Chapter 17 - The Urinary System Urinary system - fnc. producing & excreting urine

1. Chapter 17 - The Urinary System • Urinary system - fnc. producing & excreting urine • Essential function in maintaining homeostasis & survival: • body fluid volumes • levels of chemicals (electrolytes) • normal composition of blood (clean waste products - if not > uremia uremic poisoning )

2. Kidneys - two • Location - posterior back, above waist • R little lower than L • Under muscles of back - & retroperitoneal • Cushion of fat - place • Renal arteries - large • 20% total blood vol/min • High blood flow & normal B/P essential for urine formation

3. Internal Structure of the Kidneys - • Cortex - Outer layer • Medulla - Inner port. • Pyramids - Triangular divisions of medulla • Papilla - narrow, end of a pyramid • Pelvis - Expansion of upper end of ureter • Calyx - Divisions in renal pelvis where the papilla open into

4. Microscopic Structure • Nephron - microscopic unit • Millions in each kidney (2 million) • Shaped like a funnel w/ convoluted stem • Two principle components: • Renal corpuscle (2) • Renal tubule (4)

5. Renal corpuscle - 2 parts • Bowman’s capsule - cup-shaped top of the nephron (sacklike) • Glomerulus -network of blood capillaries tucked into Bowman’s capsule • Afferent arteriole - delivers blood (larger) • Efferent arteriole - drains blood(smaller) • Creates hydrostatic pressure > filtration

6. Renal Tubule – (4) • Proximal convoluted tubule - 1st segment, lies nearest to Bowman’s capsule (bends) • Loop of Henle - extension of proximal tubule - straight descending limb, hairpin loop, & straight ascending limb

7. Distal convoluted tubule - distal to loop of Henle, extension of the ascending limb • Collecting tubule - straight part of renal tubule, distal tubules of several nephrons join into these collecting ducts

8. Renal corpuscles, proximal & distal convoluted tubules - located in cortex • Loop of Henle & collecting ducts - located in medulla • Urine exits from the pyramids thru the papilla & enters calyx & renal pelvis > to ureters

9. Functions - • Efficient formation of urine is vital • Filtration - 1st step in urine formation-fluid, electrolytes, & waste products from metabolism • Secretion - in tubules, additional waste products • Reabsorption - useful substances the body needs • Protein metabolism > nitrogenous waste • Artificial kidney - may be used if kidneys fail to fnc. appropriately

10. Waste Products - toxins, products that contain nitrogen (urea & ammonia) • Regulating chemical levels - chloride, sodium, potassium, & bicarbonate • Water and Salt Balance - retaining or excreting • B/P Regulation - hormone secretion from juxtaglomerular apparatus to make constrict & raise B/P • Normal Characteristics of Urine - pg. 441 • Color - Components • Odor - pH - Specific Gravity

11. Filtration - Bowman’s capsules of the renal corpuscles • Blood pressure causes filtration thru membrane • If B/P drops below certain level < filtration & urine formation < • Glomerular filtration rate = 125ml/min • Glomerular filtrate = 180 liters/day

12. Reabsorption - mov’t of substances out of renal tubules into blood capillaries (peritubular capillaries) • Occurs in tubule sections • 97% to 99% of water (178 liters) by proximal tubule • Glucose - proximal tubules /glycosuria - DM • Sodium ions - actively transported

14. Secretion - movement of substances into the urine in the distal & collecting tubules from the blood • Assists in maintaining acid-base balance • Hydrogen & potassium ions, certain drugs are actively transported to urine • Ammonia - diffusion

15. Control of Urine Volume - • Hormone control of water & substance reabsorption • ADH (antidiuretic hormone) - • From posterior pituitary gland • Decreases the amt. of urine by making collecting tubules permeable to water > reabsorption of water • “water-retaining” hormone • “urine-decreasing” hormone

16. Aldosterone - • Hormone secreted form adrenal cortex • Controls reabsorption of sodium by stimulating the tubules to reabsorb salt at a faster rate • Also increases tubular water reabsorption • “salt- and water-retaining” hormone • ANH (atrial natriuretic hormone) - • Form heart’s atrial wall • Opposite effect of aldosterone • Stimulates tubules to secret more Na & therefore water -“salt- and water-losing”

17. Abnormal excretion of urine - • Anuria - absence of urine • Oliguria - scanty amt. of urine • Polyuria - an unusually large amt. of urine

18. Ureters - Urine begins draining from the renal pelvis • Narrow tubes (1/4 in. wide, 10-12 in. long) • Lines w/ mucous membrane • Thick muscular wall - peristaltic mov’t.

19. Urinalysis - • Physical, chemical, & microscopic examination of urine • Reveals information about the fnc. of the body • Changes in appearance or characteristics of urine may indicate disease process • Characteristics of urine provide general indicators of the composition of urine - • Color - Turbidity (cloudiness) • Odor - Specific Gravity (density) • Char. may indicate “something” is wrong, BUT will not provide detailed information

20. Chemical Analysis - • Information about: • pH - urea concentration • Presence: glucose, acetone, albumin, bile • Urine specimen - spun in a centrifuge and suspended particles are forced to the bottom of the tube (microscope - look for abnormal cells & other particles (casts)) • Usually ordered in addition to routine urinalysis (microscopic)

21. Urinary Bladder - • Lies in pelvis behind pubic symphysis • If full - projects upward into the lower abdominal cavity • Renal colic - pain associated w/ urinary tract

22. Elastic fibers & involuntary muscle fibers in walls - expands - contracts • Lined w/ mucous membrane • Rugae - surface is wrinkled & lays in folds • Trigone - triangular area - posterior surface - tightly fixed (for opens)

23. Urethra - • Lowest part of urinary tract • Exit to the exterior • Covered by the same sheet of mucous membrane (infection can spread up the urinary tract) • F - 1 1/2 inches • M - 8 inches • passageway of reproductive fluid

24. Micturition - • Urination, voiding • Passage of urine from body or emptying bladder • Reflex in infants & small children (trained between 2 to 3 yrs.) • Two sphincters assist in holding urine in bladder

25. Internal urethral sphincter - bladder exit, involuntary • External urethral sphincter - below neck of bladder, striated muscles - voluntary • Accommodates to great varying volumes w/out need to void • 150 ml (need) voiding at 350 ml (adults)

26. Emptying reflex - occurs when walls stretch & nervous impulses are sent to the 2nd, 3rd, & 4th sacral segments of the spinal cord • Bladder wall contracts Internal sph. relaxes > urine into ureter • If external sph. relaxes - voiding occurs

27. Higher centers in the brain also fnc. in voiding - integrate bladder contraction, internal & external sph. relaxation w/ cooperative pelvic & abdominal muscles. • Retention - kidneys work but no urine • Suppression - kidneys don’t work, but bladder will fnc. • Incontinence - pt. voids involuntarily