16th February 2024

Renal system

Kidneys

The kidneys are retroperitoneal and are located at the level of T12-L3, with the right kidney slightly lower than the left. The renal parenchyma is divided into the renal cortex and medulla. The renal cortex is the outer aspect of renal parenchyma, which contains renal corpuscles (glomeruli, vessels), proximal portions of collecting tubules, and parts of the loop of Henle. The inner portion of renal parenchyma contains renal pyramids, distal parts of collecting tubules, and parts of the loop of Henle. 

The collecting tubules will eventually drain into the minor and major calyx before emptying into the ureter. The blood supply to the kidneys originates from the renal artery, and venous drainage occurs via the renal vein.

Ureter

The renal pelvis becomes the ureter at the pelvic ureteric junction (PUJ). The ureters are narrow fibro-muscular tubes connecting the kidneys to the urinary bladder. There are three narrowings of the ureter- at the PUJ, as it crosses the common iliac artery bifurcation, and at the vesicoureteric junction (VUJ).

Urinary bladder

The ureters drain into the urinary bladder, acting as a urine reservoir. It is a triangular structure with an apex, base and neck. The lining of the urinary bladder consists of trabeculated transitional cells except at trigone. The trigone is a small triangular area with smooth mucosa at the base of the bladder. 

Both ureteric orifices form the superolateral angles, and the internal urethral orifice forms the inferior angle. The urinary bladder is only partially covered by the peritoneum, which passes on the superior surface and continues back to cover the anterior surface of the rectum. The space created between the urinary bladder and rectum is called the rectovesical pouch and is the most dependent part in males when erect.

Urethra

The male urethra commences at the internal urethral orifice in the trigone of the bladder and opens at the external urethral meatus in the glans penis. It is divided into penile, bulbar, membranous and prostatic urethra. 

The female urethra is much shorter compared to the male (Approximately 4cm vs. 18-20cm). It starts at the internal urethral meatus at the bladder neck and opens in the vestibule of the vagina.

References

Wineski, L. E., & Snell, R. S. (2019). Snell’s clinical anatomy by regions. 

Chaurasia, B. D. (2019). Human anatomy: Regional and applied, dissection and clinical. New Delhi, India: CBS Publishers & Distributors.

Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Moore’s Clinically Orientated Anatomy (7th ed.). China: Lippincott.