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This constitutes the so-called capsule of the space. Each lacuna is generally occupied by a single cell, but during the division of the cells, it may contain two, four, or eight cells. Lacunae are found between narrow sheets of calcified matrix that are known as lamellae (/ l ə ˈ m ɛ l i / lə-MEL-ee).
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 .
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 ...
Von Baer described his laws in his book Über Entwickelungsgeschichte der Thiere.Beobachtung und Reflexion published in 1828. [5] They are a series of statements generally summarised into four points, as translated by Thomas Henry Huxley in his Scientific Memoirs: [6]
Aerenchyma in stem cross section of a typical wetland plant. Aerenchyma or aeriferous parenchyma [1] or lacunae, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and the root. [2]
The chorion undergoes rapid proliferation and forms numerous processes, the chorionic villi, which invade and destroy the uterine decidua and at the same time absorb from it nutritive materials for the growth of the embryo.
Borys Ivanovych Balinsky (23 September 1905 – 1 September 1997) was a Ukrainian-South African biologist, embryologist, entomologist.. A professor at Kiev University and later the University of the Witwatersrand, Johannesburg, [1] Balinsky was a pioneer researcher in the field of experimental embryology, electron microscopy and developmental biology and the author of a popular textbook in ...
The connecting stalk, or body stalk, is an embryonic structure that is formed by the third week of development and connects the embryo to its shell of trophoblasts.The connecting stalk is derived from the extraembryonic mesoderm. [1]