embryology
1. What happens during gastrulation
(Week 3)?
The bilaminar embryonicdisc becomes trilaminar(Endoderm, Mesoderm, Ectoderm). The primitive streak and notochord develop.
2 What is neurulation(Week 4)
Neural plate thickens to form a neural tube. Neural crest cells contribute to cranial nerves, Adrenal medulla and other structures.
3. Name the major derivatives of the ectoderm
Neuroectoderm: Central nervous system, Retina optic nerves.
Surface ectoderm: Skin, Hair, nails, glands, epithelium of oral/nasal cavities.
4. What structures arise from
the mesoderm
Axial mesoderm: Notochord(Forms intervertebral discs)
Paraxial mesoderm: Somites( sclerotone-> spine/ribs, myotome-> muscles, dermatome-> dermis).
5. List the key derivates of the endoderm
Epithelium of respiratory and digestive tracts, thyroid, liver, pancreas and urinary bladder( expect vesical trigone).
6. When does the embryonic period occur?
Weeks 3-8 of intrauterine life.
7. What major changes occur during the embryonic period?
-Organ system form.
- Lateral and craniocaudal folding shape the embryo
- Growth, morphogenesis and differentiation process
8. When does the fetal period begin?
Around week 9 after fertilization.
9. What are key milestones during the fetal period?
-Week 13-16: Hair appears, sex determination possible.
- Week 21-25: Surfactant forms in alveolar cells
- Week 26-29: Fetus viable it born prematurely.
- Week 35-38: Skin covered in vernix caseosa; weight ~ 3-3.5 kg.
10. What are the functions of the placenta?
• Gas exchange (oxygen and COz).
• Nutrition (carbohydrates, amino acids).
• Excretion (urea, creatinine).
• Hormone secretion (e.g., hCG, progesterone).
• Immune protection (transfer of maternal IgG).
11. What is the role of the amnion?
•Produces amniotic fluid.
• Protects the fetus, maintains tempature and allows movement.
12. What is the yolk sac resposible for?
• Early nutrition (Weeks 2-3).
• Formation of the primitive gut.
• Extraembryonic blood formation (hematopoiesis).
13. What is the function of the umbilicard cord?
• Connecta the fetus to the placenta
• Contains 2 arteties and one vein for nutrient and waste exchange.