What is a placental cotyledon?: (A) All branches from one stem villi, (B) Area supplied by one spiral aery, (C) Quaer of placenta, (D) Area drained by one terminal villi
Answer is A. Each of the truncal or main stem villi and their ramifications constitutes a placental lobule or cotyledon. Each lobule is supplied with a single truncal branch of chronic aery. And each lobule has a single vein so that lobules constitute functional units of placental architecture. Ref: Williams 24e pg 94.