It is the male organ of copulation which comprises of an attached portion called root (that lies within the perineum) and a free, pendulous part called body which is completely covered by a thin, dark colored skin. At the neck of the penis, the skin is folded upon itself to form the prepuce (foreskin) which covers the glans to a varying extent and that can be retracted back and forth. The root consists of three masses of erectile tissue, which includes two crura and a bulb, while the body is composed of three masses of erectile tissue (two corpora cavernosum and one corpus spongiosum). The shape of the penis in a flaccid state is cylindrical, and during erection, it resembles a triangular prism with rounded angle. Erection of the penis is a neurovascular phenomenon independent of muscular compression. Factors responsible for the erection are the rapid inflow of blood from the helicine arteries which fill the spaces of corpora cavernosa leading to distention of the erectile tissue. The distended corpora cavernosa retards the outflow of blood by compressing the veins (Woodhouse and Kellett 1984).

It is a cutaneous fibromuscular sac containing the testes and the lower part of the spermatic cords (Fig. 1.2). The layers of this sac from outside to inside include the skin, dartos muscle, external spermatic, and cremasteric and internal spermatic fasciae. The scrotum is divided into right and left halves by a cutaneous raphe. The scrotal skin is thin and pigmented and bears scattered hairs. In addition, it has numerous sweat glands and sebaceous glands whose secretion has a characteristic odor. The external appearance of the scrotum varies according to the temperature and age of the male. It is smooth, elongated, and flaccid in elderly men and under warm conditions, whereas it is short, corrugated, and closely applied to the testes in cold conditions and also in the younger age groups. The movement of the testes away from and close to the body depending on the temperature is possible due to the contraction and relaxation of the dartos muscle (Waites 2012).

Testes are the primary reproductive organs or male gonads. They are responsible for sperm production (gametogenesis) and testosterone production (steroidogenesis) in the male. During the fetal period of life, these organs are located high in the abdominal cavity. However, before birth, they descend downward to the inguinal canal into a sac known as the scrotum. An adult man has a pair of testis which measures about 4–5 cm in length, 3 cm in width, and 2.5 cm in thickness, weighing around 10–15 g each. Each testis lies obliquely within the scrotum with a convex anterior aspect and nearly straight posterior aspect which is attached to the spermatic cord. The testis is covered by three layers, which are, from outside to inside, the tunica vaginalis, a thick fibrous layer of tunica albuginea, and tunica vasculosa. The testis invaginates the tunica vaginalis from behind, and hence the layer covering closely to testis becomes the visceral layer, while the other is called the parietal layer. Both the layers are (Fig. 1.3) separated from one another by a space filled with serous fluid which acts as a lubricant and allows the movement of the testis within the scrotum. The testicular capsule is made up of collagenous and hard tunica albuginea which covers the testis all round and is thickened in the posterior aspect to form the mediastinum testis. A thin layer of connective tissue with blood vessels is present below this layer. The blood vessels, lymphatics, and the genital ducts enter or leave the testis at mediastinum (Johnson 2012).

Each testis contains around 400–600 seminiferous tubules measuring 70–80 cm in length and 0.12–0.3 mm in diameter. Each tubule is surrounded by a basal lamina which has stratified epithelium consisting of spermatogenic stem cell and the support cells called Sertoli cells (Tubules 1992).

The efferent ductules perforate the tunica albuginea at the mediastinum and leave the testis to form the epididymis. It can be divided into three parts: a globular head or caput, body, and tail or cauda region. In the head region, the ductules form conical lobules which open into the single duct of epididymis through lobular ducts measuring 15–20 cm in length. The lobular ducts coil and form the body and tail of epididymis. The coils are held together by fibrous connective tissue. The epithelial lining of the epididymal duct contains mainly principal and basal cells and few apical and clear cells. The principal cells are tall columnar cells with apical microvillus termed as stereo cilia. The cells help in reabsorbing the fluid generated from the testicular secretions (Bedford 1978).

It is a collection of vessels (testicular artery, testicular veins, testicular lymph vessels, cremasteric artery, and artery of vas deferens), nerves (autonomic nerves and genital branch of the genitofemoral nerve), remnants of the processus vaginalis, and vas deferens which suspends the testis in the scrotum. The left cord is slightly longer than the right, and therefore left testis is at a lower level than the right (Moore et al. 2013).

It is a cordlike structure which can be palpated between the finger and thumb in the upper part of the scrotum. It is a thick-walled muscular duct measuring approximately 45 cm in length that helps in transporting the spermatozoa from the epididymis to the urethra. It is tortuous in its initial part but becomes straight as it ascends upward (Moore et al. 2013).

It is about 20 cm in length and extends from the neck of the bladder to the external meatus of the glans penis. It can be divided into three parts: prostatic urethra, membranous urethra, and penile urethra. Prostatic urethra is around 3 cm in length which passes through the prostate from base to the apex. It is the widest and the most dilatable portion of the urethra. The membranous urethra on the other hand is the least dilatable portion of urethra measuring about 1.25 cm in length and lies between the urogenital diaphragm, surrounded by the sphincter urethra muscle fibers. The penile urethra is about 15.75 cm in length and is enclosed in the bulb and corpus spongiosum of the penis (Standring 2015).