56 THE MALE ORGANS OF GENERATION. 
THE MALE ORGANS OF GENERATION. 
PENIS. 
What are the parts of the penis to be considered ? 
The corpora cavernosa, the corpus spongiosum, and the urethra, 
Describe the structure of the corpora cavernosa and the corpus 
spongiosum. 
Both portions of the organ are surrounded by a dense connective- 
tissue sheath, from which septa or trabeculae blended with smooth 
muscle tissue pass inwards and form an intricate series of spaces filled 
with blood and lined with flattened epithelium. The urethra runs 
through the corpus spongiosum in a longitudinal direction. 
Describe erectile tissue. 
Tt may consist simply of a collection of larger and smaller veins, or, 
of numerous large and small irregular communicating cavities separated 
by narrow interlacing bundles of connective tissue and smooth muscle 
fibres. These spaces are lined with endothelium, and are in commu- 
nication with arterial trunks and capillary bloodvessels. Normally 
they contain but little blood and appear as narrow slits in the tissue. 
When filled with blood they appear as spheroidal or elongated cavities, 
and cause a marked increase in the size of the part in which they are 
located. 
URETHRA. 
Describe the structure of the urethra. 
It is composed of three coats : 
The muscular coat, which is made up of two layers of smooth 
muscle, the fibres of which run longitudinally and circularly. 
The sub-mucous coat, composed of areolar tissue, is so rich in blood- 
vessels that it resembles erectile tissue. 
The mucous membrane composed of fibrillar connective tissue con- 
tains many elastic fibres and cells. The cells which cover the mucous 
membrane differ in shape in different parts. At the meatus and fossa 
navicularis they are flat. In the portion traversing the corpus spongi- 
osum (spongy portion) they are cylindrical. In the prostatic portion 
of the urethra they are pear shaped, polygonal and flattened. They 
lie in several layers and resemble the layer of transitional cells lining the 
bladder. Here and there in the spongy portion of the urethra are 
small, irregular depressions in the mucous membrane called lacunz 
Morgagni. Imbedded in the mucous membrane are also seen racemose 
