Urinary System Anatomy


The urinary system is one of the excretory systems of the body and consists of four main parts:

  • 2 kidneys – excretory organs
  • 2 ureters – ducts draining the kidneys
  • The bladder – reservoir of urine
  • The urethra – channel from bladder to exterior

                                                                                (Ross, J. et al. 1990)

The kidneys


The kidneys are bean shaped organs approximately 10-12cm long, 5-7cm wide, and 3cm thick. They lie behind the peritoneum and the posterior wall of the abdomen between last thoracic (T12) and third lumbar vertebrae (L3). The right kidney is slightly lower that the left one because of the presence of the liver superiorly (Tortora, J.G et al. 2003).

The medial concave border contains a notch called the renal hilus (see diagram below), the area where structures enter and leave kidney. These structures include the renal artery and vein, lymphatic vessels and nerves (Mace, J.D. et al. 1998).

                                       Tortora, J.G. et al. (2003), p.952

A fibrous layer of connective tissue, called the renal fascia, connects the kidney to the abdominal wall and to the surrounding structures (See Appendix A). Beneath the renal fascia is a fatty layer known as the adipose capsule, which surrounds the renal capsule and aids in protection of the kidney. The renal capsule is a thin transparent membrane that serves to hold kidney together and helps to maintain its shape (Tortora, J.G et al. 2003).

                                               Tortora, J.G et al. (2003), p.951  

A frontal section through kidney reveals two distinct regions: the renal cortex and the renal medulla, which consists of 8 to 18 renal pyramids. The base of each pyramid faces the renal cortex and its apex, called renal papilla, points toward the renal hilus. The renal papilla project into minor calyces, which lead into the major calyces and into the renal pelvis. Each kidney has between 8 to 18 minor calyces and 2 to 3 major calyces. The area between the renal cortex and renal pyramids are known as renal columns (Vander, A. 1995).


According to Seeley, R. et al. (1992), at a microscopic level, the kidney is seen to be composed of:

  • Glomerular capsule – also called renal corpuscles, malphigian bodies or Bowman’s capsules (see diagram below).



The wall of the glomerular capsule consist of a single layer of flattened epithelial cells that act as a filter and are required to be more permeable than other capillaries to allow the constituents of the plasma to pass through (Ross, J. et al. 1990).

  • Tubules:
  1. Proximal convoluted tubule
  2. Loop of Henle
  3. Distal convoluted tubule

  • Blood vessels, nerves, lymph vessels and interstitial tissue (supporting fibrous tissue).

The combination of glomerular capsule and its associated tubules is called a nephron (diagram below) and each kidney contains approximately one million of these.


The kidneys are supplied with blood via the renal arteries that enter at the renal hilus. The summary of the blood supply to the nephrons and its return to the venous circulation through the renal vein into the inferior vena cava is illustrated below:



                                            Carola, R., et al. 1992, p. 853  


Renal   →  Segmental  →  Interlobar  →  Arcuate →  Interlobular  →  Afferent      

artery          arteries              arteries          arteries           arteries            arterioles




Renal ←  Interlobar  ← Arcuate  ←  Interlobular  ←  Peritubular  ← Efferent

 vein            veins             veins               veins              capillaries       arterioles                                                                                    



The ureters

The ureters are the 25-30cm long ducts that collect the urine secreted by the kidneys and transport it to the bladder (Tortora, J.G et al. 2003). There are two ureters one attached to each kidney and each ureter is made of three layers:

  1. The inner layer, or mucosa, secretes mucous to prevent the urine coming into contact with the walls
  2. The middle layer, the muscularis, is composed of smooth muscle, which allows a peristaltic contraction to take place enabling urine to be passed into the bladder.
  3. Outer layer is the adventitia that is made of areolar connective tissue containing the blood vessels, lymphatic vessels and nerves.

                                                                                                                  (Vander, A. 1995)



Join now!

The bladder

The bladder is a pear shaped muscular sac that is made up of three layers: the mucosa, transitional epithelium and lamina propria and is used as a reservoir for urine (Tortora, J.G et al. 2003). It is situated in the pelvic cavity posterior to the symphysis pubis. In males, the bladder lies in front of the rectum, but in the female is separated from the rectum by the uterus and vagina (Linn-Watson, T. 1996). The differences are shown in the diagram below.

The female bladder                   ...

This is a preview of the whole essay