The%20Urinary%20System

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The Urinary System

• Part 4 Regulation Maintenance

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The Urinary System

• Goals of the Urinary System Regulate chemical
  composition of the bodily fluids eliminate
  waste products from the body.
• Organs of the Urinary System Two kidneys, two
  ureters, the urinary bladder, the urethra.

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The Kidneys

• The Kidneys Bean-shaped organs, part of the
  urinary system, that filter wastes excess
  products from the bloodstream so they can be
  removed from the human body.
• Retroperitoneal Located posterior to the
  peritoneum of the abdominal cavity technically
  outside the abdominal cavity.
• 0.5 of the total body weight.
• 20-25 of the total arterial blood is received by
  the kidneys.

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Functions of the Kidneys

• Filter waste products from the blood, returning
  useful materials eliminating wastes and
  excesses of normal components.
• Regulate the chemical composition of blood.
• Regulate volume composition of bodily fluids.
• Regulate blood volume pressure.
• Regulate the osmolarity of bodily fluids.
• Secrete renin (an enzyme that helps to control
  blood pressure electrolyte balance).
• Secrete erythropeitin (hormone that stimulates
  red blood cell production).
• Help regulate acid-base balance of body fluids.
• Synthesize calcitriol (hormone that helps
  regulate calcium balance).
• Detoxify free radicals some drugs.
• Gluconeogensis The synthesis of glucose from
  non-carbohydrates to release glucose in the blood
  maintain blood glucose levels at normal.
• Regulate blood ion levels.
• Participate in Vitamin D synthesis.

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External Kidney Anatomy

• The Kidneys Bean-shaped reddish-colored organs,
  lying just above the waist between the peritoneum
  the posterior wall of the abdomen, behind the
  abdominal cavity.
• The right kidney is slightly lower than the left
  due to the placement of the liver superior to the
  right kidney.
• Lateral Surface is convex.
• Medial Surface is concave.
• Renal Hilus The point at which the ureter, blood
  vessels, lymphatic vessels, nerve endings
  connect.

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Kidney Anatomy

• Three layers of tissue surrounding each kidney
• Renal Capsule The deep inner layer of smooth,
  transparent dense irregular connective tissue
  that is continuous with the other layer of the
  urethral covering.
• Provides a barrier against trauma helps
  maintain the shape of the organ.
• Adipose Capsule The fatty tissue surrounding the
  renal capsule helps protect the kidney hold
  it in place.
• Renal Fascia Outermost layer of thin, dense
  irregular connective tissue hat anchors the
  kidneys to the surrounding structure the
  abdominal wall.

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Internal Kidney Anatomy

• Two internal regions
• Renal Cortex The superficial, reddish, smooth
  textured area running from the renal capsule to
  the bases of the renal pyramids.
• Divided into the cortical and juxtamedullary
  zones.
• Renal Columns The portions of the renal cortex
  that extends between the renal pyramids.
• Renal Medulla The deep, reddish-brown inner
  region.
• Renal Pyramids 8-18 fan-shaped structures
  consisting of the straight segmented renal
  tubules the vasa recta.
• The base facing the renal cortex and the apex
  (aka renal palilla) pointing toward the renal
  hilus.
• Renal Lobe The renal pyramid, its overlaying
  cortex, and ½ of each adjacent renal column.

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Internal Kidney Anatomy

• Parenchyma Composed of the renal cortex the
  renal pyramids.
• Nephrons 1 million microscopic structures
  designed to filter the blood located within the
  parenchyma.
• Papillary Ducts Ducts that drain the urine
  formed in the nephrons into the
• Minor Calyces 8-18 in each kidney, which receive
  urine from the papillary ducts delivering it to
  the major calyces.
• Major Calyces 2-3 in each kidney, receive urine
  from the minor calyces drain it into the large
  cavity of the renal pelvis.
• Renal Pelvis Drains the urine into the ureter to
  be taken to the urinary bladder.

