The villi and microvilli on the surface of the small intestine

The rhythmic contractions of the esophagus are called

Bone—forming cells are termed

A species that interacts in critical ways with many other elements of an ecosystem is called a ___________ species.

The uterine lining proliferates during the female cycle and then sloughs off in the process of

The vertebrate kidney produces a fluid called _____________ that enters tubules and is modified to become urine.

Cells called __________ contain hemoglobin and serve in oxygen transport.

Which factor is responsible for most of the cases of threatened and endangered species.

The optimal gestational age for measuring the nuchal translucency is _______ weeks.

Normal amniotic fluid volume cannot exclude renal agenesis before _____ weeks’ gestation.