Explain how the structure and functions of the placenta maintain pregnancyThis is a featured page



  • After an embryo implants in the uterine wall, tissues of the uterus and fetus form the placenta.
  • The placenta has 2 major functions: 1) production of estrogen & progesterone, and 2) exchange of molecules between maternal & fetal blood.
  • Progesterone and estrogen are needed to prevent menstruation and build up the wall of the uterus.
  • The placenta begins to form when the fetus develops a villus, a finger-like growth into the uterus.
  • The number of villi increases steadily to meet the needs of the growing fetus.
  • Maternal blood flows out of capillaries into inter-villous spaces surrounding each villus.
  • Fetal capillaries are very close to the surface of each villus (within 5 µm of the maternal blood).
  • The cells separating fetal and maternal blood form a selectively permeable barrier known as the placental barrier.
  • Microvilli project from each villus to increase surface area, which allows rapid diffusion of molecules.
  • Nutrients and O2 diffuse from maternal blood to fetal blood, and carbon dioxide diffuses from fetal blood to maternal blood.
  • Fetal blood flows toward the placenta in the umbilical artery, and away from the placenta in the umbilical vein.

Explain how the structure and functions of the placenta maintain pregnancy - IB Biology Syllabus


boultont
boultont 		Latest page update: made by boultont , May 13 2009, 12:53 AM EDT (about this update About This Update boultont Edited by boultont


view changes
- complete history)
Keyword tags: None
More Info: links to this page

Threads for this page

There are no threads for this page.  Be the first to start a new thread.