Renal 1: Functional Organization of the Kidney

Plasma clearance

Cleans the bodily fluids of non-volatile end products (e.g. urea and creatinine)

Excretory, regulatory (homeostasis), synthesis of hormones

Main functions of kidney

Extracellular fluid volume and osmolality, electrolyte composition of the bodily fluids and osmolality, blood pressure, acid-base balance

What do the kidneys regulate?

Renin (RAA), erythropoietin (synthesis of RBCs), vitamin D3 (calcitriol), prostaglandins

What hormones do the kidneys synthesize?

Everything except cells and large proteins

What do the kidneys filter?

Water, Na+, Cl-, glucose, amino acids, urea, Ca+, Mg+, phosphate, lactate

What do the kidneys reabsorb?

Organic acids, organic bases, sometimes K+

What can the kidneys secrete?

High pressure and flow rate for filtration

Effect of having a short renal artery directly from the aorta

Sympathetic

What is the only type of innervation of renal tubules and blood vessels?

NE

Major neurotransmitter of kidneys

Alpha-1

Major receptor of kidneys

Two, two, in series

The kidney has __ arterioles and __ capillary beds ___.

Maintain pressure, fine control of filtration rate

Effects of the kidney having two arterioles

Co-transporters, exchangers, channels

What is on the apical side of the proximal tubule cell?

Na+/K+/ATPase

What is on the basolateral side of the proximal tubule cell?

Na+/K+/ATPase

Force generator for absorption in proximal tubule

Retaining or excreting water and salt, H+, and bicarbonate

How can the regulatory functions of the kidney be achieved?

Sodium

The kidney’s ability to reclaim ___ is one of its most important functions.

• If it fails, fatal volume depletion will occur in minutes.

Kidney handling of Na+

What determines the body’s net Na+ balance and thus the total body volume?

Juxtaglomerular apparatus

Monitors and regulates tubular reclamation and glomerular filtration

Regulates blood pressure and fluid balance

What does the renin angiotensin aldosterone system (RAAS) do?

Cortical nephron

1. 80-85%

2. Loops into outer medulla

3. Shorter PCT; salt-losing

Juxtamedullary nephron

1. 15-20%

2. Loops into inner medulla

3. Large perfusion (e.g., vasa recta)

4. Large GFR

5. Longer PCT; salt-conserving

6. Conserves water

7. Concentrate urine

Erythropoietin

Synthesizes RBCs

Renal erythropoietin-producing cells

What do REP cells stand for?

Rate of intake, rate of production

Mass balance in the whole body:

Rate of excretion = ___ + ___

Glomerular filtration rate (GFR)

How much fluid passes into Bowman’s space per unit time (e,g., 180 L/day)

Filtered fraction

Fraction of total fluid arriving at glomerulus that gets filtered

Para-aminohippuric acid

What does PAH stand for?

Tubular maximum (Tmax)

1. Maximum resorptive or secretory capacity of the tubules

2. Rate when transport becomes saturable and constant

   1. Difference between linear portion of filtered load rate and excretion rate

Renal threshold

Plasma concentration at which Tmax is reached

Para-aminohippuric acid (PAH)

Diagnostic agent useful in medical tests involving the kidneys

Used to measure renal plasma flow