EXCRETORY SYSTEM

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EXCRETORY SYSTEM
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Function

• Disposes of wastes excess ions
• Regulates volume chemical makeup of blood by
  maintaining proper balance between water
• salts, acids bases

UREA
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• Produces renin to regulate blood pressure
  kidney function
• Produces erythropoietin to stimulate RBC
  production in bone marrow
• Metabolizes vitamin D
• to its active form

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Organs

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• Kidneys
• Ureters
• Urinary Bladder
• Urethra

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Anatomy of Kidney

• Bean-shaped
• Located between 12th thoracic vertebra and 3rd
  lumbar vertebra (partial protection)
• Rt. kidney lies lower than left
• Concave cleft on medial surface called- hilus
  which leads to the renal sinus

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• Adrenal Glands lie on top of each kidney 

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• External anatomy
• surrounded by renal capsule (protects from
  surrounding infection and trauma),  
• adipose capsule (holds kidneys in place and
  protects from trauma),
• renal fascia (anchors).

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• Internal anatomy
• renal cortex - outer region
• renal medulla - inner region with cone shaped
  renal pyramids
• renal columns separate pyramids
• renal pelvis - continuous with the ureter leaving
  the hilus
• major and minor calyces

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Renal column
Renal pyramid
Renal calyx
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Blood and Nerve Supply

• renal arteries - deliver 1/4 total cardiac output
  to kidneys per minute 
• lobar arteries
• interlobar arteries 
• arcuate arteries 
• Interlobular arteries

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• Nephron (this is where the action is!)
• Interlobar, Interlobular, Arcuate, Lobar, Renal
  veins 
• Renal Plexus sympathetic nerve fibers

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Nephron

• over 1 million/ kidney filtering unit of kidney
  results in production of urine 

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• renal corpuscle - consisting of glomerulus,
• Bowman's
• capsule
• proximal
• convoluted
• tubule (PCT) 
• loop of Henle

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• distal convoluted tubule (DCT) 
• collecting tubule (urine collecting duct)
• papillary ducts (collection of all collecting
  tubules)

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Nephron
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1. Bowmans Capsule
2. PCT
3. DCT
4. Loop of Henle
5. Collecting Tubule
6. Renal artery

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• 7. Renal vein
• 8. Interlobular artery
• 9. Afferent artery
• 10. Glomerulus
• 11. Efferent artery
• 12. Peritubule capillaries

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Kidney Physiology

• 3 Steps involved in kidney filtration
• Glomerular Filtration 
• Passive
• Mechanical

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• based on hydrostatic pressure
• enhanced by permeability of filtration membrane
• filtration membrane consists of 3 layers

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• porous endothelium - prevents passage of cells
  large proteins
• thin basement membrane charged to repel charged
  proteins

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• visceral membrane with slit-like openings
  prevents passage of large plasma proteins
• Net Filtration Pressure
• Glomerular hydrostatic pressure Bowman's
  hydrostatic pressure (opposing forces)

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• Filtration Rate rate at which fluid
• is forced from blood into Bowman's capsule
  dependent upon
• - surface area
• - filtration membrane permeability 
• - Net filtration pressure

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• Glomerular filtration rate
• is proportional to Net filtration pressure
• anything changing pressure at the membrane also
  changes the GFR, therefore higher blood pressure
  higher GFR dehydration lower GFR

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• Tubular Reabsorption - reclamation of tubule
  contents
• difference b/t filtrate urine
• filtrate - everything in blood plasma except
  proteins cells
• urine - wastes unneeded substances

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• reclamation begins in PCT (both active/passive
  transport)
• active - glucose a.a., vit, Na, Ca, Cl, K, P,
  most require a carrier molecule. When all
  carrier molecules are bound, excess are excreted
  into urine

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• passive - (diffusion, osmosis)
• usually tied to active transport of Na
• other anions move with Na to balance charges in
  the blood.
• The anions that move depend on the blood pH
• H2O moves passively (osmosis) due to its linkage
  to Na

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• solvent drag occurs when filtrate becomes
  concentrated solvent follows the concentration
  gradient back into the body
• Explains why some drugs toxins are not excreted
  easily

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• Nonreabsorbed substances
• Urea (40 reabsorbed)
• Creatine
• uric acid
• Tubule absorption capabilities
• PCT most reabsorption occurs here

Uric Acid
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• DCT
• permeable to Na but not H2O
• urine concentration determined here
• dependent on blood pressure or volume
• dependent on hormone release

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• aldosterone - increases Na reabsorption
  therefore H2O
• ANF - opposes this
• sex hormones
• glucocorticoids

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• Tubular Secretion Reabsorption in reverse
• ammonia (secreted into the collecting tubule from
  the blood)
• Active process
• Some drugs (penicillin)

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Pathology

• Suppression - holding back
• Pyuria - tract infection
• Ptosis (hydronephrosis) - kinked ureter
• Pyelonephritis
• kidney inflammation

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• Pyelitis - inflammation of pelvis
• Anuria - no output due to low pressure
• Urethritis - inflammation of urethra
• Cystitis- inflammation of bladder

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• Dysuria- painful urination
• Incontinence - sphincter control
• Retention - involuntary suppression
• Diabetes insipidus lack of ADH
• Addison's Disease not enough aldosterone
• Excess Cl indicate stone formation

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• Excess phosphates - alkaline urine
• Cushing's Disease - hyperaldosteronism
•  Dehydration low GFR
• Hypotonic hydration water intoxication
  Hyponatremia, too much ADH
• Renal calculi kidney stones