Search results
Results from the WOW.Com Content Network
Gastrulation is the stage in the early embryonic development of most animals, ... A description of the gastrulation process in a human embryo in three dimensions.
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 .
An alternative way to develop two openings from the blastopore during gastrulation, called amphistomy, appears to exist in some animals, such as nematodes. [3] [4] In humans, the perforation of the mouth and anus happen at four weeks and eight weeks respectively. [5]
Gastrulation occurs when pluripotent stem cells differentiate into the three germ cell layers: ectoderm, mesoderm and endoderm. [7] During gastrulation, cells of the epiblast migrate towards the primitive streak, enter it, and then move apart from it through a process called ingression .
This early embryonic form undergoes gastrulation, forming a gastrula with either two or three layers (the germ layers). In all vertebrates, these progenitor cells differentiate into all adult tissues and organs. [5] In the human embryo, after about three days, the zygote forms a solid mass of cells by mitotic division, called a morula.
Gastrulation is the next phase of embryonic development, and involves the development of two or more layers of cells (germinal layers). Animals that form two layers (such as Cnidaria) are called diploblastic, and those that form three (most other animals, from flatworms to humans) are called triploblastic.
Organogenesis is the phase of embryonic development that starts at the end of gastrulation and continues until birth. During organogenesis, the three germ layers formed from gastrulation (the ectoderm, endoderm, and mesoderm) form the internal organs of the organism. [1] The endoderm of vertebrates produces tissue within the lungs, thyroid, and ...
Invagination of the archenteron during sea urchin gastrulation. Sea urchin gastrulation is another classic model for invagination in embryology. One of the early gastrulation movements in sea urchins is the invagination of a region of cells at the vegetal side of the embryo (vegetal plate) to become the archenteron, or future gut tube. There ...