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Blood Supply to the Kidneys

• Renal Arteries The main blood vessel bringing
  blood into the renal area.
• Segmental Arteries The subdivisions of the renal
  arteries that branch into the parenchyma.
• Interlobar Arteries Pass through the renal
  columns between the renal pyramids.
• Arcuate Arteries The branches that arch between
  the renal medulla renal cortex.
• Interlobular Arteries The divisions of the
  arcuate arteries.

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Blood Supply to the Kidneys

• Golmerulus The ball-shaped capillary network
  serving the nephrons these are part of both the
  cardiovascular urinary systems.
• This is a unique capillary bed since it is
  located between two arterioles instead of an
  arteriole an a venule!
• Afferent Arterioles The divisions of the
  interlobular arteries that enter the renal cortex
  supply the glomerulus with blood.
• Efferent Arterioles Carry blood back out of the
  glomerulus.
• Peritubular Capillaries Further divisions of the
  efferent arterioles that surround the tubular
  portions of the nephron reclaim most of the
  filtrate the glomerulus produces.
• Vasa Recta The long loop-shaped capillaries that
  extend from some efferent arterioles that supply
  the tubular portions of the nephron in the renal
  medulla.

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Blood Supply to the Kidneys

• Peritubular Venules The first veins that the
  peritubular capillaries reunite into.
• Interlobular Veins The merged peritubular
  venules, also receiving blood from the vasa
  recta.
• Arcuate Veins The next largest set of veins the
  interlobular veins drain into.
• Interlobar Veins Drain the blood from between
  the renal pyramids.
• Renal Vein The large, single vein that all blood
  exits the kidneys through.
• Exits from the renal hilus varies venous blood
  back to the inferior vena cava.

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Blood Flow to the Kidneys

• Control of blood flow to the kidneys occurs via
  the renal nerves, formed in the celiac ganglion
  pass through the renal plexus along with the
  renal arteries.
• The sympathetic division of the Autonomic Nervous
  System regulates the flow of blood through the
  kidneys via vasodilation or vasoconstriction.

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Blood Flow to the Kidneys

• Path of Blood Flow through the kidneys
• Renal Arteries
• Segmental Arteries
• Arcuate Arteries
• Interlobular Arteries
• Afferent Arterioles
• Glomerular Capillaries
• Efferent Arterioles
• Peritubular Capillaries
• Interlobular Veins
• Arcuate Veins
• Interlobar Veins
• Renal Vein

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The Nephron

• Nephron The functional unit of the kidney
  consisting of a microscopic tube open at one end
  and closed at the other.
• Over 1 million nephrons in each kidney.
• Nephrons are the unit that form the urine.
• Two Parts to a Nephron
• Renal Corpuscle The portion where the blood
  plasma is filtered.
• Glomerulus The capillary network where blood
  enters to be filtered.
• Glomerular (Bowmans) Capsule The double-walled
  epithelial cup that surrounds the glomerular
  capillaries.
• Renal Tubule The tube into which the filtered
  fluid is passed.

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The Nephron

• Glomerular (Bowmans) Capsule The double-walled
  epithelial cup that surrounds the glomerular
  capillaries.
• This is where blood plasma is actually filtered
  before moving into the renal tubule.
• Capsular Space aka Lumen of the Bowmans Capsule
  The place where plasma leaves the glomerular
  capillaries plasma is now known as filtrate.
• Filtrate Similar to blood, but lacking blood
  cells large proteins.
• Two layers of the Bowmans Capsule
• External Parietal Layer The simple squamous
  epithelium layer not involved in filtrate
  formation.
• Visceral Layer Made up of podocytes (highly
  branching epithelial cells) and is involve in
  filtrate formation.

