7 Transmission Electron Microscopy for the Quantitative Analysis of Testis Ultra Structure Saeed Shokri 1* , Masoud Hemadi 2 and Robert John Aitken 3 1 Anatomy Department, School of Medicine, Zanjan University of Medical Sciences, Zanjan, 2 Fertility and Infertility Research Center, Imam Khomeini Hospital, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, 3 ARC Centre of Excellence in Biotechnology and Development, Discipline of Biological Sciences, University of Newcastle, NSW, 1,2 Iran 3 Australia 1. Introduction 1.1 Testes structure The testes have two functions: they produce the male gametes, spermatozoa, and also produce the male sexual hormone, testosterone, which stimulates the accessory male sexual organs and causes the development of the masculine extragenital sexual characteristics. The testis is surrounded by a thick capsule, the tunica albuginea, from which a conical mass of connective tissue, the mediastinum testis, projects into the testis [1]. The tunica albuginea is covered externally by a serosa. From the mediastinum, delicate fibrous septa radiate towards the tunica albuginea and divide the parenchyma of the testis into about 300 lobuli testis, which communicate peripherally. Each lobule contains 1-4 convoluted seminiferous tubules (about 150-300 μm in diameter, 30-80 cm long). Interstitial tissue between the convoluted tubules is continuous with a layer of loose vascular connective tissue, the tunica vasculosa testis, which is found beneath the tunica albuginea. Each seminiferous tubule continues near the mediastinum into a straight tubule, a tubules rectus. The straight tubules continue into the rete testis, a labyrinthine system of cavities in the mediastinum [1, 2]. 1.2 The convoluted seminiferous tubules These tubules are enclosed by a thick basal lamina and surrounded by 3-4 layers of smooth muscle cells (or myoid cells). The insides of the tubules are lined with seminiferous epithelium, which consists of two general types of cells: spermatogenic cells and Sertoli cells (fig 3, 5). * Corresponding Author