1. Where does pee come from? Rachel Boggus Boggusrl@email.uc.edu

2. The Kidney Pretty kidney But of course you need to know more about it than this

4. The kidney in detail Why does the cortex have a granular appearance? Why does the medulla have a striated appearance?

5. The kidney in detail Why does the cortex have a granular appearance? –Because of the presence of renal corpuscles Why does the medulla have a striated appearance? –Because of the radially oriented tubules that it is composed of.

6. More Kidney fun In your notes, Dr. Michaels talks about the ureter expanding into the renal pelvis  calyx, etc. In the REVERSE order of the flow of urine. I’m presenting it here in the order that urine flows through it. Because I think that makes more sense.

7. More Kidney fun Formed urine passes through large collecting ducts in the papilla and into the minor calyx

8. Several minor calyxes come together to form a major calyx.

9. The major calyces come together forming the renal pelvis which then forms the ureter

10. So go over the flow of formed urine

11. –Formed urine begins in the large collecting ducts in the renal papilla. From there it enters the minor calyces which come together forming the major calyces which come together forming the renal pelvis which constricts forming the ureter.

12. More GROSS kidney Lobes and lobules –Each lobe has a medullary pyramid (the papilla is at the tip of the pyramid) and a cortex that sits on top of the medullary pyramid –Renal columns (of Bertin, if you will) are cortical tissue that extend beyond the pyramid

13. Dr. Michaels thinks its like an ice cream cone… whatever

14. Lobules –Are cylindrical and have a central core, a medullary ray/pars radiata consisting of radially-oriented tubes –Peripheral to medullary rays are the proximal and distal convoluted tubules (PCT and DCT) in the pars convoluta/cortical labyrinth

15. What is contained in the medullary rays? What is contained in the pars convoluta?

16. What is contained in the medullary rays? –Descending and ascending thick limbs and collecting ducts What is contained in the pars convoluta? –Proximal and distal convoluted tubules, the connecting tubules and the renal corpuscles

17. BLOOD SUPPLY Renal artery  interlobar arteries  arcuate arteries  interlobular arteries  afferent arterioles  glomerular capillaries  efferent arterioles  either peritubular plexus or vasa recta

18. Interlobar arteries

19. Nephron

20. Proximal end of nephron  renal corpuscle 2 parts of a renal corpuscle? –Glomerulus and bowman’s capsule –Remember that between the bowman’s capsule and the glomerulus is the bowman’s space – filled with pee

21. The rest of the nephron is tubular Begins with proximal convoluted tubule (PROXIMAL to the glomerulus) –Extends to medullary ray where it descends toward the medulla as the straight portion of the proximal tubule or descending thick limb

23. Proximal convoluted tubule  straight portion/thick descending limb  in the medulla abrupt transition to the thin descending limb

25. Glomerulus  proximal convoluted tubule  straight portion of proximal convoluted tubule/thick descending limb  thin descending limb  Hairpin loop upwards towards cortex as thin ascending limb

27. Glomerulus  proximal convoluted tubule  straight portion of proximal convoluted tubule/thick descending limb  thin descending limb  thin ascending limb  Straight portion of the distal tubule/thick ascending limb

29. Glomerulus  proximal convoluted tubule  straight portion of proximal convoluted tubule/thick descending limb  thin descending limb  thin ascending limb  thick ascending limb/straight portion of the distal tubule  Enters medullary ray, extends to pars convoluta, crosses vascular pole and becomes distal convoluted tubule

31. Glomerulus  proximal convoluted tubule  straight portion of proximal convoluted tubule/thick descending limb  thin descending limb  thin ascending limb  thick ascending limb/straight portion of the distal tubule  distal convoluted tubule  Connecting tubule (branch of collecting duct) which extend from pars convoluta to medullary ray

33. Collecting ducts descend in medullary ray in cortex all the way through the medulla and the papilla  papillary ducts

34. What regions of the nephron are in the pars convoluta? –Renal corpuscle, PCT, DCT, connecting tubule What regions of the nephron are located in the pars radiata (medullary ray)? –Portions of the straight proximal (descending thick limb) and straight distal tubule (ascending thick limb), part of collecting duct

35. What parts of the nephron are located in the medulla? –Descending thick limb, descending and ascending thin limbs of the loop of Henle, and ascending thick limb –Collecting ducts, papillary ducts

36. Down and dirty with the PCT

37. Simple cuboidal epithelium Irregular apical surface Lots of mitochondria  acidophilic Lateral cell membranes not visible because of interdigitation 3 segements, s1, s2, s3

38. EMs of proximal and distal convoluted tubules

39. Another EM of a proximal convoluted tubule… note the brush border Also notice the crap-load of mitochondria

40. What are the functions of the proximal convoluted tubules? –Reabsorption of 60-80% of the glomerular filtrate –Active transport of Na –Removal of virtually all glucose and proteins from provisional urine *** If people are confused, REABSORPTION is from the pee tube into the interstitium, SECRETION is from interstitium to the pee tube ***

