Placental Function
1. Protection/ Placental barrier function
Placenta protect from infection and diseases.
Fetal membrane; protective barrier to fetus against noxious agents circulating in maternal blood.
Maternal infection during pregnancy by virus; rubella, chicken pox, measles, mumps, poliomyelitis.
Bacteria; Treponemia pallidum, Tubercle bacillus
Protozoa; Toxoplasma gondii, malaria parasites
Prevent the fetal cross placenta barrier and prevent fetus in utero.
Note; Drug such as; aspirin, tetracycline cross the placental barrier.
Rubella infection can cross the placental barrier.
2. Nutritive function
Transfer of nutrients and waste products between mother and fetus, glucose.
Transfer protein for facilitated diffusion.
1. Glucose; Energy
2. Lipids; Fetal growth and development
3. Amino acids; IgG
4. Water and electrolytes
Sodium, potassium, chloride
Calcium, phosphorus, iron
Water soluble vitamins
Fat soluble vitamins
3. Respiratory function
Placenta serves as fetus lung and allow transmission of oxygen. Support developing fetus transferring oxygen and nutrients from maternal to fetal circulation and transferring CO2 and waste away fetal to maternal circulation.
Oxygen supply to fetus at rate of 8ml/kg/min
Placenta is organ of respiratory gas exchange.
Intake of oxygen and output of CO2 taken place by simple diffusion across fetal membrane.
Mechanism involved in transfer of substances across the placenta are;
Simple diffusion
Facilitated diffusion; transporter protein
Active transfer; against concentration gradient
Endocytosis; Immunoglobulin IgG taken up by endocytosis from maternal circulation.
Transfer to fetus via exocytosis.
Exocytosis
Leakage
Break in placental membrane.
4. Excretion
By simple diffusion.
Filtering waste products from fetus. CO2, Urea, Uric acid, creatinine excreted to maternal blood.
5. Endocrine function
Placenta produce hormones that support and maintain pregnancy.
It produces steroids hormone (estrogen and progesterone), insulin (growth factor of fetus), thyroid.
Placenta regulates amount of maternal thyroid hormone passing through into fetus.
It secreted of hCG hormone.
hPL (Human placental lactogen) released by placenta and prepare/ stimulation of milk gland.
Note; Parathormone, calcitonin not cross placenta.
6. Immunological function
Transfer maternal IgG to fetus.
Placental hormone/proteins/hCG/steroids
Decidual natural killer (NK) cell.
IgG
7. Enzymatic function
1. Diamine oxidase
Histamine degradine enzyme produced by placenta, act as barrier to to prevent/ inactives excessive entry of histamine from placenta into maternal or fetal circulation.
2. Oxytocinase
Neutralize the oxytocin.
3. Phospholipase
Help in synthesis of arachidonic acid and prostaglandins.
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