Passage
Neurulation refers to the early formation of the nervous system in vertebrate embryos and begins when the notochord, a rodlike mesodermal structure, induces neural tube and neural crest cell formation in the ectoderm. Neural tube defects (NTDs) arise from abnormalities in the development of the neural tube and can range from mild to severe, depending on which portion of the tube is affected. Spina bifida, a form of NTD, is divided into three categories. The most serious subclassification of spina bifida is myelomeningocele, which occurs when the lower spine fails to close, which leaves the spinal cord and nerve roots in the lower back damaged and exposed.NTDs are thought to be caused in part by folate deficiency. Folate plays a critical role in normal cell division and growth as it is a necessary coenzyme for DNA synthesis and methylation. Mutations in several genes involved in folate metabolism have been associated with an increased risk for NTDs. It has been hypothesized that folate decreases NTD risk by ameliorating oxidative stress, thereby reducing damage to developing cells in the embryo. Certain maternal conditions, such as high blood glucose, increase the risk of NTD development by enhancing embryonic oxidative stress during crucial developmental periods.A study was conducted to examine how supplementation with folic acid, the dietary form of folate, affected pregnant women who were identified to have preexisting diabetes, pregestational obesity (another risk factor for NTD), or no preexisting conditions (control group). Higher folic acid intake decreased the incidence of embryonic NTDs among pregnant women with diabetes, but no significant effect was found for pregnant women who were obese.
Adapted from Parker SE, Yazdy MM, Tinker SC, Mitchell AA, Werler MM. The impact of folic acid intake on the association among diabetes mellitus, obesity, and spina bifida. Am J Obstet Gynecol. 2013;209(3):239.e1-8.
-The germ layer that gives rise to the notochord also gives rise to which of the following cell types?

Question

Passage
Neurulation refers to the early formation of the nervous system in vertebrate embryos and begins when the notochord, a rodlike mesodermal structure, induces neural tube and neural crest cell formation in the ectoderm.  Neural tube defects (NTDs) arise from abnormalities in the development of the neural tube and can range from mild to severe, depending on which portion of the tube is affected.  Spina bifida, a form of NTD, is divided into three categories.  The most serious subclassification of spina bifida is myelomeningocele, which occurs when the lower spine fails to close, which leaves the spinal cord and nerve roots in the lower back damaged and exposed.NTDs are thought to be caused in part by folate deficiency.  Folate plays a critical role in normal cell division and growth as it is a necessary coenzyme for DNA synthesis and methylation.  Mutations in several genes involved in folate metabolism have been associated with an increased risk for NTDs.  It has been hypothesized that folate decreases NTD risk by ameliorating oxidative stress, thereby reducing damage to developing cells in the embryo.  Certain maternal conditions, such as high blood glucose, increase the risk of NTD development by enhancing embryonic oxidative stress during crucial developmental periods.A study was conducted to examine how supplementation with folic acid, the dietary form of folate, affected pregnant women who were identified to have preexisting diabetes, pregestational obesity (another risk factor for NTD), or no preexisting conditions (control group).  Higher folic acid intake decreased the incidence of embryonic NTDs among pregnant women with diabetes, but no significant effect was found for pregnant women who were obese.
Adapted from Parker SE, Yazdy MM, Tinker SC, Mitchell AA, Werler MM. The impact of folic acid intake on the association among diabetes mellitus, obesity, and spina bifida. Am J Obstet Gynecol. 2013;209(3):239.e1-8.
-The germ layer that gives rise to the notochord also gives rise to which of the following cell types?

Quizplus · Accepted Answer

11ecba2d_0fc0_7b4c_a3bf_1dfd3d33e1e8_MD0008_00 Gastrulation is the process by which the germ layers (endoderm, mesoderm, ectoderm) form in the developing embryo. Following fertilization, the zygote undergoes cleavage (successive mitotic cell divisions) and forms the blastula, a hollow ball of cells that implants into the uterine wall. The human equivalent of the blastula is the blastocyst, which is divided into two layers: the trophoblast (a hollow sphere of cells) and the inner cell mass (a cluster of cells inside the trophoblast). The two-layered blastocyst then transforms into a three-layered structure (gastrula) through the process of gastrulation. Gastrulation begins with the formation of the primitive streak (a transient structure that facilitates cell migration) on the bilaminar disk, a double-layered sheet of cells that takes shape in the trophoblast. Cells migrate through the primitive streak and the area between the two layers to displace the bottom (hypoblast) layer and form the endoderm. Additional cells migrate through the streak to form the new middle layer (mesoderm). All three germ layers develop into specific structures within the human body as follows: Endoderm (innermost layer): gives rise to accessory digestive organs (eg, liver, pancreas) as well as to the lining (epithelium) of the digestive and respiratory tracts. Mesoderm (middle layer): gives rise to the circulatory system, the musculoskeletal system, and parts of the urinary and reproductive systems. Ectoderm (outermost layer): gives rise to the nervous system (neurulation) and develops into the integumentary system, which includes hair, skin, nails, and the lining of the mouth, nostrils, and anus. The passage states that the notochord is a mesodermal structure. Of the answer choices given, only osteocytes (bone cells) are also derived from the mesoderm. (Choices A and D) Alveolar cells are epithelial lung cells, and islet beta cells are pancreatic insulin-secreting cells. Both are derived from the endoderm. (Choice C) Melanocytes are pigment-producing cells in skin derived from the ectoderm. Educational objective: The three primary germ layers (endoderm, mesoderm, ectoderm) form during gastrulation. Each gives rise to particular cell types in specific organ systems.

Passage Neurulation Refers to the Early Formation of the Nervous System