What hormone is secreted by the gland labeled 2?

Indentify number 3.

Which heart valve prevents the backflow of blood from the left ventricle into the left atrium?

Gastrulation produces an oval, three-layered sheet known as the          

Compared to arteries, veins      

The secretion of the seminal vesicles contains ________, which forms a temporary semen clot within the vagina after ejaculation.  

Contractions of the papillary muscles  

Identify number 5.  

What structure covers the trachea during swallowing?

The physical maturation of sperm is called