1. 4/9/08 Urinary System Chapter 24 – Day 2

2. 4/9/08 Review Nephron Structure  Network with blood vessels  Two types of nephrons ♦Cortical Nephrons – loop of Henle does not extend below cortex ♦Juxtamedullary nephrons – loop of Henle extends into medulla ♦Vasa recta – feature of jextamedullary nephrons ♦85% are cortical nephrons Majority of process is done here ♦15% are juxtamedullary Important role in concentrating urine Conserving water in the body

3. 4/9/08 Renal corpuscle  Renal arteries branch into afferent arterioles in the cortex  One afferent arteriole enters the renal corpuscle  Wall of the renal corpuscle is the Bowman’s capsule  Afferent arteriole branches into capillary network ♦Glomerulus, inside the corpuscle within the bowman’s capsule  A second efferent arteriole connects to the glomerulus – brings blood out of the renal corpuscle ♦(Efferent arteriole is thinner than afferent)  Efferent arteriole branches around nephron as peritubular capillaries and vasa recta  Eventually the efferent arteriole connects to venules – carries blood to renal veins and out of the kidney

4. 4/9/08 Nephrons & blood supply Fig. 24.7

5. 4/9/08 Kidneys – Blood supply Fig. 24.5

6. 4/9/08 Glomerulus  Surrounded by 2 layers ♦Bowman’s capsule: Visceral epithelium Parietal epithelium ♦Separated by capsular space  Blood in the glomerulus is bounded by 2 walls ♦Endothelial cells of the blood vessels ♦Visceral layer of the bowman’s capsule Fig. 24.8

7. 4/9/08 Glomerulus  Endothelial cells of blood vessels ♦Have large diameter pores: Fenestrations Basement membrane  Visceral Layer of the Bowman’s capsule ♦Special basement membrane = lamina densa ♦Special cells = podocytes These have special feet like structures called pedicels Spaces between pedicels = filtration slit/slit pore  Special structures of the endothelial cells and visceral layer restrict the passage of particles according to size (analogous to the filter paper)  Capsular space = place where filtrate is released

8. 4/9/08 Glomerulus - barriers Fig. 24.8

9. 4/9/08 Glomerulus blood boundaries Fig. 24.8c

10. 4/9/08 Filtration in the Glomerulus  Blood rushes into glomerulus via the afferent arteriole  Difference in diameter between afferent & efferent arterioles results in High Blood Pressure inside the Glomerulus ♦= Effective Filtration Pressure (EFP)  This pushes blood against the endothelial cells ♦Filtration takes place ♦Fenestrated capillaries – stops blood cells from passing through, but all other contents go through ♦Basement membrane – stops large proteins ♦Pedicels/filtration slits – stops medium-sized proteins from leaving blood

11. 4/9/08 Glomerular Filtration Fig. 24.10

12. 4/9/08 Filtrate  Remaining contents end up in the capsular space and are called filtrate  Contents of filtrate: ♦Water ♦Small proteins ♦Glucose ♦Amino acids ♦Vitamins ♦Citric acid ♦Ions: Na +, Cl -, K +, HCO 3 ♦ ammonia ♦Urea ♦Bilirubin ♦Neurotransmitter ♦Hormones

13. 4/9/08 Filtrate - PCT  Filtrate passes to proximal convoluted tubule (PCT) ♦PCT walls = simple cuboidal epithelium ♦Outside fluid = peritubular fluid ♦Then peritubular capillaries  PCT – reabsorption begins ♦99% of the reabsorption is of organic materials Glucose, amino acids, vitamins, citric acid ♦Facilitated diffusion ♦Transport of Ions = active transport & passive ♦Water reabsorption = osmosis  Enters peritubular fluid, then to capillaries

14. 4/9/08 Filtrate – Loop of Henle  Tubular fluid with remaining contents flows into Loop of Henle ♦Descending & Ascending Limbs  Juxtamedullary nephrons – in contact with the vasa recta  Reabsorption of water & solutes ♦(specifically Na + & Cl - )  Descending & Ascending limbs have different properties – very important in concentrating urine

15. 4/9/08 Loop of Henle  Descending limb = thin ♦Permeable to H 2 O ♦Mostly impermeable to salts (Na +,Cl -)  Ascending limb = thick ♦Impermeable to H 2 O and solutes ♦Prevents diffusion by concentration gradient ♦Allows selective permeability ♦Only Na + & Cl - can leave via active transport while wastes stay in ♦Salts (Na +,Cl - ) are pumped out by active transport = reabsorption of Na + & Cl - into blood Fig. 24.13

