Memmler’s
The Human Body in Health and Disease
11th edition
Chapter 22
The Urinary System
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Excretion
Body systems work interdependently to maintain
homeostasis by excretion
• Urinary
• Digestive
• Respiratory
• Integumentary
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Organs of the Urinary System
• Two kidneys
• Two ureters
• Single urinary bladder
• Single urethra
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Male urinary
system, showing
blood vessels.
Zooming In:
What vessel
supplies blood to
the kidney?
What vessel
drains the
kidney?
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Kidney Activities
• Excretion
– Urea
• Water balance maintenance
• Body fluid acid–base regulation
• Blood pressure regulation
– Angiotensin
– Aldosterone
• Red blood cell production regulation
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Kidney Structure
• Membranous renal capsule of fibrous connective tissue
• Adipose capsule of fat
• Fascia anchors kidney to peritoneum and abdominal wall
• Retroperitoneal space
• Right kidney lower than left to accommodate liver
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Blood Supply to the Kidney
• Renal artery supplies blood
• Nephrons are functional units
• Renal vein drains blood
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Kidney Organization
• Hilum
• Renal cortex (outer portion)
• Renal medulla (inner portion)
– Renal pyramids
• Renal pelvis
– Calyces
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Longitudinal section through the kidney. Its internal structure is shown
(left), along with an enlarged diagram of nephrons (right). Each kidney
contains more than 1 million nephrons.
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The Nephron
Functional kidney unit
• Glomerular (Bowman) capsule
– Glomerulus
– Afferent arteriole
• Peritubular capillaries
• Proximal convoluted tubule (PCT)
• Nephron loop (Loop of Henle)
– Descending limb
– Ascending limb
• Distal convoluted tube (DCT)
• Collecting duct
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A nephron and its
blood supply. The
nephron regulates
the proportions of
water, waste, and
other materials
according to the
body’s constantly
changing needs.
Materials that enter
the nephron can be
returned to the blood
through the
surrounding
capillaries.
Zooming In: Which of
the two convoluted
tubules is closer to
the glomerular
capsule? Which
convoluted tubule is
farther away?
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Formation of Urine
• Glomerular filtration
–
Glomerular filtrate
• Tubular reabsorption
–
Diffusion
–
Osmosis
–
Active transport
• Tubular secretion
• Countercurrent mechanism
–
Concentration of urine
–
Antidiuretic hormone (ADH)
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Summary of urine formation in a nephron.
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Control of Blood Pressure
• Juxtaglomerular apparatus: Specialized cells that
regulate kidney function
• Triggered by low blood pressure
– Secretes renin enzyme
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Structure of the juxtaglomerular (JG) apparatus. Note how the distal
convoluted tubule contacts the afferent arteriole (right). Cells in these two
structures make up the JG apparatus.
Zooming In: The JG apparatus is made up of cells from which two structures?
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The Ureters
• Long, slender, muscular tubes
– Epithelial cell lining
– Involuntary muscle layer
– Fibrous connective tissue coat
• Entirely extraperitoneal
• Extend from kidney to urinary bladder
• Move urine by gravity and peristalsis
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The Urinary Bladder
Temporary reservoir for urine
• Multiple layers
• Mucous membrane
– Transitional epithelium
– Rugae
– Connective tissue
– Three-layered coat of involuntary muscle tissue
– Incomplete coat of peritoneum
• Trigone
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The Urethra
Tube that extends from the bladder to the outside
• Male
– Part of both reproductive and urinary systems
• Female
– Entirely separate from reproductive system
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Urination
Process of expelling urine from bladder (micturition)
• Involuntary control
– Internal urethral sphincter
• Voluntary control
– External urethral sphincter
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The Urine
• 95% water, 5% dissolved solids and gases
• pH averages 6.0
• Specific gravity measures amount of dissolved
substances
– Normal range 1.002 to 1.040
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Normal Constituents
Dissolved solids normally found in urine
• Nitrogenous waste products
–
Urea
–
Uric acid
–
Creatinine
• Electrolytes
–
Sodium chloride
–
Sulfates
–
Phosphates
• Pigment
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Abnormal Constituents
Urinalysis is evaluation of urine
• Glucose
–
Glycosuria
• Albumin
–
Albuminuria
• Blood
–
Hematuria
• Ketones
–
Diabetes mellitus and starvation
• White blood cells
–
Pyuria
• Casts
–
Nephron disease
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Disorders of the Urinary System
Portion of urinary system most prone to disorders is kidney
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Kidney Disorders
Kidney disorders may be acute or chronic
• Acute glomerulonephritis
–
Most common kidney disease
• Pyelonephritis
• Hydronephrosis
• Polycystic kidney
• Tumors
• Kidney stones (calculi)
• Renal failure
–
Leads to uremia, high levels of nitrogenous waste in the blood
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Renal Dialysis and Kidney Transplantation
• Dialysis
– Hemodialysis
– Peritoneal dialysis
• Kidney transplantation
– Final option for treatment of kidney failure
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Disorders of the Ureters
• Subdivision at renal pelvis
• Constricted or abnormally narrow parts (strictures)
• Renal ptosis
• Ureterocele
• Ureteral stones
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Bladder Disorders
• Rupture
• Cystitis
–
Interstitial cystitis
• Tumors
–
90% arise from epithelial lining
–
If bladder removed (cystectomy), ureters diverted to part of
ileum in an ilial conduit
• Urinary incontinence
–
Stress incontinence
–
Urge incontinence
–
Overflow incontinence
–
Enuresis
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Disorders of the Urethra
• Congenital anomalies
– Narrowing of opening or urethra itself
– Presence of valve-like structure at junction of urethra
and bladder
– Hypospadias
• Urethritis
• Straddle injuries
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The Effects of Aging
• Loss of ability to concentrate urine
• Decrease in number and size of nephrons
• Increase in blood urea nitrogen (BUN)
• Urinary infections
• Prostate enlargement
• Decreased bladder capacity
• Incontinence
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End of Presentation
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