Renal Histo Short 8131MED PDF

Basic Histology RENAL SYSTEM Associate Professor Vinod Gopalan Medical Education & Histopathology School of Medicine & Dentistry Griffith University Vinod Gopalan, Histopathology, School of Medicine, Griffith University Kidney-Histology The kidney is divided into a pale outer cortex, and a darker i...

Basic Histology RENAL SYSTEM Associate Professor Vinod Gopalan Medical Education & Histopathology School of Medicine & Dentistry Griffith University Vinod Gopalan, Histopathology, School of Medicine, Griffith University Kidney-Histology The kidney is divided into a pale outer cortex, and a darker inner medulla. The cortex consists of numerous straight and convoluted tubules, blood vessels, and the renal corpuscles. The medulla consists of 8 to 12 conical structures called renal pyramids. The tissue between the pyramids is called a renal column. Vinod Gopalan, Pathology, School of Medicine, Griffith University http://www.vetmed.vt.edu/education/curriculum/vm8054/Labs/Lab23/lab23.htm Kidney-Functional units The functional unit of the kidney is the uriniferous tubule. It consists of a nephron plus its collecting tubule. The various components of a uriniferous tubule are: Renal corpuscle = Bowmans capsule + glomerulus Nephron = renal corpuscle + convoluted and straight tubules Uriniferous tubule = nephron + collecting tubule The glomerulus is a tuft of capillaries that is contained within a doublelayered cup, called Bowmans capsule. Vinod Gopalan, Pathology, School of Medicine, Griffith University Renal corpuscles Renal cortex  Each renal corpuscle consists of a tuft of capillaries (the glomerulus) sitting inside a double walled epithelial capsule (Bowman’s capsule). Image obtained from Wheater’s functional histology  Blood enters the glomerular capillaries through the afferent arteriole and exits the glomerulus through the efferent arteriole.  The spaces between the capillary loops in each glomerular lobule are filled by basement membrane-like material called mesangium*, which contain mesangial cells Vinod Gopalan, Pathology, School of Medicine, Griffith University Renal cortex Renal corpuscles- Glomerular filtration  During the filtration of plasma from glomerular capillaries into the renal tubule, the filtrate passes through three layers - Capillary endothelium - Glomerular basement membrane and the - Podocyte layer. Capillary endothelium: The capillary endothelium consists of numerous large round fenestrations which occupy around 20% of the endothelial surface. Glomerular basement membrane: Is prominent and well characterised between capillary endothelial cells and podocytes. Podocyte layer: Is formed by the long cytoplasmic extensions called processes (primary and secondary). Vinod Gopalan, Pathology, School of Medicine, Griffith University GLOMERULUS – STRUCTURE 1- DCT 2- PCT 3- PCT ? Bowman's capsule 2 1 2 1 3 1 colour eosinophilic at proximal, brush border ? mesangium capillary loops ? Vinod Gopalan, Histopathology, School of Medicine, Griffith University podocytes ? Renal tubules  The tubular system can be divided into proximal and distal tubules, which in turn have convoluted and straight portions.  Intermediate tubules connect the proximal and distal tubules.  Running from the cortex of the kidney towards the medulla, the tubules form the loop of Henle. http://www.proteinatlas.org/dictionary/normal/kidney+1 Vinod Gopalan, Pathology, School of Medicine, Griffith University Renal tubules Renal cortex Proximal convoluted tubules (PCT) The proximal tubule is the longest section of the nephron. The convoluted part of the proximal tubules coils close to the glomerulus in the cortex. Their walls are formed by a low columnar epithelium. The eosinophilic cells of the epithelium have a wide brush border and are active in endocytosis. Function: c They almost completely resorb substances such as glucose, amino acids, protein, vitamins etc from the glomerular filtrate. small molecules In the proximal tubules, the volume of the glomerular filtrate is reduced by about 75%. massive passive diffusion brush border PCT nucleus red special stain PCT glycogenated c http://www.visualphotos.com/image/1x8803230/glomerus_and_proximal_convoluted_tubule In PCT, sodium ions are actively resorbed from the glomerular filtrate. They are followed by passively diffusing chloride ions and the osmotic absorption of water. Vinod Gopalan, Pathology, School of Medicine, Griffith University water absorbed Renal tubules Renal Medulla Loop of Henle- The thick descending limbs of the loop of Henle look similar to the proximal tubule, with apical brush borders. The thick ascending limbs are composed of cuboidal cells, but unlike the proximal convoluted tubule, they do not have 3 apical brush borders. proximal has brush border epithelium 3 lat boundaries are visible Collecting ducts can also be seen on this slide. They can be easily distinguished by the presence of prominent lateral borders between adjacent cells. 1- PCT 2- DCT 3- CD 2 1 1 2 2 not found here 1 3 1 Function: Descending parts of the straight proximal and intermediate tubules are permeable to water but not to solutes. Vinod Gopalan, Pathology, School of Medicine, Griffith University Renal tubules Renal cortex Distal convoluted tubules (DCT) - Distal tubules are found within the cortex among the proximal convoluted tubules. - The first part of the distal tubule forms the macula densa while the remainder makes up the DCT. specialised sensors - sodium/chloride regulate blood flow - afferent arteriole concentration control constriction DCT can be differentiated from PCT by the absence of brush border. DCT lumen will be larger, clearer and have more nuclei per cross section (DCT cells are smaller than PCT). They have paler cytoplasm. Function: DCT DCT DCT http://php.med.unsw.edu.au/embryology/index.php?title=File:Renal_histology_03.jpg Epithelial cells in the ascending parts of distal tubules cells transport chloride (active) and sodium ions (passive) out of the tubular lumen into the surrounding peritubular space. The epithelium can not be penetrated by water. Vinod Gopalan, Pathology, School of Medicine, Griffith University Vinod Gopalan, Histopathology, School of Medicine, Griffith University Email: [email protected] Phone: 0756780717