attaches and embeds into the uterine wall.
• Trophoblast cells invade the uterine lining, establishing a connection for nutrient exchange.

5. Gastrulation (Week 2-3)

• Formation of the three germ layers:
  • Ectoderm (nervous system, skin, hair).
  • Mesoderm (muscles, bones, circulatory system).
  • Endoderm (digestive tract, respiratory system, glands).

6. Neurulation (Week 3-4)

• Development of the neural tube, which later forms the brain and spinal cord.
• Somites (blocks of mesoderm) appear, forming muscles and vertebrae.

7. Organogenesis (Week 4-8)

• Major organs (heart, liver, lungs, kidneys) begin forming.
• Limb buds appear, and the heart starts beating by week 4.

8. Fetal Stage (Week 9-Birth)

• Growth and maturation of organs and systems.
• Development of facial features, limbs, and sensory organs.
• By the end of the third trimester, the fetus is fully developed and prepared for birth.