HIST AA Uro Lecture 2024 PDF

Form and Function 141: HISTOLOGY Urinary system Dr Mandi Alblas [email protected] Medicine and Health Sciences | EyeNzululwazi ngez...

Form and Function 141: HISTOLOGY Urinary system Dr Mandi Alblas [email protected] Medicine and Health Sciences | EyeNzululwazi ngezoNyango neMpilo | Geneeskunde en Gesondheidswetenskappe  ion Primary tis sue revis 4 Primary tissues All tissues consist of cells & extracellular matrix (ECM) A. Epithelial tissue B. Connective tissue D. Muscle tissue D. Nerve tissue  Outcomes: Kidneys 1. Describe the general microscopic structure of the kidney (basic tissue components, such as cortex – medulla – pyramid – calyx – pelvis – proximal ureter) 2. Identify the structure-function relationship of the kidney structures with regards to the: a. Nephron b. Renal corpuscle c. Glomerular filter membrane d. Juxtaglomerular apparatus 3. Describe the filtration barrier between blood and urine in the renal corpuscle 4. Explain the microvasculature - blood supply and drainage of kidney (afferente arteriole – glomerulus – efferente arteriole) 5. Describe the parts of the lower urinary system (bladder and ureter) 6. Annotate simple sketches (see class notes) and understand the photomicrographs Material which is made available by way of an electronic database may be subject to certain licensing conditions. These conditions normally entail that you may only use the material for your own private study and research at the University and not for any other purpose. It is expected of you to adhere to these conditions at all times. Printed material is also only made available for class discussion, private study and research purposes. Further reproduction of such material is prohibited Urinary system structure: Urine is produced in kidneys & flows down ureters to bladder where it is 2 Kidneys stored until voided via urethra - urine production 2 Ureters – conduction of urine to bladder 1 Urethra – conduction of urine to outside 1 Bladder – urine storage my a to An  lo gy Renal system function: si o y Ph 1. Concentrates the filtrate by glomerular filtration - end product of these processes is urine. 2. Purpose of urine formation: Maintains homeostasis by regulating volume & composition of blood Maintenance of water, electrolyte & acid-base homeostasis Excretion of toxic metabolic waste products, e.g. nitrogenous molecules, urea and creatinine (compounds that can be dissolved in water). Regulation of osmotic concentration of blood plasma by kidneys (osmoregulation) ensures osmotic regulation of all other body fluids. 3. Reabsorbs and retains useful substances Kidneysthat are usually used by produce other tissues: sugars and amino acidsconcentrated urine: 1200-1400 4. Hormonal and metabolic functions: mOsm/L  Renin  gy General kidney structure: o l o i st H 3. Medulla 1. Fibrous capsule - lighter coloured inner  irregular dense part, have: connective tissue Pyramids  no septa Calyxes Capsule continuous at hilum 4. Pelvis 2. Cortex open space lined with - outer part (will stain urothelium (epithelium) Pelvis is darker than medulla), continuous with have: calices Renal corpuscle Convoluted tubule 5. Calyces Calices = collect urine (epithelium) cup-shaped structures which fit which comes from over tip of each pyramid, lined pyramid with urothelium (epithelium) Section (l.s.) through kidney Pyramid in medulla Medullary ray (paler stained) Renal artery and vein Medulla Major calyx Cortex Ureter (darker stained) Minor calyx Capsule (continuous with hilum)  Section (l.s.) through kidney g y Microscopically to lo Hi s cor tex me dull a calyx  Kidney lobule g y Consist of: to lo Hi s A collecting duct & all nephrons One medullary pyramid & cortex directly above it lobule x corte glomerulus nephron collecting duct a. interlobularis a. arcuata d py rami v. arcuata ullary med  Renal papillae projects into pelvicalyceal space PCS. ducts of Bellini DB join = drain urine through cribriform area at tip of papilla. pelvicalyceal system is proximal end of ureter U wall of pelvis contains smooth muscle SM lined by urothelium E.  o lo g y Cortex st Hi 1. Nephron Consist of: Renal corpuscles Convoluted & straight tubules 2. Collecting tubule & ducts 3. Medullary rays  lo g y Cortex: Medullary rays sto Hi Each medullary Regions between ray contains medullary rays straight tubules (cortical labyrinths) contain collecting ducts – renal corpuscles – convoluted tubules – collecting tubules  Medulla Consist of: cortex 1. Straight tubules 2. Collecting ducts medull 3. Vasa recta a (special capillary network) Tubules collectively At apex – opens into minor form pyramids with calyxes that join to form major Drain to apex inwards calyxes pelvis Flow to Flow to Flow to ureter of urethra bladder kidney  Nephron Functional & structural unit of 2. kidney 1-4 million per kidney 1. Each nephron = 50-55um Each nephron is divided into 5 4. parts 1. renal corpuscle  glomerulus 5. 