16. 4/9/08 Loop of Henle  As tubular fluid moves up, salts enter peritubular fluid via active transport into vasa recta  Results in a high solute concentration of peritubular fluid  Know: ♦Direction of H 2 O? Direction of salts? ♦From which limb? ♦What is the significance/importance? ♦How does the countercurrent work? Fig. 24.13

17. 4/9/08 Loop of Henle  Countercurrent flow drives reabsorption ♦Osmotic concentration is constantly maintained ♦Allows reabsorption of H 2 O into blood b/c osmotic concentration is high in the peritubular fluid (due to high salts) ♦= contercurrent multiplication (exchange increases)  Loss of H 2 O from descending limb concentrates solutes in urine  Tubular fluid containing mostly wastes & some ions enters distal convoluted tubule (DCT)

18. 4/9/08 Filtrate – Distal Convoluted Tubule  Further reabsorption of salts (Na + & Cl - ) ♦Active and Passive  Presence of aldosterone alters rate of Na + reabsorption  Ca 2+ may be reabsorbed depending on calcitriol  Secretion also occurs in DCT  Wastes are not reabsorbed – moves forward to collecting tube Fig. 24.15

19. 4/9/08 Filtrate – Distal Convoluted Tubule  Further reabsorption of salts (Na + & Cl - ) ♦Active and Passive  Presence of aldosterone alters rate of Na + reabsorption  Ca 2+ may be reabsorbed depending on calcitriol  Secretion also occurs in DCT  Wastes are not reabsorbed – moves forward to collecting tube Fig. 24.15

20. 4/9/08 Urinary System Chapter 24 – Day 3

21. 4/9/08 Nephron - Secretion  Reabsorption & secretion take place in the DCT  Secretion: ♦Other wastes that did not enter the nephron during filtration ♦Transported later by secretion ♦Peritubular capillaries → nephron ♦PCT & DCT are involved in secretion ♦K + and H + ions – depends on blood levels/blood conditions Example: H + ions increase from CO 2 conversion, they are secreted to maintain balance Diabetes: ketones are released = acidic, so more H + is secreted ♦NH 4 + ions (comes from removal of NH 3 group from amino acids) ♦Other secreted compounds = drugs, creatinine, neurotransmitters

22. 4/9/08 Filtrate – Collecting Duct  Urine moves into the collecting tubule (urine) ♦Some reabsorption: Na + ions HCO 3 - ions Some urea reabsorption (helps to maintain high salt concentration in peritubular fluid)  Concentration gradient is very important to keep the flow of things moving properly ♦Ions & H 2 O enter peritubular fluid, then go to vasa recta Keeps a constant concentration gradient of high salt levels in the peritubular fluid  H 2 O reabsorption in kidney = very important process ♦Helps to keep H 2 O balanced in the body ♦Depends on solute concentration

23. 4/9/08 Urine - hydration  If the body is well hydrated H 2 O absorption occurs only in the descending limb of Loop of Henle  Solute concentration gradient in Loop of Henle & Collecting Tubule** Fig. 24.13

24. 4/9/08 Urine - hydration  Dilute urine = large volume because high amounts of water are retained  Only ions are reabsorbed heavily  If the body is dehydrated – activates pituitary gland to produce antidiuretic hormone (ADH) ♦Body conserves H 2 O in the kidney & thirst response for more H 2 O intake ♦Special H 2 O channels open in collecting tubule ♦H 2 O is reabsorbed from collecting tubule ♦Driven by diffusion because salt concentration is already high outside ♦Yields concentrated urine – small volume (conc. urea)  Diuretics like caffeine: ♦Prevent H 2 O reabsorption in collecting tubule, force H 2 O out of cells ♦Leads to dilute urine but reduces blood volume ♦Are also used to alter blood pressure

25. 4/9/08 REVIEW & LEARN Fig. 24.16

26. 4/9/08 REVIEW & GET THE “GIST” Fig. 24.17

27. 4/9/08 Urine Collection and Reabsorption  After filtration, reabsorption & secretion – urine is produced  From the papillary duct it enters the minor calyx  There it joins with other to form the major calyx  Then it joins the renal pelvis Fig. 24.7, 24.4

28. 4/9/08 Urine Collection and Reabsorption  Urine collects in the renal pelvis  Urine is then delivered & eliminated through the urinary tract: ♦Ureters Transport ♦Urinary bladder Storage ♦Urethra Elimination Fig. 24.1

