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Renal%20Structure%20and%20Function

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Renal Structure and Function Kidneys Paired Retroperitoneal Partially protected by the 11th and 12th ribs Right slightly lower due to liver Surrounded by renal ... – PowerPoint PPT presentation

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Title: Renal%20Structure%20and%20Function


1
Renal Structure and Function
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

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Anatomy
  • Hilum (hilus)
  • Renal artery and vein
  • Cortex
  • Medulla
  • Renal pyramids and renal papillae
  • Major and minor calyces
  • Renal Pelvis
  • Ureters

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  • Ureters connect kidneys to urinary bladder
  • Urethra leads from bladder outside the body

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  • 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

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  • 2. Regulation
  • Blood volume and composition
  • Electrolytes
  • Blood pH
  • Blood pressure

11
Nephron
  • Functional unit of the kidney
  • Filtration, tubular reabsorption, tubular
    secretion
  • Renal corpuscle
  • Glomerulus capillaries
  • Glomerular or Bowmans capsule

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  • Bowmans capsule
  • Receives filtrate
  • Proximal convoluted tubule
  • Reabsorption of water and solutes
  • Nephron loop or Loop of Henle
  • Regulates concentration of urine
  • Distal convoluted tubule and Collecting duct
  • Reabsorption of water and electrolytes
  • ADH, aldosterone, ANP
  • Tubular secretion

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Filtration
  • Renal corpuscle
  • Filtration membrane
  • Fenestrated endothelium of capillaries
  • Basement membrane of glomerulus
  • Slit membrane between pedicels of podocytes

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Forces that influence filtration
  • Glomerular blood hydrostatic pressure
  • Opposing forces
  • Plasma colloid osmotic pressure
  • Capsular hydrostatic pressure

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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

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GFR influenced by
  • Blood pressure and blood flow
  • Obstruction to urine outflow
  • Loss of protein-free fluid
  • Hormonal regulation
  • Renin angiotensin
  • Aldosterone
  • ADH
  • ANP

23
Juxtaglomerular apparatus
  • Juxtaglomerular cells lie in the wall of afferent
    arteriole
  • Macula densa in final portion of loop of Henle
    monitor Na and Cl- conc. and water
  • Control blood flow into the glomerulus
  • Control glomerular filtration

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Tubular reabsorption
  • Water, glucose, amino acids, urea, ions
  • Sodium diffuses into cell actively pumped out
    drawing water with it

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  • In addition to reabsorption, also have tubular
    secretion substances move from peritubular
    capillaries into tubules a second chance to
    remove substances from blood.

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  • 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 maximum amount of a substance
    that can be absorbed per unit time
  • Renal threshold plasma conc. of a substance at
    which it exceeds Tm.

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

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Distal convoluted tubule and collecting ducts
  • What happens here depends on ADH
  • Aldosterone affects Na and K
  • ADH facultative water reabsorption
  • Parathyroid hormone increases Ca reabsorption

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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)

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Renal diagnostic procedures
  • Urinalysis is non-invasive and inexpensive
  • Normal properties are well known and easily
    measured

39
pH
  • Normally 4.8 8.0
  • Higher in alkalosis, lower in acidosis
  • Diabetes and starvation ? pH
  • Urinary infections ? pH
  • Proteus and pseudomonas are urea splitters

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 1.010
    remains fixed 2/3 of nephron mass has been lost

41
  • Diabetes insipidus 1.003
  • Diabetes mellitus 1. 030
  • Emesis or fever 1.040

42
Microscopic analysis
  • Red blood cells should be few or none
  • Hematuria large numbers of rbcs in urine
  • Catheterization
  • Menstruation
  • Inflamed prostate gland
  • Cystitis or bladder stones

43
  • Casts precipitate from cells lining the renal
    tubules
  • Red cells tubule bleeding
  • White cells tubule inflammation
  • Epithelial cells degeneration, necrosis of
    tubule cells

44
  • Crystals
  • Infection
  • Inflammation
  • stones

45
  • White blood cells
  • Pyuria
  • Urinary tract infection
  • Bacteria

46
Substances not normally present in urine
  • Acetone
  • Bile, bilirubin
  • Glucose
  • Protein albumin
  • Renal disease involving glomerulus

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

48
Creatinine clearance
  • Creatinine is an end product of muscle metabolism
  • Muscle mass is constant creatinine is constant
  • Normal 0.7 1.5 mg/ dL in plasma
  • Can then be compared to creatinine in urine over
    24 hour period to determine clearance

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  • 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

50
Diagnostic testing
  • Inulin clearance - not absorbed or secreted
    GFR
  • PAH para-aminohippuric acid not absorbed
    actively secreted renal plasma flow
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