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The Nephron

• Renal Tubule The tube into which the filtered
  fluid is passed. 3 sections
• Proximal Convoluted Tubule (PCT) The part of the
  tubule that is attached to the flomerulus. Fluid
  flows from the PCT into the
• Loop of Henle aka the Nephron Loop The portion
  of the loop that connects the proximal distal
  convoluted tubules.
• Descending Limb of the Loop of Henle The portion
  that dips into the renal medulla.
• Ascending Limb of the Loop of Henle The portion
  that makes a U-turn returns to the renal
  cortex.
• Distal Convoluted Tubule (DCT) The part of the
  tubule that is farthest away from the glomerulus.
  Two cell types exit here
• Principal Cells Have receptors for antidiuretic
  hormone aldosterone to regulate fluid
  electrolyte balance.
• Intercalated Cells Help in the homeostasis
  regulation of blood pH.
• Collecting Duct The vessel that collects the
  filtrate from the distal convoluted tubule.
• Papillary Ducts The convergence of the
  collecting ducts (several hundred in the body).
  They drain into the minor calyces.

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The Nephron

• Glomerular Tubule The tube formed by the wall of
  the nephron pushing into the glomerolar capsule
  at the closed end of the nephron.
• Renal Tubule The final part of the ascending
  limb of each nephron, which makes contact with
  the afferent arteriole.
• Juxtaglomerular Apparatus (JGA) Helps regulate
  the blood pressure in the kidneys. Made up of..
• Macula Densa The crowded area of columnar
  tubules found in the renal tubule.
• Juxtaglomerular (JG) Cells The afferent
  arteriole containing modified, smooth muscle
  fibers that runs along side the macula densa.

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Types of Nephrons

• Cortical Nephrons Nephrons whose renal
  corpuscles are located in the outer portion of
  the renal cortex.
• Have short Loops of Henle (not entering too
  deeply into the renal medulla) with blood
  supplied by peritubular capillaries.
• Vital in assuring blood has the correct chemical
  ionic makeup.
• The most common type - 85 of nephrons.
• Juxtamedullary Nephrons Nephrons whose renal
  corpuscles located deep in the cortex, close to
  the medulla.
• Have long Loops of Henle extending deep into the
  medulla with blood supplied by the peritubular
  capillaries the vasa recta.
• Ascending limbs divide into two portions.. The
  thin ascending limb thick ascending limb.
• Allow the kidneys to produce very dilute or very
  concentrated urine.
• Make up the remaining 15-20 of nephrons.

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Urine Formation

• Blood flows into the kidneys and into the
  glomerular capillaries.
• Some of the blood in the glomerular capillaries
  is forced into the renal tubules, which flow
  alongside of the peritubular capillaries.
• 99 of water forced into the renal tubules gets
  reabsorbed into these vessels.
• Fluid is filtered from the blood into the renal
  tubules any particle small enough to pass
  through the membranes will be filtered out.
• This includes glucose, amino acids, vitamins,
  minerals.
• Any needed items are reabsorbed back into the
  blood stream while still in the renal tubules.
• Waste products, including creatinine, toxins,
  drugs are not reabsorbed are excreted via
  urine.
• Kidneys can regulate how much sodium, potassium,
  hydrogen, bicarbonate remain in the plasma.
• Urine formed through 3 basic processes
• Glomelular filtration
• Tubular secretion
• Tubular reabsorpton

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Glomerular Filtration

• Glomerular Filtration The first step of urine
  formation!
• Water most dissolved solutes in the blood
  plasma cross the capillary walls in the
  glomerulus to move into the glomerular capsule
  then the renal tubule.
• Glomerular Filtrate The fluid that enters the
  capsular space.
• Filtration Fraction The fraction of blood plasma
  in the afferent arterioles of the kidneys that
  becomes glomerular filtrate typically 16-20
• Men produce 180 liters in filtrate daily while
  women produce 150 liters of filtrate daily.
• 99 of filtrate returns to the blood via
  reabsorption.
• 1-2 liters are excreted as urine.

