Chapter Summary

I. TESTES

A. Capsule

The fibromuscular connective tissue capsule of the testes is known as the tunica albuginea, whose inner vascular layer is the tunica vasculosa. The capsule is thickened at the mediastinum testis from which septa emanate, subdividing the testis into approximately 250 incomplete lobuli testis, with each containing one to four seminiferous tubules embedded in a connective tissue stroma.

B. Seminiferous Tubules

Each highly convoluted seminiferous tubule is composed of a fibromuscular tunica propria, which is separated from the seminiferous epithelium by a basal membrane.

1. Seminiferous Epithelium

The seminiferous epithelium is composed of sustentacular Sertoli cells and a stratified layer of developing male gametes. Sertoli cells establish a blood-testis barrier by forming occluding junctions with each other, thus subdividing the seminiferous tubule into adluminal and basal compartments. The basal compartment houses spermatogonia A (both light and dark), spermatogonia B, and the basal aspects of Sertoli cells. The adluminal compartment contains the apical portions of Sertoli cells, primary spermatocytes, secondary spermatocytes, spermatids, and spermatozoa.

2. Tunica Propria

The tunica propria consists of loose collagenous connective tissue, fibroblasts, and myoid cells.

C. Stroma

The loose vascular connective tissue stroma surrounding seminiferous tubules houses small clusters of large, vacuolated-appearing endocrine cells, the interstitial cells (of Leydig).

II. GENITAL DUCTS

A. Tubuli Recti

Short, straight tubes, the tubuli recti, lined by Sertoli-like cells initially and simple cuboidal epithelium later, connect the seminiferous tubules to the rete testis.

B. Rete Testis

The rete testis is composed of cuboidal cell–lined labyrinthine spaces within the mediastinum testis.

C. Epididymis

1. Ductuli Efferentes

The ductuli efferentes compose the head of the epididymis, whose lumina are lined by simple columnar

(tall ciliated and low nonciliated) epithelium. The walls of the ductules consist of fibroelastic connective tissue and smooth muscle cells.

2. Ductus Epididymis

The ductus epididymis comprises the body and tail of the epididymis. Its lumen is lined by a pseudostratified type of epithelium composed of short basal and tall principal cells bearing stereocilia (long microvilli). The epithelium is separated by a basal membrane from the connective tissue wall that houses smooth muscle cells.

D. Ductus (Vas) Deferens

The enlarged continuation of the ductus epididymis, the ductus deferens, is a highly muscular structure. The mucosal lining of its small lumen is composed of pseudostratified stereociliated epithelium lying on a thin fibroelastic lamina propria. Its thick, muscular coat is composed of three layers of smooth muscle: an inner and outer longitudinal and a middle circular layer. A loose, fibroelastic adventitia surrounds the outer longitudinal muscle layer.

III. ACCESSORY GLANDS

A. Seminal Vesicles

As the seminal vesicles, two highly convoluted tubular structures, join the ductus deferens, they form the paired ejaculatory ducts. The highly folded mucous membrane of the seminal vesicle is composed of a pseudostratified epithelium, whose columnar cells are interspersed with short basal cells, sitting on a fibroelastic lamina propria. The muscular coat is composed of inner circular and outer longitudinal layers of smooth muscle and is invested by a fibrous adventitia.

B. Prostate Gland

The ejaculatory ducts join the urethra as these three structures traverse the substance of the prostate gland, whose

452 M A L E R E P R O D U C T I V E S Y S T E M

capsule is composed of fibroelastic connective tissue and smooth muscle cells. The dense stroma of the gland is continuous with the capsule.The parenchyma of the prostate is composed of numerous individual glands disposed in three layers: mucosal, submucosal, and external (main). The lumina of these three groups drain into three systems of ducts that lead into the expanded urethral sinus.The folded mucosa of the glands is composed of simple cuboidal to columnar (with regions of pseudostratified columnar) epithelia supported by fibroelastic vascular stroma displaying smooth muscle cells. Frequently, the lumina of the glands of older men possess round-to-ovoid prostatic concretions that are often lamellated and may become calcified.

C. Bulbourethral Glands

Each small bulbourethral (Cowper’s) gland possesses a thin connective tissue capsule whose septa subdivide the gland into lobules. The cuboidal-to-columnar cells lining the lumen of the gland possess flattened, basally located nuclei. The main duct of each gland delivers its mucous secretory product into the cavernous (spongy) urethra.

IV. PENIS

The penis, ensheathed in skin, possesses a thick, collagenous capsule, the tunica albuginea, that encloses

the three cylindrical bodies of erectile tissue. The two dorsally positioned corpora cavernosa are incompletely separated from each other by septa derived from the tunica albuginea. The corpus cavernosum urethrae (corpus spongiosum) contains the spongy portion of the urethra. The vascular spaces of the erectile tissues are lined by endothelium.

V. URETHRA

The male urethra is subdivided into three regions: prostatic, membranous, and spongy (penile) urethra.

A. Epithelium

The prostatic portion is lined by transitional epithelium, whereas the membranous and spongy portions are lined by pseudostratified-to-stratified columnar epithelium. The spongy urethra frequently displays regions of stratified squamous epithelium. Goblet cells and intraepithelial glands are also present.

B. Lamina Propria

The lamina propria is composed of a type of loose connective tissue housing elastic fibers and glands of Littré. Smooth muscle, oriented longitudinally and circularly, is also evident.

CHAPTER OUTLINE

Graphics

Graphic 19-1 Eye p.462

Graphic 19-2 Ear p. 463

Tables

Plates