1. DR.Tazeen Hassan shah M.Phil physiology
EXCRETORY SYSTEM
DR.Tazeen Hassan shah
M.Phil physiology

3. kidney Structural and functional unit of kidney is nephron glomerulus
renal tubules:pct,loop of henle,dct,collecting tubule,collecting ducts(250 each draining 4000 nephrons)

4. FUNCTIONS OF KIDNEY Removal of metabolic waste Electrolyte balance
Water balance
Regulation of blood pressure
Regulation of acid-base balance
Erythropoiesis
Vit D activation
Release of renin

5. Gluconeogenesis Release of kinins VASCULAR BEDS OF KIDNEY GLOMERULUS:60 mm of hg PERITUBULAR CAPPILLARIES:13 mm of hg

6. TYPES OF NEPHRON
Cortical nephron:present in renal cortex,short loop of henle,that is surrounded by tortuous peritubular cappillaries.
Juxtra medullary nephron(30%):present near corticomedullary junction,long loop of henle,surrounded by straight pt cappillaries,k/as vasa recta,concerned with concentration of urine.

8. URINE FORMATION GLOMERULAR FILTRATION SELECTIVE REABSORPTION
ACTIVE SEREATION

9. GLOMERULAR FILTRATION
125ml of plasma is filtered each min,or 180L/d
Of which lit are reabsorbed and 1.5 lit becomes urine/day
Whole plasma is filtered 60 times /day

10. SELECTIVE REABSORPTION
As filtrate passes via renal tubules ,nutrionally important subtances are reabsorbedto blood via peritubular cappillaries,e.g:glucose,amino acid,vitamins.
Unwanted substances are not reabsorbed eg:urea,creatinine

11. Active secreation
Some substances are actively secreated into renal tubules via peritubular cappillaries like H and K ions
EXCRETION
Substances not reabsorbed and those which are secreated together with water are finally excreted via kidney as urine.

12. GLOMERULAR FILTRATION
Through high pressure bed of glomerulus
125ml/min or 180L/day
No cells are filtered,no proteins are filtered
Donnan’s effect:cat ions less and anions more filtered
Plasma bound substances are less filtered

14. FILTRATION MEMBRANE Surface area: 0.8 msq Has three layers:
Endothelium: fenestrated .large pores.
Basement membrane:negatively charged proteoglycans,these repel and oppose the filtration of –vely charged plasma proteins.
Epithelium:has podocyted with pores called slit pores.

15. FILTRATION PRESSURE Hydrostatic pressure:60mmof hg
Plasma colloid osmotic pressure:32
Capsular pressure :18
Net filtration pressure: =+10mm of hg
Filtration coefficient:125/10=12.5/min/mm of hg

16. Factors affecting GFR Increase bp….increase GFR
Inc gcp……inc GFR(glomerulonephritis)
Inc bcp……dec GFR(UT obstruction)
Dec filtration area…dec GFR
Afferent arteriolar constriction… dec GFR
Afferent arteriolar dilation…..inc GFR
Efferent arteriolar constriction…inc GFR…long term dec GFR

17. Sympathetic stimulation-dec GFR
Angiotensin 2 …..dec GFR
FORCES FAVOURING FILTRATION
GHP=60mm of hg
bcop=0 mm of hg
FORCES OPPOSING FILTRATION
BHP=18mm of hg
GCOP=32mm of hg

18. AUTOREGULATION OF GFR OCCURS VIA JGA(JUXTRA GLOMERULAR APPARATUS)
MACULA DENSA:Proximal part of DCT,condensed cells in close contact with aff and eff arteriole,act as chemoreceptors and sense conc of Nacl reaching DCT.
JG CELLS:modified smooth muscle cells of afferent arteriole,has renin containing granules,on signals from macula densa release renin.

19. LACIS CELL:present in mesangium,act by :
afferent arterioler feedback mechanism
efferent arterioler feedback mechanism
When GFR dec less Nacl reaches macula densa in dct,It causes 2 reactions:
afferent arteriole dilation
JG cells relese more renin
more angiotensin 2 formed

20. Constriction of efferent arteriole
GFR inc toward normal