Urinary System

Kidneys:

• External features: Reddish-brown, flattened bean-shaped, with 2 surfaces (anterior, posterior), 2 borders (medial, lateral), and 2 poles (upper, lower).

• Location: Retroperitoneal, on either side of the lumbar vertebral column. The left kidney is higher than the right kidney by the width of one rib.

• Left kidney: The upper pole is at the level of the superior border of the 11th rib, the lower pole is at the level of the transverse process of the L3 vertebra, 5 cm from the iliac crest.

• Right kidney: The upper pole is at the level of the inferior border of the 11th rib, the lower pole is 3 cm from the iliac crest.

• The lower poles of both kidneys are further apart than the upper poles due to the psoas major muscle pushing them outwards.

• Structure:

• Fibrous capsule: Tightly encapsulates the renal parenchyma.

• Perirenal fat capsule: Encases the fibrous capsule.

• Renal fascia: Encloses the perirenal fat capsule and the adrenal gland. The renal fascia consists of 2 anterior and posterior layers.

• Paranephric fat: Located between the posterior layer of the renal fascia and the posterior abdominal wall.

• Relations:

• Anterior surface of the right kidney: Adheres to the bare area of the liver, with the right adrenal gland superiorly, the hepatic flexure of the colon inferiorly, and the descending duodenum medially. Separated from the liver by the hepatorenal recess.

• Anterior surface of the left kidney: The root of the transverse mesocolon crosses over, dividing the surface into upper and lower parts.

• Upper part: Relates to the spleen, pancreas, stomach, and adrenal gland.

• Lower part: Relates to the splenic flexure/descending colon, and loops of small intestine.

• Posterior surface of the kidney: The 12th rib crosses, dividing the surface into two parts: upper (thoracic)/lower (lumbar) part of the 12th rib.

• Thoracic part: Relates to the costodiaphragmatic recess/pleura, 11th and 12th ribs via the diaphragm.

• Lumbar part: Relates to the psoas major muscle, quadratus lumborum muscle, and transversus abdominis muscle via the paranephric fat.

• Lateral border of the right kidney: Relates to the liver.

• Lateral border of the left kidney: Relates to the spleen and descending colon.

• Medial border of the kidney: Contains the hilum, where the renal vessels enter/exit and the renal pelvis exits, connecting to the ureter. The adrenal gland sits atop the upper part of the hilum.

• Renal parenchyma: Consists of 2 regions: the medulla and the cortex.

• Renal medulla: Formed by the renal pyramids (Malphigi). The renal pyramids have their base facing the fibrous capsule and their apex pointing towards the renal sinus, forming the renal papillae.

• Renal cortex: Consists of renal columns (located between the renal pyramids) and renal lobules (the parenchyma between the renal pyramids and the fibrous capsule).

• Renal sinus: Contains 9-12 renal calyces, 2-3 minor calyces -> major calyces, the calyces -> renal pelvis. The minor calyces and renal pelvis are funnel-shaped. The funnel’s apex exits the hilum, connecting to the ureter.

Ureter:

• Function: Conducts urine from the renal pelvis to the bladder. Located retroperitoneally, anterior to the posterior abdominal wall, on either side of the lumbar vertebral column.

• Length: Approximately 25-28 cm long.

• Constrictions: 3 constrictions: where it joins the renal pelvis, where it crosses anterior to the iliac vessels, and where it pierces the bladder.

• Segments: Divided into 2 segments: abdominal segment (12.5-14 cm) and pelvic segment (12.5-14 cm).

• Abdominal segment: From the renal pelvis to the pelvic brim. It descends medially and anteriorly to the psoas major muscle, crossing anterior to the iliac vessels.

• The right ureter crosses anterior to the external iliac artery.

• The left ureter crosses anterior to the common iliac artery.

• The point where the ureters cross the iliac arteries is 4-5 cm from the midline.

• The right ureter relates to the inferior vena cava.

• The left ureter relates to the abdominal aorta.

