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Endochondral ossification[1][2] is one of the two essential pathways by which bone tissue is produced during fetal development of the mammalian skeletal system, the other pathway being intramembranous ossification. Both endochondral and intramembranous processes initiate from a precursor mesenchymal tissue, but their transformations into bone ...
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 .
Interior of dorsal half of heart from a human embryo of about thirty days. Endocardial cushions, or atrioventricular cushions, refer to a subset of cells in the development of the heart that play a vital role in the proper formation of the heart septa. They develop on the atrioventricular canal [2] and conotruncal region of the bulbus cordis.
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] Initially it lies caudally to the trilaminar germ disc, but, with subsequent embryonic folding, the body stalk ...
The bilaminar embryonic disc, bilaminar blastoderm or embryonic disc is the distinct two-layered structure of cells formed in an embryo. In the development of the human embryo this takes place by day eight. It is formed when the inner cell mass, also known as the embryoblast, forms a bilaminar disc of two layers, an upper layer called the ...
Rathke's pouch is a sac-like structure that gives rise to the pars distalis, pars intermedia, and pars tuberalis of the pituitary gland. The cells of Rathke's pouch proliferate and differentiate into various hormone-producing cells, including Somatotrophs, Lactotrophs, Corticotrophs, Thyrotrophs, and Gonadotrophs. [4]
Secondary chorionic villi. Diagrammatic. The syncytiotrophoblast (from the Greek 'syn'- "together"; 'cytio'- "of cells"; 'tropho'- "nutrition"; 'blast'- "bud") is the epithelial covering of the highly vascular embryonic placental villi, which invades the wall of the uterus to establish nutrient circulation between the embryo and the mother. It ...
Brain. In the brain a laminar organization is evident in the arrangement of the three meninges, the membranes that cover the brain and spinal cord. These membranes are the dura mater, arachnoid mater, and pia mater. The dura mater has two layers a periosteal layer near to the bone of the skull, and a meningeal layer next to the other meninges.