1. Kidney structure By Natalie & Rutendo

2. Kidney: Internal Structure 1 2 5 6 9 7 8 3434 10 1 – Cortex 2 – Medulla 3 - Renal pyramid 4 – Renal Papilla 5 – Minor Calyx 6 – Major Calyx 7 – Renal Artery 8 – Renal Vein 9 – Renal pelvis 10 - Ureter

3. 123123 4 Kidney: Fascial Coverings 6 5 The kidneys are surrounded by fat and supportive renal fascia 1 - Perinephric Fat 2 – Renal Fascia also covers suprarenal glands 3 – Paranephric fat 4 - Thoracolumbar fascia Tough covering of intrinsic vertebral column muscles 5 - Psoas fascia Forms sheath down to hip region – abscess spread 6 - Renal fascial space Communicates across midline, and serves as route for infection spread

4. What is the functional unit of kidney? Nephron What are the 3 elements of nephron? 1. renal corpuscle 2. tubular component 3. vascular component

5. Gross structure of Kidney (adapted from Fig. 17.2, Fox, Human Physiology, McGraw Hill)

6. Types of Nephron (Fig. 17.6, Fox, Human Physiology, McGraw Hill) Medulla Cortex Cortical nephron Juxtamedullary nephron What are 2 types of nephron? Collecting duct each collecting duct drains ~ 6 nephrons 85% Cortical (outer cortex, short loop) 15% Juxtamedullary (inner third cortex, long loop)

7. Blood supply 90% blood to kidney perfuses … cortex and cortical nephrons cortex 10% blood to kidney perfuses …… medulla and juxtamedullary glomeruli

8. What are the parts of renal corpuscle? – (4) 1.Glomerulus 2.Bowmans capsule 3.Mesangium 4.Space What is the function of renal corpuscle? The renal corpuscle is a sieve. Its function is to produce an ultrafiltrate of plasma

9. What are the parts of the nephron? 1.Glomerulus 2.Proximal convoluted Tubule 3.Descending Limb of Henle 4.Loop of Henle 5.Ascending limb of Henle 6.Distal convoluted tubule 7.Collecting duct

11. What is a Glomerulus? The glomerulus is the vascular component of the renal corpuscle What are the 3 layers of the filtration membrane? 1.The endothelium of the capillary 2. A basement membrane type 4 collagen heparan sulphate proteoglycans Laminin 3. Layer of epithelial cells, podocytes (the foot processes are known as pedicels)

12. What is a juxtaglomerular apparatus? a microscopic structure in the kidney that regulates the function of each nephron What are the 3 cellular components of the apparatus? 1. The macula densa of the distal convoluted tubule 2. Extraglomerular Mesangial cells 3. Smooth muscle cells of the afferent arteriole known as juxtaglomerular cells

13. What is the role of JGA? The juxtaglomerular cells secrete renin in response to? (3) Sympathetic stimulation Decrease in renal perfusion pressure (detected directly by the granular cells) Decrease in NaCl concentration at the macula densa

14. What is the role of the cells of JGA? 1.In response to elevated Na, the macula densa cells trigger contraction of the afferent arteriole (by the adenosine effect), reducing flow of blood to the glomerulus and reducing glomerular filtration rate. – Acute lowering of the pressure 2.The juxtaglomerular cells, derived from smooth muscle cells, of the afferent arteriole secrete renin when blood pressure in the arteriole falls. Renin increases blood pressure via the renin-angiotensin- aldosterone system (RAAS) – increase of BP 3.Lacis cells, also called extraglomerular mesangial cells, are flat and elongated cells located near the macula densa. Their function remains unclear.

15. Filtration in the glomerulus depends on? Weight and shape Size of the molecule – it needs to fit through the hole Charge negative charges basement membrane and podocytes

16. Nephron epithelium Single layer of epithelial cells throughout Each section of the nephron has a distinct function and the cell morphology varies Proximal tubule - most reabsorption here cuboidal epithelium lots of mitochondrial (energy) brush border (surface area) Loop of Henle thick - low cuboidal epithelium thin - squamous epithelium Distal convoluted tubule juxtaglomerular complex cuboidal epithelium Glomerulus podocytes Collecting duct cuboidal epithelium

17. Excretion of metabolism & waste products Regulation of body fluid composition Endocrine organ Pre-renal renal Post-renal Blood Urine storing and then transporting urine out of the body leaks blocks infected The Urinary System

18. What are the 3 fundamental processes of nephron? 1. glomerular filtration (passive) produce ultrafiltrate (protein free plasma) contains plasma electrolytes and organic solutes <60kDa finally: urinary excretion 2. tubular secretion pH regulation (H + ) active/passive K + and ammonia passive organic acids and bases foreign substances 3. tubular reabsorption 99% of water bicarb 100% glucose 50% urea 99.5% Na + active passive

19. What are the 3 fundamental processes of nephron? 1. Glomerular Filtration 2. Tubular reabsorption 3. Tubular secretion 4. Excretion

20. How does glomerulus filter? 1. Endothelial cell fenestrations (60-100nm) Stop blood cells and platelets, but some proteins get through (Oxford text book of clinical nephrology) filtration depends on weight, shape and charge 2. Basement membrane (negative charges) allows uncharged and positively charged molecules through more easily only small plasma proteins get through 3. podocytes (negative charges, slits 4-9nm) These are the restrictive barrier. Nephrin is protein that forms slits – <7kDa freely permeable – <70kDa permeable (charge affects) – >70kDa won’t normally allow through

21. Passive process Describe the process of filtration? What are Starling’s forces? Requires pressure from artery –afferent and efferent arterioles Movement of fluid between plasma and tissue – due to Starling forces 2 types of hydrostatic pressure (in both tissue and blood vessel) colloid osmotic (oncotic) pressure [due to proteins]

22. Label the forces regulating filtrate formation BP (hydrostatic pressure in arterioles) [P gc ] t hydrostatic pressure in lumen of tubule system [P t ] oncotic pressure from plasma proteins [ π gc ] Net filtration pressure [P uf ] = P gc - P t - π gc + 45 + (-10) + (-25) = ?

23. How much is the Net filtration pressure? only 10mmH If the patient has damage to the kidney that allows plasma proteins into nephron – what happen to the GFR and why?  oncotic pressure and so  GFR (eg. Early diabetic nephropathy) Use the diagram to help your reasoning: Normal: +45 + (-10) + (-25)= +10 +45 + (-10) + (- 10) = +25

24. Filtrate 180L/day PCT 65-70% (isotonic) Loop of Henle 20% CCD/MCD regulated water reabsorption Urine 1% of filtrate (1.8L) Reabsorption of H 2 O in nephron

25. filtered 100% reabsorbed (~67%) PCT reabsorbed (~25%) excreted 0.5% Distal nephron and CD Loop of Henle reabsorbed (~8%) Reabsorption of Na + in nephron