n. any of the paired segmented divisions of *mesoderm that develop along the length of the early embryo. The somites differentiate into voluntary muscle, bones, connective tissue, and the deeper layers of the skin (see dermatome; myotome; sclerotome).
the early embryo before the formation of *somites. It is a flat disc of tissue bounded dorsally by the amniotic cavity and ventrally by the yolk sac. The formation of the *primitive streak and *archenteron in the embryonic disc determines the orientation of the embryo, which then becomes progressively elongated.... embryonic disc
n. the middle *germ layer of the early embryo. It gives rise to cartilage, muscle, bone, blood, kidneys, gonads and their ducts, and connective tissue. It separates into two layers – an outer somatic and an inner splanchnic mesoderm, separated by a cavity (coelom) that becomes the body cavity. The dorsal somatic mesoderm becomes segmented into a number of *somites. See also mesenchyme. —mesodermal adj.... mesoderm
n. 1. a surgical knife used in the operation of *sclerotomy. 2. (in embryology) the part of the segmented mesoderm (see somite) in the early embryo that gives rise to all the skeletal tissue of the body. The vertebrae and ribs retain the segmented structure, which is lost in the skull and limbs.... sclerotome
n. (in anatomy) a portion of a tissue or organ, usually distinguishable from other portions by lines of demarcation. For example, the uterus consists of upper and lower segments. The anterior segment of the eye is the front portion, including the cornea, anterior chamber, iris, and lens. See also somite.... segment
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