A&p 2 Urinary System Nicole Berman Part:1

Front 1

• Glomerular Filtration:
o Name / describe what is formed:

Back 1

filtrating blood plasma into mostly protein-free filtrate

Front 2

• Tubular Reabsorption:
o What happens to reabsorbed substances?

Back 2

Substances are reabsorbed into the blood mainly in the Proximal Convoluted Tubule (99%)

Front 3

• Tubular Secretion:
o What happens to secreted substances?

Back 3

Secreted substances go into the renal tubule from the Peritubular Capillaries and is excreted in the urine

Front 4

➢ Of these substances – Water, Protein, Glucose, Urea, Creatinine – which are . . .
• Mostly reabsorbed / returned to blood?
• Mostly excreted in urine?
• About half excreted and half reabsorbed?

Back 4

water, protein, glucose
creatine
urea

Front 5

• Blood hydrostatic pressure:
• Capsular hydrostatic pressure:
• Blood colloid osmotic (oncotic) P:
• Capsular oncotic pressure:

Back 5

pushes water-->filtration membrane 55mm
Filtration membrane <--Pressure by fluid in the Capsular Space 15mm
Pressure from plasma proteins pulling on water to keep it in the capillary 30 mm

when protein escapes the membrane

Front 6

• What is the net filtration equation? NFP =

Back 6

Promoting Filtration pressure - Opposing filtration Pressure

Front 7

➢ What is the glomerular filtration rate (GFR)? Why is it important? How does it relate to NFP?

Back 7

The amount of filtrate formed each minute
Directly relates (GFR ^ = NFP ^)

Front 8

➢ Generally, describe the relationships between: BP, Renal Blood Flow (RBF), NFP and GFR:

Back 8

^ GFR = ^ NFP = ^ urine output = V blood pressure = V renal blood flow , and vice versa

Front 9

➢ What are the two ways to regulate GFR?

Back 9

Constriction and Dilation of the Arterioles
Contraction and Relaxation of Mesangial Cells in the glomerulus

Front 10

• Renal Autoregulation:

Back 10

Intrinsic control maintains GFR
The kidneys maintain a relatively stable pressure despite changes in systemic BP

Front 11

o Myogenic contraction:

Back 11

Stretching in the glomerular capillaries due to increased renal blood pressure makes myogenic contraction of smooth muscle cells in the Afferent Arterioles= reduces RBF = reduced GFR

When renal BP is too low, smooth muscle in the afferent arteriole will relax (dilate) allowing more blood to flow in

Happens within seconds

Front 12

o Tubuloglomerular feedback:

Back 12

Above normal GFR due to increased systemic blood pressure causes filtered fluid to flow more rapidly through the tubules
Results in less reabsorption of Na+, Cl-, and water in the PCT and LoH
Macula densa cells detect the increased presence of these in the tubular fluid and inhibit the release of NO (nitric oxide), a vasodilator, from the juxtaglomerular apparatus
As a result, the afferent arteriole constricts reducing blood flow to the glomerulus and decreasing NFP and GFR

Front 13

• Neural Regulation:

Back 13

supplied by sympathetic ANS fibers that release norepinephrine causing vasoconstriction

Front 14

Hormonal Regulation
o Angiotensin II:
o Atrial Natriuretic Peptide (ANP):

Back 14

a potent vasoconstrictor of both afferent and efferent arterioles (reduces GFR).

ANP causes the mesangial cell in the glomerulus to relax, increasing the surface area for filtration (increases GFR); triggered by the cardiac atria stretching due to a sudden increase in BP

Front 15

➢ Which mechanism dominates at rest?

Back 15

autoregulation

Front 16

Why is Homeostasis important?

Back 16

If GFR is Too high and needed substances may pass to quickly through the tubules to be reabsorbed adequately
Too low and nearly all the filtrate may be reabsorbed and certain waste products may not be adequately excreted

Front 17

What is Renal Clearance?

Back 17

the volume of plasma the kidney clears per unit time

Front 18

Renal Clearance:
what nephron functions is it dependent on?
why is it important?
how is it calculated?

Back 18

secretion from the peritubular capillaries to the nephron, and reabsorption from the nephron back to the peritubular capillaries

Useful in determining how fast the kidney is able to clear the blood of a substance so doctors can determine dosage and administration of drugs based on how long it takes the kidney to excrete it

Amount Excreted = Amount Filtered + Amount Secreted – Amount Reabsorbed