HISTOLOGY 143 



Ventral prostates. — In the ventral prostates (Fig. 72) the gland tubules 

 are lined by low columnar epithelium, having deeply staining spherical nuclei 

 and slightly basophilic cytoplasm. The distended tubules do not contain 

 mucous folds; in the smaller tubules folds are present. The secretion in a 

 stained preparation shows a tendency to form round, pink staining globules 

 of varying size. The gland tubules have a thin circular smooth muscle coat 

 and are held together by a common connective tissue membrane. 



The urethra, bulbo -urethral glands, penis and preputial glands. — The 

 neck of the bladder is lined by diminishing rows of transitional epithelial 

 cells. This changes into stratified squamous epithelium (two to three layers) 

 lining the ventral wall of the urethra. The colliculus seminalis is covered 

 by a continuation of the simple low columnar type of epithelium which 

 Hnes the ducts entering on this projection. Similar epithelium lines the 

 dorsal wall of the urethra. At a sHghtly lower level this also changes into 

 stratified squamous epitheHum which lines the membranous urethra 

 throughout its entire length. Loose connective tissue forms the lamina 

 propria, which is very rich in blood vessels and forms a framework for the 

 urethral glands present in the mucosa (Fig. 67). These glands, as well 

 as the thick layer of striated muscle fibers which surround them, appear on 

 the dorsal wall near to its cephalic extremity and spread gradually caudally 

 toward the ventral wall to form a complete sheath around the tube below the 

 neck of the bladder. The urethral glands (of Littre) are composed of small 

 groups of alveoli, the cells of which have oval nuclei near the base and 

 cytoplasm containing basophilic secretion granules. Their short ducts, 

 lined by cuboidal epithelial cells, open separately into the urethral lumen 

 at different levels. 



The root of the penis is attached to the pubic bone by the crura which 

 are the terminal extensions of the corpora cavernosa penis. From the 

 enlarged base of the crus penis, the ischeum, the ischio cavernosus muscle, 

 arises and passes forward. The corpus cavernosum urethra proximally 

 expands into the urethral bulb, over which extend the bulbo cavernosus 

 muscle. The urethra forms paired lateral diverticula at the region of the 

 bulb (Figs. 63 and 73). The lumen of each diverticulum shows variations 

 in size and shape, depending on the amount of secretion present. It is 

 lined by transitional epithelium, the apparent thickness depending on the 

 dilated or relaxed condition. Below the epithelium, glands similar in 

 structure to those of the membranous urethral wall are present. The diver- 

 ticulum is surrounded b}- a fibrous membrane with circularly arranged, 

 smooth muscle fibers as an inner layer. From here trabeculae composed of 



