C7 Combined PDF - Renal System Anatomy - Curtin University 8/04/2021

8/04/2021 Compendium 7 How do we get rid of toxic waste? Part 1: The anatomy of the renal system Dr Flavia Di Pietro Acknowledgement: Dr Hannah Radley [email protected] WARNING This material has been reproduced and communicated to you by or on behalf of Curtin University in accordance with sect...

8/04/2021 Compendium 7 How do we get rid of toxic waste? Part 1: The anatomy of the renal system Dr Flavia Di Pietro Acknowledgement: Dr Hannah Radley [email protected] WARNING This material has been reproduced and communicated to you by or on behalf of Curtin University in accordance with section 113P of the Copyright Act 1968 (the Act) The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice. Please note that these unit materials contain images/videos of cadaveric material obtained under the Anatomy Licence held by the Anatomy Facility at Curtin University and are bound by the regulations of the Anatomy Act of Western Australia (1930). These images/videos are for study purposes only and must not be shared or distributed outside of this Blackboard site as this constitutes a breach of the Anatomy Act. A breach of the Anatomy Act is considered to be student misconduct and is dealt with in accordance with Statute No.10 Student Discipline. 1 8/04/2021 Specific Learning Objectives 1. List the organs of the urinary system. 2. Describe the main functions of the kidneys. 3. Describe the location and external anatomy of the kidneys. 4. Describe the structure of the nephron. 5. Describe the three processes necessary for urine formation. 6. Describe the components that make up the filtration membrane. 7. Describe the role of various regions of the nephron in terms of reabsorption and secretion. 8. Explain how substances are able to move across the cell membrane of the nephron. 9. Describe the specific movement of glucose across the cell membrane of the nephron. 10. List the waste products excreted in urine. 2 8/04/2021 Textbook readings  VanPutte, C. L., Regan, J. L. & Russo, A. F. (2020). Seeley’s Anatomy and Physiology (12th edition). New York, USA: McGraw-Hill o Chapter 26: pages 964-975, 977-982 and 997-1001  VanPutte, C. L., Regan, J. L. & Russo, A. F. (2017). Seeley’s Anatomy and Physiology (11th edition). New York, USA: McGraw-Hill o Chapter 26: pages 958-969, 971-976 and 989-992  VanPutte, C. L., Regan, J. L. & Russo, A. F. (2014). Seeley’s Anatomy and Physiology (10th edition). New York, USA: McGraw-Hill o Chapter 26: pages 946-957, 959-965 and 977-980  VanPutte, C. L., Regan, J. L. & Russo, A. F. (2010). Seeley’s Anatomy and Physiology (9th edition). New York, USA: McGraw-Hill o Chapter 26: pages 957-968, 970-976 and 988-990 Gross anatomy of the renal system  2 kidneys – formation of urine formation  2 ureters – passage of urine  Urinary bladder – storage of urine  Urethra – passage of urine 3 8/04/2021 Location of the kidneys  Posterior to the parietal peritoneum, on the posterior abdominal wall, lateral to spine  Note the R kidney is slightly inferior to L. Why?  Partially protected by lumbar vertebrae and ribs  ~11cm long, ~5cm wide, ~130g Liver Spleen Renal vein Renal vein Kidney Kidney Abdominal aorta 4 8/04/2021 Location and gross anatomy  Renal capsule – connective tissue surrounding each kidney  Adipose tissue – surrounds the outside of the capsule for protection  Renal fascia – thin layer of connective tissue surrounds the adipose tissue; anchor kidneys to abdominal wall Kidney external anatomy Renal capsule Renal artery Hilum Ureter Renal vein 5 8/04/2021 Kidney internal anatomy  Hilum: on the concave (medial) side. Renal artery and nerves enter. Renal vein, ureter, lymphatics exit  The hilum opens into the renal sinus, which is filled with fat and loose CT  Kidneys are organised into two major regions  Outer cortex  Inner medulla  Renal pyramids – bases project into cortex  Renal columns are extensions of cortical tissue into the medulla Kidney internal anatomy Renal Hilum and Sinus Ureter (connects to bladder) Renal Cortex (outer layer) Renal Columns 6 8/04/2021 Kidney internal anatomy  Renal pyramids – bases project into cortex. Cone-shaped. The base is the boundary between cortex and medulla  Apex of pyramid is renal papilla  Papillae extend into minor calyces, which are funnelshaped chambers  Minor calyces funnel into larger chamber called major calyces  Renal pelvis, a single large funnel-shaped chamber  Renal pelvis is embedded in the renal sinus. At the hilum, it narrows, forming the ureter 7 8/04/2021 Kidney internal anatomy Renal Medulla Pyramids Papilla Minor calyces Major calyces Renal pelvis The nephron  The functional unit of the kidney  4 separate regions of the nephron: renal corpuscle, proximal convoluted tubule, loop of Henle, distal convoluted tubule  Blood enters the nephron for filtration  Filtrate/urine is produced  Urine flow: nephron  papillary ducts  minor calyces  major calyces  renal pelvis  ureter 8 8/04/2021 Types of nephrons  Approximately 1.3 million nephrons in each kidney  Approximately 50-55 mm in length  Juxtamedullary nephrons:  the renal corpuscle is deep in the cortex near the medulla  Long loop of Henle extending deep into the medulla  15% of nephrons  Cortical nephrons:  Renal corpuscles located near the periphery/cortex  Shorter loop of Henle  85% of nephrons 9 8/04/2021 Renal corpuscle  The filtration portion of the nephron  Consists of the glomerulus and the Bowman capsule  Glomerulus:  Network/ball of capillaries  Bowman Capsule:  enlarged end of the nephron, double walled chamber. Filters blood/fluid, which then enters the proximal convoluted tubule.  Blood enters glomerulus through afferent arteriole, filtered blood exits through efferent arteriole  Note size difference – pressure difference Bowman capsule  Parietal layer:   Outer layer. Simple squamous epithelium. Becomes cuboidal in the PCT Visceral layer:  Inner layer. Constructed of specialised cells called podocytes, which wrap around the glomerular capillaries 10 8/04/2021 The filtration membrane  Fenestrae: the glomerular capillaries are highly permeable. Fenestrae are little windows  Basement membrane: sandwiched between the endothelial cells of the glomerular capillaries and the podocytes  Filtration slits: gaps between the cell processes of the podocytes  Thus, the filtration membrane is specialised for filtration Filtration membrane Podocytes Podocyte cell body Podocyte primary processes SEM: High Magnification Filtration slits Podocyte secondary processes 11 8/04/2021 The renal tubules  Proximal convoluted tubule: filtrate drains into here from the Bowman capsule.  Loop of Henle: has a descending and an ascending limb  Distal convoluted tubule: shorter than the PCT.  Collecting duct: several DCTs connect to a single collecting duct. Large diameter. Extends through medulla towards renal papilla  ureter Nephron histology  Proximal convoluted tubule: Simple cuboidal epithelium with many microvilli. Mitochondria. Active reabsorption of Na+, K+ & Cl-  Loop of Henle: Thick parts simple cuboidal epithelium. Thin parts - simple squamous epithelium – for osmosis/diffusion.  Distal convoluted tubule: Simple cuboidal epithelium, and very few microvilli. Numerous mitochondria. Active reabsorption  Collecting duct: simple cuboidal epithelium. 12 8/04/2021 Major Renal Veins and Arteries Abdominal aorta Rt. renal vein Rt. renal artery Lt. renal vein Lt. renal artery Inferior vena cava Major renal veins and arteries 13 8/04/2021 Urine Movement Pressure forces urine through nephron Smooth muscle forces urine through ureters. Peristalsis moves urine from the renal pelvis in the kidneys  ureters  urinary bladder. Ureters enter bladder obliquely through trigone. Pressure in bladder compresses ureter and prevents backflow Kidneys Ureters Bladder Ureters  Passageway for urine.  From renal pelvis  urinary bladder.  Lined with transitional epithelium Transitional epithelium Mucosa Muscularis Adventitia 14 8/04/2021 Urinary bladder  Urinary bladder: hollow muscular container. Located in pelvic cavity posterior to symphysis pubis.  Trigone: histologically unique region. Triangular area on posterior wall, between the entry of the two ureters and the exit of the urethra. Urethra  Transports urine from the urinary bladder to the outside of the body  Transitional epithelium at the top of the urethra; the remainder is stratified columnar  At the junction of the urinary bladder and the urethra is the Internal urinary sphincter   Elastic CT and smooth muscle, prevents urine leakage External urinary sphincter: skeletal muscle surrounds urethra as it extends through pelvic floor.  We can voluntarily start/stop flow of urine. 15 8/04/2021 Urethra Male urethra: extends from the inferior part of the urinary bladder through to the tip of the penis. Female urethra: shorter; opens into vestibule anterior to vaginal opening Compendium 7 questions 1. What are the main organs of the urinary system? 2. Which of these organs produce urine and which transports urine? 3. What are the internal structures of the kidney? 4. What is a nephron and what are its parts? 5. How does each part of a nephron contribute to urine formation and excretion of wastes? 6. What do we reabsorb from urine during its production? 7. What do we secrete into the urine as it is being produced? 16 9/04/2021 Compendium 7 How do we get rid of toxic waste? Part 1: The physiology of the renal system Dr Flavia Di Pietro Acknowledgement: Dr Hannah Radley [email protected] WARNING This material has been reproduced and communicated to you by or on behalf of Curtin University in accordance with section 113P of the Copyright Act 1968 (the Act) The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice. Please note that these unit materials contain images/videos of cadaveric material obtained under the Anatomy Licence held by the Anatomy Facility at Curtin University and are bound by the regulations of the Anatomy Act of Western Australia (1930). These images/videos are for study purposes only and must not be shared or distributed outside of this Blackboard site as this constitutes a breach of the Anatomy Act. A breach of the Anatomy Act is considered to be student misconduct and is dealt with in accordance with Statute No.10 Student Discipline. 1 9/04/2021 Specific Learning Objectives 1. List the organs of the urinary system. 2. Describe the main functions of the kidneys. 3. Describe the location and external anatomy of the kidneys. 4. Describe the structure of the nephron. 5. Describe the three processes necessary for urine formation. 6. Describe the components that make up the filtration membrane. 7. Describe the role of various regions of the nephron in terms of reabsorption and secretion. 8. Explain how substances are able to move across the cell membrane of the nephron. 9. Describe the specific movement of glucose across the cell membrane of the nephron. 10. List the waste products excreted in urine. 2 9/04/2021 Textbook readings  VanPutte, C. L., Regan, J. L. & Russo, A. F. (2020). Seeley’s Anatomy and Physiology (12th edition). New York, USA: McGraw-Hill o Chapter 26: pages 964-975, 977-982 and 997-1001  VanPutte, C. L., Regan, J. L. & Russo, A. F. (2017). Seeley’s Anatomy and Physiology (11th edition). New York, USA: McGraw-Hill o Chapter 26: pages 958-969, 971-976 and 989-992  VanPutte, C. L., Regan, J. L. & Russo, A. F. (2014). Seeley’s Anatomy and Physiology (10th edition). New York, USA: McGraw-Hill o Chapter 26: pages 946-957, 959-965 and 977-980  VanPutte, C. L., Regan, J. L. & Russo, A. F. (2010). Seeley’s Anatomy and Physiology (9th edition). New York, USA: McGraw-Hill o Chapter 26: pages 957-968, 970-976 and 988-990 Function of the renal system  Excretion: rid the body of waste products. Urine production occurs in the kidneys via filtration of the blood and reabsorption of nutrients. Metabolic wastes and toxic molecules are excreted in urine  Regulation of blood volume and blood pressure – we control our extracellular fluid volume by producing large amounts of dilute urine or small amounts of concentrated urine.  Also – solute concentration in the blood, extracellular pH, regulation of red blood cell synthesis, regulation of vitamin D synthesis… 3 9/04/2021 The production of urine  Kidneys: regulate body fluid composition. Sorts chemicals in the blood for removal or for return into the blood.  Nephrons: the structural component of the kidneys that ‘sorts’ the blood.  Urine production: recall 3 stages – filtration, tubular reabsorption, tubular secretion. Process 1. Filtration  Movement of fluid, derived from blood flowing through the glomerulus, across filtration membrane.  Filtrate: water, small molecules & ions that can pass through membrane.   Doesn’t include red blood cells, proteins or large molecules. Renal fraction: the proportion of total cardiac output that passes through the kidneys.  Varies from 12-30% in a healthy resting adult.  Glomerular filtration rate (GFR): amount of filtrate produced each minute – 125ml/minute; 180 L/day.  Average urine production/day: 1-2 L.  