Pathology > Study Images > Male Genitals > Testis > Anatomy & Histology
Objectives Anat & Hist Congenital Vascular Neoplasms

I. Gross Anatomy and Histology

Objectives:

After completing this section you will be able to:

  • List the various parts and structures that form the testis
  • describe the basic gross anatomy and histology of the testis
  1. Anatomy
    2.

    The testis is the paired male gonad located outside the body cavity in the scrotum. Each testis is a roughly egg-shaped, and in the adult, measures approximately 4 cm between the rounded superior and inferior poles, 3 cm wide and 2.5 cm deep. Each testis is invested with a serous sac, the tunica vaginalis and covered by a smooth white capsule, the tunica albuginea, from which septa extend into the organ to divide it into approximately 250 pyramidal lobules. Each lobule contains about 3 tightly packed and highly convoluted seminiferous tubules, which contain gametes in various stages of development. The tubules in each lobule join to form a short, straight tube called the tubulus rectus. Towards the posterior portion of the testis, tubuli recti from all lobules form a network of interconnecting tubes called the rete testis, which empties into highly convoluted efferent ductules. Attached to the posterior aspect of the testis and running longitudinally along its postero-lateral aspect is the C-shaped epididymis, which is made up of a tightly coiled tube, the duct of the epididymis. The efferent ductules drain into the duct of the epididymis in the upper portion of the epididymis (called the head or caput), descends in the body of the epididymis to the tail at the inferior pole where it becomes the ductus or vas deferens. The vas ascends behind the testis into the spermatic cord, which also contains the artery, vein and lymphatics.

    Question: What lymph node group do lymphatics from the testes drain into?

  2. Histology
    3.

Each seminiferous tubule is surrounded by a well-defined basement membrane. The epithelium is composed of two basic cell types: the support or sustentacular cells called the Sertoli cells, and spermatogenic or germ cells. The Sertoli cells are non-proliferating elongated cells whose cytoplasm extends from the basement membrane to the lumen of the tubule. The spermatogenic cells are actively replicating cells at various stages of a complex differentiating process called spermatogenesis.

Before onset of sexual maturity at puberty, the tubules contain only small numbers of the most immature germ cell, the spermatogonia. After puberty, the spermatogonia, which are located near to the basement membrane, undergo mitosis to produce primary spermatocytes. The primary spermatocytes undergo first meiotic division to produce transient secondary spermatocytes, which in turn undergo second meiotic division to produce haploid spermatids. The spermatids then mature by the process of spermiogenesis into spermatozoa. As the germ cells proliferate and undergo maturation, they move toward the lumen of the seminiferous tubules such that more differentiated forms are nearer the lumen.


Section through the wall of a seminiferous tubule in the testis showing the various cell types that make up the epithelium. The arrows point to spermatogonia, which are located close to the basement membrane. Primary spermatocytes have large nuclei with condensed chromatin and deep to them (closer to the lumen) are the round spermatids. Spermatozoa are located closest to the lumen of the tubule.


Portions of three seminiferous tubules. Sertoli cells have irregular or pear-shaped nuclei with prominent single nucleolus. Spermatogonia, primary spermatocytes, spermatids and spermatozoa are located as in the previous photomicrograph.

The tubules are embedded in the interstitium, loose connective tissue, which contains blood vessels, lymphatics and nerves. Also present in the interstitium are Leydig or interstitial cells, large, polygonal cells with round nuclei and abundant eosinophilic cytoplasm, which may contain rectangular crystalloids (Reinke crystals).


Section of portions of four seminiferous tubules and intervening interstitium. Several Leydig cells with abundant cytoplasm and round nuclei and fibroblasts with spindle-shaped nuclei are seen.

Question: What is the function of Leydig or interstitial cells?
Objectives Anat & Hist Congenital Vascular Neoplasms