Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Gastrulation in Frogs Cells located where the gray crescent was begin to invaginate into the blastocoel, forming the blastopore. This area is now known as the dorsal lip of the blastopore and is a key player in the future development of tissue. Tissue rolls over the dorsal lip of the blastopore as it moves into the embryo. This process is called involution.The new cavity is called the archenteron (primitive gut) and will eventually become the digestive tract.The blastopore will become the anus in the frog. The mouth will form elsewhere (“second the mouth”) Early on, the dorsal lip of the blastopore forms due to the contraction of bottle cells. The blastopore continues to develop from the early "frown" until it can be observed as a complete circular ring of involuting cells. Convergent extension closes the blastopore at the yolk plug and elongates the embryo along the anterior--posterior axis. The posterior end of the embryo is pointed at you. How does the the blastopore lip form? A small group of cells change shape, narrowing at the exterior edge of the blastula. This change in cell shape, called apical constriction, creates a local invagination, which pushes more interior cells upwards and begins to roll a sheet of cells towards the interior. The constricted cells are called bottle cells, due to their shape 1 Mammalian Gastrulation In mammals, gastrulation is achieved in a very different way. This is because the outer layer of the mammalian blastocyst, which is roughly equivalent to the blastula, becomes the mammalian placenta and is not available to create the primary germ layers of the embryo. Instead, the inner cell mass, or ICM, has to form the three primary germ layers of the mammalian embryo after the blastocyst has implanted in the uterine wall. Instead of forming a hollow ball and invaginating to create the gut tube and the three cell layers, the ICM of the mammalian embryo forms a single layer of cells called the epiblast. As these epiblast cells proliferate, some of them migrate out of the epiblast to form the endoderm, which is this layer here, and then after that more cells migrate out to form the mesoderm, which is this cell layer here. The cells that remain in the epiblast form the ectoderm. What the Different Germ Layers Become Gastrulation is accomplished when the hollow blastula invaginates to form an inner layer of cells called the endoderm and an outer layer of cells called the ectoderm. A third, middle layer of cells called the mesoderm is formed as cells begin to populate the space between the endoderm and the ectoderm. These three layers, the endoderm, the ectoderm and the mesoderm, are called the primary germ layers. With the formation of the three primary germ layers, the embryo has begun the process of tissue differentiation. Each of the three primary germ layers will form a different set of specific organs and tissue types in the animal. The ectoderm will form the nervous system, the epithelial cells of the mammary glands, the lens of the eyes, hair, pigment cells and the epidermis of the skin. The mesoderm will form skeletal muscle, smooth muscle, the heart, blood vessels, blood cells, kidney, spleen, fat cells, the skeleton, most connective tissues and most of the urogenital system. The endoderm will form the entire epithelial lining of the gastrointestinal tract, as well as the liver, pancreas, gall bladder, thyroid, the epithelial 2 lining of the trachea and the respiratory surface of the lungs. 3