primitive groove

groove (grldbomacv) a narrow, linear hollow or depression.

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branchial groove  pharyngeal g.

Harrison's groove  a horizontal groove along the lower border of the thorax corresponding to the costal insertion of the diaphragm; seen in advanced rickets in children.

medullary groove , neural groove that formed by beginning invagination of the neural plate of the embryo to form the neural tube.

pharyngeal groove  the embryonic ectodermal cleft between successive pharyngeal arches.

primitive groove  a lengthwise median furrow in the primitive streak of the embryo.

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primitive groove,

a furrow in the posterior region of the embryonic (primordial) disk. It indicates the cephalocaudal axis that results from the active involution of cells forming the primitive streak.

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primitive

first in point of time; existing in a simple or early form; showing little evolution.

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primitive groove

longitudinal furrow in the primitive streak of the embryo.

primitive knot

see hensen's node.

primitive node

enlarged cranial end of the primitive streak.

primitive streak

the thickened median area of the epiblast which sets out the future longitudinal axis of the early embryo.