Chapter 23 - Section 23.7 - Study Guide - Assess Your Learning Outcomes - Page 922: 2

The urinary bladder is a muscular organ that functions as a reservoir for storing urine until it is expelled from the body during urination. Here's an overview of the anatomy and histology of the urinary bladder, including its detrusor muscle, mucosal epithelium, rugae, trigone, and internal urethral sphincter: 1. **Detrusor Muscle**: - The detrusor muscle is the smooth muscle layer of the urinary bladder wall. It consists of three layers of smooth muscle fibers: inner longitudinal, middle circular, and outer longitudinal layers. - Contraction of the detrusor muscle allows the bladder to expel urine during urination. Relaxation of the detrusor muscle enables the bladder to fill and store urine. 2. **Mucosal Epithelium**: - The innermost layer of the bladder wall is lined with mucosal epithelium, which is composed of transitional epithelial cells. These cells can stretch and change shape as the bladder fills and empties. - The transitional epithelium forms a protective barrier against the potentially harmful effects of urine. 3. **Rugae**: - When the bladder is empty, its mucosal lining is folded into irregular folds known as rugae. As the bladder fills with urine, the rugae unfold and the bladder expands to accommodate the increasing volume of urine. 4. **Trigone**: - The trigone is a triangular area on the bladder floor formed by the openings of the two ureters and the urethra. - The mucosa of the trigone is smooth and lacks rugae. It is important for maintaining proper urine flow and preventing reflux of urine into the ureters. 5. **Internal Urethral Sphincter**: - The internal urethral sphincter is a smooth muscle located at the junction of the bladder and the urethra. It is not under voluntary control. - The internal urethral sphincter helps prevent urine from flowing back into the bladder from the urethra and assists in maintaining continence. It's important to note that the external urethral sphincter, a voluntary skeletal muscle, is also a crucial component of urinary control. It surrounds the urethra and is under conscious control, allowing us to voluntarily initiate or inhibit urination. Overall, the anatomy and histology of the urinary bladder are designed to allow it to efficiently store urine, expand as it fills, and contract to expel urine during urination while maintaining proper urinary function and preventing urinary tract infections.

The urinary bladder is a muscular organ that functions as a reservoir for storing urine until it is expelled from the body during urination. Here's an overview of the anatomy and histology of the urinary bladder, including its detrusor muscle, mucosal epithelium, rugae, trigone, and internal urethral sphincter: 1. **Detrusor Muscle**: - The detrusor muscle is the smooth muscle layer of the urinary bladder wall. It consists of three layers of smooth muscle fibers: inner longitudinal, middle circular, and outer longitudinal layers. - Contraction of the detrusor muscle allows the bladder to expel urine during urination. Relaxation of the detrusor muscle enables the bladder to fill and store urine. 2. **Mucosal Epithelium**: - The innermost layer of the bladder wall is lined with mucosal epithelium, which is composed of transitional epithelial cells. These cells can stretch and change shape as the bladder fills and empties. - The transitional epithelium forms a protective barrier against the potentially harmful effects of urine. 3. **Rugae**: - When the bladder is empty, its mucosal lining is folded into irregular folds known as rugae. As the bladder fills with urine, the rugae unfold and the bladder expands to accommodate the increasing volume of urine. 4. **Trigone**: - The trigone is a triangular area on the bladder floor formed by the openings of the two ureters and the urethra. - The mucosa of the trigone is smooth and lacks rugae. It is important for maintaining proper urine flow and preventing reflux of urine into the ureters. 5. **Internal Urethral Sphincter**: - The internal urethral sphincter is a smooth muscle located at the junction of the bladder and the urethra. It is not under voluntary control. - The internal urethral sphincter helps prevent urine from flowing back into the bladder from the urethra and assists in maintaining continence. It's important to note that the external urethral sphincter, a voluntary skeletal muscle, is also a crucial component of urinary control. It surrounds the urethra and is under conscious control, allowing us to voluntarily initiate or inhibit urination. Overall, the anatomy and histology of the urinary bladder are designed to allow it to efficiently store urine, expand as it fills, and contract to expel urine during urination while maintaining proper urinary function and preventing urinary tract infections.