Anatomy notes
Prostate:
Blood supply:
Prostatic arteries are branches of inferior vesical arteries, internal pudendal and middle rectal
arteries, which are all branches from internal iliac.
The prostatic venous plexus is continuous superiorly with the vesical venous plexus and
communicates posteriorly with the internal vertebral venous plexus.
Nerve supply: inferior hypogastric plexus.
Lymphatic drainage: internal iliac lymph nodes.
Urethra:
Blood supply:
- Pre-prostatic and prostatic urethra: arterial supply by
prostatic branches of inferior vesical and middle rectal
arteries. Venous drainage is by the prostatic venous plexus.
- The bulbourethral artery supplies the membranous and
bulbar urethra.
- The penile urethra is supplied by the deep penile artery, a branch of the internal pudendal artery. In
general, venous drainage mirrors the arterial supply.
- Female urethra: internal pudendal and vaginal arteries. Veins follow the arteries and have the same
names.
Nervous supply:
- Male urethra: nervous supply by prostatic nervous plexus, which is an extension of inferior
hypogastric plexus and pudendal nerve (external urethral sphincter). The internal sphincter is supplied
by greater cavernous sympathetic nerves.
- Female urethra: vesical nervous plexus and pudendal nerve (external urethral sphincter, no internal
sphincter in females).
Lymphatic drainage:
- The prostatic and membranous urethra drain to the obturator and internal iliac nodes.
- Lymphatic drainage from the spongy urethra (mostly the anterior part) drains to the deep and
superficial inguinal nodes.
Urethra parts
Pre-prostatic About 1 cm long.
urethra. Extends from the base of the bladder to the prostate.
Associated with the internal urethral sphincter.
Contraction of this sphincter prevents movement of semen into the bladder during ejaculation.
Prostatic 3-4 cm long and surrounded by the prostate.
urethra The lumen of the prostatic urethra contains a longitudinal fold of mucosa urethral crest.
(widest). The depression on both sides of the urethral crest prostatic sinuses.
The ducts of the prostate empty in the prostatic sinuses.
Midway along its length, the urethral crest is enlarged seminal colliculus (also called
verumontanum).
2 structures open into the seminal colliculus (verumontanum):
Prostatic utricle: remnant of uterus in males (during early fetal life everyone was female).
Openings of the 2 ejaculatory ducts.
- Therefore the connection between urinary and reproductive tracts in males occurs in
prostatic urethra.
Membranou Passes through the deep perineal pouch (between superior and inferior fascias of
s urethra urogenital/pelvic diaphragm)
(shortest and Surrounded by skeletal muscle of external urethral sphincter (sphincter urethrae muscle) in
most both males and females.
delicate).
Spongy Bulbar (bulbous) portion of spongy urethra (prone to tear in straddle injury).
urethra: *** mechanism of straddle injury: occurs to the groin area between the thighs, in female
injury to the vulva, in males scrotum, penis, testes. An example is falling while riding a
bicycle and hitting the middle bar.
Penile portion of spongy urethra (longest part).
Surrounded by erectile tissue of the penis (corpus spongiosum) increased blood flow in this
tissue is what causes erection.
Both the external urinary and external anal sphincters are innervated by the pudendal nerve (S2, S3, S4).
Note: sympathetic innervation causes ejaculation, while parasympathetic innervation causes erection.
Ureter:
- Blood supply: branches divide into superior and inferior and anastomose together.
Upper part: branches from renal artery.
Middle part: branches from abdominal aorta, gonadal (testicular/ovarian) artery, common iliac
artery.
Lower part: branches from internal iliac artery.
- The blood supply is very rich so anything causing damage to the ureter will cause severe bleeding.
- Blood supply: branches divide into superior and inferior and anastomose together.
Upper part: branches from renal artery.
Middle part: branches from abdominal aorta, gonadal (testicular/ovarian) artery, common iliac
artery.
Lower part: branches from internal iliac artery.
- The blood supply is very rich so anything causing damage to the ureter will cause severe bleeding.
Constrictions of ureter:
1. ureteropelvic junction.
2. bifurcation of common iliacs = level of the pelvic brim, which separates the true pelvis from the false
pelvis
3. ureterovesical junction (as it enters the bladder).
Bladder:
- Arterial supply:
Males: superior vesical arteries + inferior vesical arteries.
