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Free Content The Current Embryology of the Foregut and Its Derivatives

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The initial development of the foregut precedes the future development of a number of derivatives that all arise from it. These structures include the pharynx, tongue, larynx, trachea, thyroid, and parathyroid glands. Because the larynx embryology was discussed in an earlier review in this series, it will not be discussed in this present review. Each of the remaining areas develop in their own specialized way, and an understanding of how these areas arise allows a fuller understanding of their anatomy. In addition, the embryology provides insight into the congenital problems that can happen when normal development does not occur. We are starting to understand the molecular pathways that drive this embryology, and this information is allowing an even greater insight into both the normal and abnormal development of these structures. The molecular biology presented is primarily based on work in animal models. The text is highly illustrated to make the embryology more easily understood.

Learning Objective: Understand how the complex embryology of the foregut produces anatomic variants and pathology in its derivative tissues.

Keywords: ACT1β = actin-1β, a nonmuscle cytoskeletal actin; ALK = activin receptor-like kinase (now ACVR); BMP = bone morphogenetic protein; CDX = caudal type homeobox protein; Crescent = frizzled related protein-2 or frzb2, a dorsal-ventral patterning protein; EOMESODERMIN = T-box brain protein-2 (Tbr2), a T-box transcription factor; EYA = eyes absent homolog, a transcription factor; FGF = fibroblastic growth factor; FOXA = forkhead box transcription factor; GATA= transcription factors binding to the “GATA” DNA sequence; GLI2/3 = hedgehog-dependent transcription factors; GSC = homeobox protein Goosecoid; HOXA = a homeobox protein; Hh = Hedgehog signaling pathway; LIM = Lin1/Isl1/Mec3 class of zinc finger transcription factors; Laminin = a major protein in the basal lamina, a layer of the basement membrane; MASH-1/ASCL1 = mammalian achaete-scute homologous gene/achaete-scute complex homolog-1; MRF = myogenic regulatory factors; MYOD= myogenic differentiation gene, a muscle specific basic-helix-loop-helix transcription factor; Myogenin = a muscle-specific basic-helix-loop-helix transcription factor; NKX1, 2 = homeobox proteins; Neurotrophin = a family of proteins that promote the survival, development, and function of neurons; Nodal = a secreted ligand that belongs to the TGFβ superfamily; Noggin = a BMP antagonist involved in many forms embryonic of development; P63 = a member of the p53 family of transcription factors; PAX = paired box transcription factor; PDX = pancreatic and duodenal homeobox 1, also known as insulin promoter actor 1; PHOX2b = paired-like homeobox 2b, also known as neuroblastoma PHOX (NBPHOX), a “homeodomain” transcription factor expressed in the autonomic nervous system; PTCH = patched protein, a receptor in the Hedgehog signaling pathway; RA = retinoic acid; RET proto-oncogene = “rearranged during transfection,” a receptor tyrosine kinase; SHH = Sonic hedgehog protein; SOX = Sry-related homeobox gene; TBX1 = T-box protein-1 aka testis-specific T-box, a transcription factor; TFC = thyroid follicular cell; TGF = transforming growth factor; TITF1/TTF-1 = thyroid transcription factor 1 (now known as Nkx2‐1, a homeobox factor); TNF = tumor necrosis factor; WNT = wingless/int1 family of secreted signaling molecules

Document Type: Research Article

Publication date: January 1, 2016

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