Ovaries are organs found in female organisms. Ovaries are part of the reproductive system needed to reproduce sexually. Most vertebrates have ovaries. Usually animals have two ovaries. Birds usually have only one working ovary; snakes have one ovary in front of the other. The ovaries are similar to testicles in men, in that they are both gonads and endocrine glands. The ovary (for a given side) is located in the lateral wall of the pelvis in a region called the ovarian fossa. The fossa usually lies beneath the external iliac artery and in front of the ureter and the internal iliac artery. The ovaries are not attached to the fallopian tubes but to the outer layer of the uterus via the ovarian ligaments. Usually each ovary takes turns releasing eggs every month; however, if there was a case where one ovary was absent or dysfunctional, then the other ovary would continue providing eggs to be released.