Presentation on theme: "Department of Histology and Embryology"— Presentation transcript:
1 Department of Histology and Embryology 15th The Urinary SystemDepartment of Histology and Embryology
2 : components and functions 2. Kidney 1. Introduction: components and functions2. Kidney2.1 General organization※ 2.2 Nephron※ 2.3 Filtration apparatus of the kidney※ 2.4 Juxtaglomerular apparatus2.5 Kidney tubule function※ Proximal convoluted tubules※ The loop of HenleDistal convoluted tubulesCollecting tubules and collecting ducts2.6 Blood supply3.Excretory passages
3 Introduction Components Functions 1. The kidneys conserve body fluid andelectrolytes and remove metablic wastesProduction of the urine2.Synthesis and secretion the renin and erythropoietin3.Hydroxylation of 25-OH vitaminD3 to hormonally active 1,25(OH)2vitamin D3to regulate the calcium balance.
5 Lobe: one renal pyramid and the cortical tissue at its base and sides Lobule : a single medullary ray and the cortal tissue surrounding itUriniferous tubule:it consists of nephron and it collecting tubuleUriniferous tubulelobulelobe
6 1. Fuctions The 1st key point -Nephron 1) Filtration of most small molecules from blood plasma to forman ultrafiltrate of plasma.2) Selective reabsorption of most of the water and some other moleculesfrom the ultrafiltrate,leaving behind excess and waste materials to beexcreted3) Secretion of some excretory products directly from blood into the urine.4) Maintenance of the acid-base balance by selective secretion of H+ ionsinto the urine.
7 2. Structure 2.1 Renal corpuscle 2.2 Renal tubules ConvolutedProximal thick segmentStraightThin segmentThe tubules of the loop of theHenle acompanied by a capillarynetwork.these vessels representthe vascular part of thecountercurrent exchange systemthat regulates the concentrationof the urine.ConvolutedDistal thick segmentStraightLoop of HenleIt forms the entire U-shapedportion of nephron.
10 (2) Bowman’s capsule Glomerulus Urinary pole Parietal layer Afferent arterioleEfferent arterioleUrinary poleVascularpoleParietal layerVisceral layerThe basment memberane of the tubules and that of bowman’s capsule stains blue in Azan staining method
11 The 2nd key point - Filtration apparatus (Function of the nephron)Visceral layer of Bowmans’s capsule--PodocyteGlomerular basement membrane,GBMEndothelium of the glomerular capillaries
12 Diagram of podocyte Secondary process GBM Primary process Fenestrated endothliunGBMFiltration slit membrane
13 Scanning electron micrograph of Podocyte Cell bodyPrimary processSecondary process
14 Endothelium of the glomerular capillaries 1.It possesses numerous fenestrations.1)These fenestrations are larger,more numerous,and more irregularin outline than fenestrations in other capillaries.2)The diaphragm aren’t spaned the fenestrations in capillaries.2.Endothelial cells possess a large number of water channelsthat allow the fast movment of water through the epithelium.
15 Renal filtration barrier The fenestrated endothelium of the glomerular capillariesThe basal laminaThe filtration slitsIt permits passage of water, ions, and small molecules from the blood stream into the capsular space but prevents passage of large and/or most negatively charged proteins, thus forming an ultrafiltrate of blood plasma in Bowman’s space.
16 Glomerular basement membrane,GBM 1. It is a thick( nm) basal lamina that is joint productof the endothelium and the podocyte, PAS(+).2. It acts as a physical barrier and an ion-selective filter.Three portions of GBM:The lamina rara internaThe lamina densa(electron-dense layer)The lamina rara externa(more electron-lucent layer)
17 location Lamina rara externa Lamina rara interna Lamina densa Adjacent to the podocyteAdjacent to the capillary endotheliumSandwiched between the laminea raraecomponentsRich in polyanionsSimilar to rara externaType IV collagen is organized into a networkfunctionImpede the passage of negatively charged moleculesIt act as a physical filter
18 The glomerular filtrate has chemical composition similar to that of blood plasma but contains almost no protein.The glomerular basement membrane is a selective macromolecularfilter ,in which the lamina densa act as a pysical filter,whereas theanionic sites in the laminae rarae act as a charge barrier.1) Particals greater than 10nm in diameter do not readily cross thebasal lamina.Neatively charged proteins with a molecular mass greater thanthat of albumin(69kDa) pass across only sparingly.
19 3. Type of nephron 1. Superfacial nephron (cortical nephron) 2. Midcortical nephron3. Juxtamedullary nephronCriterion :location of the renal corpuscles in the cortex
20 Clinical Considerations Diabetes mellitus and GlomerulonephritisThe glomerular filter is damaged and markedly its filtering ability is reduced , it becomes much more permeable to proteins, with the subsquent release of protein into the urine.
21 Mesangium Structure The function of the mesangial cell mesangial matrixStructureThe function of the mesangial cell1 Phaocytosis to clean the GBM2 Structure support to provide support for the podocytesin the areas where the epithelial basementmemberane is absent or incomplete.3 Secretion interleukin-1 and platelet-derived growth factor(PDGF),which play a central role in response toto glomerular injury.
22 2. Components 1. Location: 3. Function: The 3rd key point -Juxtaglomerular (JG) apparatus1. Location:3. Function:They are senstive to the ionic content and water volum of thetubular fluid,producing molecular signals that promote theliberation of the ezyme renin in the circulation .Lying directly adjacent to the afferent and efferent Arterioles at the vascular pole of the renal corpusleThey have a cytoplasm full of secretory granules. Secretion of JGCells played a role in the maintance of blood pressure.2. ComponentsJuxtaglomerular (JG) apparatus ：1、Juxtaglomerular cells部位：入球微A近血管球处，管壁平滑肌细胞演变成上皮样C形态结构：粗面内质网、高尔基复合体、分泌颗粒功能：分泌肾素、红细胞生成素2、 Macula densa cells部位：远端小管近血管极侧上皮细胞变高，密集排列而成形态结构：基底面有指状突起伸向近血管球细胞功能：离子感受器3、Extraglomerular mesangial cells （球外系膜细胞）部位：出、入球微A与致密斑间的三角区形态结构：短小突起、分泌颗粒功能：不清4、极周细胞部位：肾小囊脏层和壁层上皮移行处，包绕血管极形态结构：体积大，有分泌颗粒Extraglomerular mesangial cellsMacula densa cellsJuxtaglomerular cells
23 2.Structure and Function Contain secretorygranules of reninChemoreceptorperceiving thechange of Na +in distal tubule lumenRenin-angiotension-aldosterone-system
24 Chemical composition difference between primary urine(ultrafiltrate) and final urine The two kidneys produced 125ml of filtrate per minute,but just only 1ml is released into the ureters as urine.The glomerular filtrate haschemical compositionsimilar to that of bloodplasma but contains almostno protein.The final urine contains water, electrolytes as well as waste products, such as urea, uric acid, and creatinine,and breakdown products of various substances.Where did it go to?Where are they from?
26 Function : It is the initial and major site of reabsorption The 1st key point-Proximal convoluted tubuleFunction : It is the initial and major site of reabsorptionStructure :The cuboidal cells of it have the elaberate surface specializationsassociated with cells Engaged in absorption and fluid transport.1. A brush border2. A juctional complex3. Folds located on the lateral surface of the cells4. Interdigitation of basal process of adjacent cells5. Basal striations
27 1.A brush border The 1st key point-Proximal convoluted tubule It greatly increases the free cellsurface area, correlating with itsabsorptive capacity.1)At the electron microscopiclevel , the microvilli constitutethe brush border apically.2)The PAS staining method hasbeen used to demonstrate theprominent brush border.
28 The 1st key point-Proximal convoluted tubule The cytoplasm immediately beneath thebrush border contains many pinocytoticveicles V and lysoomes L which areinvolved in reabosorption and degradationof small amounts of protein that haveleaked through the glomerular filter.reaborbed solutes are transported intosurrounding cap with attenuatedendothelium E resting on a very thinbasement memberane.
29 2. Folds located on the lateral surface of the cells They creates interdigitating cytoplasmic process of adjoining cells.no discrete limites can be observed (in the LM) between cells of the proximal tubule .They increase the lateral surface area of the cell and are particularlyprominent in epithelia that are engaged in fluid and eletrolyte ransportIn active fluid transport ,sodium ions are pumpedout the cytoplasm memberane by Na+/K+ATPaselocated in the memberane.
30 Na+-K+-ATPase Location : Function : It is a kind of transmembrane proteins that are localizedIn the lateral folds of the plasma membrane.Location :The active transport of Na+ out of the cell is acompanied by facilitated transport into the cells of Cl- , glucose and amino acids by means of transport proteins .almost 100% of filrated glucose and amino acids is reabsorbed by the PCT。Function :When the amount of glucose in the filtrate exceedsthe absorbing capacity of the proximal tubule, urinebecome more abundant and caintain glucose.Clinical thinking:
31 3. Iterdigitation of basal process Some of the interdigitating process extendthe full height of the cell.the process arelong in the basal region and create anelaberate extracelluar compartment adjacentto the basal lamina.They increase the basal surface area of the cell and are particularlyprominent in epithelia that are engaged in fluid and eletrolyte ransport.
32 4. Basal striations Mitochondria M are present in the cell within the interdigitating process P. M areresponsible for the appearance of the basalStriations in LM.The cytoplasm of PCT epithelial cells stain intensely due to a high content of organelles, principally mitochondria.
33 5. A juctional complexIt consists of a narrow ,tight junction that seals off the intercelluar space from the lumen of the tubule and a zoula adherens that maintains the adhension between neighboring cells .The tight junction at the apical end of the intercelluar spaceprevents fluid from moving in the opposite direction.
34 Components: Function : The 2nd key point-Loop of henle The pars recta of the proximal tubuleThe thick ascending limb(the distalstaight tubule)The thin descending limbThe thin ascending limbFunction :It is to produce an increasingosmotic gradient from the cortexto the lip of renal papilla by the counter-currentmultiplier mechanism.
35 Structure : 1. The pars recta of the proximal tubule The 2nd key point-Loop of henleStructure :1. The pars recta of the proximal tubuleThe cells of it are not as specialized for absorption as are those ofthe proximal convouluted tubule.1) They are shorter, with a less well developed brush border and withfewer and less complex lateral and basal-lateral processes.2) The mitochondria are smaller than those of the cells of theconvoluted segment and are randomly distributed in the cytoplasm.3) There are fewer apical invaginations and endocytotic vesicles, aswell as fewer lysosomes.
36 2. The thin limb, TThe thin limbs T are lined by a flattened squamous epithelium Which has no capicity for active transport .The thin desending limb allows free diffusion of H2Obut impermeable to NaCl .The thin asending limb has also active function but allows passive diffussion of NaCl into the interstitium, not H2O.The vasa recta take up water from the medullary interstitium and return it to the general circulation.
37 2. The thin limb, TThe interstitial fluid in the medulla is hyperosmoticWater diffuses out of ,salt diffuses into the nephron at this sitePassive momment of water into the connective tissue,and of salt and urea into the thin desending limb.
38 3.The thick ascending ,A Active transport of NaCl again occurs here The appearance of the cuboidal epithelium1) Basolateral process interdigitate with eachother forming an extensive intercellularspace in a similar maner to the PCT.2) The active transport process is fuelled byATP produced by many mitochondria found in these process .3) It is also impermeable to water which maybe related to its thick glycocalyx composed of the glycoprotein, tamm-horsfall protein.
39 Light microscope: The distal convouluted tubule DCT The 3rd key point- DCT maybe differentiated from PCT by1) the absence of brush border (PAS-positive)2) A larger more clearly defined lumen3) more Nuclei per cross section (since DCTcells Are smaller than PCT cells)4) paler cytoplasm5) Sections of DCT are much less numeroursthan sections of PCT since the DCT is amuch more shorter segment of the renaltubule than the PCT
40 The main features of Electron micrograph 1. Lateral cell interdigitations andlarge numbers of mitochondria.2.The basal plasma memberanecontains the Na+-K+ATPase.3.It have only a few irregularMicrovilli at the luminal surface4.The overlaying cytoplam containsLarge number of tiny vesiles.
41 Function of DCT The distal convoluted tubule exchanges Na+for K+into the ultrafiltrate to conserve Na+ under aldosterone regulation.1. Reabsorption of Na+and secret K+into the the ultrafiltrateto conserve Na+2. Reabsorption of bicarbonate ion3.Conversation of ammonia to ammonium ion.
42 collecting tubule 1. Structure: 2.Function The simple columnar epithelium consist two types of cells:1) Light cells are princinple cells of the system.2) Intercated cell : occur in considerably smaller numbers.2.Function1) They concentrate urine by paasive reabsorption of H2O Into the medullary interstium following te osmotic gradient Creeated by the counter-current multiplier system of the Loop of henle.2) The amount of H2O reabsorbed is controled by antidiuretic hormone(ADH) secreted by the posterior pituitary in response to dehydration.3) They can secrete H+.They are readily ditinguished by Virtue of the cell boundaries that can be seen in the LM
43 Medical application Aldosterone deficiency in adrenalelectromized animalsand in humans with Addison diseaseresult in an excessive loss of sodium in the urine.
47 1.An interlobular artery IA can be seen branching to form the afferent Aterioles AA of a glomerulus G.2.The efferent aterioles EA leavingG is of much smaller diameterthan theAA, to maintain pressure withinG capfor plasma to be filtered intoBowman’s space BS. Blood pressurewhithin G is controlled by variation ofthe diamter of the AA and EA3.In the superficial and midcortex asshown here , EA give rise toa networkof cap which surround the renal tubulesRT.Towards the medula EA give rise tothe vasa recta.moleculesreabsorbed fromG filrtrate returned tothe generalcirculation via this cap net which draininto the renal venous system.Section from kidney which has been perfused witha red dye in order to demonstrate the renal blood supply.Nephrons remain unstained.
48 Bladder and urinary passages Structure of the wall :They have same basic histologicStructure:Transitional epithelium1. Mucosa :Lamina propria of loose –to –denseconnective tissue2.The muscular layer3.Adventia
49 Review Test (A) a renal corpuscle (B) a distal convoluted tubule 1. A nephron includes all of the following components EXCEPT(A) a renal corpuscle(B) a distal convoluted tubule(C) a thin limb of the loop of Henle(D) a collecting tubule(E) pars recta of the proximal tubule
50 2. Which cells form the visceral layer of Bowman’s capsule (A) Medullary interstitial cells(B) Mesangial cells(C) Podocytes(D) Cells lining the proximal convoluted tubule(E) Juxtaglomerular cells3. Renal filtration barrier consists of all of the following components EXCEPT(A) The fenestrated endothelium of the glomerular capillaries(B) The basal lamina(C) The filtration slits with diaphragms between pedicels(D) Medullary rays
51 Summary 1.The components of the urinary system The paired kidneys and uretersand the unpaired bladder andurethra.the maintenance of water and electrolyte homeostasis, which requires that any input into the system is balanced by an equivalent output.2. The principal function of the urinary system
52 Renal filtration barrier It is composed of the fenestrated endothelium of the glomerular capillaries, the basal lamina, and the filtration slits with diaphragms between pedicels.The structure of theRenal filtration barrierIt permits passage of water, ions, andsmall molecules from the blood streaminto the capsular space but preventspassage of large and/or most negativelycharged proteins, thus forming anultrafiltrate of blood plasma in Bowman’sspace.The function of theRenal filtration barrier
53 homeworkGive me a summary on what we talked about the structure of the renal tubule associated with its function in the class.