Download Urinary System

Role of Kidney
renal system – referring to the kidney
1.
2.
3.
4.
5.
blood filtration
waste excretion
acid / base balance
blood pressure regulation
hormone secretion
Kidney Blood Flow
Blood enters the kidney through the renal artery.
 renal arteries stem from the:
Filtered blood exits the kidney through the renal vein.
 renal veins flow into the:
Kidney Blood Flow
Blood and the Nephron
Renal artery blood is filtered through
nephrons. About a million
nephrons make up the kidney.
Nephrons collect liquid to be
excreted.
Fluids are exchanged between the
nephron before blood is returned
to renal vein.
Blood Flow
The renal artery is split into afferent arterioles.
 blood brought to glomerulus (a capillary bed)
 blood leaves through the efferent arterioles
 no veins involved
Efferent arterioles are the beginning of a network of
peritubular capillaries, that wrap around the nephron.
Glomerulus and Bowman’s Capsule
Nephron
Nephron
Nephrons begin surrounding the glomerulus with
the Bowman’s capsule structure.
 What is the pathway taken by the waste
solution once it is collected by the Bowman’s
capsule?
Kidney Structure
renal cortex – outside of
kidney; location of
Bowman’s capsule
renal medulla – middle of
kidney; location of loop of
Henle
renal pelvis – location of the
ends of collecting ducts
Urine Flow
Urine leaves the renal pelvis through the ureters
and travels to the bladder. Fluid leaves the body
through the urethra.
Urinary Tract
Nephron Structure
efferent arteriole
proximal
tubule
glomerulus
Bowman’s
capsule
distal
tubule
collucting
duct
afferent arteriole
Loop of
Henle
Urinary System
aorta
inferior vena
cava
renal
cortex
renal
medulla
renal artery
renal vein
kidney
ureter
bladder
renal
pelvis
nephrons
urethra
ureter
Three Functions of Urine Formation
1.
filtration –
2.
reabsorption –
3.
secretion –
Filtration
Nutrients move from glomerulus into Bowman’s
capsule due to high blood pressure (65 mm Hg;
normal ~ 25 mm Hg)
Nutrient Flow
Solute
Glomerulus  Bowman’s
Capsule?
water
NaCl
H+ ions
yes
yes
yes
amino acids
glucose
yes
yes
plasma proteins
no
red blood cells
(erythrocytes)
no
platelets
no
Reabsorption
Reabsorption saves us from having to continuously
replenish our body with fluid.
 20% of fluid flowing into kidney is filtered into
nephrons
 less than 1% of nephron fluid is used to make urine
Reabsorption vs. Secretion
Reabsorption
 protein transporters
move nutrients
molecules from
nephron into the blood
Secretion
 protein transporters
move wastes from
blood to nephron
1. Bowman’s Capsule
water and dissolved solutes leave
glomerulus; enter Bowman’s
capsule
water
Na+
H+
Clglucose
amino acids
vitamins
minerals
urea
uric acid
2. Proximal Tubule
HCO3-, K+
Na+, ClH2O
amino acids
glucose
vitamins
selective reabsorption of
nutrients (need transporters)
pH determined by HCO3reabsorption and H+ secretion
H+
NH3
3. Loop of Henle – Descending Limb
only permeable to H2O (osmosis)
impermeable to salt
fluids in tube are being
concentrated
H2O
4. Loop of Henle – Ascending Limb
only permeable to salt (need ionic
transporters)
impermeable to water
NaCl
5. Distal Tubule
HCO3Na+, ClH2O
selective reabsorption of nutrients
(need transporters)
pH determined by HCO3reabsorption and H+ secretion
H+
NH3
K+
6. Collecting Duct
urine formation by concentration
nephron fluid
any urea and urine that is
reabsorbed is less than that was
filtered into nephron
NaCl
urea
water
Kidney Stones
crystallization of some urine
solutes
a 2 – 3 mm stone can
obstruct flow to the ureter
Treatment:
 increased water
consumption
 surgery