Download Urinary System Notes

Functions of the Urinary System
 Elimination of waste products
 Nitrogenous wastes (urea, uric acid, creatinine)
 Toxins
 Drugs
 Regulate aspects of homeostasis
 Water & electrolyte balance
 Acid-base balance in the blood
 Blood pressure (enzyme renin)
 Red blood cell production (hormone erythropoietin)
 Activation of vitamin D
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Organs of the Urinary System
 Kidneys
 Produce urine
 Ureters
 Tubes that transport urine from kidneys to bladder
 Urinary bladder
 Muscular sac that stores urine until export from
the body
 Urethra
 Tube that carries urine from bladder to body
exterior by peristalsis
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Organs of the Urinary System
Figure 15.1a
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Organs of the Urinary System
Figure 15.1b
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Location of the Kidneys
 Against the dorsal body wall
 At the level of the T12 to L3 vertebrae
 The right kidney is slightly lower than the left (due
to position of the liver)
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Kidney Features
 Renal hilum
 A medial indentation where several structures
enter or exit the kidney (ureters, renal blood
vessels, and nerves)
 An adrenal gland sits atop each kidney
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Organs of the Urinary System
Figure 15.1a
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Coverings of the Kidneys
 Renal Capsule
 Fibrous tissue
 Surrounds each kidney
 Perirenal Fat Capsule
 Fatty mass that surrounds each kidney to
protect it from blows
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Regions of the Kidney
 Renal cortex—outer region
 Renal medulla—inside the cortex
 Contains funnel-shaped structures called
renal pyramids
 Pyramids separated by renal columns (cortexlike tissue)
 Renal pelvis—inner collecting tube
 Pouch that narrows & extends into the ureter
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Regions of the Kidney
Figure 15.2b
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Nephrons
 The structural and functional units of the kidneys
 Responsible for forming urine
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Urine Formation
 Glomerular filtration
 Tubular reabsorption
 Tubular secretion
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Tubular Reabsorption
 The peritubular capillaries reabsorb useful
substances back into blood:
 Water
 Glucose
 Amino acids
 Ions
 Some reabsorption is passive, most is active
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Tubular Reabsorption
 Materials not reabsorbed
 Nitrogenous waste products
 Urea—protein breakdown
 Uric acid—nucleic acid breakdown
 Creatinine—associated with creatine
metabolism in muscles
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Pathway of Urine
 Urine is continuously made in the kidneys
 Travels down the ureters by peristalsis
 Enters the urinary bladder where it is stored
 Eventually sent out of the body via the urethra
 8 inches long in males
 1.5 inches long in females
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Urinary Bladder Capacity
 A moderately full bladder is about 5 inches long
and holds about 500 mL of urine
 Capable of holding twice that amount of urine
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Position and Shape of a Distended and an Empty
Urinary Bladder in an Adult Man
Figure 15.7
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Characteristics of Urine
 In 24 hours, about 1.0 to 1.8 liters of urine are
produced
 Yellow color due to the pigment urochrome (from
the destruction of hemoglobin) and solutes
 Sterile
 Slightly aromatic
 Normal pH of around 6
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Characteristics of Urine
 Solutes normally found in urine:
 Sodium and potassium ions
 Urea, uric acid, creatinine
 Ammonia
 Bicarbonate ions
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Characteristics of Urine
 Solutes NOT normally found in urine:
 Glucose
 Blood proteins
 Red blood cells
 Hemoglobin
 White blood cells (pus)
 Bile
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Abnormal Urine Constituents
Table 15.1
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