Maria CardenasProf. SmeeApril 17, 2009

Pathophysiology 210.01 Homework Assignment # 4

1. Explain the countercurrent exchange system of concentrating and diluting

urine. A countercurrent exchange system, is when the fluid flows in opposite

directions through the parallel tubes of the loop of Henle. The process is initiated

in the thick ascending limb of the loop of Henle with the active transport of

chloride and sodium out of the tubular lumen and into medullary interstitium.

Because the lumen of the ascending limb is not permeable to water, the ascending

tubular fluid is hypoosmotic, where the water stays, and chloride and sodium

move out; so the fluid becomes more dilute as it encounters the distal tube. The

medullary interstitium is hyperosmolic, which move water out of the descending

tubule, and remaining fluid becomes very concentrated and moves to the tip of

medulla.

2. Explain why women are more likely than men to get infections of the urinary tract.

Women tend to get urinary tract infections more often than men because bacteria can reach the bladder more easily in women. The urethra is shorter in women than in men, so bacteria have a shorter distance to travel.

The urethra is also located near the rectum in women. Bacteria from the rectum can easily travel up the urethra and cause infections.

Having sex may also cause urinary tract infections in women because bacteria can be pushed into the urethra. Using a diaphragm can lead to infections because diaphragms push against the urethra and make it harder to completely empty the bladder. The urine that stays in the bladder is more likely to grow bacteria and cause infections.

3. An important parameter that is measured in a patient who is critically ill is urine output. What information does urine output tell the medical provider?

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4. Ms. Cornwall is admitted with pyelonephritis. She has chills, and her temperature is 101° F. She is complaining of flank pain, frequency, and dysuria. Her urine has white blood cell casts, and her urine culture is growing E. coli. Why does she have bacteria and white blood cell casts in her urine?

5. What are the differences among prerenal acute renal failure, intrarenal acute renal failure, and postrenal acute renal failure? Give examples of each.

6. Your patient has been admitted to the hospital with glomerulonephritis. You have noticed that he has developed lower extremity edema and has become

hypertensive. A 24-hour urine sample was obtained as part of his initial workup. The results of this test show that the patient has excreted 4.3 grams of protein in his urine over the previous 24 hours. What do you suspect has occurred in this patient as a consequence of his glomerulonephritis? Briefly explain the pathophysiology of this problem.

7. Analyze the similarities and differences between emphysema and chronic bronchitis.

8. Mr. Rusch is being evaluated for multiple pulmonary emboli. What risk factors and clinical findings are commonly associated with pulmonary emboli?

9. How does respiratory disease lead to heart disease?

10. Explain why croup is primarily a disease of children. The symptoms of croup are caused by inflammation, swelling and the buildup of mucus in the larynx, trachea and bronchial tubes. Since younger infants and children have smaller airways, it makes sense that they are the ones most affected by croup. In contrast, older children will often just develop cold symptoms when they are infected by the same virus.

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