صدق الله العظيم الاسراء اية 58

By Dr. Abdel Aziz M. Hussein Lecturer of Medical Physiology

Test Yourself The cortex of the kidney contains the a. hilus. b. glomeruli. c. perirenal fat. d. renal pyramids. e. renal pelvis.

A layer of fibrous connective tissue that surrounds each kidney is the a. hilum. b. renal pelvis. c. renal sinus. d. renal capsule. e. perirenal fat.

Def.: It is the fraction of CO that supplies both kidneys i.e. renal fraction RBF

Value: ¼ CO or 1200 ml/min or 4 ml/ 1 gm kidney tissues Significance: Is high to ensure high GFR NOT to supply excess O2 for excess metabolism

Distribution: A) 10% supply non-functioning structures of kidney a) capsule b) pelvis c) perinephric fats B) 90% functioning structures Cortex → 88% - 89% Medulla → 1- 2%

Cortex Outer Medulla Inner Medulla 4-5 ml/ min 1 gm ml /min/ 1gm 0.2 – 0.25 ml /min/ 1gm

2. High length of vasa recta 1. Small number of vessels 3. High viscosity of medullary blood flow

Mechanisms: 2 mechanisms; Autoregulation -ve tubuloglomerular feedback mechanism Myogenic theory Extrinsic regulation Nervous mechanism Humoral mechanism e.g. ADH, AII, ……

Def.,: It is the ability of the kidney to keep its RBF and GFR at nearly normal levels in the face of reasonable changes of ABP Range of Autoregulation: From 80 – 180 mmHg is not perfect 100% since RBF and GFR show changes by less than 10% with previous range of ABP

15 ABP 180 mmHg80 mmHg GFR mL / min RBF

Significance: To minimize effect of change of ABP on GFR and hence on Na + and water excretion or helps to decouple renal regulation of salt and water excretion from fluctuation of ABP Mechanism of Autoregulation: Mainly by variation of afferent arteriolar resistance Two theories; 1.Myogenic theory 2.Tubuloglomerular –ve feedback theory

Increased ABP Increased RBF GFR High NaCl Adenosine V.C. of afferents Decreased RBF

Decreased ABP Decreased RBF GFR Low NaCl PGI2 V.D. of afferents Renin release Angiotensin II

V.D. wall of arteriole ↓ Renal Blood Flow Decreased stretch of vessel wall Decrease of ABP Increase of RBF to Normal Level

V.C. wall of arteriole ↑ Renal Blood Flow Increased stretch of vessel wall Increase of ABP Decrease of RBF to Normal Level

The extrinsic regulation of RBF is mediated by nervous and chemical factors 1.Nervous Factors: sympathetic N.S. 2.Humeral Factors: autacoids and hormones A) Angiotensin II (strong V.C. agent) At low concentration → V.C. of efferent → protect GFR At high concentration → generalized V.C. → ↓GFR and RBF b) ADH, serotonin, and endothelin → V.C. of renal blood vessels →↓ RBF c) Prostaglandins (PGE 2 & PGI 2 ), NO, ANP, dopamine and bradykinin → V.D. d) Hormonal changes during pregnancy → ↑ RBF by 50% e) High protein diet → ↑ RBF by 30%

Angiotensin converting enzyme inhibitors (ACEIs) are a group of drugs that inhibits AII thus dilate the efferent arteriole and reduce GFR. These drugs also reduce the hyperfiltration occurring in DM, thereby minimizing the occurrence of nephropathy.

