Describe the events of embryonic development from conception until the fetal stage, including development of the primary germ layers
What will be an ideal response?
A fertilized egg (zygote) undergoes rapid mitotic cell division in a stage called cleavage. Cleavage provides the building blocks for constructing the embryo, which develops until it has about 100 cells and then hollows out to form a blastocyst. The blastocyst has two areas: the trophoblast and the inner cell mass. The inner cell mass forms three primary germ layers which are the ectoderm, the endoderm, and the mesoderm. The ectoderm gives rise to the nervous system and the epidermis of the skin. The endoderm forms the mucosae and associated glands. The mesoderm gives rise to everything else. The trophoblast develops projections called chorionic villi which form the placenta along with tissues from the mother's uterus. By the eighth week, all the organ systems have been laid down and the embryo looks distinctly human. Beginning in the ninth week, the embryo is referred to as a fetus.
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Which of the following would stop the reabsorption of glucose at the apical surface of the cells in the PCT? A) loss of Na+-K+ ATPase in the basolateral surface of PCT cells B) loss of K+ leak channels at the apical surface C) increasing Na+ concentration in the filtrate D) increasing Na+ in the interstitial fluid
Inhibitory postsynaptic potentials (IPSPs )
A) result in local depolarizations. B) result in local hyperpolarizations. C) prevent the escape of potassium ions. D) prevent the escape of calcium ions. E) increase membrane permeability to sodium ions.
A hammertoe is a condition sometimes seen in newborns.?
Indicate whether the statement is true or false
The flexor (withdrawal) reflex
A. has a monosynaptic component. B. is initiated by stretching muscle spindle fibers. C. is initiated by stimulation of the Golgi tendon organ. D. stimulates contraction of the ipsilateral flexor muscle and inhibits contraction of the ipsilateral extensor muscle. E. stimulates contraction of the contralateral flexor muscle and inhibits contraction of the contralateral extensor muscle.