Download Chapter 14 The Kidneys and Regulation of Water and Inorganic Ions

Chapter 14
The Kidneys and
Regulation of Water
and Inorganic Ions
Functions of the kidneys
Urea, uric acid, creatinine
Drugs, pesticides, food additives
Amino acids → glucose
Urinary system in a women
Gross anatomy of the kidney
Kidney:
(1) 11 cm long, 6 cm wide, 4 cm deep, 115-170 g
(2) Right kidney is lower than left kidney
(3) Outer: Cortex → blood filtration
Middle: Medulla (8-18 renal pyramids) → urine collection
Inner: papilla → minor calyx → major calyx → renal pelvis →
ureter → urinary bladder
Nephron:
(1) 1,000,000 nephrons/kidney
(2) The functionl unit of the kidney
(the glomerulus + the renal tubule)
To urinary bladder
Section of a human kidney
Renal pyramid
Minor calyx
Major calyx
Loops of Henle
+
Collecting ucts
Papilla
Basic structure of a nephron
106 nephrons/kidney
Part of thick segment
of ascending limb
10-15%
80-85%
Nephron types and the collecting duct system
Receive 90% of renal blood supply
Renal corpuscle;
Glomerular capillaries
Glomerular capsule
Glomerular (Bowman) capsule
PCT → PST → DTL → ATL → TAL → DCT → CNT → CCD → OMCD → IMCD
Loop of Henle
CD
Basic structure of a nephron
Nephron
Anatomy of the renal corpuscle
JGA
Thick segment of
ascending limb
Glomerular filtrate
Cell-free, protein-free
(20% of the plasma)
Mesangial cells
The glomerulus and its filtration barrier
Pore size  70 nm
GFR (glomerular filtration rate)
= Kf [(PGC-PBS) - (GC-BS)]
Hydrostatic
pressure
Colloid osmotic
pressure
GC: glomerular capillary
BS: Bowmen space
< 5,000 Da
(1)
(2)
(3)
Lamina rara interna
Lamina densa
Lamina rara externa
TEM of a glomerular capillary and the glomerular membranes
Podocytes (fltration slits)

Basement membrane

Endothelia (fenestrae)
The juxtaglomerular apparatus (JGA)
(JG)
Renin
JGA
The three basic components of renal function
@ renal corpuscle
@ varies sites
along the tubule
Not all these processes apply
to all substances
Amount
Amount
Amount
=
+
excreted
filtered
secreted
Amount
reabsorbed
Renal handling of three hypothetical filtered substrances
Forces involved in glomerular filtration
Forces favoring glomerular ultrafiltration
PBS: Bowman space
PGC: glomerular capillary hydrostatic pressure
GC: glomerular capillary colloid osmotic pressure
+ 20 mm Hg
+ 8 mm Hg
Forces controlling fluid reabsorption by peritubular capillaries
PC  25 mm Hg in
all other regions of
the body
PC 
35 mm Hg
20 mm Hg
Other systemic capillary beds
 35 mm Hg
Control of GFR by constriction or dilation of afferent aRterioles (AA)
or efferent arterioles (EA)
GFR (glomerular filtration rate)
AA: afferent arteriole
EA: efferent arteriole
Average values for several components that undergo
filtration and reabsorption
Diagrammatic representation of tubular epithelium
Transcellular route
(by transporters)
Paracellular route
(by diffusion)
Apical
Pathways for reabsorption from the tubule lumen
Determined by tight junction structure
Requires the assistance of channels or transporters
ATP-dependent pumps
The relationship between plasma glucose concentration and
the rate of glucose filtered (filtered load), reabsorbed, or excreted
The maximum rate at
which glucose can be absorbed
Example of renal handling of inulin
The clearance of inulin is equal to
the glomerular filtration rate
Ureters
2-6 cm/s
Circular and longitudinal
smooth muscle layers
The urinary bladder
SNS: T11-L2, hypogastric nerve
(1) detrusor  relaxation
(2) bladder neck & urethra  contraction
PSNS: S2-S4, pelvic nerve
(1) detrusor  contraction
(2) urethra internal sphincter  relaxation
Transitional epithelium
Pudenal nerve from the
sacral spinal cord
Intravascular ureteral valve preventing urine reflex
Control of the bladder
Average daily water gain and loss in adults
Daily sodium chloride intake and loss
Mechanism of Na+ reabsorption in the proximal tubule
and cortical collecting duct
Coupling of water and Na+ reabsorption
The regulation and function of aquaporins (AQPs) in the
medullary-collecting-duct cells to increase water reabsorption
ADH receptor
ADH
Vasopressin-sensitive
Vasopressin-insensitive
Diabetes insipidus caused by the failure to release vasopressin
or non-respond to vasopressin  25 L/day
Generating a hyperosmolar medullary renal interstitium
Countercurrent multiplier system
Impermeable tp H2O
Simplified depiction of the generation of an interstitial fluid
osmolarity gradient by the renal countercurrent multiplier system
and its role in the formation of hyperosmotic urine
in the presence of vasopressin
Functions of the vasa recta to maintain the
hypertonic interstitial renal medulla
Urea recycling
Direct and neurally mediated reflex pathways
when plasma volume decreases
Summary of the renin-angiotensin system and the stimulation of
aldosterone secretion by angiotensin II
RASS
(renin-angiotensin-aldosterone system)
ACE
@ cortical collecting ducts
Pathways by which decreased plasma volume leads to increased
Na+ reabsorption
Atrial natriuretic peptide (ANP) increases Na+ excretion
Osmoreceptor pathway that decreases vasopressin secretion
and increases water excretion when excess water is ingested
Baroreceptor pathway by which vasopressin secretion increases
when plasma volume decreases
Pathways by which Na+ and water excretion decrease
in response to severe sweating
Inputs controlling thirst
Simplified model of the basic renal processing of potassium
Pathways by which an increased potassium intake
induces greater K+ excretion
Summary of the control of aldosterone and its effects
on Na+ absorption and K+ secretion
Summary of “Division of labor” in the renal tubules
Sources of hydrogen ion gain and loss
Reabsorption of HCO3-
H+-ATPase
or
Na+/H+ countertransporters
H+/K+-ATPase pumps
Renal contribution of new HCO3- to the plasma as achieved
by tubular secretion of H+
H+-ATPase
or
Na+/H+ countertransporters
H+/K+-ATPase pumps
Renal contribution of new HCO3- to the plasma as achieved by
renal metabolism of glutamine and excretion of ammonium (NH4+)
Proximal tubule
Renal responses to acidosis and alkalosis
Changes in the arterial concentrations of H+, HCO3-,
and carbon dioxide in acid-base disorders
Simplified diagram of hemodialysis
400 mL/min
1000 mL/min