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Glomerular Filtration

• Filtration Membrane A layer of 3 barriers that
  fluid must pass through to move from the
  bloodstream to the capsular space.
• Fenestrated Epithelium Found in the glomerular
  capillaries large pores permit entry of blood
  plasma into the capillaries, but prevent blood
  platelets from passing.
• Mesangial Cells Cells specifically in charge of
  regulating glomerular filtration.
• Basal Lamina Layer of acellular material located
  between the endothelium podocytes, consisting
  of collagen fibers proteoglycans prevets the
  filtration of larger plasma proteins.
• Slit Membrane Extends across each filtration
  slit to permit the passage of small diameter
  (less than 6-7nm) molecule
• E.g., water, glucose, vitamins, amino acids,
  small proteins, ammonia, urea, ions.
• Pedicels Footlike processes located on the
  podocytes (thousands on each) that wrap around
  glomerular cavities.
• Filtration Slits Spaces between the pedicles.

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Glomerular Filtration

• In order for filtration to occur, pressure is
  needed to force fluids solutes through the
  membranes.
• Renal corpuscles filter the largest volume of
  fluid of all capillaries due to.
• Large surface areas of the glomerular capillaries
  mesangial cells can relax to maximize surface
  area increase filtration or contract to
  decrease surface area and filtration.
• Filtration membrane is thin porous.
• Glomerular capillary blood pressure is high due
  to afferent arteriole diameter exceeding efferent
  arteriole diameter.

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Glomerular Filtration

• Glomerular Pressure dependent on 3 processes
• Glomerular Blood Hydrostatic Pressure (GBHP) The
  blood pressure in the glomerular capillaries
  promotes filtration by forcing water solutes
  from the blood plasma through the filtration
  membrane. Normally 55 mm Hg.
• Capsular Hydrostatic Pressure (CHP) The measure
  of the hydrostatic pressure exerted against the
  filtration membrane by fluid already in the
  capsular space renal tubule, which opposes
  filtration creates a back pressure. Normally
  15 mm Hg.
• Blood Colloid Osmotic Pressure (BCOP) Opposes
  filtration also due to the presence of
  proteins. Normally 30 mm Hg.

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Glomerular Filtration

• Net Filtration Pressure (NFP) The total pressure
  that promotes filtration. Normally 10 mm Hg
• Determined as
• NFP GBHP CHP BCOP
• 10 mm Hg 55 15 30 mm Hg

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Glomerular Filtration

• Glomerular Filtration Rate (GFR) The amount of
  filtration formed in all the renal corpuscles of
  both kidneys each minute.
• Regulated via net filtration rate, adjustment of
  blood flow into out of the glomerulus, and
  altering of the glomerular capillary surface
  area.
• Efferent afferent arteriole diameters can
  coordinate control.
• Rate increases with capillary blood flow
  increase.
• If too high urine output increases dehydration
  electrolyte depletion may occur due to
  shortened tubular reabsorption.
• If too low Tubular reabsorption is increased and
  wastes may be reabsorbed that should be
  eliminated.

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Glomerular Filtration

• Glomerular Filtration Rate controlled by 3
  mechanisms
• Renal Auto Regulation The ability of the kidneys
  to maintain a relatively stable GFR despite blood
  pressure changes. Occurs via..
• Myogenic Mechanism Stretching triggers smooth
  muscle contractions afferent arterioles can
  constrict to reduce blood flow into the
  glomerulus, while efferent arterioles can be
  dilated to allow increased outflow of blood. Can
  be reversed to compensate for decreased blood
  pressure.
• Tubuloglomerular Feedback Sodium, chlorine,
  water build up in the loop of Henle due to
  increased blood pressure faster blood flow
  through the renal tubules Macula densa cells
  detect the imbalance inhibit nitric oxide (NO)
  production.
• Nitric Oxide (NO) Produced in the
  juxtaglomerular apparatus (JGA) causes
  vasodilation. Decrease leads to vasoconstriction
  in the afferent arterioles slows blood flow
  into the glomerular capillaries decrease in
  GRF. Increases occur if blood pressure GRF fall
  too low.
• Neural Regulation Sympathetic nervous system
  activation causes adrenal epinephrine to
  stimulate vasoconstriction in the afferent
  arterioles to reduce GRF urine production.
• Conserves blood volume redirects blood to the
  heart, brain, skeletal muscles.
• Hormonal Regulation Hormones are produced to
  change the GRF rate.
• Angiotensin II Reduces GRF through
  vasoconstriction of the afferent efferent
  arterioles reduces renal blood flow.
• Atrial Natriuretic Peptide (ANP) Hormone
  secreted by cells in the atria of the heart
  increases capillary surface area by relaxing the
  mesangial cells GRF increases due to faster
  filtration.

