Although gonadotropins are secreted in a pulsatile manner (as a result of pulsatile GnRH release), unlike the case of GnRH and GnRH agonists , constant/non-pulsatile activation of the gonadotropin receptors by the gonadotropins does not produce functional inhibition. This can be seen during the first 7–10 weeks of pregnancy, where constantly high and progressively-increasing levels of hCG circulate and mediate production of estrogen and progesterone by the corpus luteum until the placenta takes over the production of these hormones. 
Many eukaryotes have long slender motile cytoplasmic projections, called flagella , or similar structures called cilia . Flagella and cilia are sometimes referred to as undulipodia ,  and are variously involved in movement, feeding, and sensation. They are composed mainly of tubulin . These are entirely distinct from prokaryotic flagellae. They are supported by a bundle of microtubules arising from a centriole , characteristically arranged as nine doublets surrounding two singlets. Flagella also may have hairs, or mastigonemes , and scales connecting membranes and internal rods. Their interior is continuous with the cell's cytoplasm .