Placenta is the connecting link between the mother and her developing child in her womb. Whereas, placental barrier is the layer of tissue which is semipermeable and serves as a selective membrane.

The function of placental barrier is to select the substances which are passing from the maternal blood to fetal blood. The circulation of the placenta creates the relationship between the circulatory system of both the mother and her baby.

The blood supply to the placenta is influenced by factors like uterine contractions, hormones, tobacco use, medications and arterial blood pressure. Any of these factors increases or decreases in their quantity it will directly affect the placental circulation and will act as the placental barrier.

Placental circulation is very necessary for the growing fetus as circulation is the only means of nutrition for it. Any kind of fluctuation in the circulation will directly affect the growth of the fetus.

Structure Of Placental Barrier:

Placental barrier is the structure which acts as guard for the foetus. It allows only the selective molecules to enter and ultimately reach the growing fetus. It is the structure which separates the mother and the foetal blood. Its structure changes along the passage of the pregnancy. Like:

• In the first trimester of the pregnancy, placental barrier comprises of those cells which which forms the thick lining and have a large surface area. Some structures have hairy lining to perform the excretory tasks.
• In the fourth month of the pregnancy, few cells which had made the outer layer thick disappear, increasing the surface area of the barrier. The structures having hairy lining also increases to meet the increasing demand.
• In the fifth month the vessels reaching up to the fetus increases and it multiplies into small capillaries, so that a large amount of nutrient can reach up to the fetus.
• In the sixth month, proliferation knots are formed to increase the blood flow and supply of nutrient to the fetus.