Implantation 1

Question 1

List the functions of the placenta.

Answer 1

• Interface between maternal circulation and fetal circulation
• Gas exchange
• Excretory functions, water balance, pH regulation
• Catabolic and resorptive functions, nutrition
• Synthetic and secretory endocrine functions
• Metabolic functions, conjugating waste
• Hematopoiesis in early pregnancy
• Temperature regulation, partially
• Immunologic functions (tolerance of pregnancy - fetal antigens need to be ignored by the maternal immune system)

Question 3

Describe the process of excretory functions, water balance, and pH regulation of the placenta.

Answer 3

• Water transfer across placenta
  
  • depends on hydrostatic and osmotic pressure
  • most movement is passive, but there may be a trophoblast water channel (aquaporins)
• Sodium and chloride levels in fetus and mother are similar
• Potassium, calcium, and phosphate are higher in the fetus
  
  • enter by active transport

Question 5

Describe the role of the placenta in catabolic and resoprtive functions as well as nutrition.

Answer 5

• Glucose transported via GLUT-1 transporter and other GLUT transporters (facilitated diffusion)
• Amino acid metabolism and transport is complex
• Lipid metabolism and transport primarily through diffusion mediated by material surface with lipoprotein lipase
  
  • generates free fatty acids and glycerol

Question 7

Describe the synthetic and secretory endocrine functions of the placenta.

Answer 7

• Hypophyseal-like hormones
  
  • hCG is the primary one
    
    • released by syncytiotrophoblasts
• Steroidogenic hormones
  
  • derived from metabolism of maternal cholesterol
  • progesterone (syncytio- and cytotrophoblasts)
  • estrogen
    
    • from androgens secreted by fetal adrenal gland
    • much of it is conjugated
• Placental peptides similar to hypothalamic factors
• Chorionic cytokines, growth factors, and peptides
• Eicosanoids and prostanoids

Question 9

What are the mteabolic functions of the placenta as well as its role in conjugating waste?

Answer 9

• Syncytiotrophoblast has many export pumps (ex. multidrug resistance protein 1, MDR1)
• Placenta has numerous cytochrome P450 enzymes that metabolize xenobiotics
• Most proteins do not corss the placenta
  
  • some are transported by pinocytosis
  • maternal IgG antibodies provide the fetus with passive immunity