RT Book, Section A1 Maygarden, Susan J. A2 Reisner, Howard M. SR Print(0) ID 1173780643 T1 Urologic Pathology of the Lower Urinary Tract, Male GU System, and Kidney T2 Pathology: A Modern Case Study, 2e YR 2020 FD 2020 PB McGraw-Hill Education PP New York, NY SN REISNERPATHOL LK accessmedicine.mhmedical.com/content.aspx?aid=1173780643 RD 2024/03/28 AB REVIEW OF NORMAL HISTOLOGY OF THE LOWER URINARY TRACT “QUICK REVIEW”The outflow of the kidneys (renal pelvis, ureters, bladder, and urethra) comprises the lower urinary tract (Figure 14-1). The basic histology is that all are lined by urothelium (transitional epithelium), which covers a connective tissue layer of lamina propria, a variably thick layer of smooth muscle (muscularis propria), and adventitia (Figure 14-2). Urothelium is specialized epithelium that is multilayered with large surface superficial cells (umbrella cells), which can change shape as the bladder dilates and contracts. These contain specialized cell junctions that are resistant to permeation by urine. Beneath this are five to six layers of smaller urothelial cells. The muscularis propria is well developed in the bladder. Coordinated contraction of this muscle (detrusor muscle) helps in emptying the bladder. Muscle is less prominent in the ureters and the urethra. The distal urethra is lined by squamous epithelium, which is in continuity with the squamous epithelium of the external genitalia. Both the male urethra and female urethra contain mucinous glands in their walls.