What are the three major anatomical regions of the kidney?

Renal Cortex

Renal Medulla (Pyramids)

Renal Pelvis (Center)

Trace the route that an erythrocyte would take as it passes from the renal artery, through the vasculature of the kidney, and then back into the renal vein. Include all vessels mentioned in class.

The renal corpuscle is the glomerulus (network of blood vessels)+ the bowman's capsule (extension of the nephron that encapsulates the glomerulus) surrounding it.

It functions as the blood filtering component of a nephron

Trace the path that an individual water molecule would take as it diffuses from the glomerulus, into Bowmen’s/glomerular capsule, through the tubule system, and into the renal pelvis. 

List all tubule structures encountered along the way.

Slide 5

water molecule comes out of the blood in the efferent arteriole, into the glomerulus, into the bowman's capsule, filtrate -> proximal convoluted tubule, descending limb of the loop of Henle, acending limb of the Look of Henle, distal convoluted tubule, collecting tubule, collecting duct ->renal pelvis-> ureter

Explain the roles of fenestrated endothelium, basement membrane, and podocytes during the process of filtrate formation.

What are the major components of the filtrate within Bowman’s capsule?

Fenestrated endothelium filters RBCs (why you don't or shouldn't piss blood)

Basement membrane filters out large proteins

Podocytes ultrafilter supersmall proteins

The resultant Filtrate in the bowman's capsule consists of:

H2O

Na+, Cl-, K+

H+

Urea

Glucose

Some smaller proteins

Structure of the Capillaries in the Glomerulus

(inside to outside)

Fenestrated endothelial cell

basement membrane

Podocytes

6. An individual has a CO = 6 L/min.

 Estimate the values of a.) renal flow

and b.) renal plasma flow.

Renal flow= 20% CO (6x.2=1.2L/min)

Renal Plasma Flow= 55% CO (6x.55=3.3L/min)

 The “filtration pressure” in the renal corpuscle is determined by what two opposing forces (pressures)?

Hydrostatic Pressure (push of pressurized liquid plasma)

Osmotic Pressure (the pull of plasma proteins)

Glomerular filtration rate (GFR) is controlled by both extrinsic and intrinsic mechanisms.

Explain the functional significance of why low mean arterial pressure causes an increase in GFR and whether the mechanism represents intrinsic or extrinsic regulation.

At low MAP, afferent arterioles dilate which decreases resistance and increases renal flow which increases Glomerular filtration rate. If you have too hi of a filtrate volume then you will constrict the afferent arterioles to decrease GFR.

This represents an intrinsic autoregulation mechanism

In the proximal convoluted tubule, 66% of the filtrate is reabsorbed in the form of isosmotic fluid. 

a. What molecules and ions are reabsorbed and why is this the only place in the tubule where reabsorbed fluid is said to be isosmotic?

Ions reabsorbed are Na+, Cl-

It is said to be isosmotic because there is a similar osmolarity between filtrate and fluid outside of nephron.

Requires osmosis and active transport

Osmosis plays a role in the transport of water from the proximate convoluted tubule. Yet, the tubule, intersitial fluid, and blood plasma all remain at about 300 mOsm solution.

Explain this apparent contradiction in physiological rules that we have learned to date.

Loop of Henle

a. Prepare a diagram of the descending and ascending limbs and label the changes in interstitial osmolarity as the tubule extends from the cortex into the medulla.  

b. Indicate in what region is water reabsorbed and in what region are Na⁺, K⁺ and Cl^-.

c. Explain why the water and ions were reabsorbed in the regions indicated in “b”. 

d. Explain how the arrangement of vasa recta and the loop of Henle are arranged as a countercurrent exchanger? 

As you get deeper in the kidney, the Osm increases (300-400-600-900-1200)

descending limb= water recovery

ascending limb=ion recovery

Filtrate and blood flows in opposite directions which maximizes exchange

Vasa Recta are peritubular caps that surround the LOH  and serve the cells of the LOH by absorbing water/ions around the LOH

Distal Convoluted Tubule, Collecting Tubule, and Collecting Duct

 What percentage of the original filtrate has not been reabsorbed by the time that it has reached the distal convoluted tubule?

 What active transport mechanism allows the obligatory reabsorption of ions in the distal convoluted tubule?

What ions or molecules are regulated in the collecting tubule?

15% of original filtrate reaches distal tubule

Greater or lesser quantities of ions and water are reabsorbed through hormonal control

K+, H+, HCO3-, are regulated in the collecting tubule

.If the interstitial fluid around the collecting tubule has an osmolarity of 300 mOsm, explain why water readily leaves the filtrate? 

What hormone is responsible for the regulation of water in the collecting tubule?

Water readily leaves filtrate because of ADH makes CT and CD permeable to H2O

ADH= a neurohypophyseal hormone

Countercurrent exchange (vaso recta) as soon as h2o in the descending or ions in the ascending leave the loop, they are reabsorbed immediately by the vasorecta. THere is a completely equal exchange happening. =no change in the osmolarity in the cortex

Collecting duct is permeable to urea, so urea diffuses out and helps maintain high osmolarity in the deep kidney

ADH

 What are the approximate percentage values for water among the cytosol, interstitial fluid, and blood plasma?

What are the major intracellular and extracellular cations and anions?

Cytosol: h20=67%

Major Cation: K+

Major anion: proteins

Osmolarity: 300 mOsm

ISF/BloodPlasma : H20 = 33%

Major cation: Na+

Major anion: Cl-

Osmolarity : 300 Osm

ADH

Why is it that, during dehydration, water loss occurs mainly within the interstitial fluid rather than in the intracellular or the blood plasma compartments?

ADH

What is the cellular mechanism by which ADH increases the permeability of the tubule? 

In which tubule regions would you find ADH receptors?

ADH (1st mess) comes out of capillaries and starts cAMP (2nd Mess) cycle, which allows a vesicle to release water channels to the membrane, which allows water to enter

descending limb of the LOH

What are the values for ADH under normal hydration, diuresis, and anti-diuresis?

Normal Hydration: 1L urine a day

Diuresis: 300ml Conc urine (high ADH)

Anti-diuresis: 30 L dilute urine (low ADH)