The skeleton and muscles originate in the development from or During embryonic development endoskeleton and muscles develop from which germinal layer
Ectoderm
Endoderm
Mesoderm
Yolk plug
Inhibition of uterine contraction ceases and the bleeding and cramps of menstruation begin due to
A boy who has not passed through puberty sustains an injury to his anterior pituitary such that $FSH$ is no longer released, but $LH$ secretion is normal. After he grows to maturity, one would expect that he would
Which cell organelle is absent in human sperm?
In mammals the female secondary sexual characters are developed by the hormone
Which one of the following events immediately follows the entry of a spermatozoan into an oocyte