Page 625 - First Aid for the USMLE Step 1 2020, Thirtieth edition [MedicalBooksVN.com]_Neat

Renal ` RENAL—ANAtomy Renal ` RENAL—PhysioLogy SeCTIOn III 581

Course of ureters Course of ureter A : arises from renal pelvis, Water (ureters) flows over the iliacs and under
travels under gonadal arteries Ž over common the bridge (uterine artery or vas deferens).
A
iliac artery Ž under uterine artery/vas deferens
(retroperitoneal). Median Ureter
umbilical
Gynecologic procedures (eg, ligation of ligament Vas
uterine or ovarian vessels) may damage ureter Uterine deferens
artery
Ž ureteral obstruction or leak. (in female) (in male)
Bladder contraction compresses the intravesical
ureter, preventing urine reflux. Detrusor
muscle
Blood supply to ureter: Ureteral orifice
ƒ Proximal—renal arteries Trigone
ƒ Middle—gonadal artery, aorta, common and Internal urethral orifice Prostate
internal iliac arteries
ƒ Distal—internal iliac and superior vesical
arteries
3 common points of ureteral obstruction:
ureteropelvic junction, pelvic inlet,
ureterovesical junction.

` RENAL—PhysioLogy

Fluid compartments

+
Body mass: 70 kg HIKIN’: HIgh K INtracellularly.
Total body water (TBW) Non water mass (NWM) 60–40–20 rule (% of body weight for average
60% of body mass = 42 kg ≈ 42 L 40% of body mass = 28 kg person):
ƒ 60% total body water
+
2+
1/3 Extracellular fluid (ECF) ~ 14 kg (20% of 70 kg) Interstitial fluid = 75% ECF ≈ 10.5 L ≈ 10.5 kg ƒ 40% ICF, mainly composed of K , Mg ,
organic phosphates (eg, ATP)
ƒ 20% ECF, mainly composed of Na , Cl ,
–
+
Plasma = 25% ECF ≈ 3.5 L ≈ 3.5 kg
HCO , albumin
–
RBC volume ≈ 2.8 L Blood volume ≈ 6 L Normal Hct = 45% Plasma volume can be measured by
3
radiolabeling albumin.
Extracellular volume can be measured by inulin
2/3 Intracellular fluid (ICF) ~ 28 kg (40% of 70 kg) Hct (%) ≈ 3 [Hb] in g/dL Plasma volume = TBV × (1 – Hct). 2
or mannitol.
Serum osmolality = 285–295 mOsm/kg H O.

Glomerular filtration Responsible for filtration of plasma according to Charge barrier—all 3 layers contain ⊝ charged
barrier size and charge selectivity. glycoproteins that prevent entry of ⊝ charged

A Composed of: molecules (eg, albumin).
Endothelial ƒ Fenestrated capillary endothelium Size barrier—fenestrated capillary endothelium
cell pore ƒ Basement membrane with type IV collagen (prevents entry of > 100 nm molecules/blood
chains and heparan sulfate cells); podocyte foot processes interpose with
GBM ƒ Visceral epithelial layer consisting of glomerular basement membrane (GBM);
FP
FP podocyte foot processes (FPs) A slit diaphragm (prevents entry of molecules
GBM > 50–60 nm).

FAS1_2019_14-Renal.indd 581 11/7/19 5:42 PM