Milky line - protein stripe
Spermatogonia, developing, produce spindle-shaped cells that mature in spermatogyny. From each of the latter, a network of thin branching channels - strands - diverges at a right angle, each of which is called a milky passage (or milky channel), or a roller. It consists of thousands of small wriggling cells concave inward. On the outside they are lined with a layer of flat cells. These cells receive nutrients from the roller. The convoluted parts of the cells are filled with the underlying substance of the cell. Contraction of smooth muscle