Lecture 8a Anatomy Urinary System Chptr 26 PDF

Urinary (AKA Renal) System Anatomy Chapter 26  The Urinary System Learning Outcomes 1) Know the structures and functions of the Urinary System 2) Understand Nitrogen Waste and Urea as the main component of Urine 3) Know the internal structures of the...

Urinary (AKA Renal) System Anatomy Chapter 26  The Urinary System Learning Outcomes 1) Know the structures and functions of the Urinary System 2) Understand Nitrogen Waste and Urea as the main component of Urine 3) Know the internal structures of the Kidneys associated with Filtration of blood 4) Know the structure of the Nephrons and relate to their filtration ability to retain or release water, electrolytes and glucose 5) Know what is anatomy and physiology of micturition (A.K.A urination) 6) Understand reflex mechanisms associated with Urination © 2018 Pearson Education, Inc.  The urinary system organs are the kidneys, ureters, urinary bladder, and urethra Urinary system  Two kidneys – Production of URINE Retain or Remove water an other components of blood Receive 25 percent of the cardiac output (blood circulation) Major excretory organs of the urinary system Produce urine (fluid containing water, ions, urea (nitrogen waste) and small soluble substances (like glucose) © 2018 Pearson Education, Inc.  Urinary system organs The Urinary tract – Storage and Release of Urine  Ureters—receive urine from the kidneys Conduct urine to the urinary bladder by gravity and peristalsis (wave like movement via smooth muscles)  Urinary bladder—receives and stores urine Contraction of muscle in walls drives urination  Urethra—conducts urine from the bladder to outside the body © 2018 Pearson Education, Inc.  Major Functions of the Urinary System Urea - MAIN chemical component of Urine (Next to water of course) Urea is a NITROGEN waste product created by cells during metabolism of amino acids and nucleotides which have NITROGEN in the chemical structures When Urea builds up in the cells it is TOXIC © 2018 Pearson Education, Inc.  The kidneys are paired retroperitoneal organs Kidney structure (Two Kidneys)  Reddish brown Renal Artery – Blood entering to  Dimensions be filtrated ~10 cm (4 in.) long; ~5.5 cm (2.2 in.) wide; ~3 cm (1.2 in.) thick; Weight: ~150 g (5.25 oz)  Renal Hilum Renal Vein – Medial indentation Blood Leaving after filtration Point of entry/exit for the renal artery, renal nerves, renal vein, Ureter – Drains to and the ureter the Bladder © 2018 Pearson Education, Inc.  Kidney location and structure  Located in a retroperitoneal position Between the muscles of the posterior body wall and the parietal peritoneum There are POSTERIOR and SUPERIO within the Abdominal Cavity  Connected to the urinary bladder by the ureters Empty into the posterior, inferior surface of the urinary bladder © 2018 Pearson Education, Inc.  Kidney location and structure (Posterior location)  Lateral on either side of vertebral column  You can do superficial palpitation on the kidneys from the back (posterior) to see if they are inflamed  Protected by: Anteriorly – Other Visceral organs (covered anteriorly by other organ like liver and stomach which are in front) Posteriorly -Body wall musculature and the 11th and 12th ribs © 2018 Pearson Education, Inc.  Tissue Anchoring and Protecting The Kidneys Connective tissues protecting kidney and connecting to peritoneal cavity and other adjacent visceral organs  Fibrous capsule (layer of collagen fibers) Covers the outer surface of the kidney Projects collagen fibers through the perinephric fat to the renal fascia  Adipose Tissue – Surrounds and cushions the kidney and supplies biomolecules for energy (fatty acids) Main Vessels To and From the Heart © 2018 Pearson Education, Inc.  Tissue Anchoring and Protecting The Kidneys Connective tissues supporting kidney (continued)  Perinephric fat (perinephric fat capsule) Thick layer of adipose tissue  Renal fascia (dense, fibrous outer layer) Anchors the kidney to surrounding structures © 2018 Pearson Education, Inc.  Deep anatomy of The kidneys - the gross and microscopic anatomy Major structural landmarks  Fibrous capsule Lines the renal sinus (cavity lining the kidney)  Renal cortex (superficial cortex of the kidney)  Renal medulla (Deep region of the kidney) Renal pyramid (conical structure in the medulla) – Renal papilla (tip of the pyramid) Renal column (separates adjacent pyramids) © 2018 Pearson Education, Inc.  Deep anatomy of The kidneys - the gross and microscopic anatomy Major structural landmarks (continued)  Kidney lobe (pyramid, the overlying cortex, and adjacent renal columns) Each kidney contains 6–18 lobes © 2018 Pearson Education, Inc.  