1. Chapter 18 Lecture Slides
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2. Functions 1. Excretion 2. Blood volume and blood pressure control
3. pH regulation
4. Concentration of solutes
5. Vitamin D production
6. Red blood cell concentration

5. Components of Urinary System
2 kidneys
2 ureters
1 urinary bladder
1 urethra

6. Figure 18.2a

7. Kidney Characteristics
Shape and size:
- bean shaped
- weighs 5 oz. (bar of soap or size of fist)
Location:
between 12th thoracic and 3rd lumbar vertebra

9. Kidney Structures Renal capsule:
- connective tissue around each kidney
- protects and acts as a barrier
Hilum:
- indentation
- contains renal artery, veins, nerves, ureter

10. Renal sinus:
contains renal pelvis, blood vessels, fat
Renal cortex:
outer portion
Renal medulla:
inner portion

11. Renal pyramid:
junction between cortex and medulla
Calyx:
tip of pyramids
Renal pelvis:
- where calyces join
- narrows to form ureter

14. Nephron What is it? - functional unit of kidneys
- over 1 million/kidney

16. Components of Nephron Renal corpuscle:
structure that contains a Bowman’s capsule and glomerulus
Bowman’s capsule:
- enlarged end of nephron
- opens into proximal tubule
- contains podocytes (specialized cells
around glomerular capillaries)
Glomerulus:
contains capillaries wrapped around it

18. Filtration membrane:
- in renal corpuscle
- includes glomerular capillaries, podocytes,
basement membrane
Filtrate:
fluid that passes across filtration membrane
Proximal tubule:
where filtrate passes first

19. Loop of Henle:
- contains descending and ascending loops
- water and solutes pass through thin walls
by diffusion
Distal tubule:
structure between Loop of Henle and collecting duct
Collecting duct:
- empties into calyces
- carry fluid from cortex through medulla

20. Figure 18.5a

21. Figure 18.4

22. Flow of Filtrate through Nephron
Renal corpuscle
Proximal tubule
Descending loop of Henle
Ascending loop of Henle
Distal tubule
Collecting duct
Calyx
Renal pelvis
Ureter

23. Blood Flow through Kidneys
Renal artery
Interlobal artery
Arcuate artery
Interlobular artery
Afferent arteriole
Glomerulus
Efferent ateriole
Peritubular capillaries
Vasa recta
Interlobular vein
Arcuate vein
Interlobar vein

26. Urine Formation-Filtration
Movement of water, ions, small molecules through filtration membrane into Bowman’s capsule
19% of plasma becomes filtrate
180 Liters of filtrate are produced by the nephrons each day
1% of filtrate (1.8 L) become urine rest is reabsorbed

27. Only small molecules are able to pass through filtration membrane
Formation of filtrate depends on filtration pressure
Filtration pressure forces fluid across filtration membrane
Filtration pressure is influenced by blood pressure

30. Urine Production-Reabsorption
99% of filtrate is reabsorbed and reenters circulation
Proximal tubule is primary site for reabsorption of solutes and water
Descending Loop of Henle concentrates filtrate
Reabsorption of water and solutes from distal tubule and collecting duct is controlled by hormones

35. Urine Production-Secretion
Water, small ions, by products of metabolism, drugs, urea are found in urine

36. Ureters, Urinary Bladder, Urethra
small tubes that carry urine from renal pelvis of kidney to bladder
Urinary bladder:
- in pelvic cavity
- stores urine
- can hold a few ml to a max. of 1000 ml
Urethra:
- tube that exits bladder
- carries urine from urinary bladder to
outside of body

38. Renin-Angiotensin-Aldosterone Mechanism
Renin acts on angtiotensinogen to produce angiotensin I
Angiotensin-converting enzyme converts angiotensin I to angtiotensin II
Angiotensin II causes vasoconstriction
Angiotensin II acts on adrenal cortex to release aldosterone
Aldosterone increases rate of active transport of Na+ in distal tubules and collecting duct
Volume of water in urine decreases

40. Antidiuretic Hormone Mechanism
ADH is secreted by posterior pituitary gland
ADH acts of kidneys and they absorb more water (decrease urine volume)
Result is maintain blood volume and blood pressure

42. Atrial Natriuretic Hormone
ANH is secreted from cardiac muscle to right atrium of heart when blood pressure increases
ANH acts on kidneys to decrease Na+ reabsorption
Sodium ions remain in nephron to become urine
Increased loss of sodium and water reduced blood volume and blood pressure

45. Urine Movement Micturition reflex:
activated by stretch of urinary bladder wall
Action potentials are conducted from bladder to spinal cord through pelvic nerves
Parasympathetic action potentials cause bladder to contract
Stretching of bladder stimulates sensory neurons to inform brain person needs to urinate

47. Thirst Regulation
Water intake is controlled by hypothalamus in thirst center
Conc. of blood increase thirst center responds by initiating sensation of thirst
When water is consumed, conc. of blood decreases and sensation of thirst decreases

49. Regulation of Acid-Base Balance
Buffers
Chemicals resist change in pH of a sol’n
Buffers in body contain salts of weak acids or bases that combine with H+
- 3 classes of buffers: proteins, phosphate buffer, bicarbonate buffer

50. Respiratory System
Responds rapidly to change in pH
Increased resp. rate raise pH due to rate of carbon dioxide elimination being increased
Reduced respiratory rate reduced pH due to rate of carbon dioxide elimination being reduced

51. Kidneys
Nephrons secrete H+ into urine and directly regulate pH of body fluids
More H+ if pH is decreasing and less H+ if pH is increasing

53. Acidosis and Alkalosis
Acidosis occurs when pH of blood falls below 7.35
2 types are resp. acidosis and metabolic acidosis
Alkalosis occurs when pH of blood increases above 7.45