Thorax
Questions
DIRECTIONS: Each item below contains a question or incomplete
statement followed by suggested responses. Select the one bestresponse to
each question.329.Where would you find the specialized cardiac muscle cells that con-
trol the rate of the heartbeat?
a. In the muscular wall of the interventricular septum
b. In the arch of the aorta
c. In the wall of the left atrium between openings of the pulmonary veins
d. In the wall of the right atrium near the opening of the superior vena cava
e. On the surface of the heart330.Which of the following statements is true of cardiac development?
a. During formation of the heart loop, a single-tube heart remains suspended by a
complete dorsal mesocardium (mesentery)
b. The atria are represented by cranial portions of the endocardial tubes
c. The heart bends into an S-shape because the caudal regions of the endocardial
tubes grow faster than the cranial regions
d. The left and right sides of the heart result directly from the side-by-side appo-
sition of the left and right endocardial tubes
e. The sinus venosus becomes incorporated into the atrium prior to the formation
of the heart loop459Copyright © 2007 by The McGraw-Hill Companies, Inc. Click here for terms of use.