Lecture 14 - Anatomy (Urinary Anatomy & Histology) Week 10 PDF

ANATOMY AND HISTOLOGY OF THE KIDNEY Thomas Wilson Adapted from material by Nick Milne Graphics from Grant’s Method of Anatomy, Netters Atlas of Human Embryology, Larsen’s Anatomy, Human Embryology and Developmental Biology, Moore’s Before We Are Born, Analysis of Vertebrate Structure,...

ANATOMY AND HISTOLOGY OF THE KIDNEY Thomas Wilson Adapted from material by Nick Milne Graphics from Grant’s Method of Anatomy, Netters Atlas of Human Embryology, Larsen’s Anatomy, Human Embryology and Developmental Biology, Moore’s Before We Are Born, Analysis of Vertebrate Structure, McMinn’s & Abrahams Clinical Atlas of Anatomy, Human Anatomy Colour Atlas & Textbook, Histology-online, University of Leeds, Histology A Text and Atlas [email protected] Goal: Understand how the organisation and anatomical structure of the kidney aids in its functional efficiency Outline: Outcomes: Gross anatomy of the kidney Identify the gross anatomical and histological components of the adult kidney, ureter, and bladder. Renal histology Explain how the structure of the kidney, its blood supply, and its nephrons influence the efficiency and effectiveness of kidney function. Anatomy and histology of the ureters Identify and differentiate the tubules of the nephron in histological sections, by explaining how the structure of the cells/tubules relates to functional tasks of that tubule. Anatomy of the bladder Explain the processes involved in creating, transporting, storing, and evacuating urine. Describe how the development and complex cellular anatomy makes the glomerulus such an effective filter. Gross renal anatomy Blood filters that control our propensity to turn into ‘human prunes’… AKA Osmotic regulators blood vessels critical → all are 5 segments: defined by non-anastomosing blood supply  surgical implications Renal  Segmental  Interlobar  Arcuate  Radiate/interlobular  Afferent arteriole → autonomics µ because autonomic connections lost ☆ fat packs around hilum Nerve supply: Vasomotor (hormone control required post-transplant) ° Parasympathetic: Vagus  ↑ renal arterial flow  ↑ GFR Sympathetic: Lesser splanchnics (T10-11) via aorticorenal plexus → ganglia that sit around the renal a. & aorta ✓ where the synapse of pre synaptic neurons - SEGMENTS & post synaptic - neurons for the kidneys is. ↳↳ constrict renal a. & try to redirect blood cardiac output* flow to more active tissue as :É÷÷!É÷÷÷jEto.  Gross renal anatomy µ -7 Renal lobes = Cortex + medullary pyramid Cortex = Outer tissue with renal column extensions (into medulla) " medullary tissue found cortex " in "" "" "" " " " Glomeruli + convoluted tubules (proximal/distal) + medullary rays → connect uptominorcalyo.es Medulla (marrow) = Pyramids contain the long tubules of the nephrons Ah / I ¥ Loop of Henle + Collecting ducts + Papilla → whereallofthe.co/Iectingductsfromthat lobe - calyx enter into a minor Medullary pyramid = Papilla + pyramidal body + medullary rays (in cortex) :≈ Ko B off to :3 ÷÷ ÷÷≤ % Waste collection component: Minor calyces cup the papilla  Major calyces (cranial/caudal split) Renal pelvis  Ureter ↳2 minor calyces connecting ?⃝ Renal histology vasculature pole → urinary pole Nephron (~1 million/kidney) 6 major components, each with a distinct job 1. Glomerular/Bowman’s capsule so 2. glomerulus (1+2=renal corpuscle) ⑥ 3. Proximal convoluted tubule 4. Loop of Henle IL0H) 5. Distal convoluted tubule Ld 6. Collecting ducts Process of making urine: 1. Filter the blood: Glomerular filtration (~180l/day) Must be selective! BP dependent (1BP=↓GFR=↓ urine) 2. Reabsorb: water, salts, and glucose (~179l/day) 3. Secrete some proteins: Notably creatinine (things you don’t want) ↳ by-product of tissue breakdown ‘Passive’ mechanisms: Right place, right time, remembered the