Transcript Chapter 28/29/30

Urinary system
Ch. 28,29,30
Consists of:
•
2 kidneys that filter blood
•
2 ureters
•
Urinary bladder
•
urethra
Kidneys

Reddish brown, bean shaped, 12 cm
long, enclosed in fibrous capsule
 Location
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Either side of vertebral column
Between 12th thoracic and 3rd lumbar
Left kidney slightly higher
Kidney structure
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Medial depression – sinus (entrance
of blood vessels, nerves, lymphatic
vessels and ureter.)
Divided into major and minor calyces
Renal papillae project inward
2 regions
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Renal medulla
Renal cortex – contains nephrons
(functional regions of the kidney)
Kidney function
Regulate volume composition, and ph of
body fluids
 Remove metabolic wastes
 Control rate of red blood cell formation
(erythropoietin secretion)
 Regulate blood pressure (renin
secretion)

Renal blood vessels
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Abdominal aorta
gives rise to renal
arteries leading to
kidneys
Branch into smaller
arteries
Venous blood
returned through
vessels that
generally
correspond to
arterial pathways.
Nephrons

Structure
 Renal
corpuscle
 Renal tubule
Urine formation

Glomerular filtration, tubular reabsorption, tubular
secretion
 Glomerular filtration
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Urine forms when fluid portion of blood leaves
glomerulus and enters glomerular capsule
Filtration pressure – hydrostatic pressure of blood
Filtration rate factors

Filtration pressure, glomerular osmotic pressure, and
hydrostatic pressure in capsule.
 Sympathetic nervous system – filtration declines
 Parasympathetic – filtration increases
 Average filtration rate: 125 ml per minute, 180 liters in
24 hours (most is reabsorbed)
Tubular reabsorption
Most reabsorption –
promimal convoluted
tubule
 Glucose and amino acids
reabsorbed by active
transport, water by
osmosis, proteins by
pinocytosis.
 Sodium by active
transport
 Water – osmosis
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Presence of ADH causes
kidneys to retain water
Ureters and
Urinary bladder

Ureters move urine to
bladder
 Bladder is hollow,
distensibe, muscular
Floor of bladder
called trigone –
openings to urter and
urethra
 Muscular wall
 Internal sphincter
controls release to
urethra
urethra
Tubes that
takes urine
from bladder to
outside
 Peristalisis
moves urine
out
 Secretes
mucus for
lubrication

Urine composition

Urea and uric acid
– product of amino acid metabolism
 Uric acid - nucleic acid metabolism
 Varies – reflects amount of water and
solutes
 Urea
 95%
water, urea, uric acid, amino acids,
electrolytes.
Urine elimination
Path - nephron, renal
papillae, calyces, renal
pelvis, ureter, bladder,
urethra
 Ureters – muscular
tubes. From kidneys to
bladder
 Peristaltic waves take
urine to bladder

Micturation
Muscle contracts and sphincter relaxes
 Stretching triggers micturation reflex
 Strong contractions open sphincter

 Under
some conscious control
Water, Electrolyte, and AcidBase Balance
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To be in balance, quantities of fluids and
electrolytes leaving body should be equal
to quantities entering body.
Fluids occur in compartments
Intracellular
 Extracellular
 Transcellular (fluid of eye, cerebrospinal etc.)
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Female – 52% water
Male – 63% water