Histology Guide

virtual microscopy laboratory

Chapter 16 - Urinary System

The urinary system is composed of the kidneys, ureters, urinary bladder, and urethra. Its main function is the production, storage, and expulsion of urine.


Kidneys have several functions:

Examine the overall structure of the kidney.

The nephron is the functional unit of the kidney. Each nephron includes a filter (renal corpuscle), and a single, long tubule (renal tubule) through which the filtrate passes before emerging as urine.

Each nephron is supported by a thin layer of connective tissue.

Urine is unchanged after it leaves the kidney.

Fetal Kidney

During the development of the kidney, additional renal corpuscles form in the outer cortex as the kidney grows. Those found deeper in the inner cortex are more mature.


The ureters are fibromuscular tubes that transport urine by peristalsis from the kidney to the bladder. Like the bladder, it is lined by transitional epithelium (urothelium).

Urinary Bladder

The urinary bladder is a muscular sac that stores urine, allowing urination to be infrequent and voluntary. It is lined by transitional epithelium (urothelium), and has a thick layer of smooth muscle.

(relaxed and stretched bladder)