keys… membrane transport Counter current flow between peritubular capillaries and tubules 1. Pressure Concentration gradient established by selective transporters (LoH) } _ 2. Opening Osmosis and diffusion Anatomy of a ‘ball of thread’… Glomerulus: Multi-layered electro-mechanical filter, representing joining of filtration and excretion sides of system Filtration side: Coiled fenestrated capillary (70-90nm) Juxta glomerular apparatus: 3 cell type contribute 1. Mesangial cells in between (clean proteinaceous debris) 2. Juxtaglomerular cells (JGC): Modified smooth muscle of afferent arteriole Release renin in response to stretch and macula densa cell input 3. Macula densa: Cells of DCT in contact with glomerulus Sensitive to [Na+ & Cl-]  stimulate JGC Excretion side: Basement membrane (~8nm) and 2-sides of Bowman’s capsule cells Parietal: Cells of capsule wall Visceral: Podocytes and their pedicel extensions Subpodocyte space Gaps between pedicels are only ~40nm Bridged by ‘slit diaphragm’ loose intercellular connection (~8-14nm) Deficient in genetic proteinuric disease  Basement membrane of Bowman’s capsule (~8nm) Parietal cells Visceral cells Afferent/efferent arterioles Fenestrated capillaries (70-90nm) Vascular pole Podocyte & pedicels (40nm) Slit diaphragm (~8-14nm) Mesangial cells PCT & DCT Macula densa cells Juxtaglomerular cells Urine space Urinary pole  Renal cortex → / close to the capsule rothe length of the L0H relates to how much you can concentrate Nat, urea & reclaim Nate's water Cortical Nephrons = short loops of Henle Glomeruli found further away from medulla Mid-cortical is a hybrid of cortical and juxta Efferent arteriole  peritubular network (not efficient at concentrating salts) Juxtaglomerular nephrons At junction of cortex and medulla (1/10 glomeruli) Loops of Henle descend deeper into medullary pyramid & concentrate urine the most Distal convoluted tubule interacts with afferent arteriole ?É Macula densa cell: detect [Na+ & Cl-] the dregs of what the PCT couldn’t manage… If NaCl flow is low  signal juxtaglomerular cells to release renin  ↑GFR ↑Jy If high  signals constriction in juxtaglomerular cells of afferent arteriole  ↓GFR Primary result: retention of water, Na+, and Cl- T E. * fkwinDCT.to/NaTmeans&GFR&l-BP. space within T Efferent arteriole  Vasa recta the capsule → in ascending & descending limbs Counter current multiplication with selective ion channels ÷: : × vascular Recycles urea between ductules, interstitial fluid, vasa recta pole forthe glomerulus Creates scaled medullary concentration gradient macula. densa cells  ☆ structure helps * efficiency Peritubular Vs Vasa recta medullary rays it - ↑ in size closerto medulla as collects from ↑ # of nephrons juxtaglomerata nephrons gradient of cortical nephron s → ☆ ↳ ' / to glomeruli are one of these may drain into this - medullary ray - collection of collecting ducts cut trans versly glomeruli ¥; ¥ , * ↳ are in directional formation for more efficient transport across c the membranes 0 R : i - L M E D U : Structure and function: Cortical tubules D= distal P ≤ thinner section proximal thick section of of L0H L0H ↓ PC not marked ones ↓ Mostly from straight tubules (more cortical aspect of L0H) Proximal convoluted tubules: Fluffy! Bigger High amount of ACTIVE transport Salts, water, amino acids, small peptides → can Slough into the lumen (artifact) High surface area = microvilli (brush border) Lots of mitochondria  lots of space = columnar-ish do tall cuboid cells ] " " Large irregular shaped cells Fewer nuclei in tubular cross-section concentrations needs cellular machinery highest so more ⑥ lumen more irregular Distal convoluted tubule: Crisp! a. No microvilli (negligible if at all) More nuclei in tubular cross-sections Outer diameter more similar to inner diameter vs PCT Less ACTIVE