In the fetus, blood can flow from the right atrium to the left atrium through the ________.
A. tricuspid valve
B. foramen ovale
C. ductus arteriosus
D. ductus venosus
Answer: B
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Photoreceptor cells that are most useful in dim light are
A) rods. B) cones. C) amacrine cells. D) horizontal cells. E) bipolar cells.
A structure that allows the middle ear to communicate with the nasopharynx is the
A) auditory meatus. B) eustachian tube. C) bony labyrinth. D) membranous labyrinth. E) pinna.
_______ Tissue is highly vascular, whereas _______________ is not.
A) Epithelial; cartilage. B) Muscular; osseous tissue. C) Dense regular connective; dense irregular connective tissue. D) Areolar; cartilage. E) Nervous; osseous tissue.
At about day nine of development of the blastocyst, the cells of the inner cell mass are organized into an oval sheet that is two layers thick, called the ________.
Fill in the blank(s) with the appropriate word(s).