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The heart is the first functional organ in vertebrate embryos. The tubular heart quickly differentiates into the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and the sinus venosus. The truncus arteriosus splits into the ascending aorta and the pulmonary trunk. The bulbus cordis forms part of the ventricles.
It is the fetal heart and not the mother's heart that builds up the fetal blood pressure to drive its blood through the fetal circulation. Intracardiac pressure remains identical between the right and left ventricles of the human fetus.
Nine-week-old human embryo from an ectopic pregnancy. Organogenesis is the development of the organs that begins during the third to eighth week, and continues until birth. Sometimes full development, as in the lungs, continues after birth. Different organs take part in the development of the many organ systems of the body.
The endoderm is the inner most germ layer of the embryo which gives rise to gastrointestinal and respiratory organs by forming epithelial linings and organs such as the liver, lungs, and pancreas. [5] The mesoderm or middle germ layer of the embryo will form the blood, heart, kidney, muscles, and connective tissues. [5]
The heart rate increases, but generally not above 100 beats/ minute. Total systematic vascular resistance decreases by 20% secondary to the vasodilatory effect of progesterone. Overall, the systolic and diastolic blood pressure drops 10–15 mm Hg in the first trimester and then returns to baseline in the second half of pregnancy. [ 6 ]
A fetus receives oxygen not from its lungs, but from the mother's oxygen-rich blood via the placenta. Oxygenated blood from the placenta travels through the umbilical cord to the right atrium of the fetal heart. As the fetal lungs are non-functional at this time, the blood bypasses them through two cardiac shunts.
The tubular heart or primitive heart tube is the earliest stage of heart development. [1] The heart is the first organ to develop during human embryonic development. [2]From the inflow to the outflow, the tubular heart consists of sinus venosus, primitive atrium, the primitive ventricle, the bulbus cordis, and truncus arteriosus. [3]
A portion remains open as a branch of the anterior division of the internal iliac artery. The umbilical artery is found in the pelvis, and gives rise to the superior vesical arteries, which in males usually supplies the artery to the ductus deferens. Alternately, the latter artery can be supplied by the inferior vesical artery in some individuals.