EXCRETORY EXCRETORY SYSTEMSYSTEM

FunctionFunctionDisposes of wastes Disposes of wastes

& excess ions& excess ionsRegulates volume & Regulates volume &

chemical makeup of chemical makeup of blood by maintaining blood by maintaining proper balance proper balance between water & between water &

salts, acids & basessalts, acids & basesUREA

Produces Produces reninrenin to regulate to regulate blood pressure & kidney blood pressure & kidney functionfunction

Produces Produces erythropoietinerythropoietin to to stimulate RBC production stimulate RBC production in bone marrowin bone marrow

Metabolizes Metabolizes vitamin Dvitamin D to its active formto its active form

OrgansOrgans  

KidneysKidneysUretersUretersUrinary Urinary BladderBladder

UrethraUrethra

Anatomy of KidneyAnatomy of KidneyBean-shapedLocated between 12th thoracic

vertebra and 3rd lumbar vertebra (partial protection)

Rt. kidney lies lower than leftConcave cleft on medial surface

called- hilus which leads to the renal sinus

Adrenal Adrenal GlandsGlands lie lie on top of on top of each each kidney kidney 

External anatomyExternal anatomysurrounded by surrounded by renal renal

capsulecapsule (protects from (protects from surrounding infection surrounding infection and trauma),  and trauma),  

adipose capsuleadipose capsule (holds kidneys in place (holds kidneys in place and protects from and protects from trauma), trauma),

renal fasciarenal fascia (anchors). (anchors).

Internal anatomyInternal anatomyrenal renal cortexcortex - outer - outer

regionregionrenal renal medullamedulla - inner - inner

region with cone shaped region with cone shaped renal pyramidsrenal pyramids

renal renal columnscolumns separate separate pyramidspyramids

renal renal pelvispelvis - continuous - continuous with the ureter leaving with the ureter leaving the hilusthe hilus

major and minor major and minor calycescalyces

Renal pyramid

Renal column

Renal calyx

Blood and Nerve SupplyBlood and Nerve Supply

renal arteries - deliver 1/4 total cardiac output to kidneys per minute 

lobar arteriesinterlobar arteries arcuate arteries Interlobular arteries

Nephron (this is where the action is!)

Interlobar, Interlobular, Arcuate, Lobar, Renal veins 

Renal Plexus – sympathetic nerve fibers

NephronNephron

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

renal corpusclerenal corpuscle - consisting of - consisting of glomerulus, glomerulus,

Bowman's Bowman's capsulecapsuleproximal proximal convoluted convoluted tubuletubule (PCT)  (PCT) loop of Henleloop of Henle

distal convoluted tubuledistal convoluted tubule (DCT) (DCT) 

collecting tubulecollecting tubule (urine (urine collecting duct)collecting duct)

papillary ductspapillary ducts (collection (collection of all collecting tubules)of all collecting tubules)

Nephron

1. Bowman’s Capsule

2. PCT

3. DCT

4. Loop of Henle

5. Collecting Tubule

6. Renal artery

7. Renal vein

8. Interlobular artery

9. Afferent artery

10. Glomerulus

11. Efferent artery

12. Peritubule capillaries

Kidney PhysiologyKidney Physiology

3 Steps involved in kidney 3 Steps involved in kidney filtrationfiltrationGlomerular Filtration Glomerular Filtration 

PassivePassiveMechanicalMechanical

based on based on hydrostatic hydrostatic pressurepressure

enhanced by permeability of enhanced by permeability of filtration membranefiltration membrane

filtration membrane consists filtration membrane consists of 3 layersof 3 layers

porous endotheliumporous endothelium - - prevents passage of cells & prevents passage of cells & large proteinslarge proteins

thin basement membranethin basement membrane – – charged to repel charged charged to repel charged proteinsproteins

visceral membranevisceral membrane with slit-like with slit-like openings; prevents passage of openings; prevents passage of large plasma proteinslarge plasma proteins

Net Filtration PressureNet Filtration Pressure – –

Glomerular hydrostatic pressure Glomerular hydrostatic pressure + Bowman's hydrostatic pressure + Bowman's hydrostatic pressure (opposing forces)(opposing forces)

Filtration RateFiltration Rate: rate at which fluid : rate at which fluid

is forced from blood into Bowman's is forced from blood into Bowman's capsule; dependent upon:capsule; dependent upon:

