2. Kidneys
⢠Paired
⢠Retroperitoneal
⢠Partially protected by the 11th and 12th ribs
⢠Right slightly lower due to liver
⢠Surrounded by renal capsule
⢠Adipose capsule
⢠Renal fascia
2
9. ⢠Kidneys make up 1 % of body mass, but
receive about 25% of cardiac output.
⢠Kidney has two major functions:
1. Filtration of blood
⢠Removes metabolic wastes from the body,
esp. those containing nitrogen
9
11. Nephron
⢠Functional unit of the kidney
⢠Filtration, tubular reabsorption, tubular
secretion
⢠Renal corpuscle:
â Glomerulus â capillaries
â Glomerular or Bowmanâs capsule
11
12. ⢠Bowmanâs capsule
â Receives filtrate
⢠Proximal convoluted tubule
â Reabsorption of water and solutes
⢠Nephron loop or Loop of Henle
â Regulates concentration of urine
⢠Distal convoluted tubule and Collecting
duct
⢠Reabsorption of water and electrolytes
â ADH, aldosterone, ANP
â Tubular secretion
12
20. Glomerular Filtration Rate
⢠Volume of plasma filtered / unit time
⢠Approx. 180 L /day
⢠Urine output is about 1- 2 L /day
⢠About 99% of filtrate is reabsorbed
20
22. GFR influenced by:
⢠Blood pressure and blood flow
⢠Obstruction to urine outflow
⢠Loss of protein-free fluid
⢠Hormonal regulation
â Renin â angiotensin
â Aldosterone
â ADH
â ANP
22
23. Juxtaglomerular apparatus
⢠Juxtaglomerular cells lie in the wall of
afferent arteriole
⢠Macula densa in final portion of loop of
Henle â monitor Na+ and Cl- conc. and
water
⢠Control blood flow into the glomerulus
⢠Control glomerular filtration
23
29. ⢠In addition to reabsorption, also have
tubular secretion â substances move from
peritubular capillaries into tubules â a
second chance to remove substances
from blood.
29
31. ⢠By end of proximal tubule have
reabsorbed:
⢠60- 70% of water and sodium
⢠about 100% of glucose and amino acids
⢠90 % of K+, bicarb, Ca++, uric acid
⢠Transport maximum â maximum amount
of a substance that can be absorbed per
unit time
⢠Renal threshold â plasma conc. of a
substance at which it exceeds Tm.
31
32. Loop of Henle
⢠Responsible for producing a concentrated
urine by forming a concentration gradient
within the medulla of kidney.
⢠When ADH is present, water is
reabsorbed and urine is concentrated.
⢠Counter-current multiplier
32
36. Distal convoluted tubule and
collecting ducts
⢠Tubular secretion to rid body of
substances: K+, H+, urea, ammonia,
creatinine and certain drugs
⢠Secretion of H+ helps maintain blood pH
(can also reabsorb bicarb and generate
new bicarb)
36
38. Renal diagnostic procedures
⢠Urinalysis is non-invasive and inexpensive
⢠Normal properties are well known and
easily measured
38
39. pH
⢠Normally 4.8 â 8.0
⢠Higher in alkalosis, lower in acidosis
⢠Diabetes and starvation â pH
⢠Urinary infections â pH
â Proteus and pseudomonas are urea splitters
39
40. Specific gravity
⢠Normal values 1.025 -1.032
⢠High specific gravity can cause
precipitation of solutes and formation of
kidney stones
⢠When tubules are damaged, urine specific
gravity approaches that of glomerular
filtrate â 1.010 â remains fixed = 2/3 of
nephron mass has been lost
40
42. Microscopic analysis
⢠Red blood cells â should be few or none
â Hematuria â large numbers of rbcâs in urine
â Catheterization
â Menstruation
â Inflamed prostate gland
â Cystitis or bladder stones
42
43. ⢠Casts â precipitate from cells lining the
renal tubules
â Red cells â tubule bleeding
â White cells â tubule inflammation
â Epithelial cells â degeneration, necrosis of
tubule cells
43
46. Substances not normally present in
urine
⢠Acetone
⢠Bile, bilirubin
⢠Glucose
⢠Protein â albumin
â Renal disease involving glomerulus
46
47. Blood Urea Nitrogen BUN
⢠Urea produced by breakdown of amino
acids - influenced by diet, dehydration,
and hemolysis
⢠Normal range 10-20 mg/ dL
⢠If the GFR decreases due to renal disease
or blockage, or decreased blood flow to
kidney - BUN increases
⢠General screen for abnormal renal
function
47
48. Creatinine clearance
⢠Creatinine is an end product of muscle
metabolism
⢠Muscle mass is constant; creatinine is
constant
⢠Normal 0.7 â 1.5 mg/ dL in plasma
⢠Can then be compared to creatinine in
urine over 24 hour period to determine
clearance
48
49. ⢠Creatinine clearance is an indirect
measure of GFR and renal blood flow
⢠Creatinine is neither reabsorbed nor
secreted, just freely filtered.
⢠Amount excreted = amount filtered
⢠Useful to monitor changes in chronic renal
function
⢠Increases with trauma with massive
muscle breakdown
49
50. Diagnostic testing
⢠Inulin clearance - not absorbed or
secreted = GFR
⢠PAH â para-aminohippuric acid â not
absorbed ; actively secreted = renal
plasma flow
50