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Tubular Reabsorption

• Tubular Reabsorption The return of most of the
  filtered water solutes back into the
  bloodstream from the renal tubules 99 of the
  filtered water is reabsorbed.
• Any substances not reabsorbed is secreted via the
  urine.
• 3 Membranes substances must pass through to
  re-enter the blood stream
• Luminal Membrane of the Tubule Cell
• Basolateral membrane of the Tubule Cell
• Capillary Endothelium

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Tubular Reabsorption

• Two paths for fluid absorbed into the tubule
  lumen
• Moving between adjacent tubule cells
• Passing through an individual tubule cell.
• Tight junctions join neighboring cells to one
  another.
• Atypical Membrane Contacts the tubular fluid
  lacks a sodium-potassium pump to ensure the
  reabsorption of Na only goes one way.
• Most sodium ions crossing this membrane will be
  pumped into the interstitial fluid.
• Basolateral Membrane Contacts the interstitial
  fluid at the base sides of the cells.
• Cells lining the renal tubule have a low Na
  concentration in the cytosol due to
  sodium-potassium pumps.
• Sodium-Potasium Pumps eject Na from the renal
  tubule cells.

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Tubular Reabsorption

• Paracellular Reabsorption When fluid leaks
  between the cells.
• Accounts for up to 50 of the reabsorption of
  certain ions the water that follows via
  osmosis.
• Transcellular Reabsorption Where a substance
  passes from the fluid in the tubular lumen
  through the apical membrane of a tubule cell,
  across the cytosol, out into the interstitial
  fluid through the basolateral membrane.

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Tubular Reabsorption

• Primary Active Transport Occurs when energy is
  derived from hydrolysis of ATP is used to pump
  a substance across a membrane.
• Secondary Active Transport Occurs when the
  energy stored in an ions electrochemical
  gradient drives a substance across the membrane.
• Symporters Membrane proteins that perform
  secondary active transport.
• Antiporters Move two or more substances in
  opposite directions across a membrane.
• Transport Maximum (Tm) The upper limit on how
  fast each transporter can work measured in
  mg/min.

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Tubular Reabsorption

• Osmosis The method by which water is reabsorbed
  occurs when water moves from an area of high
  concentration to an area of low concentration.
• Obligatory Water Reabsorption Water that is
  reabsorbed along with solutes its obligated
  to follow solutes.
• 90 of water reabsorption.
• Occurs in the PCT descending loop of Henle.
• Facultative Water Reabsorption Water
  reabsorption that is not dependent on solutes.
• Remaining 10 of water reabsorption.
• Occurs in the collecting ducts.
• Regulated via antidiuretic hormone.

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Tubular Reabsorption

• PCT The site where most reabsorption of water
  solutes occurs.
• Loop of Henle Accounts for 20-35 of filtered
  solute reabsorption 85 of filtered water
  reabsorption.
• Creates the osmotic gradient between the renal
  cortex renal medulla.
• Aldosterone Stimulates active NaCl reabsorption
  and indirectly stimulates passive water
  reabsorption.
• Antidiuretic Hormone (ADH) Triggers water
  reabsorption to occur in the collecting duct
  produces more concentrated urine.
• If not present, more diluted urine is produced.

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Tubular Secretion

• Tubular Secretion The transfer of materials from
  the blood and tubule cells into the tubular fluid
  materials are transported from the peritubular
  capillaries into the renal tubule lumen via
  active transport.
• Secretes hydrogen, creatine, potassium, etc. from
  the peritubular capillaries into the renal
  tubules if not filtered at the glomerulus.
• Hydrogen secretion is increased to raise blood pH
  decreased to lower pH maintains homeostasis.
• Eliminates other substances from the body to
  remove wastes and regulate blood levels of
  certain ions includes substances in excessive
  levels natural poisons.
• Ions removed from the blood stream are deposited
  into the fluid within the tubules.

