Download Lab 8 Urinary System Fall 2014

Urinary System Organs
 Kidney – Filters blood, allowing toxins, metabolic
wastes, and excess ions to leave the body in urine
 Urinary bladder – provides a temporary storage
reservoir for urine
 Paired ureters – transport urine from the kidneys to
the bladder
 Urethra – transports urine from the bladder out of
the body
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Figure 25.1 The urinary system.
Hepatic veins (cut)
Esophagus (cut)
Inferior vena cava
Adrenal gland
Aorta
Iliac crest
Rectum (cut)
Uterus (part of female
reproductive system)
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Renal arte
Renal hilu
Renal vein
Kidney
Ureter
Urinary
bladder
Urethra
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Kidneys -Overview
 Blood passes through kidney – filtration occurs at
capillaries – 20% of plasma becomes filtrate
 Filtrate passes through nephrons – water and
electrolytes are reabsorbed
 Some electrolytes, drugs and toxins may be secreted
into filtrate by tubular secretion
= Urine
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Figure 25.9 A schematic, uncoiled nephron showing the three major renal processes that adjust plasma composition.
Afferent
arteriole
Glomerular
capillaries
Efferent arteriole
Cortical
radiate
artery
1
Glomerular capsule
Renal tubule and
collecting duct
containing filtrate
2
Peritubular
capillary
3
To cortical radiate vein
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Three major
renal processes: Urine
1 Glomerular filtration
2 Tubular reabsorption
3 Tubular secretion 10/20/13
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Figure 25.8 Juxtaglomerular complex (JGC) of a nephron.
Glomerular
capsule
Efferent
arteriole
Afferent
arteriole
Glomerulus
Parietal layer
of glomerular
capsule
Capsular
space
Foot
processes
of podocytes
Podocyte cell body
(visceral layer)
Red blood cell
Proximal
tubule cell
Efferent
arteriole
Juxtaglomerular
complex
• Macula densa
cells
of the ascending
limb of nephron loop
• Extraglomerular
mesangial cells
• Granular
cells
Afferent
arteriole
Lumens of
glomerular
capillaries
Endothelial cell
of glomerular
capillary
Glomerular mesangial
cells
Juxtaglomerular complex
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Renal corpuscle
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Figure 25.10 The filtration membrane.
Efferent
arteriole
Glomerular
capsular space
Cytoplasmic extensions
of podocytes
Filtration slits
Podocyte
cell body
Afferent
arteriole
Proximal
convoluted
tubule
Glomerular capillary
covered by podocytes
that form the visceral layer
of glomerular capsule
Parietal layer
of glomerular
capsule
Glomerular capillaries and the visceral layer of
the glomerular capsule
Fenestrations
(pores)
Glomerular
capillary endothelium
(podocyte covering
and basement
membrane removed)
Foot processes
of podocyte
Filtration slits
Podocyte
cell body
Filtration membrane
• Capillary endothelium
• Basement membrane
Capillary
• Foot processes of podocyte
of glomerular capsule
Foot
processes
Filtration
slit
Plasma
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Fenestration
(pore)
Filtration slits between the podocyte foot processes
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Filtrate
in capsular
space
Slit
diaphragm
Foot
processes
of podocyte
Three layers of the filtration membrane
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Figure 25.5 Location and structure of nephrons.
Renal cortex
Renal medulla
Glomerular capsule: parietal layer
Renal pelvis
Ureter
Kidney
Renal corpuscle
• Glomerular capsule
• Glomerulus
Distal
convoluted
tubule
Basement
membrane
Podocyte
Fenestrated endothelium
of the glomerulus
Glomerular capsule: visceral layer
Apical
microvilli
Mitochondria
Highly infolded basolateral
membrane
Proximal convoluted tubule cells
Proximal
convoluted
tubule
Cortex
Apical side
Medulla
Thin segment
Nephron loop
• Descending limb
• Ascending limb
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Thick
segment
Basolateral side
Distal convoluted tubule cells
Nephron loop (thin-segment) cells
Collecting
duct
Principal
cell
Intercalated cell
Collecting duct cells
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Renal Tubule
 Proximal convoluted tubule (PCT) – composed of
cuboidal cells with numerous microvilli and
mitochondria
 Reabsorbs water and solutes from filtrate and
secretes substances into it
 Reabsorbs 100% of glucose, amino acids, escaped
proteins, some vitamins, 60-70% of Na+, K+, Cl-,
Ca++ and water
 Secretes H+, NH3 (ammonia), drugs, toxins, uric
acid and histamine
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Renal Tubule
 Loop of Henle – a hairpin-shaped loop of the renal
tubule
 Descending Limb
 Impermeable to electrolytes, permeable to water
 80% Water is absorbed, filtrate becomes
hypertonic
 Ascending Limb
 Permeable to Na+ and Cl- but not water
 Filtrate becomes hypotonic
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Renal Tubule
 Distal convoluted tubule (DCT)
Reabsorbs:
 Na+ directed by aldosterone
 Water directed by ADH
 Ca++ directed by PTH
 Some HCO3-, depending on pH of blood
Secretes:
 NH3, K+, drugs, toxins, and creatinine
 Some H+, depending on pH of blood
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Collecting Tubule
Reabsorbs
 Na+ directed by aldosterone
 HCO3- depending on blood pH
 Urea to maintain hypertonic interstitial fluid around
nephron tubules
 Water directed by ADH
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Capillary Beds of the Nephron
 Every nephron has two capillary beds
 Glomerulus
 Peritubular capillaries
 Each glomerulus is:
 Fed by an afferent arteriole - larger
 Drained by an efferent arteriole - smaller
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Figure 25.8 Juxtaglomerular complex (JGC) of a nephron.
Glomerular
capsule
Efferent
arteriole
Afferent
arteriole
Glomerulus
Parietal layer
of glomerular
capsule
Capsular
space
Foot
processes
of podocytes
Podocyte cell body
(visceral layer)
Red blood cell
Proximal
tubule cell
Efferent
arteriole
Juxtaglomerular
complex
• Macula densa
cells
of the ascending
limb of nephron loop
• Extraglomerular
mesangial cells
• Granular
cells
Afferent
arteriole
Lumens of
glomerular
capillaries
Endothelial cell
of glomerular
capillary
Glomerular mesangial
cells
Juxtaglomerular complex
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Renal corpuscle
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Figure 25.7 Blood vessels of cortical and juxtamedullary nephrons.
Cortical nephron
• Short nephron loop
• Glomerulus further from the cortex-medulla junction
• Efferent arteriole supplies peritubular capillaries
Renal
corpuscle
Glomerulus
(capillaries)
Efferent
arteriole
Juxtamedullary nephron
• Long nephron loop
• Glomerulus closer to the cortex-medulla junction
• Efferent arteriole supplies vasa recta
Cortical radiate vein
Cortical radiate artery
Glomerular
capsule
Afferent arteriole
Collecting duct
Proximal
convoluted
tubule
Distal convoluted tubule
Afferent arteriole
Efferent
arteriole
Peritubular
capillaries
Ascending
limb of
nephron loop
Cortexmedulla
junction
Arcuate vein
Kidney
Vasa recta
Arcuate artery
Descending
limb of
nephron loop
Nephron loop
Peritubular
capillary bed
Glomerulus
Afferent
arteriole
Efferent
arteriole
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Hemodialysis
 Diffusion of solutes through semipermeable
membrane
 Dialysis machine- group of tubules that act like a
nephron
 Membrane allows free passage of glucose,
electrolytes and nitrogenous wastes
 Filtration and production of filtrate is not required
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