The renal corpuscle consists of a capillary bed called the glomerulus and a capsule of epithelial cells. The renal corpuscle is composed of two structures, the glomerulus and the Bowman's capsule. The glomerulus is a small tuft of capillaries containing two cell types. It is also characterized as a cluster of capillaries around the end of a kidney tubule, where waste products are filtered from the blood. Other surfaces that separate body cavities from the outside environment are lined by simple squamous, columnar, or pseudostratified epithelial cells.The gastrointestinal tract, the insides of the lungs, and the reproductive and urinary tracts where other epithelial cells line up make up the exocrine and endocrine glands.