Most of the interior of the testis is composed of seminiferous tubules, the small lumens in HA9. These are cut in transverse, oblique (neither parallel nor perpendicular) and longitudinal sections due to the coiling of the tubules. The lumens of the tubules give the section a porous appearance. In between the tubules there are blood vessels and connective tissue, as well as clusters of cells called interstitial (in between) cells (large arrows, IC) because of their location. These cells are responsible for the synthesis and secretion of testosterone and other steroid hormones.