Deep anatomy of The kidneys - the gross and microscopic anatomy Other features of the kidney  Hilum Medial indentation in the kidney  Minor calyx Collects urine from a single kidney lobe  Major calyx Forms from the fusion of 4–5 minor calyces  Renal pelvis Funnel-shaped structure that collects urine from major calyces Continuous with the ureter © 2018 Pearson Education, Inc.  Renal Sinus – Blood pools up and circulation SLOWS to ensure MAXIMUM Filtration Deep anatomy of The kidneys - the gross and microscopic anatomy © 2018 Pearson Education, Inc.  The Nephron – The Filtration Unit within the Kidney Roughly 1 million Nephrons per Kidney Two types of nephrons  Microscopic functional units of the kidney 1. ​Cortical nephrons 85 percent of all nephrons Located primarily in the cortex Responsible for most regulatory functions 2. J​ uxtamedullary nephrons 15 percent of all nephrons Long nephron loop extending deep into medulla Essential to producing concentrated urine © 2018 Pearson Education, Inc.  The Anatomy of A nephron - divided into Components; each has specific functions Two components 1. ​Renal corpuscle Blood pressure forces water and solutes out of the glomerular capillaries in a process called filtration – Produces filtrate (protein-free solution, similar to blood plasma) Collected in the surrounding capsular space 2. ​Renal tubule Tubular passageway up to 50 mm long Receives filtrate and modifies it to create urine © 2018 Pearson Education, Inc.  Renal Corpuscle and Renal Tubules of the Nephron © 2018 Pearson Education, Inc.  Nephron – First interaction or Filtration with Blood Circulation  Renal corpuscle Glomerular capsule (Bowman’s capsule) Cup-shaped chamber Capillary network (glomerulus) AFFERENT Blood is Initially filtered at the Renal corpuscle – Water and soluble molecules like Urea, electrolytes, glucose are sent to the tubules to stay in the kidney and travel through the Nephron for further filtration Larger components of blood like cells and large proteins (like antibodies) stay in circulation (are not filtrated) and go back to circulation EFFERENT FLOW © 2018 Pearson Education, Inc.  Nephron – First interaction or Filtration with Blood Circulation Afferent Flow Efferent Flow Re-Collects Secondary filtration farther down the nephron © 2018 Pearson Education, Inc.  Segments of a nephron – Secondary Filtration of Primary Filtration through the Nephron Tubule  1) Proximal convoluted tubule (PCT) Beginning of Secondary filtration - Reabsorbs nutrients from the primary filtrate (now called tubular fluid) This is the first part of the tubule just after the Glomerulus (which is the site of primary filtration – Afferent Blood Flow) This Portion of the tubule is twisted an convoluted NOT straight © 2018 Pearson Education, Inc.  Module 24.4: Segments of a nephron  2) Loop of Henle Long Linear Loop of the Nephron Tubule Establishes osmotic gradient for water reabsorption This area can be adjusted to RETAIN or REMOVE more water depended on the need (low and high blood pressure) ; Dehydration etc. © 2018 Pearson Education, Inc.  Module 24.4: Segments of a nephron  3) Distal convoluted tubule (DCT) Adjusts fluid composition by reabsorption and secretion The last part (distal from the Glomerulus) of the Nephron Before the Collecting Duct The Collecting Duct leads to the Ureter and to the Bladder © 2018 Pearson Education, Inc.  Segments of a nephron – Continuous Filtration and Reabsorption Secondary Filtration occurs along the entire TUBULE. Water and electrolytes that are filtered from the tubule are reabsorbed in the EFFERENT Arteriole Flow © 2018 Pearson Education, Inc.  Segments of a nephron – Urine Collection and Final Reabsorption Collecting system  Series of tubes carrying tubular fluid away from the nephron  Last step of water and solute reabsorption before leaving the kidney to the bladder via the Ureter.  Collecting duct Collects fluid from many nephrons Carries fluid through the renal medulla © 2018 Pearson Education, Inc.  Segments of a nephron – Urine Collection and Final Reabsorption  Collecting duct Continued Lined with two main types of cells: – Intercalated cells (play a role in secreting and reabsorbing hydrogen and bicarbonate ions) – Principal cells (reabsorb water and secrete potassium)  Papillary duct Collects fluid from multiple collecting ducts Delivers fluid to minor calyx No Filtration or Reabsorption happens in the Papillary duct © 2018 Pearson Education, Inc.  The Nephron and collecting system © 2018 Pearson Education, Inc.  Arterial Circulation patterns into the kidney Arterial system – Smaller Arteries branch from the Renal Artery to ensure blood circulation is diffused across the cortex from maximum filtration in the glomerulus of each nephron  Renal artery → Segmental arteries → Interlobar arteries → Arcuate arteries → Cortical radiate arteries, which branch into: Afferent arterioles, which supply each nephron, specifically a capillary knot known as a glomerulus (which is the site of primary filtration into the Nephron) © 2018 Pearson Education, Inc.  Venous Circulation patterns leaving the kidney Venous system – Blood as been completely filtered and now need to return to circulation  Cortical radiate veins collect blood from the capillaries at the of the nephron in the cortex and drain into: Arcuate veins, then to: – Interlobar veins, which drain into the: o Renal vein, which leaves the kidneys and drains into the inferior vena cava © 2018 Pearson Education, Inc.  Circulation patterns in the kidney Blood flow around a cortical nephron  1) Afferent arteriole Supplies blood to each individual nephron  2) Glomerulus (Primary Filtration)  3) Efferent arteriole Connects site of primary filtration at glomerulus to the site of reabsorption (Peritubular capillaries) due to secondary filtration along the nephron tubule. Simply put.. Carries blood from the glomerulus to the peritubular capillaries where water and solutes that were filtered at the glomerulus are reabsorbed © 2018 Pearson Education, Inc.  Circulation patterns in the kidney Blood flow around a cortical nephron 4) Peritubular capillaries Connection Between Efferent Arteriole Blood and Venous Return Blood Surround the entire renal tubule Collect water and solutes absorbed by the nephron Deliver other solutes to the nephron for secretion Drain into cortical radiate the renal vein and out of the kidney © 2018 Pearson Education, Inc.  Renal vein Renal artery Segmental artery Interlobar vein Interlobar artery Circulation patterns in the kidney Arcuate vein Arcuate artery Cortical radiate vein Cortical radiate artery Venule Afferent arteriole NEPHRON Peritubular Glomerulus capillaries Efferent arteriole A flowchart of renal circulation © 2018 Pearson Education, Inc.  Circulation patterns in the kidney Nephron innervation  Each kidney has ~1.25 million nephrons  Both cortical and juxtamedullary nephrons are innervated by renal nerves Enter at the hilum and follow the branches of the renal artery  Most of the nerve fibers are sympathetic postganglionic fibers from the celiac plexus and inferior splanchnic nerves Sympathetic stimuli adjust blood flow and blood pressure at the glomeruli Also stimulate the release of renin © 2018 Pearson Education, Inc.  Physiology of the Kidney - maintain homeostasis by removing wastes, reabsorbing water and electrolytes as needed and producing urine Renal physiology  Urinary system maintains homeostasis by regulating the volume and composition of blood  Concentrates urine to by reabsorbing water throughout the Nephron tubule  Regulates the amount of water and solute reabsorption BACK into circulation depending on need (I.E. Dehydration)  Excretes solutes, especially metabolic wastes © 2018 Pearson Education, Inc.  Renal physiology – Waste Removal Examples of metabolic wastes  Urea Most abundant organic waste By-product of amino acid and nucleotide breakdown  Creatinine By-product of creatine phosphate breakdown in muscles  Uric acid Formed during recycling of nitrogenous bases of RNA © 2018 Pearson Education, Inc.  Renal physiology – Basic Steps in Production of Urine 3 basic processes in urine formation 1. ​Filtration and production of Tubular Fluid Blood pressure forces water and solutes across the membranes of the glomerular capillaries of the glomerulus into the capsular space of the ​renal corpuscle and then into the Proximal Tubule of the Nephron (first step – production of Tubular Fluid that flows through the tubules of the nephron) Tubular fluid in the Tubule of the Nephron © 2018 Pearson Education, Inc.  Renal physiology – Basic Steps in Production of Urine 3 processes in urine formation 2. ​Reabsorption due to secondary filtration of tubular fluid Transport of water and solutes from the tubular fluid in the tubules across tubular epithelium into the peritubular fluid which will be reabsorbed by the blood at the peritubular capillaries Nephron 3. ​Secretion Transport To The Peritubular Tubule of remaining solutes Capillaries and water in the tubular fluid (concentrated Urine) from the Nephron to the Collecting Duct (at this point there is Urine which leaves the Kidneys via the Ureter to the bladder. © 2018 Pearson Education, Inc. Renal physiology – Basic Steps in Production of Urine A)Filtration – Afferent Blood is filtered through the Glomerulus - water, urea, electrolytes and other small soluble molecules (like glucose) enter the Nephron tubule as Tubular Fluid B) Reabsorption – some Secretion water and solutes that makeup the tubular fluid are filtrated out while traveling through the nephron and reabsorbed into the blood. C) Secretion –The Efferent Arterioles release more components AFTER the initial filtration that will enter into the