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Questions and Answers
During which week does the heart consist of a pair of tubes situated on either side of the midline?
What forms the inner, thinner layer of the heart tubes?
At what stage are the heart tubes forced to the midline during a folding process?
Which part of the developing system does the heart tube connect with at the cephalic end?
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Which layer forms the outer, thicker layer of the heart tubes?
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At which end does the heart tube connect with the sinus venosus?
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What forms the sinus venosus?
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Which structure divides into the right and left atria upon development of the interatrial septum?
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What does the primitive ventricle contribute to in the heart?
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Which part of the bulbus cordis will form the apical portion of the left ventricle?
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What does the distal bulbus cordis form?
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What will ultimately form the right and left ventricular outflow tracts?
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Which structure will rise to form five pairs of aortic arches?
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What does the right sixth arch form?
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What occurs as muscular contractions begin to occur in the heart tubes?
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At what rate does the heart beat initially?
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What is one of the first functioning systems in the embryo?
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Study Notes
- Prior to week three, the heart consists of tubes on either side of the midline, composed of an inner endocardium and outer myocardium.
- Around 21-23 days, the heart tubes are pushed toward the midline and fuse into a single endocardial heart tube. This tube connects with the developing circulatory arch system at the cephalic end and sinus venosus at the caudal end.
- The inflow portion of the heart is called the Minus Venosus, formed by the union of three pairs of veins - common or cardinal, umbilical, and vitelline. The superior vena cava, inferior vena cava, pulmonary veins, coronary sinus, oblique vein of the left ventricle, and posterior portions of the right and left atria are formed from the sinus venosus.
- The primitive atrium will divide into the right and left atria upon development of the interatrial septum. The atrioventricular sulcus separates the primitive atrium and primitive ventricle. The primitive ventricle originates superior to the primitive atrium but will assume its proper position inferior to it. The primitive ventricle will give rise to a trabecular expansion with inferior growth, forming the quital portion of the left ventricle and contributing to the inlet portion of the right ventricle.
- The interventricular sulcus divides the primitive ventricle and bulbus cordis. The bulbus cordis can be divided into three parts: the left ventricle, the proximal bulbus cordis (forming the apical portion of the right ventricle), and the mid portion called the conus cordis (connecting the primitive right ventricle with the truncus arteriosus, forming the right and left ventricular outflow tracts). The distal bulbus cordis forms the aorta and main pulmonary artery.
- By week four, the heart tubes have completely fused into a single tube, and muscular contractions begin. A simple pattern of flow is established, and the heart rate is approximately 60-70 beats per minute. By birth, the heart rate is approximately 130-150 beats per minute.
- The cardiovascular system is one of the first systems to function in the embryo.
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Description
Test your knowledge of basic embryology of the heart and fetal circulation. Evaluate the development of the heart up to the seventh week and understand the circulatory changes that occur at birth.
