Physiology Chapter 18: Urinary System

Front 1

Functions of the Urinary System (5)

Back 1

-Regulate plasma ionic composition
-Regulate plasma volume
-Regulate plasma osmolarity
-Regulate plasma pH
-Remove metabolic waste products and foreign substances from plasma

Front 2

Other Functions of the Kidneys (4)

Back 2

-Secrete erythropoietin
-Secrete renin
-Activate vitamin D3 to calcitriol
-Gluconeogenesis

Front 3

Urinary System (4)

Back 3

-Kidneys—form urine
-Ureters—transport urine from kidneys to bladder
-Bladder—store urine
-Urethra—excrete urine from bladder to outside of body

Front 4

Anatomy of the Kidneys (3)

Back 4

-Paired, bean shaped
-Approximate size of fist, 115–170 grams
-Retroperitoneal

Front 5

Microscopic Anatomy of the Kidney (2)

Back 5

-Nephron = functional unit
-Renal corpuscle and renal tubules

Front 6

Anatomy of the Nephron (3)

Back 6

-Renal corpuscle
+Glomerulus = capillary network for filtration
+Bowman’s capsule
=Receives the filtrate
=Inflow to renal tubules

Front 7

Renal Tubules (2)

Back 7

-Proximal tubule
+Proximal convoluted tubule
-Loop of Henle
+Descending limb
+Thin ascending limb
+Thick ascending limb

Front 8

Renal Tubules (2)

Back 8

-Distal convoluted tubule
-Collecting duct

Front 9

Cortical versus Juxtamedullary Nephrons (3)

Back 9

-Juxtamedullary nephron
+Long loop of Henle extends into medulla
+Responsible for the medullary osmotic gradient
-Cortical
+Short loop of Henle
+Most numerous, 80–85%
-Both types produce urine

Front 10

Basic Renal Exchange Processes (3)

Back 10

-Glomerular filtration
-Reabsorption
-Secretion

Front 11

Basic Renal Processes (4)

Back 11

-Glomerular filtration—from glomerulus to Bowman’s capsule
-Reabsorption—from tubules to peritubular capillaries
-Secretion—from peritubular capillaries to tubules
-Excretion—from tubules out of body

Front 12

Regulation of GFR (3)

Back 12

-180 liters fluid filtered/day
+Only 1.5 liters urine excreted/day (<1%)
+>99% of filtered fluid is reabsorbed
-Small increase in GFR  large increase volume fluid filtered and excreted
-GFR highly regulated

Front 13

Extrinsic Control of GFR

Back 13

-Decreases in BP can decrease GFR
+Directly (decrease in filtration pressure)
+Indirectly through extrinsic controls

Front 14

Reabsorption

Back 14

Selective transport; renal tubules to interstitial fluid
Movement from tubules into peritubular capillaries (returned to blood)
-Most occurs in proximal tubule
-Most is not regulated

Front 15

Renal Threshold

Back 15

-For a solute which is normally 100% reabsorbed
+If solute in filtrate saturates carriers, then some solute excreted in urine
+Solute in plasma that causes solute in filtrate to saturate carriers and spillover into urine = renal threshold

Front 16

Example: Glucose Reabsorption (3)

Back 16

-Freely filtered at glomerulus
-Normally 100% actively reabsorbed in proximal tubule
-Normally, no glucose appears in urine

Front 17

Secretion (3)

Back 17

-Solute moves from peritubular capillaries into tubules
-Barriers same as for reabsorption
-Transport mechanisms same but opposite direction

Front 18

Secretion

Back 18

-Secreted substances
+Potassium
+Hydrogen ions
+Choline
+Creatinine
+Penicillin

Front 19

Water Conservation due to Loop of Henle (2)

Back 19

-Loop of Henle establishes conditions necessary to concentrate urine
-Minimizes water loss

Front 20

Ascending Limb LH (2)

Back 20

-Impermeable to H20; permeable to salt
-Active transport of salt causes filtrate to become dilute (100 mOsm) by end of LH

Front 21

Use of Creatinine to Estimate GFR (6)

Back 21

-Creatinine = by-product of muscle metabolism
-Produced in body
-Freely filtered
-Not reabsorbed
-Small amount secreted
-Clearance = “estimate” of GFR
+Clearance a little greater than GFR, 140 mL/min

Front 22

Micturition (4)

Back 22

Micturition = urination

-Urine formed in renal tubules
-Fluid drains into renal pelvis and into ureter
-Ureters lead to bladder
-Bladder stores urine until it is excreted

Front 23

Urinalysis (7)

Back 23

-Glucose - lack of insulin
-Blood cells - vessel damage (kidney)
-WBC - kidney infection
-Bilirubin - liver damage
-Creatinine – Used to test kidney clearance
-Ketones - FA breakdown (diet)
-Density

Front 24

Diuretics (3)

Back 24

-Caffeine - blocks Na+ transport out of tubules (water stays as well)
-Alcohol - ADH inhibition
-Lasix - K+ transport from blood (lose water and potassium)