41. Straight Portion of Proximal tubule

42. Straight proximal tubule Mostly segment S3 When tubule enters medullary ray Interdigitations less pronounced Brush border more variable When epithelium changes to squamous  thin descending limb of the loop of henle

43. How do I tell PCT from straight PT? BECAUSE you are a genius and you know that PCTs are in the cortex in the pars convoluta and that the straight PT is in the medullary ray

44. Thin segment descending and ascending

45. Thin segments Located in the medulla Simple squamous epithelium Lateral interdigitations present

46. Thick Ascending Limbs

47. Blue Yellow  thick descending limbs Joins thin ascending limb at junction of inner and outer medulla Also located in the pars radiata/medullary rays

48. Distal Convoluted tubule When it enters the pars convoluta Macula densa is adjacent to afferent arteriole (we’ll talk about this later) No brush border Has lots of lateral interdigitations Primary function is reabsorption of ions

49. DCT

50. Macula densa

51. Where the DCT crosses the vascular pole Cells of DCT adjacent to arteriole become tall and narrow, nuclei look close together Helps distinguish DCT Is part of the juxtaglomerular apparatus

52. Connecting duct/tubule/whatever Connects the DCT to the collecting duct Within the pars convoluta Gradual transition of epithelium from DCT  Collecting duct

53. Cortical Collecting Duct

54. Epithelium transition: DCT—cuboidal, lots of interdigitations, mitochondria Connecting tubule cells—many small mito Intercalated cells—have microplicae on lumenal surface, vesicles in apical cytoplasm, little interdigitation with adjacent cells – note these for a possible EM Principal (light cells)—collecting duct cells, have short microvillae, fewer mitochondria

55. As collecting duct descends in medullary ray, the epithelium becomes progressively taller, less interdigitation between lateral cells, and less mitochondria  able to see the lateral plasma membranes Unite to form papillary ducts of bellini Permeability responsive to ADH/vasopressin

56. Just beautiful

57. Cortical vs. Juxtamedullary nephron Cortical—short loops of henle, only in medulla for a little bit –Supplied by peritubular plexus of capillaries –Venous return is via interlobular vein Juxtamedullary—long loops of henle  medulla –Create a concentration gradient that you love to hate in physiology –Efferent arterioles form vasa recta –Venous return is via arcuate vein or interlobular vein

58. Lets love the renal corpuscle Bowman’s capsule and urinary pole –Capsule Two layers Between them is the urinary space (US) –Urinary pole Continuous with PCT (TP) and Also on the opposite side is a vascular pole (EA AND AA)

59. Vascular pole 2—bowmans capsule – parietal layer 3—vascular pole 4—urinary pole – can see leading to PCT

60. Vascular pole Region where afferent and efferent arteriole enter and leave glomerulus Blood enters the glomerular capillaries from the afferent arteriole Efferent arteriole leads away from renal corpuscle carrying blood that was NOT filtered  second capillary network This is an arteriole portal system! From efferent arterioles, the peritubular plexus and the vasa recta are formed (depending on the location of the nephrons— cortex/medulla)

61. Interlobar artery – wow, its SO big ;)

62. Lobule separated by interlobular arteries

63. Green arrow—arcuate artery Blue arrow—arcuate vein Remember the lumen size and wall size differences from last block?

64. LAB STUFF

65. This is all you need to know: KIDNEY

66. HAHAAHA. You wish.

67. GROSS FEATURE OF THE KIDNEY YOU NEED TO KNOW Cortex Medulla – including papilla (papilla drains into MINOR CALYCES Hilum – where all the shiznit comes together Renal sinus – fat here, along with renal pelvis Renal pelvis – the “expanded ureter” Calyces – minor calyces together = major calyces. major calyces together = renal pelvis. Fun! Renal artery – branches into interlobar, arcuate, interlobular –Don’t mess up lobar and lobular!!!!!!!

68. Nice gross kidney

70. Only need to know interlobar, arcuate, interlobular in this pic Follow renal artery to interlobar arteries to arcuate arteries to interlobular arteries. A kidney lobule lies between two interlobular arteries.

71. CORTEX = PARS CONVOLUTA + PARS RADIATA –Convoluta = convoluted tubules (PCT and DCT) and glomeruli and connecting tubule –Radiata = medullary ray = straight portions of tubules = thick ascending and descending limbs and collecting ducts –Also look for INTERLOBULAR ARTERIES in convoluta MEDULLA = renal pyramids + papilla = thick tubes, thin tubes, collecting ducts

72. cortex radiataconvoluta

73. So in the cortex you have convoluta and radiata, and the RADIATA is the CENTER of the lobule. So each lobule has a radiata center with the edges formed by convoluta. Remember the interlobular arteries are between lobules so they will be where? In the convoluta! This should be obvious b/c they have to give off the afferent arterioles which clearly need to be by the glomerulus

74. Notice the interlobular arteries in the convoluta

75. cortex So they can label a variety of things in the convoluta: –Glomerulus –Renal corpuscle = glomerulus plus bowmans –Interlobular arteries –DCT – light colored, can see cell borders –PCT – CANNOT see lateral membranes, fuzzy

76. DCT PCT

77. Proximal and distal convoluted tubules (EM). Distal has no brush border. capillaries lie in the connective issue between tubules. NO BRUSH BORDER NICE BRUSH BORDER

78. radiata The medullary ray is composed of proximal and distal tubules going to and from the medulla, and collecting ducts. These tubules serve the adjacent glomeruli

79. Bowman's capsule: Squamous epithelium forming a double-walled cup surrounding the glomerular capillaries. The portion of the wall applied to the capillaries is termed the visceral epithelium. The visceral epithelium is separated from the outer wall by Bowman's space. Bowman's space is continuous with the lumen of the proximal tubule at the urinary pole. Vascular pole: The point of entry of the afferent arteriole into Bowman's capsule. The arteriole immediately forms the tuft of glomerular capillaries and exits as the efferent arteriole.

80. Juxtaglomerular cells: Myoepithelioid cells replace typical smooth fibers in the wall of the afferent arteriole as it approaches the glomerulus. These cells secrete a hypertensive factor, renin. JG CELLS THE AFFERENT ARTERIOLE vs. MACULA DENSA IN DCT

82. Love the glomeruli

83. What are these podocytes you speak of?

84. Cell types make up the glomerulus: endothelial (red), mesangial (blue) and the visceral epithelial cell, and podocyte (yellow). Squamous epithelial cells of the Bowman capsule are easily seen(green). The macula densa (black) is part of the distal tubule.

85. So if they label a cell IN the glomerulus and it is roundish and not part of any form of vasculature = mesangial cell. If they label a very even looking row of nuclei pressed all up on the glomerulus’ shit then it’s the macula densa If they label a nice gathering of cells in the afferent arteriole = JG cells

86. Say hi to the macula densa

87. medulla Here are some longitudinal cuts of pale collecting tubules. Epithelium of collecting tubules is regular, block- like, simple cuboidal, with clear cell walls. Other tubules in the field are thick and thin limbs of loops of Henle.

88. medulla So if you know you are in the medulla (i.e. you see ZERO glomeruli) it can be descending limb (fuzzy like PCT), ascending limb (NOT as fuzzy, looks like DCT and can see lateral cell borders), thin limb (squamous epithelium), or collecting duct (really pale) DO NOT confuse thin limbs with blood vessels – blood vessels will have RBCs in the lumen

89. Do not let them trick you. They can cut medulla in cross section so it looks like pars convoluta, but you know its not because of no glomeruli Collecting duct Ascending thick limb

91. the innermost zone of the medulla (lowest section of the picture) contains only thin limbs of the loop of Henle, plus collecting ducts. This is the area where the counter-current mechanism for urine concentration (carried out between the tubules and the surrounding peritubular capillaries) is most active.

92. Appreciate the Collecting ducts of papilla open into minor calyx, with transitional epithelium and muscularis in its wall. So this is the lowermost part of the medulla, right???? You know this, you do

93. Now for a REALLY short quiz because I am getting sick of this material

94. Identify

96. Identify Green arrow

97. Hints: –Border? –Can you see lateral cell borders? –What part of the kidney are we in? Answer: PCT Blue arrow is a DCT – note the macula densa

98. Identify—green arrow

99. Hints: What type of epithelium? Where in the kidney are we? Answer: –Thin limb of loop of henle – NOT a capillary because NO RBC –Blue arrow is a collecting duct because you can see the lateral cell borders

101. Well it comes right from the urinary pole of the glomerulus So you would say “proximal convoluted tubule” Remember the GROSS anatomy, helps with the microscopic

102. Grey arrow

103. Arcuate vein. You know that the arcuate vessels are found in between the cortex and medulla so what else could it be? From there just decide if it is an artery or a vein. You know this from last block. Collapsed lumen = vein, thick wall and nice round lumen = artery.

104. What 3 things can they label in the medullary ray? Don’t let the cross section fool you, we are still in the cortex. You see glomeruli, DON’T YOU???

105. 1. Collecting duct 2. Ascending thick limb 3. Descending thick limb For extra credit is the ray the peripheral part or the center of the lobule?

106. Center Cortex plus interlobular vessels are in the periphery

107. Done. Q? C? boggusrl@email.uc.eduboggusrl@email.uc.edu