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The Countercurrent Multiplier

• Countercurrent Mechanism Creates an osmotic
  gradient in the interstitial fluid of the renal
  medulla.
• Enables formation of concentrated urine when ADH
  is preset.
• Countercurrent Flow Where the descending limb of
  the loop of Henle transports tubular fluid from
  the renal cortex to the medulla the ascending
  limb carries it in the reverse direction.

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The Countercurrent Multiplier

• Descending Limb of the Loop of Henle Permeable
  to water, but impermeable to most solutes.
• Water leaves this limb via osmosis, causing the
  osmolarity (concentration) of the tubular fluid
  to increase.
• Ascending Limb of the Loop of Henle Not
  permeable to water, but permeable to salt
  (NaCl-) salt is secreted into the surrounding
  interstitial fluid.
• The osmolarity (concentration) of tubular fluid
  decreases as it flows through the ascending limb.

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Osmolarity

• Osmolarity The measure of the total number of
  dissolved particles (solutes) per liter of
  soution.
• Kidneys maintain a constant osmolarity of 300
  milliosmoles per liter via regulation of the
  concentration volume of urine.
• Osmotic Gradient The difference in osmolarity of
  two solutions on opposite sides of a
  semi-permeable membrane. Maintained via..
• Differences in permeability in the ascending
  descending limbs of the loops of Henle the
  collecting ducts.
• Countercurrent flow in the two limbs of the loops
  of Henle.

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Osmotic Gradient
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Hormones that Regulate Reabsorption Secretion

• Renin-Angiotensin-Aldosterone System System that
  activates when blood pressure blood volume
  decrease
• Afferent arterioles are less stretched,
  triggering juxtaglomerular cells to secrete renin
  enzymes into the blood.
• Renin causes angio tensinogen to convert to
  angiotensin IO.
• Angiotensin I changes to the active hormone
  Angiotensin II.

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Hormones that Regulate Reabsorption Secretion

• Angiotensin II A hormone converted from
  Angiotensin I that serves 3 main roles
• Decrease glomerular filtration rate via
  casoconstriction of the afferent arterioles.
• Enhance reabsorption of Na, Cl-, water in the
  proximal convoluted tubules via stimulation of
  the sodium-hydrogen antiporters.
• Stimulates the release of aldosterone to
  stimulate the principal cells in the collecting
  ducts to reabsorb more Na and Cl- secrete more
  potassium also increases water reabsorption to
  increase blood volume.

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Hormones that Regulate Reabsorption Secretion

• Antidiuretic Hormone (ADH) aka Vasopressin
  Causes increased water reabsorption in the distal
  convoluted tubules collecting ducts, producing
  less urine volume but higher urine concentration.
  
• Osmotic pressure of bodily fluids increase as the
  concentration of water in the blood decreases.
• This stimulates osmoreceptors in the hypothalamus
  that then trigger the posterior pituitary gland
  to release ADH.
• ADH controls whether concentrated or diluted
  urine is formed, depending on the fluid intake
  and kidney functioning of the individual.

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Hormones that Regulate Reabsorption Secretion

• Atrial Natriuretic Factor (ANF) aka Atrial
  Natriuretic Peptide (AND) Secreted by the heart
  in response to high blood pressure stretching
  of the atria - inhibits sodium water
  reabsorption inhibits aldosterone and ADH
  secretion.
• Increases the excretion of sodium water in
  urine, which reduces blood volume blood
  pressure.

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Urine Composition

• Urine A combination of metabolic wastes
  (including urea), dissolved salts, and organic
  material.
• Color Ranges from pale or colorless (dilute) to
  deep yellow (concentrated).
• Urochrome The pigment caused by the breakdown of
  bib, contributing to the yellow color of urine.
• Degredation of bilirubin urobilin affect yellow
  color.
• Medications can cause a reddish-brown color.
• Can also be affected by bacteria, blood, sperm,
  mucous, and some dietary components.

