In what order do the prostate gland, seminal vesicles, and bulbourethral glands add fluids to the semen?

 

The answer seems obvious, but all over the internet responses claim seminal vesicles are the last to add fluids to the semen. The information that is available states, albeit indirectly, the sequential order is the prostate gland, the seminal vesicles, and lastly the bulbourethral glands. In addition, the picture of the reproductive system verifies the above-stated order of secretion. Can you confirm?

Bulbourethral gland (Cowper's gland) is first:

 

 

The secretions produced by the Cowper’s glands help to protect sperm as it passes through the urethra during ejaculation. In response to sexual stimulation prior to ejaculation, the Cowper’s glands begin producing an alkaline mucous secretion known as pre-ejaculate. Pre-ejaculate neutralizes acidic urine that may still be present in the urethra while also lubricating the urethra and external urethral orifice to protect sperm from mechanical damage during ejaculation.

 

http://www.innerbody.com/image_repmov/repo16-new2.html