Females: superior vesical arteries + vaginal arteries.
There is also a contribution from obturator and inferior gluteal arteries.
- Venous drainage:
In males the vesical venous plexus is enveloping the base of the bladder, it is connected to the
prostatic venous plexus and drains into the inferior vesical veins internal iliac veins, or it can
drain directly into the internal vertebral venous plexuses.
In females the vesical venous plexus envelops the neck of the bladder and the pelvic part of the
urethra and communicates with the vaginal or uterovaginal venous plexus.
- Nerve supply:
Sympathetic: T11-L2 or L3 inferior mesenteric ganglion hypogastric plexuses vesical
plexus.
Parasympathetic: S2-S4 inferior hypogastric plexus vesical plexus.
Sympathetic causes ejaculation, while parasympathetic causes erection (discussed in next
lecture).
Sympathetic innervation contracts (closes) the internal urethral sphincter in males, and relaxes
the detrusor muscle to inhibit excretion of urine.
Parasympathetic innervation on the other hand relaxes (opens) the internal urethral sphincter,
and contracts the detrusor muscle to cause excretion of urine.
Sensory fibers for pain sensation follow parasympathetic nerves, except the superior surface of
the bladder = sympathetic.
Lymphatics: Lateral vesical lymph nodes internal/external iliac lymph nodes common iliac lymph nodes.
Kidneys:
Blood supply:
- The right renal artery is longer than the left and passes posterior to the vena cava.
- Left renal artery is a little more superior than the left, both of them emerge at level L1/L2.
- The renal veins are anterior to the renal arteries.
- The left renal vein is longer and can be compressed by superior mesenteric artery, which crosses over it.
Nerves/ lymphatics:
- Drained by lateral aortic (lumbar) nodes around the origin of the renal artery.
- Efferent (motor) innervation: sympathetic branches T10-L2.
- Afferent (sensory) innervation/pain: least splanchnic nerve (sympathetic T12), referred pain: flanks (in the
back between the last rib and the iliac crest).
Coverings of the kidney:
- Deep to superficial:
Fibrous capsule: directly covering the kidney.
Perinephric/perirenal fat, around kidneys and suprarenal/adrenal glands.
Extraperitoneal fascia/ renal fascia (Gerota’s fascia): encloses kidneys as well as suprarenal/
adrenal glands and hilum, a membranous layer. Fuses with transversalis fascia, fascia covering
the diaphragm, quadratus lamborum fascia, and psoas major fascia.
Paranephric/pararenal fat: not a continuous layer, posterior and posterolateral to each kidney.
- Ptosis of the kidney: happens in conditions such as (starvation, diabetes, cancer) when the paranephric &
perinephric layers of fat covering the kidney go away, so the kidney drops = ptosis.
Calculations:
1. Filtration rate (mg/min) = glomerular filtration rate (ml/min) x plasma concentration (mg/mL) .
2. Urinary excretion rate= Us (urine concentration) (mg/mL) x V (urine flow rate) (mL/min)
3. Urinary Excretion Rate of Substance = Filtration Rate + Secretion Rate – Reabsorption Rate.
o Urinary excretion rate of substance= Filtration Rate (creatinine)
o Urinary excretion rate of substance= Filtration Rate- Reabsorption Rate (sodium)
o Urinary excretion rate of substance= Filtration Rate- Reabsorption completely (glucose)
o Urinary excretion rate of substance= Filtration Rate + secretion (Organic acids and bases)
4. Renal Plasma Flow RPF= Us (urine concentration) (mg/mL) x V (urine flow rate) (mL/min)/ Ps (plasma
concentration) (mg/mL)
PAH: RPF= 5.85 x 1 / 0.01 = 585 ml/min
Correction factor is 0.9
∴ RPF=585/0.9 = 650 ml/min
5. Filtration Fraction = GFR/ RPF
6. Henderson-Hasselbalch equation: pH = 6.1 + log [HCO3- / 0.03 x PCO2]
7. Plasma anion gap (mEq/L ) = [Na+] – [HCO3 –] – [Cl-]
8. Q = ∆ P /R
∆ P = difference in hydrostatic pressure between artery and vein, R= resistance.
9. GFR (ml/min) = net filtration pressure x filtration coefficient K f