transport  less machinery in cell = less space = more cuboidal shaped epithelium ☆ Outer diameter of a DC will be the same as the inner diameter of a PC Structure and function: Medullary tubules → only seeing straight tubules not convoluted because they're all in the cortex Loop of Henle Proximal thick segment  similar to PCT Distal thick segment  similar to DCT Thin segments have simple squamous epithelium " ↳ cell membrane that makes in the wall " bulge ① a ↳ there arethin areas in the wall & tend to be surrounded closely by vasculature ' small → capillary components travelling between the kidney tubules Collecting ducts KD) ① Inner diameter roughly equal to outer diameter of DT/DCT ① ① Still cuboidal with crisp luminal surface Sensitive to aldosterone Hormonal regulation of urine concentration ← increases Regulate aquaporin density: water permeability More nuclei that take up more space in cells ①  0 0 000 Ureter histology rounded stratified squamous → from calyces to the bladder → a Transitional epithelium in ureter protects against stretch  stratified squamous near external opening (distal urethra) Layers: → highly folded Mucosa (epi + lamina propria) Muscularis external: Inner circular Outer longitudinal Ureter & Urethra move urine by… Ureter (bladder input pipe): Peristalsis Urethra (bladder output pipe): Bladder & abdominal pressure external← smooth muscle - muscularis Bladder pressure from stretch and detrusor muscle activation ↳ on internal wall of bladder Tracing the ureter he passes behind most things because its primary retroperitoneal Passes through retroperitoneal fat (posterior to secondarily retroperitoneal structures!) Cross the pelvic brim at bifurcation of common iliac arteries Blood and nerve supply: Upper ureter: Branches from renal arteries Parasympathetic: Vagus Sympathetic: Least splanchnic (T12) ↳ named after a vertebral region Lower ureter and bladder: Branches from vesicular arteries Parasympathetic: Pelvic splanchnics (S234) (relates to HG) Via hypogastric plexus  detrusor contraction (SM) Carry stretch-sensitive afferent nerve fibres Micturition reflex: Stretch triggers detrusor contraction Felt as urge to wee, but can be consciously overridden Sympathetic: Sacral splanchnics (L1 spinal nerves) Tighten sphincter… Derived from L1 spinal nerves But synapse in the S1-5 ganglia to reach these components Before Pathway and relations µ followed by gonadal vessels that go infront of ureter Note relation of ureter to gonadal vessels and vas deferens Prostate forms support/restriction for internal urethral sphincter *URETHRAL SPHINCTERS SUBJECT OF REPRO BLOCK*  Triangular pyramid 4 surfaces: Histology ← inferior 2 lateral: Against the pubic bones Smooth muscle sac lined by transitional epithelium Superior: covered in peritoneum Very similar to ureter including folded mucosa (expansion) Posterior: Receives ureters (trigone internally) Lacks a sub mucosa Detrusor muscle within the wall (meaning “thrust down”): 4 points: Thickening in the muscularis externa 2 lateral: Originally receive ureters ↳ very thick Ureters move down posterior wall Inferior: ‘Neck’ region, exit of urethra Anterior: ‘Apex’, urachus (within median umbilical lig.) IN ↓ "" "" ° IN ↳ reaches upto the umbilicus more so than in an adult * OUT University of Leeds ?⃝  A full tank… ☆ extra peritoneal space Peritoneal coverings: Allows safer expansion prevent intestines wrapping around pelvic structures No pouches in front of the bladder due to urachus’ connection to the umbilicus ↳detrusorm. contracting Ureter has no sphincter with the bladder…So why doesn’t urine flow UP the ureter?? - during development the ureters slip down into the posterior wall bladder so of the bladder & isactually running in the muscular wall of the when the detrusor muscle contracts it acts as valvular sphincter