Post-Implantation On day 9, lacunae or spaces form within the syncytiotrophoblast. The placental barrier is not a true barrier as it allows many substances to pass between the maternal and fetal circulations. Harmful substances such as nicotine from cigarette and addictive drugs such as heroin can pass through placenta.
Even the foetal part of placenta is retained and gets absorbed to provide nourishment.
Through the placenta oxygen passes from the maternal blood to the foetal blood, and carbon dioxide passes from foetal blood to maternal blood.
The trophoblast cells form the placenta. Human placenta uterine side. The uterine glands, on the other hand, decrease in activity and degenerate around 8 to 9 days  after ovulation in absence of pregnancy. The placental barrier is much thinner and the cytotrophoblast layer beneath the syncytiotrophoblast is lost.
However, before that disappearance, some glands secrete unequally much. Placenta with only three barriers, the maternal part of placenta eroded. This increases the diameter and reduces the resistance of the vessels. Oxygen passes from the maternal blood to the foetal blood through the placenta and CO2 passes in reverse direction.
Cotyledons receive their blood supply through spiral arteries that pierce the decidual plate. By means of placenta the developing embryo obtains nutrients and oxygen from the mother and gives off carbon dioxide and nitrogenous waste. The production and release of milk is called lactation L.
Uterine epithelium and connective tissue eroded only four barriers left. IgMhowever, cannot cross the placenta, which is why some infections acquired during pregnancy can be hazardous for the fetus.
They appear between day 19 and day 21  of gestational age. The type of placenta in man is of described as deciduate intimate contact between loetal and maternal tissuediscoidal villi occur in the form of dischaemo-chorial chorionic epithelium in direct contact with maternal blood.
However, some elements of the decidualization remain throughout pregnancy.Essay on Adaptations of the Placenta and Foetus to Improve Oxygen Availability - The placenta is an extraordinary organ that links the foetus to the mother whilst keeping the blood supply separate and carrying out functions that the unborn child cannot on its own.
Placenta functions as an endocrine gland it secretes hormones such as oestrogen, progesterone and human chorionic gonadotropin (HCG). Parturition (Birth): The gestation period or the baby carrying period is the time from conception to birth.
Essay on the Classification types and Function Placenta! Placenta is an organic connection between the foetus and uterine wall, for physiological exchange between foetus and mother’s blood. The placenta develops at the point of implantation. The placenta is the composite structure of embryonic and maternal tissues that supplies nutrients to the developing embryo.
The placenta serves three main functions: The placenta serves three main. The placenta functions as a fetomaternal organ with two components: the fetal placenta (Chorion frondosum), which develops from the same blastocyst that forms the fetus, and the maternal placenta (Decidua basalis), which develops from the maternal uterine tissue.
At very early stages, the exchange of nutrients, oxygen and excretory materials between the cells of the blastocyst and the maternal blood (in the uterus) take place through these chorionic villi (this function is later taken over by the placenta).Download