Page 1048 - Fundamentals of anatomy physiology
P. 1048
Chapter 26 The Urinary System 1035
Clinical Note can only be slowed. Eventually, symptoms of end-stage renal
failure develop. Hemodialysis is a treatment that “cleanses” the
Renal Failure and Kidney Transplant Renal failure blood by serving as a substitute for normal kidney function-
occurs when the kidneys cannot filter wastes from the blood ing. It can relieve the symptoms of end-stage and acute renal
and maintain homeostasis. When kidney filtration slows for failure. However, this treatment is not a cure.
any reason, urine production decreases. As the decrease con-
tinues, signs and symptoms of renal failure appear because In terms of overall quality of life, probably the most sat-
water, ions, and metabolic wastes are retained. Virtually all isfactory solution to the problem of end-stage renal failure is
systems in the body are affected. The person generally be- kidney transplant. This procedure involves implanting a
comes hypertensive; anemia develops due to a decrease in new kidney from a living donor or a deceased donor. Of the
erythropoietin production; and CNS problems can lead to 16,812 kidneys transplanted as of June 2013, 11,043 trans-
sleeplessness, seizures, delirium, and even coma. plants came from deceased donors and 5,769 came from
living donors. At the writing of this text, 96,645 people were
Acute renal failure occurs when filtration slows suddenly awaiting a kidney transplant. The recipient’s nonfunctioning
or stops due to renal ischemia, urinary obstruction, trauma, kidney(s) may be removed, especially if an infection is pres-
or nephrotoxic drugs. The reduction in kidney function takes ent. The transplanted kidney and ureter are usually placed
place over a few days and may persist for weeks. Sensitized in- extraperitoneally in the pelvic cavity (within the iliac fossa).
dividuals can also develop acute renal failure after an allergic The ureter is connected to the recipient’s urinary bladder.
response to antibiotics or anesthetics. Patient survival is more than 90 percent at two years after the
transplant.
In chronic renal failure, kidney function deteriorates
gradually. The associated problems accumulate over years.
This condition generally cannot be reversed. Its progression
control of the external urethral sphincter is lost, so the person A Decrease in the Number of Functional Nephrons. The total
cannot prevent the reflexive emptying of the urinary bladder.
Damage to the pelvic nerves can abolish the micturition reflex number of kidney nephrons decreases by 30–40 percent
entirely, because those nerves carry both afferent and efferent between ages 25 and 85.
fibers of this reflex arc. The urinary bladder then becomes greatly
distended with urine. It remains filled to capacity while the ex- A Reduction in the GFR. This reduction results from fewer
cess urine flows into the urethra in an uncontrolled stream. The
insertion of a catheter is often needed to facilitate the discharge glomeruli, cumulative damage to the filtration apparatus in
of urine. the remaining glomeruli, and reduced renal blood flow.
Checkpoint A Reduced Sensitivity to ADH. With age, the distal portions
1 7. What effect would a high-protein diet have on the of the nephron and collecting system become less respon-
composition of urine? sive to ADH. Water and sodium ions are reabsorbed at a
reduced rate, and more sodium ions are lost in urine.
18. Obstruction of a ureter by a kidney stone would interfere
with the flow of urine between which two points? Problems with the Micturition Reflex. Three factors are in-
19. The ability to control the micturition reflex depends volved in such problems: (1) The sphincter muscles lose
on your ability to control which muscle?
26muscle tone and become less effective at voluntarily retain-
See the blue Answers tab at the back of the book.
ing urine. This leads to incontinence, often involving a
26-7 Age-related changes affect slow leakage of urine. (2) The ability to control micturition
can be lost due to a stroke, Alzheimer’s disease, or other
kidney function and the micturition reflex CNS problems affecting the cerebral cortex or hypothala-
mus. (3) In males, urinary retention may develop if the pros-
Learning Outcome Describe the effects of aging on the urinary system. tate gland enlarges and compresses the urethra, restricting
the flow of urine.
In general, aging is associated with an increased incidence of
kidney problems. One example—nephrolithiasis, the formation Checkpoint
of calculi, or kidney stones—is described in the Urinary Ob-
struction Clinical Note (p. 1034). Other age-related changes in 20. List four age-related changes in the urinary system.
the urinary system include the following: 2 1. Define nephrolithiasis.
22. Describe how incontinence may develop in an elderly
person.
See the blue Answers tab at the back of the book.
