1. Chapter 19 The Urinary System

2. Kidneys
Location—under back muscles, behind parietal peritoneum, just above waistline; right kidney usually a little lower than left
Internal structure
Renal cortex—outer layer of kidney substance
Renal medulla—inner portion of kidney
Renal pyramids—triangular divisions of medulla
Renal papilla—narrow, innermost end of pyramid

3. Kidneys Renal papilla—narrow, innermost end of pyramid
Renal pelvis—expansion of upper end of ureter; lies inside kidney
Renal calyces—divisions of renal pelvis

4. Kidneys
Renal Microscopic structure—nephrons are microscopic units of kidneys; consist of (Figure 19-3):
Renal corpuscle—Bowman’s capsule with its glomerulus
Bowman’s capsule—the cup-shaped top
Glomerulus—network of blood capillaries surrounded by Bowman’s capsule
Cortical nephrons—85% of total
Juxtamedullary nephrons—specialized role in concentrating urine

5. Kidneys Renal tubule Proximal convoluted tubule—first segment
Loop of Henle—extension of proximal tubule; consists of descending limb, loop, and ascending limb
Distal convoluted tubule—extension of ascending limb of loop of Henle
Collecting tubule—straight extension of distal tubule

6. Kidneys Functions Excretes toxins and nitrogenous wastes
Regulates levels of many chemicals in blood
Maintains water balance
Helps regulate blood pressure

7. Formation of Urine
Occurs by a series of three processes that take place in successive parts of nephron
Filtration—goes on continually in renal corpuscles; glomerular blood pressure causes water and dissolved substances to filter out of glomeruli into Bowman’s capsule; normal glomerular filtration rate 125 ml per minute

8. Formation of Urine
Reabsorption—movement of substances out of renal tubules into blood in peritubular capillaries; water, nutrients, and ions are reabsorbed; water is reabsorbed by osmosis from proximal tubules
Secretion—movement of substances into urine in the distal and collecting tubules from blood in peritubular capillaries; hydrogen ions, potassium ions, and certain drugs are secreted by active transport; ammonia is secreted by diffusion

9. Formation of Urine
Control of urine volume—mainly by posterior pituitary hormone’s ADH, which decreases it
Urinalysis—examination of the physical, chemical, and microscopic characteristics of urine; may help determine the presence and nature of a pathological condition

10. Ureters
Structure—narrow long tubes with expanded upper end (renal pelvis) located inside kidney and lined with mucous membrane and muscular layer
Function—drain urine from renal pelvis to urinary bladder

11. Urinary Bladder Structure Functions
Elastic muscular organ, capable of great expansion
Lined with mucous membrane arranged in rugae, like stomach mucosa
Functions
Storage of urine before voiding
Voiding

12. Urethra Structure Functions
Narrow tube from urinary bladder to exterior
Lined with mucous membrane
Opening of urethra to the exterior called urinary meatus
Functions
Passage of urine from bladder to exterior of the body
Passage of male reproductive fluid (semen) from the body

13. Micturition
Passage of urine from body (also called urination or voiding)
Regulatory sphincters
Internal urethral sphincter (involuntary)
External urethral sphincter (voluntary)
Bladder wall permits storage of urine with little increase in pressure

14. Micturition Emptying reflex
Initiated by stretch reflex in bladder wall
Bladder wall contracts
Internal sphincter relaxes
External sphincter relaxes, and urination
Enuresis—involuntary urination in young child

15. Micturition Urinary retention—urine produced but not voided
Urinary suppression—no urine produced but bladder is normal
Incontinence—urine is voided involuntarily
May be caused by spinal injury or stroke
Neurogenic bladder—paralysis or abnormal function of the bladder, preventing normal flow of urine out of the body
Types include urge, stress, and reflex

16. Renal and Urinary Disorders
Obstructive disorders interfere with normal urine flow, possibly causing urine to back up and cause hydronephrosis or other kidney damage
Renal calculi (kidney stones) may block ureters, causing intense pain called renal colic
Tumors—renal cell carcinoma (kidney cancer) and bladder cancer are often characterized by hematuria (blood in the urine)

17. Renal and Urinary Disorders
Urinary tract infections (UTIs) are often caused by gram-negative bacteria
Urethritis—inflammation of the urethra
Cystitis—inflammation or infection of the urinary bladder
Pyelonephritis—inflammation of the renal pelvis and connective tissues of the kidney; may be acute (infectious) or chronic (autoimmune)
Hydronephrosis—enlargement of renal pelvis and calyces

18. Renal and Urinary Disorders
Glomerular disorders result from damage to the glomerular–capsular membrane of the renal corpuscles
Nephrotic syndrome accompanies many glomerular disorders
Proteinuria—protein in the urine
Hypoalbuminemia—low plasma protein (albumin) level; caused by loss of proteins to urine
Edema—tissue swelling caused by loss of water from plasma as a result of hypoalbuminemia

19. Renal and Urinary Disorders
Acute glomerulonephritis is caused by delayed immune response to a streptococcal infection
Chronic glomerulonephritis is a slow inflammatory condition caused by immune mechanisms and often leading to renal failure

20. Renal and Urinary Disorders
Kidney failure or renal failure occurs when the kidney fails to function
Acute renal failure—abrupt reduction in kidney function that is usually reversible
Chronic renal failure—slow, progressive loss of nephrons caused by a variety of underlying diseases
Early in this disorder, healthy nephrons often compensate for the loss of damaged nephrons

21. Renal and Urinary Disorders
Loss of kidney function ultimately results in uremia (high BUN levels) and its life-threatening consequences
Complete kidney failure results in death unless a new kidney is transplanted or an artificial kidney substitute is used