Embryology: gametogenesis, fertilization, implantation is a core MBBS — Pre-Clinical (Phase 1) concept in MBBS. This guide explains what it is, walks through a fully worked example, and lists the key equations you need — with a short quiz to test yourself.

Key equations and worked example

Week 4: the embryo is ~2 mm with a beating heart tube. Week 8: ~1.6 cm, all organs started (end of embryonic period). Week 12: ~5.4 cm, recognisably human. Week 20: ~25 cm, mother feels movement. Week 38: ~48 cm, ~3 kg — full term. Drag the week slider through the timeline.

• <code>Embryonic period: weeks 1–8 (organogenesis)</code>
• <code>Fetal period: weeks 9–38 (growth and maturation)</code>
• <code>Heartbeat detectable ≈ week 6</code>
• <code>Full term ≈ 38–40 weeks (~48 cm, ~3 kg)</code>

Embryology: gametogenesis, fertilization, implantation in detail

Embryology: gametogenesis, fertilization, implantation is one of the central ideas in MBBS — Pre-Clinical (Phase 1), and it appears in MBBS curricula under Human Anatomy. It is worth learning deeply because it connects to so many other topics in this section.

Fertilisation (usually in the fallopian tube) forms the zygote, which divides into a blastocyst that implants in the uterus. Weeks 1–8 (embryonic period) build all organ systems — the most vulnerable window. Weeks 9–38 (fetal period) grow and mature them. The placenta feeds the fetus via the umbilical cord.

For exams, the pattern is predictable: first a definition or statement of the result, then a direct numerical application of one of the equations above, then a "why" question — why the formula takes that form, or what changes when a variable is doubled or halved. The worked example and quiz below cover exactly that progression.

Quick self-check:

• Q: Why is the embryonic period (weeks 1–8) the most vulnerable to teratogens?<br />A: All major organs form then — disruption causes structural birth defects rather than just growth issues.
• Q: What connects the fetus to the placenta, and what does the placenta do?<br />A: The umbilical cord; the placenta exchanges nutrients, oxygen and waste between mother and fetus.
• Q: Roughly how big is the fetus at 12 weeks and at full term?<br />A: ~5.4 cm at 12 weeks; ~48 cm and ~3 kg at 38–40 weeks.