2.  Bowman’s capsule 3.2. proximal convoluted tubule 3. 4.3. loop of Henle Basic 5.4. distal convoluted tubule functions: 5. collecting ducts – Filtration – Secretion – Reabsorptio  1. Renal In co Nephron 1. rtex corpuscle only Basic Function: – Performs osmoregulation & excretion (by filtration, selective reabsorption, secretion & maintenance of acid-base balance) – Production of urine (glomerular filtrate) = forms 1.5-2L urine per day) In renal corpuscle = water & low molecular weight constituents of plasma are filtered from glomerular capillaries into Bowman's space to form glomerular ultrafiltrate. Contains: 1. Glomerulus= network of afferent arteriole (supplies anastomosing capillaries, glomerulus), & efferent arteriole invaginating Bowman's capsule. (drains glomerulus) 2. Bowman’s capsule =parietal = enter & leave corpuscle at vascular single layer of flattened cells pole resting on b.m. usually situated opposite entrance to renal tubule (urinary pole) Glomerular filtrate - water, salts (NaCl), glucose, protein molecules &  Development of renal corpuscle capsule of Bowman =is the enlarged part of the renal tubule at the beginning. Bowman’s capsule consists of a single layer of cuboidal/flattened cells resting on basement membrane (b.m.) Capillary loops of glomerulus (network of anastomosing capillaries) invaginates Bowman's capsule  Thus capillary loops of glomerulus are invested by visceral layer of Bowman's capsule (octopus like podocytes)  visceral layer is continuous with parietal layer that constitutes Bowman's capsule proper. Vascular pole  space between the 2 layers = Bowman's space Urinary pole  Mudfix? Glomerulus: Bowman’s Renal corpuscle Several lobes of capsule: Glomerulus + capillary plexuses Bowman’s which join Is double layer capsule afferent & epithelium with efferent arterioles embedded glomerulus 1. Parietal layer – simple squamous epithelium (layered cup) = almost completely surrounds glomerulus, except at vascular pole 2. Visceral layer - podocytes  Renal corpuscle Afferent arteriole Efferent arteriole (EA) (AA) Bowman’s capsule mesangium mesangial cells & matrix (parietal layer; simple Function: support squamous ep) capillaries Endothelial cell (of capillary) Basal lamina Mesangial matrix Mesangial cell Bowman’s capsule: Visceral layer; podocytes Capillary (form a continuous layer over whole basal lamina) Also called lacis Proximal convoluted cells /granular Tubule (PCT) cell Nephron 2. Proximal convoluted 2. tubule (PCT) Function: reabsorption of filtered substances (Na2, Cl-, K+, Ca2+, glucose, urea) Cross section through a Located in cortex proximal convoluted Nearest to capsule of Bowman tubule Follows a convoluted course Longer than DCT Lumen appears smaller Cuboidal cells with brush border lumen (abundant microvilli) nuclei situated near base of cell microvilli At start point: open from renal nucleus corpuscle basal lamina Nephron 3. Loop of Henle 3. Function: osmotic pressure = saves water – concentrated urine Descending limb = further reabsorption of water (not solutes) Ascending limb =active transport of sodium & chloride ions from tubular fluids into peritubular fluid of medulla U shaped tube Descending & ascending limbs (into medulla) Cross section 4 parts: through a loop of Thick descending Henle (pars recta of PCT) Thin descending Thin ascending Thick ascending nucleus (pars recta of DCT) flattened epithelial cells  4. Distal convoluted tubule (DCT) Nephron 4. Function: variable reabsorption of water and substances (Na 2, Cl-, K+, Ca2+) under hormonal control Less reabsorption than PCT. Also secretions of ions, acids, drugs & toxins Cross section through a Located in cortex distal convoluted Lies against arteriole of renal tubule corpuscle Follows a convoluted course Shorter than PCT Lumen appears larger Cuboidal cells with no brush Few, short microvilli border (less microvilli) Nucleus Nuclei closer to each other At end point = open in collecting duct  Mudfix? DCT PCT Located in cortex Located in cortex Lies against arteriole of renal Nearest to capsule of Bowman corpuscle Follows a convoluted course Follows a convoluted course Longer than DCT Shorter than PCT Lumen appears smaller Lumen appears larger