Embryonic development - Week 3

✔ HomeworkClinic.com
✔ Videos.HomeworkClinic.com
✔ Ask questions here: HomeworkClinic.com/Ask
Follow us:
▶ Facebook: / homeworkclinic
▶ Review Us: trustpilot.com/review/homewor...
Week 3 (gastrulation)
• Three primary germ layers are formed which provide cells for organ formation in the following months.
• These germ cell layers are formed by a process known as gastrulation, which involves rearranging epiblast cells.
• As cells from the epiblast migrate, a faint groove called the primitive streak forms on the surface of the embryonic disc.
• With the formation of the primitive streak, it is possible to recognize the head and tail ends of the embryo.
• Some epiblast cells migrate, differentiate, and then replace the hypoblast to form the endoderm germ layer.
• Other epiblast cells migrate and differentiate to form a new layer, between the epiblast and hypoblast, identified as the mesoderm germ layer.
• The remaining epiblast cells become the ectoderm germ.
• The trilaminar embryonic disc has three germ layers:
• The ectoderm gives rise to all nervous tissue and the epithelium of the skin.
• The mesoderm gives rise to blood, muscle, bone, and connective tissue.
• The endoderm forms into the epithelium of the gastrointestinal tract, the respiratory system and many organs.
Week 3 (neural tube formation)
• Further differentiation of mesodermal cells begins the formation of the notochord.
• The notochord is important in starting (or inducing) the specialization of other cells, including those directly above them called the neural plate.
• Epiblastic cells in the neural plate are induced to begin to mound up and fold into a groove.
• The neural groove continues to fold.
• Adjacent notochord mesodermal cells are induced to form somites, the eventual source of cells to form skeletal and other connective tissues, and muscle tissue.
• The neural tube arises and its cells eventually develop to form the brain, spinal cord, and other parts of the nervous system.
Week 3 (heart and vessel formation)
• Mesodermal cells from the primitive streak rearrange to form blood vessels in the embryo, and a primitive heart begins to form.
• The chorionic villi projecting into the endometrium forms an exchange area called the intervillous space.
• Maternal and fetal blood vessels remain separate, so maternal and fetal blood don't normally mix.
• However, oxygen, antibodies, nutrients, and waste products are all exchanged via the intervillous spaces.

[@AnatomywithImran]

Very useful video, clearly described in shortest possible time

[@phumudzomamatsiari787]

nice,short clearcut summary....love it

[@annapinphet5520]

Your explanation is very clear. Thank you so much.

[@salmaboudelaa7481]

Very useful and clear thank you so much 🤩

[@zainaby8241]

Thank you💜

[@user-jc9pl6kh5r]

Thank you so much

[@fadwa_4]

Thanx🙏🏼

[@HaroonAhmad-lg9ne]

Fabulous ❤

[@mehakjoher1968]

Very nice vid and explanation 👍

[@homeworkclinic2119]

Glad it was helpful!

[@reema9377]

good video its really helpful

[@gloriousy8832]

الامبريو مو تاخذوه مرحله أولى لو اني غلطان ؟

[@areejfatima4392]

Sir g which book used?

[@giftofthewild6665]

So "week 3" is actually from 2-3 weeks? So week 4 must be 3-4 weeks?