During embryonic development, which of the following germ layers forms the nervous system?
A. Ectoderm
B. Endoderm
C. Mesoderm
D. Exoderm
The three germ layers that form during embryonic development are the ectoderm, mesoderm, and endoderm. The ectoderm is the outermost layer, and it gives rise to the skin, hair, nails, and nervous system. The nervous system develops from a specialized region of the ectoderm called the neural plate, which invaginates to form the neural tube. The neural tube ultimately gives rise to the brain and spinal cord, which make up the central nervous system, as well as the peripheral nervous system. The endoderm gives rise to the lining of the digestive and respiratory tracts, while the mesoderm gives rise to the musculoskeletal system, circulatory system, and several other organs. The exoderm is not a germ layer and does not exist during embryonic development.
Therefore, the Correct Answer is A.
More Questions on TEAS 7 Science
-
Q #1: What is the molecular geometry of a molecule of sulphur dioxide (SO2)?
A. Linear
B. Trigonal planar
C. Bent
D. Tetrahedral
Answer Explanation
The molecular geometry of a molecule of sulphur dioxide (SO2) is bent or V-shaped. This is because of the presence of two lone pairs on the sulfur atom, which cause repulsion and distort the bond angles in the molecule.
SO2 has a central sulfur atom bonded to two oxygen atoms by double bonds. The two double bonds and the two lone pairs of electrons on sulfur result in a trigonal planar arrangement of electron pairs around the sulfur atom. However, the repulsion between the lone pairs causes the two oxygen atoms to be pulled closer together, resulting in a bent or V-shaped molecular geometry.
The bent molecular geometry of SO2 affects its properties, such as its polarity and reactivity. SO2 is a polar molecule due to the asymmetric distribution of electrons, which results in a partial positive charge on the sulfur atom and partial negative charges on the oxygen atoms. This polarity makes SO2 a good solvent and reactant in chemical reactions, as well as a contributor to air pollution and acid rain.
-
Q #2: What are the three types of salivary glands and where are they located in the mouth?
A. Parotid, sublingual, and submandibular glands located in the cheeks, tongue, and roof of the mouth, respectively.
B. Sublingual, submandibular, and buccal glands located in the tongue, cheeks, and lips, respectively.
C. Parotid, sublingual, and submandibular glands located in the roof of the mouth, cheeks, and under the jawbone, respectively.
D. Sublingual, parotid, and buccal glands located in the tongue, cheeks, and lips, respectively.
Answer Explanation
The three major pairs of salivary glands are the parotid glands, sublingual glands, and submandibular glands.
- Parotid glands are located just in front of your ears.
- Sublingual glands are located below either side of your tongue, under the floor of your mouth.
- Submandibular glands are located below your jaw.
-
Q #3: What is the name of the hormone that regulates blood sugar levels in the human body?
A. Insulin
B. Glucagon
C. Estrogen
D. Testosterone
Answer Explanation
Insulin is a hormone produced by the pancreas that plays a crucial role in regulating the levels of glucose (sugar) in the blood. After a person eats a meal, the levels of glucose in the blood rise, which stimulates the pancreas to release insulin into the bloodstream. Insulin acts on various cells in the body, particularly those in the liver, muscles, and adipose tissue, to promote the uptake, use, and storage of glucose.
Insulin helps to lower the levels of glucose in the blood by increasing the uptake of glucose by cells, stimulating the liver and muscle cells to store glucose in the form of glycogen, and inhibiting the production and release of glucose by the liver. This process is known as glucose homeostasis, and it helps to keep the levels of glucose in the blood within a normal range.
Deficiencies or abnormalities in insulin production or function can lead to a range of metabolic disorders, including type 1 and type 2 diabetes. In type 1 diabetes, the body does not produce enough insulin, while in type 2 diabetes, the body becomes resistant to the effects of insulin, leading to elevated levels of glucose in the blood.
