The primary sex characters include those structures which actually take part in the process of reproduction. These also make distinction between male and female individuals. These include mainly the gonads, i.e., testes in the male and ovaries in the female.
The gonads are concerned not only with the production of gametes or sex cells (spermatozoa and ova) but also secrete hormones that are responsible for the functional state of sex accessories and, to some extent at least, influence the psychobiologic phenomena involved in the mating reaction.
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Sex accessories, on the other hand, include structures that are involved mainly in the transmission of gametes (sex cells) or developing-zygotes from the site of their origin to the exterior of the organism.
In male the sex accessories comprise a pair of attached epididymes in which sperms are stored, a pair of vasa deferentia which serve to transfer sperms from the epididymes away from the testes, a pair of seminal vesicles which provide essential nutrients and fructose to the developing sperms especially in men, bulls and other species but not in cats and dogs, a single prostate gland that serves to lubricate the passageway to the outside of the body through penis, a pair of Cowper’s glands which are also lubricatory in function and a penis that may be erected by the circulation to facilitate placement into the vagina of the female for the ejaculation of sperm.
In female the sex accessories, include a pair of fallopian tubes (oviducts) the distal ends, of which (infundibula) serve to receive ova discharged from the ovaries and the proximal ends enter the uterus a single uterus which either sloughs off periodically or develops in part into a placenta, depending on whether pregnancy occurs, a vagina that serves to receive sperms, one pair (in man) or more pairs of mammary glands which produce milk for the new born and bulbourethral glands which secrete a fluid similar to that of the glands connected to the urethra of the male.