• Pelvic segment: From the pelvic brim to the ureteric orifice in the bladder. It lies close to the lateral wall of the pelvis along the internal iliac vessels, and at the level of the ischial spine, it turns medially and anteriorly through the pelvic floor to the bladder.

• In males: It crosses posterior to the vas deferens, running between the bladder and the seminal vesicles.

• In females: It passes into the base of the broad ligament, crossing posterior to the uterine artery, about 1.5 cm from the cervix.

• Connection with the bladder: It penetrates the bladder wall from superior to inferior, and from lateral to medial. The segment within the bladder wall is 2.2 cm long. The two ureteric orifices are 2.5 cm apart when the bladder is empty.

Bladder:

• Location: Retroperitoneal, within the lesser pelvis, behind the pubic bone, anterior to the reproductive organs, and in front of the rectum.

• When empty: Its highest point does not extend beyond the pubic bone.

• When full: Its highest point extends beyond the superior border of the pubic bone, lying posterior to the anterior abdominal wall.

• Newborns: Lies posterior to the anterior abdominal wall, from the umbilicus to the pubic bone.

• Capacity: Normally 250-300ml, up to 3000ml in urinary retention.

• Structure: 1 anterior apex, 1 body, 1 posterior-inferior base, 1 neck, with 3 superior/inferior-lateral surfaces (without urine).

• Superior surface of the female bladder: Covered by peritoneum up to the posterior border of the superior surface -> it folds at the junction of the body and the cervix, covering anteriorly and inferiorly to form the vesicouterine pouch.

• Anterior surface of the male bladder: Peritoneum covers the vas deferens, seminal vesicles, and folds onto the anterior surface of the rectum to form the rectovesical pouch.

• Apex of the bladder: Where the superior and inferior-lateral surfaces meet, the site of attachment of the median umbilical ligament.

• Base of the bladder: Relates to the cervix/upper part of the vagina, seminal vesicles, vas deferens, rectum, and loops of small intestine.

• Neck of the bladder: Where the base and the 2 inferior-lateral surfaces meet, opening into the urethra = internal urethral orifice. It sits on top of the prostate gland in males.

• Bladder wall: Composed of 5 layers: serosa, subserosa, muscularis, mucosa, submucosa.

• Trigone: Contains 3 orifices: 2 ureteric orifices on either side, and the internal urethral orifice at the neck of the bladder.

Urethra:

• Male: 16 cm long, divided into 3 parts: prostatic, membranous, and spongy.

• Prostatic urethra: From the neck of the bladder to the apex of the prostate gland, 2.5-3 cm long, has smooth muscle of the urethral sphincter surrounding the neck of the bladder.

• Membranous urethra: From the apex of the prostate gland to the bulb of the penis, pierces the pelvic diaphragm, has striated muscle of the urethral sphincter, and has a venous plexus.

• Spongy urethra: Lies within the corpus spongiosum of the penis, 12 cm long.

• Anterior urethra (mobile): From the suspensory ligament of the penis to the external urethral orifice, less prone to injury.

• Posterior urethra (fixed): Consists of the prostatic, membranous, and spongy urethra from the membranous urethra to the suspensory ligament of the penis, prone to injury.

• Structure: Consists of mucosa/muscle layer. The mucosa has elasticity, the muscle has longitudinal muscle inside and circular muscle outside, superior to the opening of the ejaculatory duct.

• Female: 3-4 cm long, running from the neck of the bladder through the pelvic floor to the external urethral orifice in the vestibule of the vagina. Completely fixed, divided into 2 parts: pelvic/perineal.

• Pelvic segment: Contains the smooth muscle of the urethral sphincter.

• Perineal segment: Contains the striated muscle of the urethral sphincter.

• Narrowest point: External urethral orifice in the vestibule of the vagina, located 2.5 cm anterior to the vaginal orifice, deep to the clitoris.

Relations:

• Alongside the inferior vena cava: Medial border of the right kidney.

• Alongside the abdominal aorta: Medial border of the left kidney.

Note: This text is a summary based on the provided information and may lack some details.