Renal and Urinary System + Renal Circulation

How does the renal artery branch into the efferent arteriole

Renal artery → Segmental artery → Interlobar artery (at medullary column) → Arcuate artery → Interlobular artery (at cortex) → Afferent arteriole → Glomerulus → Efferent arteriole

What is the peritubular capillary

Efferent arteriole wrapping around proximal and distal tubules → Mixed blood

What is a glomerulus

Capillary bed

What is the renal corpuscle

Glomerulus + Bowman’s capsule

What is a nephron

Corpuscle + Tubules

What is the difference between the cortical and juxtamedullary

Juxtamedullary nephron is found in the MEDULLA, cortical nephron in cortex

Where can the renal corpuscle be found

In the renal cortex ONLY

Juxtamedullary nephron function

Concentrate urine in medulla

Cortical nephron function

Dilation of urine

Function of proximal and distal convoluted tubules

Proximal → Reabsorb solutes; distal → Electrolyte modifications

How is urine collected from each pyramid to the ureter

Collecting duct combine at the minor calyx → Many minor calyx join into major calyx → Renal pelvis → Ureter

At the UVJ, what is the importance of the ureteral tunnel length

Long tunnel will be closed when bladder expands from increased pressure; when the tunnel is short and unangled it will remain open → Reflex occurs when bladder is full

What are the sections of the urethra in MALES

Prostatic → Membranous → Bulbous → Penile (pendulous)

What is the distribution of blood flow to the kidneys and why is it so high

22% of CO → Needs to supply plasma for filtration and fluid regulation

How does RBF and O2 consumption affect filtration

Low RBF → Low GFR (less Na is filtered and reabsorbed) → Less O2 consumed

Which area of the kidney has the most vascular resistance

Interlobular arteries, afferent arterioles, efferent arterioles

Which part of the kidney receives the most blood

Cortex (99%) > > > Medulla (1%)

What systems are autoregulatory to control RBF

Myogenic mechanism and tubuloglomerular feedback

What is myogenic mechanism of GFR

Increased AP = constriction, decreased AP = relaxation

What is Tubuloglomerular feedback mechanism

Macula densa in juxtaglomerular complex detect decreased NaCl → Dilation of afferent arterioles AND renin release

What is the RAAS pathway

Renin → Renin substrate → Angiotensin 1 → Goes to lung + converting enzyme → Angiotensin II (active) → Vasoconstrict/renal retention → Increased arterial pressure

What could happen if the efferent arteriole was constricted

GFR increase → RBF decrease from high resistance BUT macula densa will increase overall pressure AND expand afferent → Final RBF change is almost 0

Why should ACEI NEVER be given to RA stenosis patients

Decrease BP BUT efferent arteriole will dilate → GFR drops → Renal failure

Function of NE, Ep, ET

Constrict and decrease blood flow

Function of angiotensin II

Constrict efferent → Prevent decrease in glomerular hydrostatic pressure and GFR + reduce RBF

Function of prostaglandin, Bradykinin and endothelial NO

Decrease renal vascular resistance and increase renal blood flow

What is the effect of ANP on renal system

Dilates afferent and constricts efferent → GFR increase → Happens ONLY in volume overload to flush out excess fluid

In renal artery stenosis, what is the compensatory effect

Perfusion low = renal pressure low → Juxtaglomerular cells release renin → RAAS system → Angiotensin II constrict efferent → Pressure increase → GFR is maintained