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Development Of placenta

 Development Of placenta 

The trophoblastic proliferates and branches from about 3 weeks after fertilization forming the chronic villi. The villi are finger-like projections that become more profuse in the area where the blood supply is rich. That is in the basal decidua. The villi erode the wall of the maternal blood vessels as they penetrate the decidua opening them up to form a lake of maternal blood in which they float. The maternal blood circulates slowly enabling the villi to absorb the food and oxygen and excrete waste. Each chorionic villus is a branching structure it consists of mesoderm fetal blood vessels and branches of the umbilical artery and vein the placenta is completely formed and functioning from 10 weeks after fertilization.

FUNCTIONS OF PLACENTA :

• Respiration:

During intrauterine life no pulmonary exchange of gases can take place, so the fetus must obtain oxygen and excrete carbon dioxide through the placenta.

 •Nutrition:
The embryo: This name is applied to the development of offspring after implantation and until 8 weeks after the conception, during the embryonic period all the organs and systems of the body are laid down in rudimentary form so that is completed they have simply to grow and mature for a further  7 months. 
 Food for the fetus is derived from the mother's diet, which has already been broken down into simpler forms by the time it reaches the placental site. Water, vitamins, and minerals are also passed to the fetus. 
• Storage:

 The placenta metabolizes glucose, stores it in the form of glycogen, and reconverts into glucose as required. It can also store iron and fat-soluble vitamins. 
• Excretion
The main substance excreted from the fetus is carbon dioxide. A very small amount of urea is excreted. 
• Protection:
 The placenta provides a limited barrier to infection. Towards the end of pregnancy immunity on the baby for the first 3 months after birth. Endocrine: small antibodies (IgG), will be transferred to the fetus and these will confirm immunity on the baby for the first three months after birth.
Endocrine.
The Fetus: It is the conceptus from 9 weeks of gestation till the birth take place nearly the last seven months of its intrauterine life.
EMBEDDING: When the blastocyst first tumbles into the uterus, it lies free for 2 or 3 more days. The trophoblast, especially the part which lies over the inner cell mass, then becomes quite sticky and adheres to the endometrium. begins to secrete substances that digest the endometrial cells, allowing the blastocyst to become embedded in the endometrium. Embedding is normally complete by day after ovulation and the endometrium closes over it completely.

Development Of placenta



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