Overview of Urinary Tract Anatomy & Function

Overview of the Urinary Tract


Adrenal Glands









The urinary tract is divided into 2 parts:

  1. Upper urinary tract: everything above the level of the bladder = kidney parenchyma (the 'meat'), the renal collecting systems (calyces, infundibuli and renal pelvis) and the ureters (paired 'straws' that conduct urine from the kidney to the bladder)
  2. Lower urinary tract: everything from the bladder to the tip of the urethra


The function of the upper urinary tract is to produce urine (eliminate excess water, waste products and electrolytes), adjust blood pressure, help in the production of red blood cells. Characteristics of the upper urinary tract:

  • Paired kidneys (most people have a 'backup'). Most people will have no short term problems if only one kidney is obstructed
  • Low pressure. The pressue of urine in the kidneys is usually very low. When the pressure rises, such as from an obstructing stone, the pain is severe and usually associated with nausea and vomiting.
  • The ureters conduct urine from the kidneys to the bladder are very small - about 2 mm in size. They can stretch a fair amount but are a common site of obstruction by kidney stones.


Urine is produced by the kidneys and then drains downstream in the following sequence (the analogy of a house is used):

  • Papilla: these are the final ducts in the kidney where the urine exits the parenchyma ('meat') of the kidney and then drains into calyces. There are about 5-10 papillae in each kidneys. 
  • Calyx: the area that the papilla drain into (the 'rooms'), there are 5-10 per kidney
  • Infundibulum: the narrower pipes that drain the calyces to the renal pelvis (the 'doorway and hall' leading from the 'rooms')
  • Pelvis: the larger central collecting area for urine from all of the papilla (the 'Great Room' of the upper tracts). Capacity is about 10-15 mL (1/2 ounce) 
  • Ureter: the long tubule from the renal pelvis to the bladder - each kidney has one ureter; they are about 20-26 cm long (about 10 inches) and about 2 mm in diameter - just under 1/8 of an inch (these are the long hallway from the great room to the entry hall)
  • Bladder: the large collecting area of the lower urinary tract where the urine is stored.


Urinary Tract

  1. Urinary Tract
  2. Kidney (Right)
  3. Renal pelvis
  4. Ureter
  5. Bladder
  6. Urethra
  7. Adrenal gland (left)
  8. Renal artery and vein (right)
  9. Vena Cava
  10. Aorta
  11. Iliac vessels 
  12. Liver
  13. Colon
  14. Pelvic bones



Use of these images is under the Creative Commons Attribution-Share Alike 3.0 Unported license. Author: Piotr Michal Jaworski


Penile Anatomy


The basic anatomy of the penis is essentially that of 2 paired cylinders, the corpora cavernosa. Each cylinder is comprosed of an elastic vascular spongy tissue fed by single blood vessel, the cavernosal argery and is surrounded by a tough elastic vascular sheath, the tunica albuginea. The two cylinders have communications in the midline, which can allow the circulation of blood, or medication, between the cylinders.


During an erection, the inflow of blood is trapped within the corpora spongiosum. The high pressure is generated by the pumping of the heart which forces blood from the cavernosal arteries into the spongy tissue. Expansion of the spongy tissue stops once the capacity of the tunica albuginea is reached.




Men are often concerned about the length of their penis.

There is quite wide range and penile lengths. It is important to note that the length of an erect penis will vary based on how it is measured. The best way to measure is from a fixed point such as the pubic bone - which removed any of the variability introduced by the suprapubic fat pad - to the very tip of the head of the penis, ideally with an erect penis but the stretched length can closely approximate tihs. It is also important to note that pictures of penises seen on the Internet or in media (e.g. pornography) are typically skewed towards above average lengths and are not a representation of what is "normal" or "average" (just in the same way that the average height of a basketball player in the NBA is not representative of the average height and the population at large).


Several studies have measured actual penile length. In general, reported erect/stretched penile length is American and European populations is between 12.5-16.5 cm (4.9-6.5 inches). Note that 'flaccid' (non-erect) length does not correlate with erect length.


On the Web

Wikipedia Urinary System