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Filtration

Secretion

Reabsorption

Test # 3 on Monday

Covers only Cardiovascular and Respiratory.

Some short answer questions and draw and label questions.

Lab next week: Urinalysis!

1 Hrbefore LabEmpty bladder; note time

Beginning of Lab:Collect Urine, measure Volume and titrate [NaCl]

Drink Test Beverage in 5 minutes or less

At 30 min intervals, collect urinemeasure V and [NaCl]

30 min 30 min30 min30 min30 min

Drink plenty of water the day of lab;Avoid coffee, caffeine, salty foods

60 min

800 ml tap water or800 ml tap water + 7 g NaCl or 80 ml tap water + 7 g NaCl

Urinalysis Lab

During intervals, diagram the negative feedback loops.

Renal Physiology

• Structures of the kidney• Four fundamental renal mechanisms

– Filtration– Reabsorption– Secretion– Metabolism

• Functions of the kidneys– Homeostasis

• Fluid balance (blood pressure)• Electrolyte balance (blood pressure, membrane excitability)• Acid-base balance (in concert with lungs)

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Special terms• Filtration: movement of fluid from blood into

the lumen of the nephron (renal tubule)

• Reabsorption: the movement of specific compounds from the tubular lumen back into the blood (peritubular capillaries)

• Secretion: the transport of specific compounds from blood into the tubular lumen

• Excretion: elimination from the body in urine

Glomerular Filtration Rate = 120 ml/ min

Table 14.02

Lab: Extra 800 ml intake!

Sidebar: some desert animals never drink and must obtain all their water in the diet.

Table 14.04

Lab: Extra 7 g intake!

Kidneys are source of 3 hormones: Renin, EPO, and Vit D.Kidneys are targets of 3 hormones: ADH, Aldosterone, ANH

Topics discussed: cortex, medulla, kidney stones, micturition (detrussor, internal and external urethra sphincters and innervation), incidence of bladder infections by gender, urethral sphincters

Tubular fluid vs urine

Nephron = tubule

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Renal artery = One way in. Two ways out of kidney (renal vein or ureter)

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Enlargedon nextpage

Fig. 14.02a

Renalcorpuscle

Juxtamedullary and Cortical Nephrons

Peritubular Capillaraies and branch thereof called vasa recta

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A Portal System

The nephron

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Fig. 14.03a

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Fig. 14.05Glomerular Filtration Rate is 120 ml/min = 180 L/day

Three stimuli for secretion of renin from JGC

Figure 14.03Ultrafiltrate of plasma enters Bowman’s space

Composition same as plasma except no formed elements and no proteins and no substances bound to proteins

Fig. 14.08

variable

Starling Forces

Fig. 14.09

Ways to alter GFR

What happens during hemorrhage?

What substances can cause this constriction?

Fig. 14.02a

Figure 14.10

Membrane proteins are segregated into apical (luminal) and basolateral membranes.

reabsorption

S e c r e t i o n

metabolismAmino acid glucose

Reabsorption and secretion in proximal tubule is NOT under hormonal control.Primary active transport of Na+ establishes a gradient for reabsorption of glucose, amino acids, etc.

Reabsorption and secretion in DCT & CCD is under hormonal control.Hormones that act here: ANH, ADH, Aldosterone.

Here, reabsorption of Na+ is linked to the secretion of K+.

Effect of ADH: insertion of more aquaporins in th the membranes

Effect: Increase H2O reabsorption

Figure 14.31Normally, all filtered bicarbonate is “reabsorbed”

Figure 14.10

Membrane proteins are segregated into apical (luminal) and basolateral membranes.

reabsorption

secretionmetabolism

Amino acid glucose

Filtration is controlled by aa and ea diameters!

Consider a substance that in filtered only, no reabsorption, no secretion.

Excretion of this substance = GFRClearance of this substance = GFR

• Clearance = volume of plasma from which a substance is completely removed (cleared) by the kidneys per unit time.

• Clearance of Inulin is 120 ml/min

• Cinulin or Ccreatinine = Glomerular Filtration Rate

Filtration + complete Secretion

Ex: Para AminoHippurate (PAH)

Measure Renal Plasma Flow

Filtration + partial reabsorption

Ex: SodiumEx: Water

Filtration + 100 Reabsorption

Ex: GlucoseEx: Amino Acids

Renal Handling of Substances

• Clearance = volume of plasma from which a substance is completely removed (cleared) by the kidneys per unit time.

• Clearance of Inulin is 120 ml/min

• Cinulin or Ccreatinine = Glomerular Filtration Rate

• If C x is greater than GFR ( which is Cinulin) then that substance undergoes NET TUBULAR SECRETION

• If C x is less than GFR ( which is Cinulin) then that substance undergoes NET TUBULAR REABSORPTION

A little more on Clearance:

Clearance of glucose = 0 ml/min which means….

Clearance of X = 120 ml/min which means….

Clearance of antibiotic XXX = 500 ml/min which means…

Calculating clearanceClearance of s = Urine concentration of s X Urine Volume

Plasma concentration of s

Special cases: Clearance of

•Inulin and creatinine (filtered only; use to measure Glomerular Filtration Rate.)

•Para Amino Hippurate (filtered and completelysecreted, use to measure Renal Plasma Flow)

“24 hour urine catch” + blood sample