Structure and functions of Placenta(Easy way to learn)

Placenta is the main link between mother and fetus. It provides oxygen,Nutrients and other substans to fetus and removes waste products produced by fetus. It also prevent fetus from infection which can be transfer from mother by placental barriers.

• Placenta developed from union of chorionic frondosum and decidua basalis.
• It start to develop at 6week and complete at 12 week of pregnancy.
• Till 12 week of pregnancy the functions of providing nutrients to fetus is done by corpus luteum.

Placenta at Term- 

• Shape- Circular dics                                                Diameter- 15 to 20cm
• Thickness-3cm (at center)                                      Weight- About 500gm
• Weight ratio of placenta with fetus:- 1:6                Occupies 30% part of uterine wall

STRUCTURE OF PLACENTA-

• Placenta consist of 2 plates, inner called basal plate and outer called chorionic plate.
• These plates also known as surface of placenta the basal plate is called Meternal surface,and chorionic plate is called as Fetal surface.

1. Meternal surface-

• It is rough and spoagy surface, which is dark red in color.
• Grayish spots are seen due to calcium deposition.
• It is less than 1/5 part of total placenta.

        2. Fetal surface-

•  It has a shiny appearance due to the amnion covering of it.
• Umblical cord is present at its center.
• Branches of umbilical vessels are visible.
• It is 4/5 of total placenta.

• Space between plates are called " Intervillious space",which contain stem villi and its branches.
• Intervillious spaces also filled by slow flowing of meternal blood.
• Stem villi originate from chorionic plate and extend toward basal plate.
• Stem villi from primary, secondary and tertiary villi according their progressive development.
• Human placenta contain about 60 villi.
• Villi are functional unit of placenta, because villi are responsible for exchange between meternal and fetal blood.
• Few villi cause anchoring of placenta to decidua and some provide nutrition to fetus.

FUNCTION OF PLACENTA-

1. Excretory function-

• Excretion of waste products like urea,uric acid, and creatinine from fetal circulation to meternal circulation by simple diffusion

      2. Respiratory function-

• fetus required oxygen supply at the rate of 8ml/kg/minute from eternal circulation because there are no gases exchanges during fetal life by immature lungs, and this amount of oxygen is achieved by 165 to 135 ml/min cord blood flow.
• Transfer of gases assisted by slight maternal respiratory alkosis and fetal hemoglobin's high level and high affinity to oxygen.

       3. Nutritive function-

• Fetus gets nutrients ( glucose, triglycerides and fatty acid, amino acid, water & electrolytes and hormones) from maternal blood by placenta. https://amzn.to/3mrMqH9

      4. Barrier function-

• Placenta inhibited entry of harmful substance from maternal circulation to fetus e.g. maternal drugs and infection like rubella, chicken pox, polio, measles, mumps and bacterial.
• Some viruses like HIV and hepatitis can cross placental barriers.
• Immunoglobulins also passes from mother to fetus in the late in late pregnancy, which provide passive natural immunity to fetus for first 6 to 12 weeks.

       5. Immunological function-

• Immunosuppressive effect by steroid hormones and HCG.
• Prevent fetal rejection by making blocking antibodies.
• Prevent deep penetration by decidual natural killer cells.

      6. Endocrine function-

• It produces protein hormones like hCG, human placental lactogen(HPL), which also called human chorionic somatomammotropin (HCS), human placental growth harmone (hPGH) and insulin growth factor.
• It also produces steroid hormones like and estrogen and progesterone during pregnancy.

        7. Storage function-

• It stores glycogen, iron and fat-soluble vitamins.