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Book

Embryology, Weeks 6-8

Mary F. Donovan  1 , Marco Cascella  2
In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan.
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Book

Embryology, Weeks 6-8

Mary F. Donovan et al.
Free Books & Documents

Excerpt

In human embryology, weeks 6 through 8 are characterized by the growth and differentiation of tissues into organs. This process is known as organogenesis and occurs from weeks 3 through 8, the embryonic period. During week 3, gastrulation occurs, establishing 3 distinct cell layers: the mesoderm, endoderm, and ectoderm. These are the primary germ cell layers from which organs arise during organogenesis. In particular:

  1. The endoderm forms the organs of the gastrointestinal and respiratory systems, as well as the thymus, parathyroid, bladder, and urethra.

  2. The ectoderm is responsible for developing the skin and skin appendages, the nervous system, and portions of sensory organs.

  3. The mesoderm forms the circulatory system, blood, lymphatic system, bone, cartilage, muscles, and many internal organs. For example, the kidney, spleen, ureters, and adrenal cortex derive from mesoderm.

At the end of week 8, organ systems have developed and are ready for further maturation. By week 9, the fetal period begins, which involves the growth and differentiation of anatomical structures and lasts until birth.

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Conflict of interest statement

Disclosure: Mary Donovan declares no relevant financial relationships with ineligible companies.

Disclosure: Marco Cascella declares no relevant financial relationships with ineligible companies.

References

    1. Rehman B, Muzio MR. StatPearls [Internet] StatPearls Publishing; Treasure Island (FL): 2023. May 1, Embryology, Week 2-3. - PubMed
    1. Zorn AM, Wells JM. Vertebrate endoderm development and organ formation. Annu Rev Cell Dev Biol. 2009;25:221-51. - PMC - PubMed
    1. Schittny JC. Development of the lung. Cell Tissue Res. 2017 Mar;367(3):427-444. - PMC - PubMed
    1. Ando H. Embryology of the biliary tract. Dig Surg. 2010;27(2):87-9. - PubMed
    1. Gutta A, Fogel E, Sherman S. Identification and management of pancreas divisum. Expert Rev Gastroenterol Hepatol. 2019 Nov;13(11):1089-1105. - PMC - PubMed

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