Menstruation, periodic discharge from the vagina of blood, secretions, and disintegrating mucous membrane that had lined the uterus. 1  The biological significance of the process in humans can best be explained by reference to the reproductive function in other mammals.
Chlamydial (kla-MID-ee-al) infections are caused by three species of microorganisms. Chlamydia trachomatis can cause eye or lung infections and can also infect the urinary and genital areas of both men and women. Chlamydia pneumoniae causes infections of the respiratory tract, and Chlamydia psittaci causes an illness, known as parrot fever, that is similar to the flu.
Chlamydia Causes. Chlamydia is an infection caused by the bacterium Chlamydia trachomatis. The infection is transmitted in 2 ways: 1  From one person to another through sexual contact (oral, anal, or vaginal).2  From mother to child with passage of the child through the birth canal. From one person to another through sexual contact (oral, anal, or vaginal). 2  From mother to child with passage of the child through the birth canal. 3  Chlamydia can cause pneumonia or serious eye infections in a newborn, especially among children born to infected mothers in developing countries.