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B.—Diagram of the female type of sexual organs. C. Greater vestibular gland, and immediately above it the urethra. cc. Corpus cavernosum clitoridis. dG. Remains of the left Wolffian duct, such as give rise to the duct of Gärtner, represented by dotted lines; that of the right side is marked w. f. The abdominal opening of the left uterine ...
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 40 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus .
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).
The main theory states that formation of the membranes of the yolk sac begins with an increase in production of hypoblast cells, followed by different patterns of migration. On day eight, the first portion of hypoblast cells begin their migration and make what is known as the primary yolk sac, or Heuser's membrane (exocoelomic membrane).
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 ...
Diagram of stages of developing blastocyst in the human until implantation. There are two stages of migration involved in implantation, the first is the migration of the zygote, and the second is the migration of the trophoblast. [13] Fertilization of the oocyte, takes place in the ampulla of the fallopian tube.
The field of comparative embryology aims to understand how embryos develop, and to research the inter-relatedness of animals. It has bolstered evolutionary theory by demonstrating that all vertebrates develop similarly and have a putative common ancestor. [1] [2]
Lacunae of Morgagni, also called the urethral lacunae of the male urethra (lacunae urethralis, urethrae masculinae or the crypts of Morgagni), ...