Male Genital System and Spermatogenesis

Male Genital System

• The male genital system consists of testes, excretory genital ducts, accessory genital glands, and penis.

Testis

• The testis is a mixed compound tubular gland formed of stroma and parenchyma.
• The stroma consists of a capsule with three coats: tunica vaginalis, tunica albuginea, and tunica vasculosa.
• The parenchyma consists of seminiferous tubules and Leydig cells.

Seminiferous Tubules

• Seminiferous tubules are convoluted tubules, 50 cm in length and 200 μm in diameter, lined with spermatogenic epithelium.
• The tubules are lined with Sertoli cells and spermatogenic cells.

Sertoli Cells

• Sertoli cells are pale staining cells with indistinct cell boundaries and pale acidophilic cytoplasm containing numerous lipid droplets.
• Ultrastructurally, Sertoli cells have numerous mitochondria, smooth endoplasmic reticulum, and lysosomes, with microfilaments and microtubules at the apex and tight junctions at the basal parts.

Blood Testis Barrier

• The blood-testis barrier is formed by tight junctions between adjacent Sertoli cells, dividing the seminiferous tubule into outer (basal) and inner (adluminal) compartments.

Spermatogenic Epithelium

• The spermatogenic epithelium consists of Sertoli cells and spermatogenic cells, including spermatogonia, primary and secondary spermatocytes, spermatids, and spermatozoa.

Spermatogonia

• There are two types of spermatogonia: dark type A (reserve cells) and pale type A (stem cells).
• Type B spermatogonia are derived from pale type A and give rise to primary spermatocytes.

Primary Spermatocytes

• Primary spermatocytes are the largest cells (18 μm) with diploid chromosomes (2N = 46).
• They undergo meiotic division to form secondary spermatocytes.

Secondary Spermatocytes

• Secondary spermatocytes are smaller cells with haploid chromosomes (N = 23).
• They rapidly enter the second meiotic division to form spermatids.

Spermatids

• Spermatids are very small cells with dark nuclei and haploid chromosomes.
• They undergo spermiogenesis to form mature sperm.

Spermiogenesis

• Spermiogenesis is the process of transforming spermatids into mature sperm through three stages: Golgi phase, acrosomal phase, and maturation phase.

Mature Sperm (Spermatozoa)

• Mature sperm are 60 μm long, consisting of a head (5 μm), neck, middle piece (5 μm), principal piece (40 μm), and end piece (10 μm).
• The head contains a condensed nucleus with an acrosomal cap rich in hydrolytic enzymes, and the middle piece has a mitochondrial sheath.