Cuboidal cells with brush border Cuboidal cells with no brush (abundant microvilli) border (less microvilli) nuclei situated near base of cell Nuclei closer to each other At start point: open from renal At end point = open in corpuscle collecting duct Nephron 5. Collecting ducts 5. Function: variable reabsorption of water and solutes (under hormonal control) Reabsorption of Na2, Cl-, urea, hydrogen bicarbonate ions Reabsorption or secretion of K+ - depends on intake) Cross section through a collecting duct Located in cortex or medulla Follows a straight course Lumen appears larger Cuboidal cells with no brush border  Mudfix? Epithelial lining of Nephron Bowman’s capsule: Proximal tubule & 1st part of descending Visceral=podocytes tubule (loop of Henle) Parietal= simple squamous Simple cuboidal epithelium with brush border 2nd part of ascending Last part of descending tubule, distal tubule & 1st part of convoluted tubule & ascending tubule collecting duct Simple cuboidal (thin part) of loop of Simple squamous epithelium without Henle) epithelium brush border  Glomerular filtration Nephron membrane 3 main Components of the filter: P e pac 1. Endothelium (E) of fenestrated (F) capillaries in ar ys FS glomerulus. The capillary is fenestrated, with no i n – ur PE diaphragm over the fenestration. US BL 2. Thick basement membrane (BL=basal lamina)= arising from the endothelial cells AND the podocytes e n F lum ry 3. Epithelial cells - visceral layer of Bowman’s capsule = E pi l la a podocyte (P) with pedicels (PE) AND Filtration slits (FS) –c CL inbetween PE (foot processes) ce pa P US – urinary space y s r r i na –u FS US PE BL F E CL – capillary lumen BL, LRI, LD, LRE – basal lamina with 3 components  Podocyte (filtration membrane) Visceral layer of Bowman’s capsule (visceral epithelial cells = inner layer, covers the glomerular capillaries) Podocyte Cell Body (CB) ---- Primary Foot Processes PB ---- Secondary Foot Processes (SB) ----- Pedicels (PE) Filtration slits (FS) occur between foot processes PE F S CB E PB CB PB S PB B SB E= Fenestrated capillaries  Podocyte The relationship between pedicles and basal lamina podocyte primary foot processes pedicel secondary foot processes b.m. of capillary Pedicels interdigitate with pedicels of neighbouring podocytes Pedicels never touch podocyte cell body Foot processes pedicel Filtration slits (FS) - spaces between interdigitating pedicels capillary (semipermeable barrier)  JGA / Juxtaglomerular apparatus A specialisation of the glomerular afferent arteriole & the DCT of the same nephron = Macula densa + mesanglial cells + Juxtaglomerular cells Also called lacis cells or granular cells Position: in nephron, where distal convoluted tubule (DCT) turns back and makes contact with afferent arteriole (AA) DCT A A  JGA / Juxtaglomerular apparatus 2. Macula densa 1. JG sells Modified epithelial cells in (Juxtaglomerular DCT, where it makes cells) =modified contact with AA smooth muscle cells – F: monitors salt of AA concentration in tubule = – F: contain renin help to maintain normal granules = maintain blood pressure normal blood pressure 3. Lacis/granular cells / extraglomerular mesangial cells = in triangular space between AA & EA and macula densa Function of JGA: (involved in the regulation of systemic blood pressure via the renin-angiotensin-aldosterone System = RAAS) Thus: acts as baroreceptor & chemoreceptor controlling systemic blood pressure by secretion of Renin ↓BP - ↓ glomerular filtration - ↓ concentration of sodium ions in the DCT – cells, acting as chemoreceptors promote secretion of Renin  Macula densa epithelium of distal convoluted tube juxtaglomerular cells cells of macula endothelium densa afferent arteriole basal lamina mesanglial (lacis/granular) cells efferent arteriole glomerular endothelium podocyte macula densa = higher & narrower (more cylindrical than cuboidal) cells in DCT (their nuclei are therefore closer together). This gives the impression of a dense spot in the wall of the tubule.  Renal vasculature Renal artery divides in hilum into branches Supplies 5 segments Segmental arteries 5 branches Interlobar Supplies between arteries lobes ascend between pyramids to corticomedullary junction. Each branch into Supplies Arcuate arteries between cortex Arc between cortex and and medulla medulla give rise to numerous cortical radial Supplies (interlobular) cortex arteries From cortico-radial arteries the afferent (supply cortex) arteries (AA) branch off to form glomerulus. (group of special capillaries). https://youtu.be/edMkB5guZkg? si=49udAafDuQMQ16CQ  Renal vasculature Renal artery divides in hilum into branches Segmental arteries 5 branches Interlobar arteries ascend between pyramids to corticomedullary junction. Each branch into Arcuate arteries Arc between cortex and medulla give rise to numerous cortical radial (interlobular) arteries From cortico-radial arteries the afferent (supply cortex) arteries (AA) branch off to form glomerulus. (group of special capillaries). https://youtu.be/edMkB5guZkg? si=49udAafDuQMQ16CQ  Renal vasculature From interlobular (cortical-radial) arteries the afferent arteries (AA) branch off to form glomerulus (group of special capillaries). Leading form glomerulus to efferent arterioles (EA) juxtamedullary Cortical glomeruli glomeruli vasa recta peritubular capillaries  associated with loop of Henle  associated with convoluted  run straight down medulla from tubule  supply all tubules in cortex. juxtamedullary glomeruli.  join together to from veins  make a '‘U" turn & run up again  These capillaries supply all the to cortex  join together to form veins tubules in the cortex. They are fenestrated capillaries, which promote reabsorption of substances from the tubules.  which drain into cortical radial (interlobular) veins  and drain further into arcuate vein,  interlobar vein and eventually Image: Human Histology, Stevens and Lowe 2nd Ed  renal vein which all run alongside arteries.  Renal vasculature Renal vein Renal artery Interlobar Interlobar veins arteries Each branch into Arcuate Arcuate veins arteries cortical radial cortical radial (interlobular) (interlobular) veins arteries From cortico-radial arteries the afferent arteries (AA) branch off to form glomerulus. (group of special capillaries).  Lower urinary system Components: from hilum of the kidney to urethra 1. Calyces in kidney 2. Renal pelvis 3. Ureter 4. Bladder 5. Urethra All these excretory passages (except urethra) have same general structure: mucosa - lined by transitional epithelium (urothelium) muscularis – smooth muscle layers adventitia - or, in some regions, a serosa Function: transport of urine in ureters to bladder (storage) and micturition via urethra  Urothelium Also called: Transitional epithelium is found only within the Umbrella cells conducting passages of urinary system Stratified cuboidal epithelium The surface cells are called umbrella cells = maintain impermeability of epithelium lamina propria to urine even when at full stretch Umbrella cells Stratified cuboidal epithelium lamina propria Medium magnification High magnification  Ureter star shaped lumen urothelium lamina propria inner longitudinal layer L middle circular layer LC L C outer longitudinal layer L adventitia Cross section layers of wall: Lumen - star shaped Epithelium lining (urothelium) Lamina propria – connective tissue Muscularis externa layers – smooth muscle: Proximal = 2 layers of muscle (circular & longitudinal layers) Distal (lower third) - 3 layers of muscle (longitudinal & circular & longitudinal layers) Adventitia – connective tissue  Bladder urothelium lamina propria inner longitudinal L muscle layer L middle circular C muscle layer C L outer longitudinal muscle layer L adventitia or serosa Cross section layers of wall: Lumen - large Epithelium lining (urothelium)=thicker than ureter Lamina propria – connective tissue Muscularis externa layers – smooth muscle: (longitudinal & circular & longitudinal layers) = middle layer thickest of the 3 Adventitia – connective tissue = covers bladder, except of top surface  Renal vasculature: summary blood vessels of capsule EA efferent arteriole interlobular v. AA afferent venues network in cortex arteriole cortical radial a. arcuate v. (cortical interlobular a.) glomerulus arcuate a. ular v. Interlobular a. peritubular capillary network in cortex interlob (convoluted tube Vasa recta network) (venulae rectae) Vasa recta (arteriolae rectae) Straight tube network. v. l o la r a bul Renal a. Lobu a re v. renalis  Renal corpuscle: summary distal conv. tubule juxtaglomerular cells macula densa efferent arteriole extraglomerul ar mesangial cells (lacis vascular pole cells) parietal layer podocyte of visceral layer mesangial cells capillaries of a ce basal lamina glomerulu sp y s endothelium nar processes of podocyte i ur urinary pole proximal conv. tubule  Nephron: summary efferent arteriole afferent arteriole cortex renal corpuscle a. interlobularis PCT medullary ray DCT descending a. arcuata loop of Henle limb (thick part) ascending medulla limb (thick part) ductus papillaris descending limb (thin part) ascending limb (thin part)