1. Chapter 26 Urinary System

2. Functions Excretion & Elimination (micturition) of Wastes
Urea, creatinine, uric acid
Homeostasis:

3. Kidneys Held in position by: Sit on either side of vertebral column
around 11-12th ribs
Right is inferior b/c of liver
adrenals on top

5. Blood Supply Receive 20-25% of total cardiac output
~1200mL each minute
Afferent arteriole-
Efferent arteriole-

6. Nephrons 4 2 5
Cortex 1
medulla 3

7. Types of Nephrons
Cortical nephrons-85%
Juxtamedullary nephrons-15%

8. 1. Renal Corpuscle F(x): Bowman’s (glomerular) capsule- surrounding
Simple squamous capsular epithelium & visceral epi
Glomerulus (capillaries)
Fenestrated (pores)
Brought by
Blood pressure

9. Glomerulus -around each glomerular capillary
Visceral layer
Podocytes/pedicles
Filtration slits
Fenestrated capillaries
Mesangial cells
Supporting cells that contract to control capillary diameter
Affected by
Glomerulus -around each glomerular capillary

10. Structures involved in Urine Formation
Filtration:
Water reabsorption:
Solute reabsorption:

11. What is Urine? Homeostasis-regulates volume & composition of blood
Urea-
Creatine-
Uric Acid-

12. Basic Processes of Urine Formation
Glomerular filtration- BP forces water/solutes across capillaries
Tubular Secretion- transport of solutes from peritubular capillaries into tubular fluid (backup to filtration, excretion of toxins)
Tubular Reabsoprtion-removal of water/solutes from filtrate. Reclaims water, electrolytes & glucose (useful materials)

13. Glomerular Filtration
Afferent > Efferent
Opposing forces
Opposing forces
Glomerular Filtration Rate: Amt of filtrate produced by kidneys each minute
Creatinine clearance test: estimate GFR in mL/min

14. Autoregulation of GFR Myogenic mechanism:
*If this fails, then endocrine system kicks in

15. Hormonal Control EPO, Aldosterone, ADH- Renin-angiotensin system
Drop in GFR = renin release by juxtaglomerular complex
Renin converts angiotensinogen to angiotensin I
Angiotensin converting enzyme (ACE) converts angiotensin I to angiotensin II in lungs
Vasocontriction = increase in BP & blood volume, restores GFR
ANP (atria) & BNP (ventricles):
Blood volume increases = GFR increases (speed up fluid loss in urine)
Dilation of afferent/constriction of efferent
Increases GFR, Na+ secretion

16. 2. Reabsorption & Secretion at PCT
Reabsorption of organic nutrients/water
Ion reabsorption
Secretion
Methods: Movement of Na+

17. 3. Nephron Loop Countercurrent Multiplication
Thin Descending Limb
Thick Ascending Limb
Water follows salt!
Sodium/chloride pumped out of ascending limb
Increases osmotic concentration around descending limb
Results in flow of water out of descending limb

18. 4. Distal Convoluted Tubule 5. Collecting Ducts
Allows further reabsorption of water
DCT CD

19. Controlling pH of Body Fluids
pH drops =
pH rises =

20. Water Reabsorption
Obligatory
Facultative
Controlled
ADH release =

21. Vasa Recta

23. Urine Urinalysis: analysis of urine sample
Density compared to distilled water
Urobilin-produced from urobilinogens made by bacteria in colon

24. Ureter
F(x):
3 layers:
Inner mucosa (transitional epi & lamina propria)
Smooth muscle
contracts about every 30 sec to move urine
Outer CT layer

25. Urinary Bladder Hollow, muscular Stabalized by Detrusor muscle:
Inner/outer longitudinal layer
Middle circular layer
Sphincters:
Internal-
External-

26. Urethra Mucous membrane (stratified squam. & lamina propria)
Concentric layers of smooth muscle
External urethral orifice (external opening)
Male carries both urine & semen

27. Micturition Distention of urinary bladder Bladder fills =
Afferent fibers >
Efferent fibers >
Voluntary relaxation of external urethral sphincter & involuntary relaxation of internal urethral sphincter

28. Aging
Incontinence:

29. Diseases of the Urinary System
Glomerulonephritis:
Kidney Stones:
Renal Failure: