Ch 17
 Main
function: Filter blood and remove
salts and nitrogenous waste.
 Maintains
normal water and electrolyte
concentration.
 Regulates pH and volume of body fluids.
 Controls red blood cell production and
blood pressure.
 Kidneys
(2) – Remove substances from
blood, form urine, and regulate RBC
production.
 Ureters (2) – Transport urine from kidneys
to bladder.
 Urinary bladder – Stores urine
 Urethra – Conducts urine outside the body
 Location
– either side of the vertebral
column on posterior wall of the abdominal
cavity
 High – T12-L3ish Left is slightly higher
than right.
 Attached to inferior vena cava and
abdominal aorta.
 Hilum
 Renal
sinus – filled
with adipose tissue
 Renal pelvis –
major/minor calyces
 Medulla
 Cortex – houses
nephrons
 Maintain
homeostasis
• Removes wastes from blood and dilute with water
and electrolytes to form urine.
 Secretes
hormone erythropoietin –
regulate RBC production
 Activates Vitamin D
 Maintains blood volume and pressure
(enzyme: renin)
 abdominal
aorta -> renal arteries ->
(kidneys) interlobar arteries -> arcuate
arteries -> interlobular arteries -> afferent
arterioles-> (nephron glomerulus) ->
efferent arteriole -> peritubular capillary
system -> interlobular vein -> arcuate vein
-> interlobar vein -> renal vein (exits
kidney) -> inferior vena cava
 Each
kidney has about
1 million nephrons.
 Two main parts: renal
corpuscle and renal
tubule.
 Corpuscle
–
 Glomerulus
– filters
fluid (step 1 of urine
production)
 Glomerular capsule –
receives filtered fluid
 Tubule
 Proximal
convoluted
tubule
 Nephron loop –
descending and ascending
 Distal
convoluted
tubule
 Collecting
Duct
 Juxtaglomerular
Apparatus – where
ascending loop,
afferent, and
efferent vessels
come together
 Involved in renin
secretion.
 Urine
formation happens through three
processes:
• Glomerular filtration
• Tubular reabsorption
• Tubular secretion
 Amount
of urine = amt. filtered-amt.
reabsorbed + amt. secreted
 Glomerular
capillaries in glomerulus filter
water and other dissolved substances to
create glomerular filtrate.
 Glomerular filtrate moves to glomerular
capsules.
 Pressure
is created by hydrostatic pressure
of blood.
 Pressure is decreased by osmotic pressure
of plasma and hydrostatic pressure inside
glomerular capsule.
 Net filtration pressure = blood’s H-S P –
(plasma’s osmotic P + glom.caps’s H-S P)
Glomerular filtration
rate (GFR) – commonly
used to measure kidney
function.
 Affected by changes in
diameter of afferent or
efferent arterioles.
 Can also change due to
kidney stones, enlarged
prostate gland, etc.

 Filtration
Rate Regulation
• Most of the time, it’s constant.
• Increases when body fluids are excessive
• Decreases when body needs to conserve fluids
 Controlled
by sympathetic nervous system
reflexes.
 Can also be affected by renin counts.
 From
renal tubule
back to blood
 Changes
concentrations in
filtrate.
 Happens in proximal
convoluted tubes
using microvilli using
carrier proteins.
 Substances
reabsorbed:
• Glucose, amino acids,
sodium – active
transport
• Water – osmosis
• Proteins – pinocytosis
• Negative ions diffusion
 From
blood back to
distal convoluted
tubule
 Substances secreted:
• Hydrogen ions and
organic compounds –
active transport
• Potassium ions – active
and passive transport
 Can
be changed by presence of hormones
• Aldosterone – secreted by adrenal glands (located
posteriorly to kidneys); stimulates reabsorption of
sodium and secretion of potassium.
• ADH – secreted by neurons in hypothalamus;
responds to decrease in water concentration or
blood volume; causes water to be reabsorbed;
negative feedback system.
 Increased ADH=more water reabsorption
 Decreased ADH=less water reabsorption
 Urea
– made by amino acid catabolism;
reflects amount of protein in diet; 20%
leaves/80% reabsorbed
 Uric acid – product of metabolism of
nucleic acids; small amounts secreted into
renal tubule and excreted in urine.
 Determined
by the amount of water in diet
and plasma.
 Changes with changes in diet and
metabolic activity.
 Should
not have
• Glucose – sign of diabetes or large glucose intake.
• Proteins – may be there after strenuous exercise
• Ketones – after a prolonged fast
• Blood – sign of disease or disorder
 From
collecting tubes in renal medulla
 To ureter
 To urinary bladder
 To urethra
 Ureters
- From renal pelvis to bottom of
urinary bladder.
 Three layers
• Mucous coat – inside
• Muscular coat – middle (smooth muscle)
• Fibrous coat – connective tissue
 Flap-like
fold acts as valve allowing urine
to enter bladder without backflow
 Urinary
bladder – hollow, distendable,
muscular organ
 Stores urine and forces into urethra
 Four layers
• Mucous coat – inner layer (transitional epithelium)
• Submucous coat
• Muscular coat – smooth muscle fiber called
detrusor muscle
• Serous coat – outer layer
 Internal
urethral sphincter
• Sustained contraction keeps bladder from
emptying
• Detrusor muscle innervated with parasympathetic
nerve fibers
 External
urethral sphincter
• Voluntary skeletal muscle
 Micturition
– Urination
 Stimulated by distension of bladder
triggering micturition reflex center
• Controlled by pons and hypothalamus
 Urge
felt at about 150 mL
 Powerful contractions felt at 300 mL
 Pain felt at about 600 mL
 Urethra
– tube that conveys urine to
outside
 Female – 4 cm
 Male – shared by urinary and reproductive
system
 Kidneys
 Nephron
 Ureters
 Urinary
bladder
 Urethra
 Renal
vein
 Renal artery
 Distal convoluted tube
 Proximal convoluted
tube
loop
 Glomerular capsule
 Glomerulus
 Renal cortex
 Renal medullary