The heart in the canine and human foetus

Canine foramen ovale
Yvette Lovis is a human obstetric sonographer, undertaking both NHS and private work. She also teaches canine pregnancy scanning to dog breeders and veterinarians. The following article is a guide to the foetal (hereafter spelt “fetal”) heart in the canine and human foetus (hereafter spelt “fetus”). A basic understanding of the carviovascular system of the developing fetus is important, and certainly, achieving a basic four-chamber view of the beating fetal heart is a must when confirming viability of a pregnancy. The circulatory system before birth Within the uterus, the canine and human fetal heart circulation is different to that following birth. Within the uterus, the fetus relies on oxygen from the mother’s circulation, which is delivered from the placenta through the umbilical vein – one of the vessels in the umbilical cord. The other vessels within the cord – two arteries – carry deoxygenated and nutrient-depleted blood from the fetus back to the placenta.   Above: Umbilical cord in the canine (left) and human (right). The image on the right is also using colour Doppler, to indicate blood flow. In normal development, both canine and human fetal hearts develop into four chambers; left atrium and left ventricle, right atrium and right ventricle. Above: The four chambers of the fetal heart, shown in the canine (left) and the human (right). The great vessels –  pulmonary artery and aorta The pulmonary artery and the aorta arise from a single structure. The aorta and pulmonary artery are initially spiralled together and connected through the ductus arteriosis, because the fetal circulation obtains its oxygen from the placental circulation. After birth, blood is sent to the lungs to gain oxygen from respiration, and the connection between the two great vessels closes. In normal dogs and humans, the ductus arteriosis begins to close within a few hours of birth. The pulmonary artery /...

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