Saturday, November 21, 2009

Anatomy of the Urinary system

Upper urinary tract

Both kidneys are situated retroperitoneally on the posterior abdominal wall.
The left kidney is higher than the right kidney.
The diagphram separates the superior poles of both kidneys from the pleura, the 11th and 12th ribs.

Both kidneys are overlying the psoas major, quadratus lumborum, and transversus abdominis from medial to lateral side.

Anteriorly, the right kidney is overlied by the 2nd part of duodenum, ascending colon, and the liver; whilst the left kidney is overlied by the spleen, stomach, tail of pancreas, and the descending colon.

At the hilum, the front-most structure is the renal veins, followed by renal artery and lastly the renal pelvis.

The abdominal ureters runs over the medial edge of the psoas major muscles, which separates it from the transverse process of the vertebras.
Then, it crosses over the bifurcation of the common iliac artery, which separates it from the sacroiliac joint.
Once it gain entry into the pelvis, it runs over the lateral pelvic wall, passing through the ischial spine.
Finally, it runs medially and enters the bladder.

Note the 3 most common site of stone impaction : Pelvi-ureteric junction, Pelvic brim, and the ureteric orifice.

Lower urinary tract



Upto 4 years of age, the bladder is an abdominal organ.
In adults, the bladder is a pelvic organ, well protected by the pelvic bone.
Superiorly, it is separated from the sigmoid colon, and loops of small bowel by a fold of peritoneum. (in females, the body of uterus as well)
Posteriorly, it's related to the seminal vesicles and vas deferens, and the rectum, in the case of male.
Whereas in females, it's related to the supravaginal cervix and vagina.
In males, the neck of bladder is encircled by the prostate, whereas in females, it fuses with the pelvic fascia.

The length of urethra is males is about 20cm, whilst in females, 3-4cm.
In male urethra, it's divided into prostatic urethra, bulbar urethra and penile urethra. The penile urethra is covered by corpus spongiosum.
It opens out to the tip of glans penis lastly.

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