Urethra

The bladder empties via the urethra. 

There are differences between the male and female urethras both on the gross level and histologically. Both have a proximal transitional, an intermediate pseudostratified and a distal stratified squamous epithelium.

Female 

In the female, the urethra runs a short course (4-5 cm) from the bladder to its termination.
 
 The lining epithelium changes over its course from transitional to pseudostratified columnar and finally to stratified squamous. Small collections of mucus-secreting cells can be found. These are called glands of Littré, which are much more well-developed in the male. 
Also, at about the midpoint, a voluntary muscular sphincter is present. 
Between the skeletal muscle and the mucosa, there is an inner longitudinal and an outer circular layer of smooth muscle.

Male 

The male urethra consists of three segments, The prostatic urethra, the membranous urethra and the penile urethra. 
As the urethra leaves the bladder, it enters and traverses the prostate, where it is called the prostatic urethra. 
About midway through, there is an elevation on the posterior wall of the urethra. 
This is the verumontanum or colliculus seminalis. There are three openings on the verumontanum, a central blind ending prostatic utricle and two lateral ejaculatory ducts. 
This portion of the urethra is lined with transitional epithelium and is easily identified due to the presence of the prostate.

Beyond the prostatic urethra, the membranous urethra spans only about one cm. 
This is where the external sphincter is present. 
This skeletal muscle provides voluntary control to the otherwise involuntary urethral sphincter. 
This segment of the urethra is lined with pseudostratified columnar epithelium. 
The urethra continues as the penile, or spongy, urethra. 
The penile portion is located within the corpus spongiosum of the penis. 
The epithelium here is mostly pseudostratified columnar and many glands of Littré are present. 
The luminal lining changes to stratified squamous near the urethral terminus.

Urethroplasty is a surgical procedure dealing with the repair of a defect or injury over the walls of the urethra. 
This surgery is carried out simply to fix the scar tissue blockage pertaining to the urethra known as urethral stricture.