Aula Embriologia | Dobramento e Organogênese - Parte 2 de 2

Embryonic Development: Weeks 5-8

Key Concepts: Embryonic development, limb development, head growth, digital rays, auricular hillocks, eye pigmentation, spontaneous movements, cervical flexure, organogenesis, umbilical hernia, vascular plexus of the scalp, fetal appearance.

Week 5: Initial Changes

• Main Topics and Key Points:
  • Limited changes compared to week 4.
  • Significant development of limbs, which start to elongate.
  • Disproportionate growth of the head, making contact with the cardiac region.
  • Embryo size: Increases from 5mm to 6mm.
  • Eminence caudal also elongates.
  • Presence of lens placode and nasal placode.
• Technical Terms: Eminence caudal, lens placode, nasal placode.

Week 6: Limb and Sensory Development

• Main Topics and Key Points:
  • Further development of limbs, with the appearance of elbows and hand plates.
  • Digital rays emerge on the distal region of the hand plate, marking the beginning of finger formation.
  • Auricular hillocks become more evident, contributing to the formation of the inner ear.
  • Eye pigmentation becomes more pronounced in the retina.
  • Spontaneous movements, characterized by abrupt contractions of the trunk and limbs, can be detected.
• Technical Terms: Digital rays, auricular hillocks, meato acústico externo.
• Examples: The hand plate develops digital rays, which are the precursors to fingers.
• Notable Quotes: "Os membros superiores desenvolvendo de forma que já consiga se identificar a presença de cotovelos placas das mãos."

Week 7: Digit Separation and Organ Development

• Main Topics and Key Points:
  • Significant limb development with the appearance of indentations (chanfraduras) between the digital rays, leading to finger separation.
  • The digestive system develops substantially, with the liver becoming a prominent organ and initiating hematopoiesis.
  • The head begins to lift due to the development of the cervical flexure.
  • Eyelids start to form.
  • The external acoustic meatus becomes well-defined.
  • Embryo size: Grows to 16mm.
• Technical Terms: Chanfraduras, hematopoiesis, cervical flexure, sutura craniana.
• Examples: The liver starts hematopoiesis, indicating advanced organ development.
• Logical Connections: The development of the cervical flexure is directly related to the embryo's ability to lift its head.

Week 8: Final Touches and Human Form

• Main Topics and Key Points:
  • The embryo takes on a more human form.
  • Limbs are well-defined with elbows, wrists, knees, and ankles.
  • Fingers and toes are separated, with the disappearance of interdigital membranes. Failure of these membranes to degenerate results in syndactyly.
  • Limbs move ventrally, a characteristic of human development.
  • Voluntary movements can be observed.
  • Ossification begins in the femur.
  • The caudal eminence regresses significantly.
  • An umbilical hernia is present due to the abdominal region's inability to accommodate all developing organs.
  • The vascular plexus of the scalp appears, aiding in skull development and ossification.
  • The head becomes more rounded.
  • Primordial gonads are present, but sex is not yet discernible.
  • Embryo size: Approximately 3 cm.
• Technical Terms: Syndactyly, umbilical hernia, vascular plexus of the scalp, gastrosquise, onfalocele.
• Examples: Syndactyly is presented as an example of what happens when interdigital membranes fail to degenerate.
• Case Studies: Onfalocele and gastrosquise are mentioned as potential problems related to the umbilical hernia.
• Logical Connections: The vascular plexus of the scalp is directly linked to the accelerated development and ossification of the skull.

Conclusion

The video details the significant transformations occurring during weeks 5-8 of embryonic development. Key milestones include the development and differentiation of limbs, the formation of facial features, the advancement of internal organs, and the gradual acquisition of a human-like form. The speaker emphasizes the importance of understanding these developmental stages and potential complications that can arise. The transition from the embryonic to the fetal period is marked by the completion of major organogenesis and the establishment of a recognizable human appearance.