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The lacuna are situated between the lamellae, and consist of a number of oblong spaces. In an ordinary microscopic section, viewed by transmitted light, they appear as fusiform opaque spots. Each lacuna is occupied during life by a branched cell, termed an osteocyte, bone-cell or bone-corpuscle.
Great Lacuna, a lacuna of eight leaves in the Codex Regius where there was heroic Old Norse poetry Lacuna (music) , an intentional, extended passage in a musical work during which no notes are played Scientific lacuna , an area of science that has not been studied but has potential to be studied
The lacuna model is a tool for unlocking culture differences or missing "gaps" in text (in the further meaning). The lacuna model was established as a theory by Jurij Sorokin and Irina Markovina (Russia), further developed by Astrid Ertelt-Vieth and Hartmut Schröder (Germany) and practical research tested in ethnopsycholinguistics (Igor Panasiuk 2000 and 2005), Russian studies (Vladimir ...
Human embryology is the study of this development during the first eight weeks after fertilization. The normal period of gestation (pregnancy) is about nine months or 36 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus.
Embryology (from Greek ἔμβρυον, embryon, "the unborn, embryo"; and -λογία, -logia) is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses.
The theory of recapitulation, also called the biogenetic law or embryological parallelism—often expressed using Ernst Haeckel's phrase "ontogeny recapitulates phylogeny"—is a historical hypothesis that the development of the embryo of an animal, from fertilization to gestation or hatching (), goes through stages resembling or representing successive adult stages in the evolution of the ...
[2] [3] They form during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg to become extraembryonic structures that do not directly contribute to the embryo. After blastulation, the trophoblast is contiguous with the ectoderm of the embryo and is referred to as the trophectoderm.
The embryo successively adds the organs that characterize the animal classes in the ascending scale. When the human embryo, for instance, is but a simple vesicle, it is an infusorian; when it has gained a liver, it is a mussel; with the appearance of the osseous system, it enters the class of fishes; and so forth, until it becomes a mammal and ...