Structure of The Kidney

Objectives 1)Define the term excretion and explain the importance of removing waste material from the body 2)Describe the process which forms urea from amino acids 3)Describe the general structure of the kidney, the nephron, and associated blood vessels

Excretion What waste material do we produce? What waste material do we produce? – CO 2  released through lungs – Feces  released through digestive tract – Urine  released through kidneys All are poisonous materials (toxins) All are poisonous materials (toxins) Where do they come from? Where do they come from? – CO 2  cellular respiration – Feces  material not absorbed by body – Urine  forms from urea; produced by the liver from excess amino acids

Deamination: Forming Urea What are our major sources of energy? What are our major sources of energy? – Carbohydrates, Fats, and Proteins How are carbs and fats stored? Proteins? How are carbs and fats stored? Proteins? – Glycogen and fat (adipose tissue) Deamination  removal of for amino group from an amino acid to form a keto acid (RCOCOOH) and ammonia (NH 3 ) Deamination  removal of for amino group from an amino acid to form a keto acid (RCOCOOH) and ammonia (NH 3 ) – Keto acids can form glucose and fat – Ammonia is toxic

Deamination: Forming Urea To prevent damage from ammonia build up, ammonia instantly combines with CO 2 and produce urea (CH 4 ON 2 ) and H 2 O To prevent damage from ammonia build up, ammonia instantly combines with CO 2 and produce urea (CH 4 ON 2 ) and H 2 O Urea passes from the liver into the blood plasma and then filtered out through the kidneys Urea passes from the liver into the blood plasma and then filtered out through the kidneys Main Nitrogenous excretory product Main Nitrogenous excretory product Uric Acid  minor nitrogenous excretory product made from the breakdown of DNA Uric Acid  minor nitrogenous excretory product made from the breakdown of DNA

Aquatic Life and Ammonia Availability of water has a great influence on how an organism deals with ammonia Availability of water has a great influence on how an organism deals with ammonia Ammonia is highly soluble and very small so in a water rich environment it can quickly diffuse through cell membranes and be released Ammonia is highly soluble and very small so in a water rich environment it can quickly diffuse through cell membranes and be released Urea, less soluble, must be filtered by kidneys Urea, less soluble, must be filtered by kidneys – Price of living on land

Structure of the Urinary System Renal artery  takes unfiltered blood to kidneys Renal artery  takes unfiltered blood to kidneys Renal vein  takes filtered blood from kidneys Renal vein  takes filtered blood from kidneys Kidney  bean-shaped network of filtering units called nephrons Kidney  bean-shaped network of filtering units called nephrons Ureter  carries urine from kidneys to bladder Ureter  carries urine from kidneys to bladder Bladder  elastic storage area for urine Bladder  elastic storage area for urine Urethra  carries urine from bladder to outside the body Urethra  carries urine from bladder to outside the body

Layers of a Kidney 2 main roles of kidneys: 2 main roles of kidneys: 1)Removal of urea 2)Regulating water levels, ion levels, and pH of blood (homeostasis) Capsule  tough outer layer to protect kidney from damage Capsule  tough outer layer to protect kidney from damage 3 main areas of a Kidney 3 main areas of a Kidney 1)Cortex  contains all glomerulus, renal capsules, and area where ultrafiltation occurs 2)Medulla  contains all loop of Henle, collecting ducts, and area where reabsorbtion occurs 3)Pelvis  where all collecting ducts meet to carry waste away through ureters

Structure of a Nephron Nephron  filtration unit a kidney Nephron  filtration unit a kidney Renal (Bowman’s) capsule  cup-shaped site where arterial blood is filtered Renal (Bowman’s) capsule  cup-shaped site where arterial blood is filtered – Blood comes in from afferent arteriole – Glomerulus  splitting capillaries in capsule to increase filtering rate – Blood leaves through the efferent arteriole

Structure of a Nephron Proximal convoluted tubule  carries filtrate from renal capsule to loop of Henle; main reabsorption site Proximal convoluted tubule  carries filtrate from renal capsule to loop of Henle; main reabsorption site Loop of Henle  located in the medulla; site of reabsorption of H 2 O and other important ions Loop of Henle  located in the medulla; site of reabsorption of H 2 O and other important ions Distal convoluted tubule  carries filtrate (after reabsorption) from loop of Henle to collecting ducts Distal convoluted tubule  carries filtrate (after reabsorption) from loop of Henle to collecting ducts Collecting ducts  carries filtrate to ureters Collecting ducts  carries filtrate to ureters

Q R S T U W V glomerulus Bowman’s capsule proximal convoluted tubule Loop of Henlé (descending limb) ascending limb distal convoluted tubule collecting duct

Convoluted tubules of the nephron Collecting duct

Bowman’s (renal) capsule neck of proximal convoluted tubule distal tubule

A B C D E F G IJ Glomeruli Collecting Ducts Proximal Convoluted Tubule Distal Convoluted Tubule Glomerulus Bowman’s capsule Collecting duct Loop of Henlé (thin section) Loop of Henlé (thick section) H Capillary (Vasa recta)

K L M N O Glomeruli Cortex Collecting ducts Medulla Pelvis

P What sort of microscope was used to make the micrograph above? Podocytes Scanning electron microscope

Ultrafiltration Renal capsule filters urea, H2O, and small molecules from the blood Renal capsule filters urea, H2O, and small molecules from the blood – Reabsorption pulls important molecules and H2O back into blood 3 layers of Filtration: 3 layers of Filtration: 1)Endothelium cells  thin layer with thousands of gaps small molecules pass through; walls of capillary 2)Basement membrane  network of collagen and glycoproteins; stops large proteins; between capillary and capsule 3)Epithelial cells  thicker layer with holes for small molecules to pass through; walls of capsule -podocytes  finger-like projections that help with filtration

Ultrafiltration Rate Average glomerular filtration rate  125 cm 3 /min Average glomerular filtration rate  125 cm 3 /min Rate maintained by water potential difference and pressure Rate maintained by water potential difference and pressure Afferent arteriole is wider and has a higher pressure than the efferent arteriole Afferent arteriole is wider and has a higher pressure than the efferent arteriole – “Traffic Jam”; pressure raises water potential in glomerulus Which has a higher solute concentration: Glomerulus or Renal Capsule? Which has a higher solute concentration: Glomerulus or Renal Capsule? – Glomerulus; large proteins cannot leave blood Shouldn’t water potential be lower in glomerulus since solute conc. is higher? Shouldn’t water potential be lower in glomerulus since solute conc. is higher? – No. The pressure difference between them is too great