194 



UKOGENITAL SYSTEM 



the lumina remain separate for a time, and the fused walls terminate in an epithelial 

 thickening which projects into the urogenital sinus between the openings of the 

 Wolffian ducts (Miillerian eminence) (fig. 248). Here, but at a much later date, 

 the opening into the sinus is effected. The thickening in which the ducts end is 

 produced by proliferation of the epithelial cells at their terminal growing points, 

 the so-called vaginal bulbs. The future history of the ducts differs in the sexes. 

 In the male they disappear throughout almost their whole length, but the head 

 end is believed to persist as the Jiydatid of Morgagni, while their fused posterior 

 ends remain as the prostatic utricle (uterus masculinus). 



kid. 



FIG. 246. SECTION THROUGH THE TRUNK OF A HUMAN EMBRYO OF 15'5 MM. AT THE LEVEL 

 OF THE HIND-LIMBS. (T. H. Bryce.) Photograph. 



s.n., spinal nerve ; c.v., c.v., cardinal veins (between 'them the aorta giving off the allantoic arteries) ; 

 kid, kidney ; ur, ureter ; w.b., Wolffian body ; w.d., Wolffian duct in Wolffian mesentery ; r, rectum ; 

 bl, bladder ; a.a., a.a., allantoic arteries. 



The glandular tissue of the prostate is developed as a series of epithelial 

 sprouts from the urogenital sinus, which appear in the fourth month, proximal 

 and distal to the opening of the Wolffian ducts. These acquire a lumen and form 

 the parenchyma of the gland, the muscular and connective tissue being derived 

 from the mesenchyme of the genital cord. Similar sprouts form the so-called 

 Skene's tubules of the female urethra. 



In the female the ducts persist, and their upper independent portions become 

 the Fallopian tubes, while their fused posterior portions form the foundation of 

 the uterus and vagina. The fusion begins near the lower end (fig. 245), and 

 proceeds both downwards towards the future orifice and upwards for a certain 

 length. The extent to which the Miillerian ducts are fused varies in different 



