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In this blog I will explain the anatomy of the “leaves of Christmas tree” which I have shown in the previous blog. The leaves of Christmas tree i. e. the periphery of the artery in the umbilical cord consists of the capillary. This part is called chorionic villi. Let’s see the component of cells of the chorionic villi. The chorionic villi consists of only two kind of cells. The outer layer coming in contact with maternal blood (retro-placental blood pool), syncytial cells and so called as a syncytiotrophoblast. The inner layer coming in contact with fetal blood consists of the cytotrophoblast cells is called as a cytotrophoblast. The capillary is filled by fetal blood occupies the inside of the leaves. The capillary consists of only endothelial cells in order to exchange substances between blood and extra-cellular spaces. At the leaves of the tree fetus is supplied with oxygen and nutrients from the retro-placental blood pool and is capable of the excretion of the waste from the fetus. The most essential exchange of vital substances for the fetus is done at this place. As I have shown in the previous blogs that angiotensin and vasopressin binds to their receptors located in the smooth muscle cell surrounding the vessels and thus contract vessels. For the hormonal action the existence of the receptor for the hormone is essential.

However the capillary is devoid of smooth muscle. Therefore the capillaries in the leaf part of Christmas tree result in the extension, when the fetus increases both angiotensin and vasopressin due to the stress.

The blood flow redistribution in the feto-placental circulation is considered to be the fetal reaction against stress. One of the typical blood flow redistribution is the increase of blood flow in the placenta. It is known that the blood flow increase is occurred also in the brain and liver of the fetus in response to the stress. The mechanisms of this blood flow redistribution in the feto-placental circulation are possibly the similar to the placenta.

Since the blood flow redistribution in the placenta results in the increase of exchange vital substances between fetus and mother, the fetus is relieved at first. However if the fetal stress is accelerated and continued, the fetal production of both angiotensin and vasopressin is much more increased.

The more increased angiotensin and vasopressin constricts vessels of the tree and branch of Christmas tree( arteries), therefore the leaf part of Christmas tree( capillaries of the villi) gradually results in the reduction of blood flow and hypoxic. In the next blog I will explain the aminopeptidases which degrade both angiotensin and vasopressin located in the villi.  Angiotensin is degraded by aminopeptidase A (APA) and vasopressin and also oxytocin are degraded by placental leucine aminopeptidase (P-LAP), respectively. These aminopeptidases are produced from villi and they are increasing with advancing gestation in maternal blood. The degradation of these hormones at placenta and also in maternal blood is namely the barrier of them from fetus to maternal site. The leakage of fetal bioactive peptide hormones from fetus to mother in the pathological condition results in abnormality of maternal physiology.   In conclusion the barrier between fetus and mother of fetal vital peptide hormones is the aminopeptidases in placenta and maternal blood.

 

 

 P-lap

 

 

 M:retro-placental maternal blood , Syn: syncytial cell, Cyt: cytotrophoblast cell, Cap: capillary of umbilical artery, End: endothelial cell

 

 

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