Answer
The testes are ovoid organs that are combined gonad and endocrine glands that produce both sperms and sex hormones. The tunica vaginalis covered laterally amdantruorly by the tunica vaginals inside of which is the testis capsule proper, the tunica albuginea. The parenchymal tissue of the testis consists of seminiferous tubules lined with germinal epithelium, and clusters of interstitial cells (Leydig cells) located between the tubules. The Leydig cells secrete the hormone testosterone.
Connective tissue from the capsule invades the parenchyma and divides it into about 300 lobes; each lobe contains 1-3 seminiferous tubules. These ducts/tubes are lined with germ cells which will transform into sperms. Around the germ cells (in the tubules) are clusters of other cells-- supporting sustentacular cells; these cells protect and nourish the germ cells.
The sustentacular cells supply the germ cells with nutrients and oxygen, and growth factors and remove their waste products. In addition the sustentacular (Sertoli) cells secrete the hormones androgen binding protein (ABP) and inhibin.
Work Step by Step
There is a blood barrier in the testes similar to the blood barrier in the brain. The testes barrier is appropriately called the blood testes barrier (BTB). It is constituted by the tight junctions between sustentacular cells . The BTB prevents immunoglobulins (antibodies) and other large molecules from the blood and the intercellular fluid (ISF) from coming into contact with the germ cells. This is an important protective mechanism because the germ cells are different genetically from the other cells of the body. Contact between the germ cells and other body molecules would induce immune attacks on the germ cells with possible consequent sterility.
