Urinary Anatomy

Question 0

What are the different layers of the kidney and its surrounding tissue?

Answer 0

Superficial layer - renal fascia

Middle layer - adipose capsule (peri-nephric fat)

Deep layer - fibrous renal capsule

Question 1

What vertebral levels are the kidneys located at?

Answer 1

Left = T11-L2
Right = T12-L3

Right kidney more inferior due to presence of liver

Question 2

When are the ureters vulnerable to damage?

Answer 2

Upper 1/3 - abdominal surgery

Lower 2/3 - pelvic surgery/hysterectomy

• risk of incontinence: ureter passes inferior to uterine artery
• risk of infertility?: ureter passes inferior to ductus deferens?

Question 3

Where is the adult bladder located when full and when empty?

Answer 3

Empty - below superior pubic rami (pelvic cavity)

Full - above pelvic rim (extends into abdominal cavity)

Question 4

Which artery crosses behind the vena cava?

Answer 4

Right renal artery

(renal vein anterior to renal artery)

note: longer than left renal artery (vice versa with renal veins)

Question 5

Where is the renal artery located in terms of aortic branches?

Answer 5

Superior to inferior:

• Coeliac trunk
• Superior mesenteric artery
• Renal arteries
• Gonadal arteries
• Inferior mesenteric artery

Question 6

How are the kidneys related to the posterior abdominal wall and peritoneum?

Answer 6

Kidneys attached to posterior abdominal wall via mesenteries

Retroperitoneal - behind parietal peritoneum

Question 7

At what vertebral level do the renal arteries arise?

Answer 7

Abdominal aorta: L1-L2

Question 8

Describe the path of the ureters.

Answer 8

Runs down tips of transverse processes

Runs anterior to medial aspect of the psoas major muscle

Crosses end of common iliac and external iliac arteries at the pelvic brim (over the sacro-iliac joint)

Descends retroperitoneally on the lateral pelvic wall

Enters bladder posteriorly at an oblique angle

Question 9

How long is the urethra in the adult male and female?

Answer 9

Male = 15-20cm

Female = 4cm

Question 10

What are the different components of the male urethra, and where are they located?

Answer 10

Pre-prostatic = between bladder and prostate

Prostatic = through prostate

Membranous = through deep peritoneal pouch

Spongy (penile) = through corpus spongiosum

Question 11

What epithelia are present in the nephron?

Answer 11

PCT - simple cuboidal + brush border (lots of mitochondria)

Descending limb - simple squamous (few mitochondria)

Thick ascending limb - simple cuboidal (lots of mitochondria)

Collecting duct - simple cuboidal (no brush border, wide lumen)

note: calcyces, ureter, bladder etc. = transitional epithelium

Question 12

Outline the structure of the bladder and urethral orifices.

Answer 12

• Fundus (body of bladder) - detrusor muscle (contracts to expel urine, relaxes to store urine) & transitional epithelium; temporary store of urine
• Bladder neck - connects bladder to urethra
• Trigone (ureteric orifices + internal urethral orifice)

Muscular units:

• detrusor muscle
• internal urethral sphincter (smooth muscle - autonomic; closes due to collapse of muscle fibres due to filling of urine)
• external urethral sphincter (skeletal muscle - voluntary; pudendal nerve = S2-S4)

Muscularis externa of detrusor muscle:

• inner: longitudinal muscle
• middle: circular muscle
• outer: longitudinal muscle

note: roughly arranged in 3 directions - allows strength of contraction irrespective of direction of stretch (prevents herniation and rupture)
& does NOT contract in response to stretch (unusual)

Bladder is hollow smooth muscle (midline structure; hindgut derivative)
located in the true (lesser) pelvis in adults

Internal urethral orifice (males) = physiological sphincter; as the bladder fills, involuntary smooth muscle fibres at the neck collapse, closing off the urethra

External urethral orifice (males & females) = anatomical sphincter (levator ani of pelvic floor); skeletal muscle (somatic pudendal nerve) allows voluntary control of voiding