470 



APPLIED ANATOMY. 



by incising up to the internal ring and drawing the vas out after freeing it of any re-strain- 

 ing fibrous bands. All bleeding vessels are to be ligated and the cord securely held. If 

 the cord slips before all the vessels are secured, the stump may retract in the abdomen 

 and dangerous bleeding result before it can again be secured and the vessels ligated. 



THE URETHRA. 



The male urethra is variable in length, as it can be stretched, therefore only 

 average measurements can be given. Its length is 20 cm. (8 in.) in the adult, 8 to 

 10 cm. at 5 years, and 10 to 12 cm. at puberty. Of this, 3 cm. (i^ in. ) is pros- 

 tatic, 0.5 cm. ( \ in. ) being in the bladder wall ; i cm. ( f in. ) is membranous; 16 cm. 

 (a little over 6 in. ) is penile. Its calibre varies, being narrowest at the meatus 

 and next narrowest at the membranous portion. The internal meatus is a little larger 

 than the membranous portion. The meatus admits a No. 24 French sound (often 



larger) , the membranous portion a 

 26 to 28. The prostatic portion is 

 the largest, admitting a No. 32 

 sound. The bulbous is almost or 

 quite as large, admitting a 30 to 32. 

 Therefore a sound which passes the 

 meatus should find no further ob- 

 struction. The fossa navicularis 

 just beyond the meatus is larger 

 than the urethra beyond (Fig. 473). 

 Distensibility . The meatus 

 and membranous portions are the 

 least distensible. The former is 

 fibrous in character and will not 

 stretch. In the membranous por- 

 tion the support of the superficial 

 and deep layers of the triangular 

 ligament prevent dilatation. The 

 prostatic is the most dilatable por- 

 tion and the bulbous urethra next. 

 Relations. The internal 

 urethral meatus lies about 6. 25 cm. 

 ( 2\ in. ) from the surface just be- 

 hind the middle of the symphysis, 

 if the body is in a vertical position. 

 The membranous portion pierces 

 the triangular ligament, 2.5 cm. (i 

 in. ) or a little less below the sub- 

 pubic ligament. The lowest por- 

 tion is just in front of the triangular 

 ligament. The urethra then rises 

 slightly, 0.5 cm. (-^ in.), and finally 

 drops to the meatus. The subpubic 

 curve of the urethra has a radius 

 of about 5 cm. (2 in.) and urethral 

 instruments are made with approx- 

 imately this curvature, though 

 they vary much. The membra- 

 nous urethra can be palpated at the apex of the prostate by the finger in the rectum. 

 Structure. The urethra is composed of an external layer of erectile tissue 

 covering a muscular layer which is continuous with that of the prostate and bladder. 

 Beneath the muscular layer is the submucous, rich in blood-vessels, on which is laid 

 the mucous layer. This latter is covered with flat, pavement epithelium in the fossa 

 navicularis, and columnar epithelium beyond. 



Ureter 



-Trigone 



Urethral crest (verumontanum) 



Prostatic ducts 



Utricle (prostatic sinus) 



Ejaculatory duct 

 Membranous urethra 

 Cowper's gland 



Opening of Cowper's gland 

 Bulbous portion of urethra 



Lacunae and glands of Littr6 



Fossa navicularis 



FIG. 473. The male urethra. 



