So, do nipples have the erectile tissue you find in the penis and the clitoris? The answer is "no". The anatomy books say, "underneath the nipple and areola, there are bundles of smooth muscle ...

whereas the muscle tissue in the real human iris is made up of smooth muscle cells, which are a type of involuntary muscle tissue. They chose to pattern skeletal muscle cells in an iris-like ...

In findings published in Clinical Cancer Research, the team identified specific proteins—fibronectin and smooth muscle ...

red), myoepithelial and fibroblasts (Smooth Muscle Actin, white), and immune cells (CD45, green) constructed from a 3D serial sectioning experiment on tissue block of a primary breast cancer sample.