Most of filtrate (99%) must be reabsorbed  Removes toxins quickly from blood 4 9/04/2021 The filtration membrane – remember the anatomy  Fenestrae: the glomerular capillaries are highly permeable. Fenestrae are little windows  Basement membrane: sandwiched between the endothelial cells of the glomerular capillaries and the podocytes  Filtration slits: gaps between the cell processes of the podocytes  Thus, the filtration membrane is specialised for filtration Filtration membrane Filtration membrane – a filtration barrier  Learn and remember the components of the filtration membrane  Filtrate consists of: Water, glucose, fructose, amino acids, urea, urate ions, creatinine, Na+, K+, Ca+2, Cl-.   Filtration is driven by pressure   Very little protein normally found in filtrate and urine. Blood pressure Filtration pressure: the force that causes filtration.  Pressure gradient responsible for forcing fluid out of the glomerular capillary across the membrane into the lumen of the Bowman capsule 5 9/04/2021 The juxtaglomerular apparatus  An important regulatory structure, located next to the glomerulus  Where the afferent arteriole enters the renal corpuscle, a cuff of smooth mm cells surrounds it – the juxtaglomerular cells  A group of specialized cells at a section of the DCT – called the macula densa  These secrete renin, important in regulation of filtrate formation and BP regulation Process 2. Tubular reabsorption  This is the return of water, small molecules and ions back into the blood.  As the filtrate flows through the lumen of the renal tubules  First, substances are reabsorbed across the renal tubule into the interstitial fluid, then from here into the peritubular capillaries  back into the circulation 6 9/04/2021 Tubular reabsorption  Substances - Water, amino acids, glucose, fructose, Na+2, K+, Ca+2, Cl-, HCO3-  Proximal convoluted tubule  Majority of reabsorption here; filtrate remaining is about 35%  Active and passive mechanisms of cell membrane transport  Note the apical surface of the PCT simple cuboidal cell lining the nephron   Borders with nephron lumen Note the basal surface borders with the interstitial fluid 7 9/04/2021 Tubular reabsorption   Loop of Henle: some reabsorption of water and ions. Remember thick and thin segments  Thin segments – simple squamous epithelium, highly permeable to water. And some solutes can move by diffusion too.  Filtrate further reduced by another ~ 15% Distal convoluted tubule and Collecting duct: : some reabsorption.  Most of this is under control of Anti-Diuretic hormone  ADH makes the tubule wall more permeable to water. Ie more reabsorption in the presence of this hormone, therefore less and more concentrated urine. Tubular reabsorption in the PCT  Active transport of Na+ across the basal surface – associated with the reabsorption of most solutes  With Na+ being pumped out of the cell, the concentration of Na+ is low inside the cell. Therefore Na+ moves into the nephron cell through apical surface. Other substances can move in by symport.  Glucose 8 9/04/2021 Process 3: Tubular secretion  The movement of non-filtered substances, toxic by-products of metabolism, drugs or molecules not normally produced by the body, into the nephron for excretion. Occurs mainly in the distal convoluted tubule.  As with reabsorption it can be active or passive.  Ammonia is a toxic by-product of protein metabolism. Diffuses into lumen of nephron.  H+, K+ and penicillin: actively secreted into nephron Urine Movement  Pressure forces urine through the nephron  Peristalsis moves the urine through ureters to urinary bladder. Every few seconds to every few minutes.   Parasympathetic stimulation: increase frequency  Sympathetic stimulation: decrease frequency Prevention of backflow of urine – trigone pressure 9 9/04/2021 What is urine?  1% of filtrate  1-2L per day produced  Proportion of water  Depending on body’s needs – dilute or concentrated  Urea, uric acid, ammonia, creatinine, H+, K+  Bile pigments  Drugs and toxins – eg penicillin The micturition reflex  While the flow of urine from ureter to bladder is continuous, the flow from bladder to urethra is not.  Bladder capacity ~1L  Micturition – elimination of urine from the bladder  Full bladder – stretch receptors CNS message  Voluntary control (CNS) of the EUS. Relax urination 10 9/04/2021 Compendium 7 questions 1. What are the main organs of the urinary system? 2. Which of these organs produce urine and which transports urine? 3. What are the internal structures of the kidney? 4. What is a nephron and what are its parts? 5. How does each part of a nephron contribute to urine formation and excretion of wastes? 6. What do we reabsorb from urine during its production? 7. What do we secrete into the urine as it is being produced? 11