Testicular seminoma originates in the germinal epithelium of the seminiferous tubules. Characteristic is the presence of abortive tubules and glomeruli surrounded by a spindled cell stroma. Sodium bicarbonate alkalizes urine to stop myoglobin from precipitating in renal tubules. Within the testes are very fine coiled tubes called seminiferous tubules. Spermatozoa are produced in the seminiferous tubules of the testes in a process called spermatogenesis. Urine then flows through the nephrons, through a system of converging tubules called collecting ducts. Capillaries are also interwoven among sweat tubules. Sodium pumps in the renal tubules operate to reabsorb sodium. From the epithelium lining of the tubules, sperm is produced. The sperm that are produced in the seminiferous tubules flow into the epididymis. In males, meiosis occurs during spermatogenesis in the seminiferous tubules of the testicles. It occurs in modified excretory organs known as Malpighian tubules in the abdomen. Angiotensin II has a direct effect on the proximal tubules to increase Na reabsorption. It is secreted from the Sertoli cells, located in the seminiferous tubules inside the testes. These extensions are in the form of vesicles, tubules, and lamellae.