What Happens to the Placenta During Pregnancy?

Placenta (placenta) is an important organ for material exchange between the fetus and the mother. It is a mother-child tissue-binding organ that grows from the embryonic membrane and the mother's endometrium during human pregnancy. The fetus develops in the womb, relying on the placenta to obtain nutrition from the mother, while the two parties maintain considerable independence. The placenta also synthesizes a variety of hormones, enzymes and cytokines to maintain a normal pregnancy. The placenta is still a traditional Chinese medicine. It is called a purple river car, and it is also called human placenta, coat, coat, placenta, and placenta.

Basic Information

English name

placenta

Visiting department

Obstetrics and Gynecology

Contagious

no

Placental structure

Amniotic membrane

The fetal part that makes up the placenta is the innermost layer of the placenta. Amniotic membrane is a translucent membrane attached to the surface of the chorionic membrane. Amniotic membrane is smooth, free of blood vessels, nerves and lymph, and has a certain elasticity. The normal thickness of human amniotic membrane is 0.05mm.

2. Leafy chorion

The fetal part that makes up the placenta accounts for the major part of the placenta of pregnancy. When the embryo develops from 13 to 21 days, villi are gradually formed. About 3 weeks after fertilization, the fetal placental circulation is established when blood vessels in the villi are formed. The villi that come into contact with the bottom decidua are called leafy chorions. The ends of the villus suspended in the villus space filled with mother's blood are called free villi, and the villi that grow into the bottom decidua are called fixed villi. The placental septum growing out of the decidual plate, the fetal leaves are not completely separated into maternal leaves, each mother leaf contains several fetal leaves, each mother leaf has its own spiral artery to supply blood. The uterine spiral artery (also known as the uterine placental artery) of the pregnant woman passes through the decidual plate and enters the mother's lobe. The material exchange between the mother and the child takes place in the villus of the fetal lobule. Maternal blood in the material exchange, the two are not directly connected. The villous trophoblast of the full-term placenta of pregnancy is mainly composed of syncytiotrophoblasts. Cell trophoblasts are only scattered. The inner layer of the trophoblast is the basement membrane, which acts as a placental barrier.

3. bottom decidua

The maternal part that makes up the placenta occupies a small part of the full-term placenta of pregnancy. The placenta maternally is divided into about 20 maternal leaves visible to the naked eye.

Placenta function

Substance exchange function

Gas exchange is oxygen exchange, carbon dioxide exchange; nutrient supply, supply all nutrients needed for fetal development; exclude metabolites in the fetus.

2. Defense function

Although the barrier effect of the placenta is extremely limited, it has a certain barrier function against some bacteria, pathogens and drugs.

3. Synthesis function

Such as human chorionic gonadotropin, human placental lactogen, estrogen, progesterone, tocolytic enzyme, thermostable alkaline phosphatase, cytokines and growth factors.

4. Immune function

The specific mechanism for making the mother able to accept and not reject the fetus is currently unknown.

5. Other functions

(1) Storage function. Such as early pregnancy, placenta grows quickly. A large number of nutrients (protein, glycogen, calcium, iron, etc.) are stored in placental cells for fetal growth needs.

(2) Metabolic regulation function. The placenta has a function equivalent to that of the liver. It not only stores nutrients, but also has a regulating effect. In the later stages of development, the fetal liver gradually grows and completes, and the placenta's metabolic regulating function gradually decreases and even disappears. The placenta can also transform and synthesize a number of substances, and perform a variety of functions of the digestive tract, lungs, kidneys, liver and endocrine glands, and can regulate these functions to protect the fetus and the mother and make the pregnancy go smoothly.

Placental maturity

There are four levels of placental maturity: 0, , , and . Level 1 signifies that the placenta is basically mature; Level 2 signifies that the placenta is mature; Level 3 signifies that the placenta is aging. Due to calcification and cellulose deposition, the ability of the placenta to deliver oxygen and nutrients is reduced, and the fetus is always at risk. In the second trimester (13-28 weeks), the placenta is grade 0; in the third trimester (30-32 weeks), the placenta is grade ; after 36 weeks, the placenta is grade (more mature). If placenta is found before 37 weeks, premature placenta should be considered, and vigilance of intrauterine growth retardation may occur. The placenta at 38 weeks entered grade III, indicating that the placenta was mature.

Placenta medicinal value

Placental serum protein and placental globulin prepared from human placenta are important biological products to rescue patients. The dried placenta, called Ziheche in traditional Chinese medicine, is a well-known tonic medicine that can be used to assist the treatment of bronchial asthma and tuberculosis. Human placenta contains interferon and -inhibitor, which can inhibit many viruses including influenza virus. The placenta contains components related to blood coagulation. There are fibrin stabilization factors similar to factor ; urokinase inhibitors and plasminogen activators. Human placenta also contains many hormones, such as: gonadotropin A and B, lactogen, thyrotropin, oxytocin-like substances, a variety of steroid hormones and estrone, Estradiol, estriol, progesterone, testosterone, deoxycorticosterone, 11-dehydrocorticosterone, Cortisone, 17-hydroxycorticosterone, tetrahydrocorticosterone, 4-pregnene-20,21-diol-3,11-dione (4-pregnen -20,21-diol-3,11-dione), chorionicgonadotropin (and other adrenocorticotropichormone), etc. The human placenta also contains a variety of useful enzymes, such as lysozyme (Lysozyme), kininase, histaminase, oxytocinase, albumin, alpha-globin, beta-globin, gamma-globin, etc. In addition, Red cell containing erythropoietin, phospholipids (phospholipid), - endorphin (-endorphin), amino polysaccharides. Placental raw milk (containing amino acids, and containing a trace of vitamin B _12, acetylcholine iodide and the like.

Common placental abnormalities

Placenta previa

Under normal circumstances, the placenta should be attached to the anterior, posterior, and lateral walls of the uterus. However, in some cases, the placenta is attached to the upper part of the cervix like a small hat, and it is worn on the fetus's head or buttocks. This situation is called placenta previa.

According to the position of the placenta, it can be divided into three types: complete (or central) placenta; partial placenta; and marginal (or low) placenta.

2. Placental abruption

The placenta in the normal position is close to the uterine wall before the fetus is born. If it is detached from the uterine wall during this period, it is called placental abruption. Placental abruption and placenta previa are the main causes of bleeding in late pregnancy.

Once the danger occurs, in principle, it is necessary to allow the fetus to produce time. Only in the fetus can the uterus quickly contract and stop bleeding.

3. Abnormal morphology placenta

During pregnancy, if the pregnant egg is implanted in the uterine horn, it may form a double placenta, a kidney-shaped placenta, a horseshoe-shaped placenta, or a deep groove in the placenta. If the leafy chorion develops around the pregnant egg, it will form a long and thin placenta, which is medically called a membrane-like placenta. The implantation site of the pregnant egg is correct, but if there is an inflammatory lesion in the uterine mucosa at the implantation site, a para-placenta will form. These various placenta are easily left in the uterine cavity during delivery, which is one of the important reasons for postpartum and postpartum hemorrhage and infection.

4. Adhesive placenta and implantable placenta

Whether it is an adhesive placenta or an implantable placenta, the placenta can be difficult to peel off during delivery, causing major bleeding.

5. White placental infarction

Placental white infarction is due to placental lesions, that is, under the amniotic membrane of the fetal surface of the placenta, there are white or yellow-white nodular degeneration tissues, which are relatively hard. If the degeneration is more and deeper, it can make the placenta function impaired and cause the fetus to die in the uterine cavity.