Accessory Sex Glands. The accessory sex glands include the seminal vesicles, the prostate gland and the bulbourethral glands. These glands secrete or contribute fluids which give the semen a characteristic composition such as buffering fluids and albumin.
Penis. A stallion's penis is likely over 50 cm long in the relaxed state with 15-20 cm lying in the prepuce. During erection the size increases about 2 fold. The penis is roughly divided into the head, body and glans. The glans, or free end of the penis, is bell shaped particularly during erection and ejaculation. The urethral process extends approximately one inch from the surface of the deep depression or fossa glands.