FIGURE 22.31 • Photomicrograph of corpus spongiosum. a. This photomicrograph of an H&E–stained section shows the corpus spongiosum and urethra. 20. b. This higher magnification of the corpus spongiosum shows the numerous irregularly shaped vascular spaces. Note the surrounding layer of smooth muscle (SM) forming the “subendothelial cushions.” 135.
 FOLDER 22.5
Clinical Correlation: Mechanism of Erection and Erectile Dysfunction
Erection of the penis is a vascular event initiated by the  Acetylcholine is released by the parasympathetic
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The male reproductive system consists of the paired testes, epididymides, and genital ducts, as well as accessory reproductive glands and the penis. The functions of the testis are the production of sperm and the synthesis and secretion of androgens, especially testosterone. The events of cell division that lead to the mature sperm involve both normal cell division, mitosis, and reduction division, meiosis, to yield a hap-loid chromosome number and haploid DNA content. Androgen secretion by the testis begins early in fetal development and is essential for continued normal development of the male fetus. At puberty, androgen secretion resumes and is responsible for initiation and maintenance of sperm production (spermatogenesis), secretion by accessory sex glands (e.g., prostate and seminal vesicles), and development of secondary sex characteristics.
Testis, monkey, H&E 65.
This section of the testis shows the seminiferous tubules and the tunica albuginea (TA), the capsule of the organ. Extending from the very thick capsule are connective tissue septa (S) that divide the organ into compartments. Each compartment contains several seminiferous tubules and represents a lobule (L).
Blood vessels (BV) are present within the inner portion of the capsule, the part referred to as the tunica vasculosa, and in the connective tissue septa.
The seminiferous tubules are convoluted; thus, the profiles they present in a section are variable in appearance. Not infrequently, the wall of a tubule is sectioned tangentially, thus obscuring the lumen and revealing what appears to be a solid mass of cells (X).
Seminiferous tubules, testis, monkey, H&E 400.
Examination at higher magnification, as in this figure, reveals a population of interstitial cells that occur in small clusters and lie in the space between adjoining tubules. They consist mostly of Leydig cells (LC), the chief source of testosterone in the male. They are readily identified by virtue of their location and by their small round nucleus and eosinophilic cytoplasm. Macrophages are also found, in close association with the Leydig cells, but in lesser number. They are, however, difficult to identify in H&E sections.
A layer of closely apposed squamous cells forms a sheath-like investment around the tubule epithelium of each seminiferous tubule. In man, several layers of cells invest the tubule epithelium. The cells of this peritubular investment exhibit myoid features and account for the slow peristaltic activity of the tubules. Peripheral to the myoid layer is a broad lymphatic channel that occupies an extensive space between the tubules. In routine histologic sections, however, the lymphatic channels are usually collapsed and, thus, unrecognizable. The cellular elements that surround the tubule epithelium are generally referred to as a lamina propria (LP) or as a boundary tissue. As a lamina propria, it is atypical. It is not a loose connective tissue. Indeed, under normal circumstances, lymphocytes and other cell types related to the immune system are conspicuously absent.