Mild Sympathetic N.S. stimulation No change in GFR Minimal effect on B.V. No change in RBF

Moderate Sympathetic N.S. stimulation Minimal decrease in GFR Equivocal V.C. of both afferent and efferent Moderate decrease in RBF

Severe Sympathetic N.S. stimulation Marked decrease in GFR Intense V.C. of both afferent and efferent Marked decrease in RBF Renal Shutdown

Given these structures: 1. major calyx 2. minor calyx 3. renal papilla 4. renal pelvis Choose the arrangement that lists the structures in order as urine leaves the collecting duct and travels to the ureter. a. 1,4,2,3 b. 2,3,1,4 c. 3,2,1,4 d. 4,1,3,2 e. 4,3,2,1

Which of these structures contains blood? a. glomerulus b. vasa recta c. distal tubule d. Bowman’s capsule e. both a and b

The juxtaglomerular cells of the ………….and the macula densa cells of the………… form the juxtaglomerular apparatus. a. afferent arteriole, proximal tubule b. afferent arteriole, distal tubule c. efferent arteriole, proximal tubule d. efferent arteriole, distal tubule

Given these blood vessels: 1. afferent arteriole 2. efferent arteriole 3. glomerulus 4. peritubular capillaries Choose the correct order as blood passes from an interlobular artery to an interlobular vein. a. 1,2,3,4 b. 1,3,2,4 c. 2,1,4,3 d. 3,2,4,1 e. 4,3,1,2

Def., It the membrane through which the plasma is filtered Composition: 3 layers; 1.Capillary endothelium 2.Basement membrane 3.Capsular epithelium

Single layer of fenestrated endothelium (each fenestra is about nm). Total fenestrations represent about 9% of total surface area of the capillary. Acts as a screen to prevent blood cells and platelets from contact with basement membrane Capillary endotheliumFenestrations Blood cells Solutes

Formed of network of fibrils embedded in a jelly-like matrix. Thickness  m. Acts as a sieve allowing retention of plasma proteins  main barrier. Basement Membrane

cellsPP endotheliumBasement m. Cap. epith. Bowman space others Glom. Memb. Blood

Single layer of podocytes, each has a finger like process that make a space with each other called slit pores of about 5 nm in diameter. Bowman's capsular epithelium

Functions: a) Laydown & maintain B.M. b) Phagocytose the escaped macromolecules. Bowman's capsular epithelium

3 factors affecting permeability of G.M. A)Molecular weight and size B)Shape and configuration C)Charge

Size: Radius below 18 A 0  freely filtered. Radius between A 0  filtered by rate dependent on the charges; cationic more filtered than anionic of same radius (as the filtering membrane has net negative charge). Radius more than 36 A 0  not filtered.

Blood components endothelium Basement m. Cap. Epith. Bowman space 18 A 36 A 18 – 36 A -+

Weight: Molecular weight below  freely filtered. Molecular weight above  difficult to pass. In between –  depend on charge & configuration.

Blood components endothelium Basement m. Cap. Epith. Bowman space –

Glomerular membrane has a net hole or cylindrical pore of 7.5 – 10 nm wide Substances of shape & configuration similar to the holes of the glomerular membrane  freely pass & vice versa.

Blood components endothelium Basement m. Cap. Epith. Bowman space CylindricalOther shapes endothelium Basement m. Cap. Epith.

Anionic  repelled & cationic pass. Loss of negative charge from glomerular membrane  early proteinuria even before any detectable microscopic changes in the membrane.

Blood components endothelium Basement m. Cap. Epith. Bowman space +ve -ve endothelium Basement m. Cap. Epith.

Blood components endothelium Basement m. Cap. Epith. Bowman space +ve -ve endothelium Basement m. Cap. Epith.

They are inter-capillary, mononucleated, stellate contractile cells embedded in the extracellular matrix

1.Phagocytic for the trapped immunoglobulins 2. Support & hold the delicate glomerular structures in position 3. Control surface area available for filtration by their contraction and relaxation

Their relaxation increases surface area AND decreases Capillary Hydrostatic Pressure Decrease GP

Their contraction decreases surface area available for filtration & increases capillary hydrostatic pressure Increase GP

Factors contractingFactors relaxing EndothelinANP AII, NE, ADHDopamine Platelet activating factorPGE Platelet derived growth factorcAMP Thromboxane A 2 Leukotriens C & D Histamine

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