Neural Crest Cells Essay

2) Why are onion root tip and whitefish blastula areas that are ideal to view mitosis?

All primates have a common ancestor, from millions of years ago. Go further back, and you will find a common ancestor for all mammals. Then a common ancestor for all vertebrates, then animals, then all life on earth. How closely two organisms are related can be deduced by looking for homologous structures, structures that look similar and have a similar function. This proves that the organisms descended from a common ancestor. Station 1 contained multiple vertebrate skeletons. They all had homologous structures, including a vertebral column and a rib cage. This shows that all vertebrates are related and come from a common ancestor with a

Embryological Evidence – similarities in early embryos can indicate they came from a common ancestor.

Our arches are the beginnings of gills in most fish, and shark species, but in humans they usually will close and form the usual structures. In most animals these same four arches can also be found, further showing their similarity to sharks. Also the arches create the same or similar structures in sharks and humans, the first arch creates the jaw, and trigeminal nerve in both humans, and sharks. The second arch creates one of the bones in the ear, but also the hyoid, a bone at the base of the skull. In sharks the second arch will create a similar bone that supports their jaws. All of these show how our heads, and many other animals heads, are all created from a similar structure.

A. Starting at the epiblast, describe five developmental events leading up to the generation of upper motor neurons that reside in layer 5 of the motor cortex.

"New standards pointed out about that discrepancies in a molecular evidence has challenged the evolutionary theory of common ancestry of all living things and that whether microevolution can be extrapolated to explain macro evolutionary changes is controversial".(LeBeau, 2007)

Schwann cells and invasion of macrophages at the distal end which clears the myelin and axonal

Schwann cells are specialized cells found in the Peripheral Nervous System; they are dedicated to forming myelin sheaths around certain nerve fibers. These myelin sheaths aid in the conduction of nerve impulses and help to protect and electrically insulate these fibers. “Schwannomatosis is a rare

Cloning in animals is described as “number of different processes that can be used to produce genetically identical copies of a biological entry” (“Cloning Fact Sheets”). In animal cloning, a wide variety of biological aspects have been cloned such as genes and tissues. Upon researching this subject, some of the most commonly asked questions was about if and how do clones happen naturally? In nature, there has been a long history of mutations and “natural” clones. Cloning is commonly seen in asexual reproduction as bacteria often reproduce identical copies. A real-life example of natural clones is seen in identical twins. These twins are seen as identical copies as well observed in both humans and other mammals.

There are nerve cells and nerve fibers located in the first layer of the cortical area

Glial cells are the most numerous cells in the brain, outnumbering neurons nearly 3:1, although smaller and some lacking axonal and dendritic projections. Once thought to play a subpar role to neurons, glial cells are now recognized as responsible for much greater functions. There are many types of glial cells, including: oligodendrocytes, microglia, and astrocytes. Oligodendrocytes form the myelin sheath in the CNS, by wrapping themselves around the axons of neurons. Their PNS counterpart, Schwann cells, are also considered glial cells. This sheath insulates the axon and increases the speed of transmission, analogous to the coating on electrical wires. Microglia are considered to be “immune system-like”; removing viruses, fungi, and other wastes that are present. Astrocytes, however, are considered to be the most prominent. Their functions span throughout the brain, including, but not limited to: the synchronization of axonal transmission via G-protein-coupled receptors, blood flow regulation via the dilation of blood vessels, and the performance of reactive gliosis in conjunction with microglia. Both astrocytes and oligodendrocytes develop from neuroepithelial cells. Other types of glial cells include Radial glia, which direct immature neuron migration during development.

Induced pluripotent stem cells are adult cells that are genetically altered in order to match embryonic stem cells. In order to achieve this embryonic stem cell-like nature, induced pluripotent stem cells are impelled to express genes and factors required to maintain the properties of embryonic stem cells. The main iPSC discussed in this paper will be derived neural crest stem cells (NCSCs). Derived neural crest stem cells are present in both the embryonic neural crest and the

The article “Transitional mammalian middle ear from a new Cretaceous Jehol eutriconodont” by Jin Meng, Yuanqing Wang, and Chuankui Li is essentially about how the jawbone became an ear. In ancient fossils it had been discovered that where the jawbone meets the skull, the four small bones that make up the middle ear: the malleus, incus, stapes, and ectotympanic, were also found there. As these bones moved from the mandible to form the middle ear the “Meckle’s cartilage” stabilized the “post- dentary bones” during their separation. Once the removal was complete the cartilage then ossified, becoming bone and remaining near the base of the mandible leaving the middle ear independent from the jaw. This evolutionary transition took years to become present, and is still highly criticized.

Look at the photo of a Pacinian corpuscle. Notice the onion-like bulb of connective tissue. Describe briefly —

The Spemann Organiser has a major role in the development of the central nervous system in the embryos of amphibians. The cells of the Spemann Organiser have a unique ability to alter the surrounding cells’ fates, in a process known as induction. The discovery of the Spemann organiser garnered large amounts of attention, causing Spemann to win the Nobel Prize in Medicine, in 1935, for his work in the discovery of induction. The Spemann organiser, as it has roles in developing the central nervous system, must turn off signals that encourage cells to transform into, for example, skin cells, and to turn on signals for cells that induce the formation of the central nervous system. It does this by releasing a number of molecules, including Chordin, Follistatin and Noggin, the main focus of this essay being on the function of Chordin. Chordin results