29. 4/9/08 Ureters  Ureters are 30cm long, muscular tubes  Ureters are attached to the posterior wall of the abdomen  Ureters are arranged differently in men & women because the placement of the bladder is different in men and women Fig. 24.19

30. 4/9/08 Urinary Bladder  The urinary bladder is a highly muscular organ  Inside layer = transitional epithelium ♦This permits stretching of the bladder without damage to the surface cells  The urinary bladder is held in place with the help of ligaments  The region near the neck ♦= Inner urethral sphincter ♦Under involuntary control  The neck leads to the urethra Fig. 24.19c

31. 4/9/08 Urethra  The urethra is placed in different places in males and females ♦Males – from bladder to penis ♦Females – short urethra, located at the front of the vagina Fig. 24.19

32. 4/9/08 Urethra  At the end of the urethra is the external urethral sphincter ♦This is a muscular sphincter ~ valve ♦Voluntary control  As pressure builds up against pressure – sensitive receptors in bladder  The external sphincter relaxes – this opens the internal sphincter & urine is eliminated Fig. 24.19c

33. 4/9/08 Urethra  At the end of the urethra is the external urethral sphincter ♦This is a muscular sphincter ~ valve ♦Voluntary control  As pressure builds up against pressure – sensitive receptors in bladder  The external sphincter relaxes – this opens the internal sphincter & urine is eliminated Fig. 24.19c

34. 4/9/08 Urine Elimination – Neural Control Fig. 24.21

35. 4/9/08 Kidney Problems Glomerular Nephritis  Caused by inflammation of the glomerulus  How does that inflammation occur? ♦Allergic reaction, bacterial infection, other pathogens lead to an inflamed, swollen glomerulus  Filtration is affected ♦There is less of a “block” to the permeability of endothelial cells and capsular membrane ♦More RBCs and proteins end up in the filtrate  Degree of affliction: acute to minimal

36. 4/9/08 Acute Glomerular Nephritis  Typical cause: ♦Strep. infection elsewhere in the body ♦Glomerulus produced inflammatory response due to antibody/antigen complex ♦Most common in children and young adults  Symptoms ♦Fever, chills, nausea, edema, urinary failure ♦Can result in kidney failure  Treatment: ♦Drugs to eliminate antibody/antigen complex ♦Steroids to reduce inflamation ♦Rest  Glomerular lesions already present will not heal

37. 4/9/08 Urinary Tract Infection  Very common, especially in females  Cystitis = infection in urinary bladder  Urethritis = infection in urethra  Pyelonephritis = infection in the kidney  Symptoms: ♦Back pain, fever, nausea, discharge ♦Urgency to urinate ♦Frequent urination  Causes: ♦Bacterial infection (entered at urethra)  Treatment ♦Antibiotics

38. 4/9/08 Incontinence  Lack of bladder control  Urinary sphincters cannot control passage of urine  May be psychological or physiological  Incontinence ♦Causes: muscle damage to sphincter Nerve damage (surgery or tumor) Medications &/or stress ♦Treatments (adult patients) Kegel exercises to improve sphincter muscle tone Electrical stimulations to suppress bladder contractions May just need absorptive pads  Read about urine retention p749 for developmental stages - Enuresis (bed wetting )

39. 4/9/08 Kidney Problems – Kidney Stones  Kidney stones = renal caliculi  Salt exchange happens in the kidney, thus crystals can be formed  Normally, protein acts as a crystal growth inhibitor  If abnormal conditions exist: ♦Crystal growth is not prevented – growth in renal pelvis  Mostly kidney stones are precipitated Ca 2+ salts like CaPO 4  These can get trapped in the ureter and this causes severe pain

40. 4/9/08 Kidney Problems – Kidney Stones  Causes of Kidney Stones: ♦No inhibition ♦Dehydration ♦Excess Ca 2+ intake ♦“Hard” water ♦Oaxalates  Treatment ♦Observe kidney stones on pyelogram (use dye for urinary tract) ♦Pass the stone? ♦Vibration to break apart crystals ♦Extracorporeal shock wave lithotripsy http://www.webmd.com/kidney-stones/extracorporeal-shock-wave-lithotripsy-eswl-for-kidney-stones

41. 4/9/08 Renal Failure  Acute & Chronic  Hemodialysis  Read about it 745-746

42. 4/9/08 Fig. 24.6

43. 4/9/08 Kidneys – Blood supply Fig. 24.7

44. 4/9/08 Kidneys – Blood supply Fig. 24.8

45. 4/9/08 Kidneys – Blood supply Fig. 24.5

46. 4/9/08 Kidneys – Blood supply Fig. 24.5