- surface area- surface area

- filtration membrane permeability - filtration membrane permeability 

- - Net filtration pressureNet filtration pressure

- Glomerular filtration rateGlomerular filtration rate - is proportional to Net is proportional to Net filtration pressurefiltration pressure

- anything changing pressure anything changing pressure at the membrane also at the membrane also changes the GFR, therefore changes the GFR, therefore higher blood pressure = higher blood pressure = higher GFR; dehydration = higher GFR; dehydration = lower GFRlower GFR

Tubular ReabsorptionTubular Reabsorption - - reclamation of tubule contents reclamation of tubule contents difference b/t filtrate & urinedifference b/t filtrate & urine

filtratefiltrate - everything in blood - everything in blood plasma except proteins & plasma except proteins & cellscells

urineurine - wastes & unneeded - wastes & unneeded substancessubstances

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

passivepassive - (diffusion, osmosis) - (diffusion, osmosis)usually tied to active usually tied to active transport of Natransport of Na

other anions move with Na to other anions move with Na to balance charges in the blood.balance charges in the blood.

The anions that move depend The anions that move depend on the blood pHon the blood pH

HH22O moves passively O moves passively

(osmosis) due to its linkage to (osmosis) due to its linkage to Na+Na+

solvent dragsolvent drag occurs when occurs when filtrate becomes filtrate becomes concentrated & solvent concentrated & solvent follows the concentration follows the concentration gradient back into the bodygradient back into the bodyExplains why some Explains why some drugs & toxins are not drugs & toxins are not excreted easilyexcreted easily

Nonreabsorbed substancesNonreabsorbed substancesUrea (40% reabsorbed)Urea (40% reabsorbed)CreatineCreatineuric aciduric acid

Tubule absorption capabilitiesTubule absorption capabilities PCT PCT most reabsorption occurs most reabsorption occurs

herehere

Uric Acid

DCT DCT permeable to Na but not Hpermeable to Na but not H22OOurine concentration urine concentration

determined heredetermined heredependent on blood pressure dependent on blood pressure

or volumeor volumedependent on hormone dependent on hormone

release:release:

aldosterone - increases Na aldosterone - increases Na reabsorption & therefore Hreabsorption & therefore H22OO

ANF - opposes thisANF - opposes thissex hormonessex hormonesglucocorticoidsglucocorticoids

Tubular SecretionTubular Secretion – – Reabsorption in reverseReabsorption in reverseammonia (secreted ammonia (secreted

into the collecting into the collecting tubule from the blood)tubule from the blood)

Active process Active process Some drugs Some drugs

(penicillin)(penicillin)

http://www.sumanasinc.com/webcontent/anisamples/majorsbiology/kidney.html

PathologyPathologySuppressionSuppression - holding  - holding

backbackPyuriaPyuria - tract infection - tract infectionPtosisPtosis

(hydronephrosis) - (hydronephrosis) - kinked ureterkinked ureter

PyelonephritisPyelonephritis – – kidney inflammationkidney inflammation

PyelitisPyelitis -  - inflammation of pelvisinflammation of pelvis

AnuriaAnuria - no output  - no output due to low pressuredue to low pressure

UrethritisUrethritis -  - inflammation of inflammation of urethraurethra

CystitisCystitis- inflammation - inflammation of bladderof bladder

DysuriaDysuria- painful urination- painful urinationIncontinenceIncontinence - sphincter control - sphincter controlRetentionRetention - involuntary  - involuntary

suppressionsuppressionDiabetes insipidusDiabetes insipidus – lack of ADH – lack of ADHAddison's DiseaseAddison's Disease – not enough – not enough

aldosteronealdosteroneExcess ClExcess Cl – indicate stone – indicate stone

formationformation

Excess phosphatesExcess phosphates - alkaline  - alkaline urineurine

Cushing's DiseaseCushing's Disease - - hyperaldosteronismhyperaldosteronism

  DehydrationDehydration – low GFR – low GFRHypotonic hydrationHypotonic hydration – “water – “water

intoxication”; Hyponatremia, too intoxication”; Hyponatremia, too much ADHmuch ADH

Renal calculiRenal calculi – kidney stones – kidney stones