1. Remove metabolic waste products

2. Remove foreign chemicals and bioactive substances

3. Regulate water and electrolyte balance

4. Gluconeogenesis

5. Produce hormones and enzymes

Synthesis of glucose from noncarbohydrate sources (from A.A and glycerol)

Most occurs in liver but alot occurs in the kidneys during a fast.

1. Erythropoietin

2. Renin

3. 1, 25 dihydroxyviatim D

Major Calyx

Minor Calyx

Papilla

Minor Calyx

1. Renal Corpuscle

2. Long Tubule

What makes up the renal corpuscle?

1. Capillary endothelium

2. Thick basal membrane

3. single layer of epithelial cells 

Glycoproteins

Proteoglycans

1. Descending thin limb

2. Ascending thin limb

3. Thick ascending limb

4. Macula densa

Afferent Arteriole

Efferent Arteriole

They are categorized by the position of their renal corpuscle.

1. Juxamedullary

2. Midcortical

3. Superficial

1. Granule cells

2. Extraglomerular mesangial cells

3. Macular densa cells

Juxtaglomerular cells

secrete the hormone renin

1. Glomerular filtration

2. Tubular secretion

3. Tubular reabsorption

For any given substance:

Amount excreted =

What is the typical hematocrit?

What about typical renal blood flow?

Hematocrit = 0.45 or 45%

RBF = 1.1 L/min  (20% of CO)

125 mL/min

(~ 20% of all plasma entering the glomeruli ends up filtering into Bowmans space)

1. Mean pressure in the renal artery vs. mean pressure in the renal vein

2. Resistance of the renal arterioles

19%

Radius

Series

Additive

1. Molecular radius/shape

2. Electrical charge

What size molecule can be free pass through the filter?

Give example

<7000 Da

Small ions, gluc, urea, A.A. and many hormones

What size molecules are almost totally blocked by the filter?

Give an example.

> 66, 000 Da

Albumin

Only above a certain size, then charge comes into play.

Since anions are still small in size, they can get filtered even with their - charge.

1. Hydraulic permeability of the capillaries

2. Surface Area of the capillaries

3. Net Filtration pressure acting across them

2 hydrostatic pressures (P) and 2 oncotic pressures (∏)

1. P_GC

2. P_BC

3. ∏_GC

4. ∏_BC

Why can we simplify the GFR equation to:

GFR = Kf (P_GC - ∏_BC - ∏_GC)

and what is Kf?

Because the ∏_BC is basically 0 due to the very low protein content in the Bowmans space. 

Kf = the filtration coefficient which is the hydraulic premeability x Glomerular S.A.

1. Glomerular disease

2. Drugs

3. Constriction or relaxation of glomerular mesangial cells

Surface Area

Kf

GFR

Decrease

Low

High

1. Fractional changes in arterial pressure are magnified in NFP and GFR

2. GC are at risk for hypertensive damage during periods of exertion

As MAP increases, the smooth muscle in the arteriole walls stretch, leads to constriction, which increases vascular resistance.

Systemic mechanism

1. Macula densa cells respond to level of Na+ in distal tubule

2. Na+ is high if GFR is high

3. High Na+ releases 'transmitter agents' from the JGA.  These lower the GFR

1. It causes constriction of the afferent arteriole

2. Causes contraction of the glomerular mesangial cells, thus decreasing the S.A. of the capillaries thus Kf.

Cs = Us x V/ Ps

Cs = clearance of S

Us = Urine [M+] of S

V = Volume of urine per unit time

Ps = Plasma [M+] of S

1. Freely filterable

2. Not Reabsorbed

3. Not secreted

4. Not synthesized by the tubules

5. Not metabolized by the tubules

Inulin

Fructose

We use creatinine

It doesnt meet the 5 criterias; it is freely filtered, not reabsorbed but is secreted by the tubules in small amounts

1 mg/dL

Indicates potential renal dysfunction

What is fractional clearance?

What does it mean if it = 1.0?

Cx/Cin

It should = 1.0

And it means that X is handled exactly like inulin; it has no reabsorption or secretion

If you have a fractional clearance < 1.0 then X is _____________________

If you have a fractional clearance > 1.0 then X is __________________.

Reabsorbed to some extent

Secreted to some extent

1. Transcellular Reabsorption

2. Paracellular Reabsorption

1. transport maximum limited systems (Tm)

2. Gradient limited systems

Into the peritubule capillaries

And occurs when the hydrostatic and oncotic forces favor reabsorption

GFR

Filtered load of water and non- waste plasma solutes

Na+

Renal Medulla

Concentrating urine

0.4 L/day; 25 L/day

(This is the obligatory water loss)

Freely filtered

Reabsorbed

Secretion

Osmosis

Na+ reabsorption

1. Creates Osmolarity gradient that drives water out of the tubules.  This dilutes the tubular lumen and creates a [M+] gradient for reabsorption of other substances.

2. Achieves reabsorption of many organic nutrients, PO4 and SO4 by cotransport

3. Achieves secretion of H+ by countertransport (these are required for reabsorption of HCO3-)

4. Achieves reabsorption of Cl- by indirect cotransporter

ADH

Antidiuretic hormone

1%

1400 mOsm/L

285-300 mOsm/L

H2O

Salt

H2O

H2O

Na+

Hypoosmotic

(more dilute)

Small, 60 Da

Water soluble

Polar

Not very membrane permeant

Free filtered

Aldosterone

(steriod hormone made by the adrenal cortex)

1. arterial blood pressure

2. sympathetic input to the JGA

3. Na+ content in the distal tubule as sensed by cells of the macula densa

reduce

inhibitory interneuron

Decrease; Increase

(and vice versa)

1. Increased activity of basolateral Na/K ATPase

2. D.P. of cells in the adrenal cortex, and subsequent release of aldosterone.