Semen is made up of water-based fluids from the prostate, seminal vesicles, and urethral glands and sperm produced by the testes. We'll discuss sperm and the process of procreation later. This one's all about the ejaculate.
Seminal vesicles - the fluid produced in the seminal vesicles is rich in fructose, a nutrient for the sperm. It also produces the chemical that gels ejaculate after release - it causes the sperm to coagulate.
Prostate - the prostate is probably the most well known of the semen-producing glands. It produces enzymes that aid the sperm in escaping the ejaculate and reaching the egg once inside the woman.
Urethral glands - lubricate the urethra to clean it of urine and make the vagina more hospitable to the sperm (the sperm need alkaline environment but the vagina is acidic).
What color should it be? White or grey, though sometimes yellowish is reported. Red or pink is indicative of a health issue (i.e. blood).
What happens if it's swallowed? It gets broken down like any other proteins and sugars. In fact, there's a cookbook available. Though I don't advise cooking with ejaculate - it can spread disease under some conditions.
|Semen in hand, by ZooFari, Wikimedia|