Tubular Fluid and removed as urine. Example H+ ions after secreted as a way to manage blood pH  Filtration, reabsorption, and secretion occur in specific segments of the nephron and collecting system Functions of each nephron segment  Three processes in urine formation: filtration, reabsorption, and secretion  Filtration occurs only in the renal corpuscle (glomerulus)  Balance between reabsorption and secretion varies in remaining nephron segments (Proximal Tubule, Loop of Henle and Distal Tubule) and is dictated by environmental situations (I.E. Chances in blood pressure or dehydration)  The of final volume water and final solute concentration in the tubular fluid is from the interaction between the collecting system and the nephron loops © 2018 Pearson Education, Inc.  Filtration, reabsorption, and secretion © 2018 Pearson Education, Inc.  Redistribution of water and solutes that where not secreted as Urine back into systemic Circulation Peritubular Capillaries absorb the water, solutes and other soluble molecules that WERE NOT secreted as Urine The Vasa Recta – Are the venules within the kidney that connect to the Peritubular Capillaries which send the Redistributed water solutes and other soluble molecules that WERE NOT secreted as Urine out of the Kidney via the Renal Vein back into systemic circulation © 2018 Pearson Education, Inc.  Primary Filtration occurs at the renal corpuscle  Afferent arteriole (delivers arteriole blood to the corpuscle)  Glomerulus (capillary knot) Site of capillaries that facilitate filtration Filtration occurs here © 2018 Pearson Education, Inc.  Primary Filtration occurs at the renal corpuscle  Efferent arteriole (delivers filtered blood to peritubular capillaries for redistribution) Smaller diameter than the afferent arteriole This increases the blood pressure in the glomerulus, aiding filtration  Juxtaglomerular complex Secretes renin (hormone) when glomerular blood is too low (feedback response to increase blood pressure) © 2018 Pearson Education, Inc.  Filtration at the Glomerulus – Filtration by Size Filtration membrane 1. Fenestrated glomerular capillaries Contain large diameter pores 2. ​Dense layer Specialized basement membrane 3. Filtration slits from podocytes  Combination of these layers prevents most plasma proteins and all cells (Too large to filter from entering the capsular space and stay in the EFFERENT arteriole and DO NOT enter the Nephron © 2018 Pearson Education, Inc.  Things that alter Filtration Rate There is a NORMAL filtration rate based on pressure in the Arteriole Blood and the Tubular Fluid in the Nephrons If blood pressure is abnormal OR blood is Too Thick or Thin this can impact the filtration rate Also, if there is too much or too little pressure in the Nephron this can also impact the filtration rate © 2018 Pearson Education, Inc.  Assessing glomerular filtration rate is how the Kidney measures Blood Pressure and can Respond When Blood Pressure is Too High or Too Low.  Two interacting levels of control help stabilize Glomerular filtration rate (GFR) and Blood Pressure 1. A​ utoregulation at the local level 2. ​Central regulation – Endocrine component o Initiated by the kidneys – Neural component o Involves the sympathetic division of the ANS © 2018 Pearson Education, Inc.  Autoregulation maintains adequate GFR and Blood Pressure © 2018 Pearson Education, Inc.  Central Regulation can also maintains adequate GFR and Blood Pressure If autoregulation is ineffective, central regulation is involved – Secretion of Renin at the Juxtaglomerular complex © 2018 Pearson Education, Inc.  Central regulation – Renin & Juxtaglomerular complex © 2018 Pearson Education, Inc.  Reabsorption predominates along the proximal convoluted tubule…  Reabsorption in the PCT includes: >99 percent of glucose, amino acids, and other organic nutrients Sodium, potassium, bicarbonate, magnesium, phosphate, sulfate ions Water (about 108 liters each day) – Solute concentration of tubular fluid decreases – Water moves into the peritubular fluid © 2018 Pearson Education, Inc.  Reabsorption © 2018 Pearson Education, Inc.  Balance between reabsorption and secretion often linked along the distal convoluted tubule  Movement of water & solutes out of peritubular fluid into the tubular fluid  Only %15–20 of initial filtrate reaches the distal convoluted tubule (DCT)  Combination of reabsorption and secretion in the DCT alters solute composition in the tubular fluid Sodium ions are reabsorbed in exchange for potassium ions: stimulated by aldosterone to regulate blood pressure Hydrogen ions are secreted in exchange for sodium ions (to increase pH of body fluids) Carrier proteins also secrete toxins or drugs © 2018 Pearson Education, Inc.  Balance Between Secretion and reabsorption © 2018 Pearson Education, Inc.