Final answer:
The main distinction between the exocrine and endocrine parts of the testis is that the endocrine portion releases hormones directly into the bloodstream, while the exocrine portion produces and transports sperm through ducts.
Step-by-step explanation:
The distinction between the exocrine and endocrine portions of the testis lies in their functions and how they release their secretions. The endocrine part of the testes, specifically the interstitial cells, produces hormones such as testosterone which are secreted directly into the bloodstream, functioning without the need for ducts. This is in contrast with the exocrine portion, which involves the seminiferous tubules where sperm is produced and eventually carried out of the testes through a system of ducts. These ducts include the epididymis, vas deferens, ejaculatory ducts, and the urethra.
Exocrine glands such as the seminal vesicles and prostate gland contribute to the formation of semen by releasing their secretions into these ducts. In terms of the testis, it does not secrete digestive enzymes or sweat-like other exocrine glands in the body but is involved exclusively in the production and emission of spermatozoa.