Knowra Pharyngeal arch Pharyngeal arch A segmented embryonic structure in the head and neck whose tissues develop into bones, muscles, nerves, and blood vessels. In vertebrates, arches form jaws, gill supports, and related anatomy.
Pharyngeal pouch : An endoderm-lined pocket between the pharynx and the surface ectoderm in a vertebrate embryo. Pouches lie between adjacent arches and help form structures such as the middle ear and tonsils.
Hox gene : A gene encoding a transcription factor that helps specify positional identity along an animal's body axis. Hox genes pattern posterior arches, while the first arch develops largely without Hox expression.
First pharyngeal arch : The embryonic arch that forms much of the jaw skeleton and associated muscles and nerves. Its derivatives include the maxilla, mandible, and muscles of mastication.
Somite : A paired block of paraxial mesoderm that segments along the embryonic trunk and forms vertebrae, skeletal muscle, and dermis. Somites segment the trunk, whereas pharyngeal arches organize much of the developing head and neck.
Pharyngeal cleft : An ectoderm-lined groove on the outer surface of the embryonic pharyngeal region. Clefts separate the arches externally, complementing the internal pharyngeal pouches.
Endothelin signaling pathway : A cell-signaling pathway in which endothelin peptides activate receptors to regulate gene expression and cell behavior. Endothelin signaling helps specify jaw identity in neural crest cells of the first arch.
Second pharyngeal arch : The embryonic arch that contributes to parts of the hyoid apparatus, facial muscles, and middle ear. Its derivatives include the stapes, styloid process, and muscles of facial expression.
Limb bud : An embryonic outgrowth that develops into a forelimb or hindlimb. Limb buds are localized appendage primordia, unlike the repeated segments of the pharyngeal region.
Pharyngeal membrane : A thin embryonic partition where a pharyngeal pouch approaches an external pharyngeal cleft. These membranes mark the boundaries where internal and external pharyngeal structures meet.
T-box transcription factor TBX1 : A transcription factor required for normal development of pharyngeal structures and the cardiac outflow tract. TBX1 regulates development of the arches and their arteries; its disruption causes DiGeorge syndrome features.
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