The placenta is a unique vascular organ that receives blood supplies from both the maternal and the fetal systems and thus has two separate circulatory systems for blood: (1) the maternal-placental (uteroplacental) blood circulation, and (2) the fetal-placental (fetoplacental) blood circulation. The uteroplacental circulation starts with the maternal blood flow into the intervillous space through decidual spiral arteries. Exchange of oxygen and nutrients take place as the maternal blood flows around terminal villi in the intervillous space. The in-flowing maternal arterial blood pushes deoxygenated blood into the endometrial and then uterine veins back to the maternal circulation. The fetal-placental circulation allows the umbilical arteries to carry deoxygenated and nutrient-depleted fetal blood from the fetus to the villous core fetal vessels. After the exchange of oxygen and nutrients, the umbilical vein carries fresh oxygenated and nutrient-rich blood circulating. J. Leandro, (2001).
There are two types of vessels, arteries and veins. Arteries are brighter, since they transport blood rich in oxygen to the organs of the body. The veins afterwards transport the blood, which is at low oxygen level and thus darker, to the lungs and the liver. For many medical applications it would be of great benefit, if the vessels could be distinguished into arteries and veins, since there are many diseases with one symptom being an abnormal ratio of the size of arteries to veins. For example in diabetic patients the veins are abnormally wide, while diseases of the pancreas lead to narrowed arteries and high blood pressure results in thickened arteries. To detect these diseases the retina is routinely examined. (Leandro2001)
An artery is a vessel that carries blood away from the heart and toward other tissues and organs. Arteries are part of the circulatory system, which delivers oxygen and nutrients to every cell of the body. Veins are the blood vessels that carry deoxygenated blood from parts of our body back to the heart.
The blood from the heart is carried through the body by a complex network of blood vessels. Arteries take blood away from the heart. The main artery is the aorta that branches into other major arteries, which take blood to different limbs and organs. These major arteries include the carotid artery, which takes blood to the brain; the brachial arteries, which take blood to the arms; and the thoracic artery, which takes blood to the thorax and then into the hepatic, renal, and gastric arteries for the liver, kidneys, and stomach, respectively. The iliac artery takes blood to the lower limbs. The major arteries diverge into minor arteries, and then into smaller vessels called arterioles, to reach more deeply into the muscles and organs of the body.
Veins and arteries both have two further tunics that surround the endothelium: the middle, tunica media is composed of smooth muscle, while the outer tunica externa is connective tissue (collagen and elastic fibers). The elastic, connective tissue stretches and supports the blood vessels, while the smooth muscle layer helps regulate blood flow by altering vascular resistance through vasoconstriction and vasodilation. The arteries have thicker smooth muscle and connective tissue than the veins to accommodate the higher pressure and speed of freshly-pumped blood. The veins are thinner walled as the pressure and rate of flow are much lower. In addition, veins are structurally different from arteries in that veins have valves to prevent the backflow of blood. Because veins have to work against gravity to get blood back to the heart, contraction of skeletal muscle assists with the flow of blood back to the heart.
According to Gordon, Z.et al (2007), the umbilical artery is a paired artery (with one for each half of the body) that is found in the abdominal and pelvic regions. In the fetus, it extends into the umbilical cord. The umbilical arteries supply deoxygenated blood from the fetus to the placenta. There are usually two umbilical arteries present together with one umbilical vein in the umbilical cord. The umbilical arteries surround the urinary bladder and then carry all the deoxygenated blood out of the fetus through the umbilical cord. Inside the placenta, the umbilical arteries connect with each other at a distance of approximately 5 mm from the cord insertion in what is called the Hyrtl anastomosis. The umbilical arteries are actually the latter of the internal iliac arteries (anterior division of) that supply the hind limbs with blood and nutrients in the fetus. Arterial blood has a inform composition of gasses in all parts of the body.
Blood from the placenta is carried to the fetus by the umbilical vein. About half of this enters the fetal ductus venosus and is carried to the inferior vena cava, while the other half enters the liver proper from the inferior border of the liver. The branch of the umbilical vein that supplies the right lobe of the liver first joins with the portal vein. The blood then moves to the right atrium of the heart. In the fetus, there is an opening between the right and left atrium (the foramen ovale), and most of the blood flows through this hole directly into the left atrium from the right atrium, thus bypassing pulmonary circulation. The continuation of this blood flow is into the left ventricle, and from there it is pumped through the aorta into the body. Some of the blood moves from the aorta through the internal iliac arteries to the umbilical arteries, and re-enters the placenta, where carbon dioxide and other waste products from the fetus are taken up and enter the maternal circulation. Some of the blood entering the right atrium does not pass directly to the left atrium through the foramen ovale, but enters the right ventricle and is pumped into the pulmonary artery. In the fetus, there is a special connection between the pulmonary artery and the aorta, called the ductus arteriosus, which directs most of this blood away from the lungs (which aren't being used for respiration at this point as the fetus is suspended in amniotic fluid).
According to Wang, Y. (2010), the umbilical vein is a vein present during fetal development that carries oxygenated blood from the placenta to the growing fetus. The blood pressure inside the umbilical vein is approximately 20 mmHg.
The umbilical veins bring the nutrient- and oxygen-rich blood from the placental villi via the umbilical cord to the embryo. Normally there exists only one umbilical vein in the umbilical cord: the unpaired umbilical vein. At the caudal rim of the navel, though, it becomes connected to the two intraembryonic umbilical veins, which go laterally from the umbilical coelom to the heart and empty into the two sinus horns with the omphalomesenteric veins that lie medial from them.
In the further development the umbilical veins become quickly included in the developing liver, so that they obtain a connection to the liver's capillary plexus. Now the blood from the left and right umbilical vein gets into the sinus venosus directly on the one hand and via the anastomoses in the liver on the other. The extrahepatic part of the umbilical veins atrophies rather soon. The blood of the umbilical veins now reaches the sinus venosus mixed with the blood of the omphalomesenteric veins passing through the liver. The posthepatic part of the left omphalomesenteric vein atrophies and the right one takes over all of the blood flowing through the liver.
In conclusion, mostly, arteries contain oxygenated blood, and veins contain carbon dioxide-rich and oxygen-poor blood; however, there is one exception. The artery leading to the lungs from the heart does not contain any oxygen, and the vein leading from the lungs to the heart does. This is so the oxygen from the lungs is brought to the heart in order for it to work. Everywhere else, the oxygenated vessels (arteries) carry blood to the rest of the body.
Histologically, veins have a large, floppy irregular lumen and a thinner wall. They also contain valves to prevent backflow when blood is being taken back up to the heart. Arteries usually have a round lumen and thick walls, but no valves.
This discussion has outlined that blood in the umbilical artery contains less glucose than blood in the umbilical vein, blood in the umbilical artery contains less carbon dioxide than blood in the umbilical vein. Blood in the umbilical vein contains less oxygen than blood in the umbilical artery. Blood in the umbilical vein contains more urea than blood in the umbilical artery.
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Wang, Y.( 2010). Vascular biology of the placenta. in Colloquium Series on Integrated Systems Physiology: from Molecule to Function. Morgan & Claypool Life Sciences.
- Quote paper
- Peter Banda (Author), 2015, Arteries and Veins. The Difference in the Composition of Blood, Munich, GRIN Verlag, https://www.grin.com/document/374375