During implantation, the trophoblast divides into a deep layer called the _________, which is composed of individual cells.
A. chorion
B. amnion
C. syncytiotrophoblast
D. cytotrophoblast
E. embryoblast
D. cytotrophoblast
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What is the role of calcium in muscle contraction?
A. It stimulates the passage of an electrical signal along the length of the sarcolemma. B. It binds to tropomyosin to expose a binding site for thick filaments. C. It provides energy for contraction. D. It binds to troponin to expose a myosin binding site. E. It binds to troponin to expose an actin binding site.
Undifferentiated spermatogenic cells are called
A. spermatids. B. primary spermatocytes. C. spermatogonia. D. secondary spermatocytes.
What is the correct chronological sequence of events for hearing?
a: The tympanic membrane vibrates. b: Ossicles vibrate. c: Spiral organ hair cells convert stimulus to nerve impulse. d: Pressure waves from oval window travel through the scala vestibuli. A. a, b, c, d B. b, c, d, a C. c, b, a, d D. a, b, d, c E. e, c, , a, b
A bundle of nerve cells or fibers is called a ____
a. fascicle b. nerve c. neuroglia d. neuron