Renal Lecture 1

Question 1

What three things do the kidneys regulate?

Answer 1

1. Body fluid osmolality and volumes
2. Electrolyte balance
3. Acid-base balance

Question 2

What other function does the kidney have?

Answer 2

Excretion of metabolic products and foreign substances and production and secretion of hormones.

Question 3

What inorganic substances do the kidneys regulate?

Answer 3

Na+, K+, Cl-, HCO3-, H+, Ca2+ and Pi (inorganic phosphate)

These are electrolytes.

Question 4

How do kidneys regulate pH and why?

Answer 4

The pH is maintained by buffers within the body fluids and coordinates it along with lungs and liver. Since many metabolic functions of the body are sensitive to pH, the pH must be maintained within narrow limits.

Question 5

What waste products to the kidneys excrete?

Answer 5

Urea, uric acid, creatine, end products of hemoglobin metabolism and metabolites of hormones. Thus, also plays a role in hormonal concentrations.

Question 6

How are the kidneys important endocrine organs?

Answer 6

Produce and secrete renin, calctriol and erthropoietin

Question 7

What does renin do?

Answer 7

Activates the renin-angiotensin-aldosterone system, which helps regulate blood pressure and Na+ K+ balance.

Question 8

What does calcitriol do?

Answer 8

It is a metabolite of vitamin D3 and is necessary for the normal absorption of calcium by the GI tract and for its deposition in bone.

Question 9

What does erythropoietin do?

Answer 9

It stimulates RBC formation by the bone marrow.

Question 10

What is GFR?

Answer 10

Glomerular filtration rate

Question 11

What is ESRD?

Answer 11

End-stage renal disease

Question 12

Point at which ureter, renal artery, and renal vein meet

Answer 12

Hilium

Question 13

Glomerulus

Answer 13

a cluster of capillaries around the end of a kidney tubule, where waste products are filtered from the blood.

Question 14

Peritubular capillary

Answer 14

tiny blood vessels that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron.

Question 15

Vasa recta

Answer 15

are a series of straight capillaries in the medulla, parallel to loop of henle

Question 16

Renal corpuscle

Answer 16

Glomerulus + Bowman’s capsule

Question 17

Bowman’s capsule

Answer 17

a capsule-shaped membranous structure surrounding the glomerulus of each nephron in the kidneys of mammals that extracts wastes, excess salts, and water from the blood.

Question 18

What is the first step in urine formation?

Answer 18

Ultrafiltration of plasma by glomerulus - plasma is cell-parts and protein free after being filtered

Question 19

Components of the filtration barrier

Answer 19

Fenestrated capilary endothelium, basement membrane, slit diaphragm

Question 20

What types of species are best filtered?

Answer 20

Small, positively charged species/

Question 21

What happens to filtration if negative charge on glomeral wall is reduced?

Answer 21

Filtered based on size (small=better) alone; not charge.

Question 22

Heparin Sulfate

Answer 22

HS is the molecular source of the negative charge on the glomerular basement membrane

Question 23

Glomerular capillary starling forces

Answer 23

Drive fluid from the lumen of glomerular capillaries across the filtration barrier into Bowman’s space.
Pnet=(glomerular capillary pressure + oncotic pressure of Bowman’s space) - (pressure of Bowman’s space + oncotic pressure of glomerular capillary)

Question 24

Glomerular filtration rate

Answer 24

GFR=(Kf) * Pnet
Kf=ultrafiltration coefficient
Can substitute in Starling forces equation for Pnet

Question 25

Constriction of afferent arteriole before glomerulus

Answer 25

Decreased Pgc, decreased GFR, decreased RBF (renal blood flow)

Question 26

Constriction of efferent arteriole after glomerulus

Answer 26

Increased Pgc, increased GFR, decreased RBF

Question 27

Dilation of efferent arteriole

Answer 27

Decreased Pgc, Decreased GFR, Increased RBF

Question 28

Dilation of afferent arteriole

Answer 28

Increased Pgc, Increased GFR, Increased RBF

Question 29

Increased GFR can be from...

Answer 29

``` Vasodilators on afferent arteriole: -prostaglandins -kinins -low dose dopamine -ANP -NO Vasoconstrictors on efferent arteriole -Angiotensin II (low dose) ```

Question 30

Decreased GFR can be from...

Answer 30

``` Vasodilators on efferent arteriole -Angio II blockade Vasoconstrictors on afferent arteriole -Angio II (high dose) -Noradrenaline (SNS) -Endothelin -Adenosina -Vasopressin -IPG blockade ```

Question 31

Describe myogenic response of afferent arterioles

Answer 31

- An increase in BP stretches the smooth muscles of the afferent arteriolar wall - Stretch sensitive Ca2+ channels are opened,, leading to Ca2+ influx and muscle contraction - Vasoconstriction minimized increase in Pgc - A decrease in BP reduces the tonic level of afferent arteriolar smooth muscle contraction - Vasodilation will sustain Pgc

Question 32

What cells make up the juxtaglomerular apparatus

Answer 32

Macula densa cells and granular cells

Question 33

Describe tubuloglomerular feedback

Answer 33

GFR increase -> flow through tubule increase -> flow past macula densa increase and so NaCl content increase -> paracrine from macula densa to afferent arterial -> afferent arteriole constricts -> resistance in afferent arteriole increase -> hydrostatic pressure in glomerulus decrease, GFR decrease

Question 34

Principle of Renal Clearance

Answer 34

Amount filtered = amount excreted (clearance of solute) x (plasma concentration of solute) = (urine concentration of solute) x urine flow rate or, Cx*[Px]=[Ux]*V

Question 35

Clearance of inulin

Answer 35

Equivalent to glomerular filtration rate (GFR), the volume of plasma filtered in one minute

Question 36

Does inulin get more absorbed or more secreted?

Answer 36

Neither! Inulin goes into the afferent arteriole, is filtered through the glomerulus, travels down tubular system and is excreted with urine. Filtered inulin = excreted inulin.

Question 37

Describe the stages of kidney disease in terms of creatine clearance and plasma creatine levels.

Answer 37

Normal GFR is high (normal) and plasma creatine level normal (low). Mild kidney disease GFR drops slightly and plasma creatine level increases slightly. Moderate kidney disease creatine clearance declines further and plasma creatine begins to grow expoentially. Severe kidney disease creatine clearance very low and creatine levels spike through the roof.

Question 38

Clearance approach to measure GFR

Answer 38

Clearance=[U]*V/[P]

Question 39

Creatine-based estimation of GFR

Answer 39

creatine clearance = [140-age]*weight[lbs]/[serum creatine]