Penile endothelium can function as lubrication, protect the glans, and prevent infection. 1 Lubrication: Penile endothelium can play the role of lubrication during sex, so that the penis slides freely and smoothly during sex, so that the penis slows down friction and reduces pain during sex. 2 protect the glans: the endothelium can slow down and share the sensitivity of the glans, control penile erection and weakness, play a protective role for the glans and delay the progress of ejaculation. 3. Prevent infection: the skin may be broken during sex and be infected by bacteria causing disease, penile endothelium can adjust the pH value, has a cleaning effect, to achieve the prevention of infection. If the penile endothelium appears itchy, red and swollen, etc., should promptly consult a doctor, under the guidance of the doctor for treatment.