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Urine Composition

• Chemical Composition Composed of 95 water 5
  electrolytes can be changed by certain
  diseases.
• Urea The main waste product of nitrogen
  detoxification the breakdown of protein
  composes 2.
• Creatine A product of creatine phosphate
  breakdown in muscle tissue.
• Uric Acid The final oxidation product of purine
  metabolism in the body.

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Urine Composition

• Specific Gravity The measure of the kidneys
  ability to form concentrated or dilute urine in
  relation to plasma - measures to amount of
  substances dissolved in urine.
• Urines Specific Gravity Typically is 1 the
  higher the concentration of solutes, the higher
  the specific gravity.
• Dehydration or low fluid intake causes an
  increase in concentration therefore a higher
  specific gravity.
• Low specific gravity can be caused by diabetes
  insipidus, glomerulonephritis, renal failure.

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Urine Composition

• pH The measure of the acidity or alkalinity of
  the urine.
• Glomerular filtrate of blood plasma goes through
  acidification by the renal tubules collecting
  ducts moves from a pH of 7.4 to 6.
• pH range is 4.6 to 8 can vary with diet.

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Urine Composition

• Quantity The overall amount of urine produced
  typically 1-2 liters per day for a healthy adult.
  
• Hydration, activity level, environmental factors,
  body size, health affect the volume produced.
• Polyuria The excessive output of urine,
  typically due to a high concentration of glucose
  in the renal tubules.
• Oliguria The scanty output of urine, typically
  due to fluid retention.
• Diuretics Chemicals that increase the volume of
  urine produced decrease the fluid volume in the
  body via increasing glomerular filtration or
  decreasing tubular reabsorption.
• Used to treat hypertension, congestive heart
  failure, and some lung disorders.

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Urine Composition

• Things that Shouldnt Be In Urine
• Proteins Due to hypertension or
  glomerulonephritis.
• Ketone Bodies Due to starvation or diabetes
  mellitus.
• Leukocytes Due to urinary tract infection.
• Erythrocytes Due to bleeding in the urinary
  tract.
• Glucose Due to diabetes mellitus.

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What if the Kidneys Shut Down?

• Dialysis The artificial filtering of the blood.
• Hemodialysis The use of an artificial kidney
  machine that takes blood in through dialysis
  tubing, filters the blood, returns it to the
  patient once cleansed.
• Continuous Ambulatory Peritoneal Dialysis (CAPD)
  The use of the periotoneal lining of the
  abdominal cavity as a dialysis membrane, allowing
  waste products to be drained out of the cavity
  into a sterile bag via gravity.

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Ureters

• Ureters Two muscular tubes leading from the
  renal pelvis of each kidney to the urinary
  bladder.
• Peristaltic Contractions Muscle contractions in
  the walls of the ureters that pushes urine down
  toward the bladder.
• Urethral Valves Valves located at the oblique
  openings of the ureters to prevent backflow of
  urine into the kidneys triggered to close by
  increased pressure from the bladder when full.
• Ureter Walls 3 layers!
• Adventitia Outermost later that helps anchor the
  ureters.
• Muscularis The middle muscular layer.
• Mucosa The innermost mucosal layer.

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Urinary Bladder

• Urinary Bladder A hallow muscular sac located on
  the floor of the pelvic cavity.
• Highly distensible expands superiorly
  700-800mL capacity.
• Located directly anterior to the rectum in males.
  
• Located anterior to the vagina inferior to the
  uterus in females.
• Serosa The layer of visceral peritoneum covering
  the superior surface.

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Urinary Bladder

• Trigone The small triangular area on the floor
  of the urinary bladder containing the openings
  for the ureters the urethra.
• Internal Urethral Orifice The opening into the
  urethra, lying in the anterior corner.

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Urinary Bladder

• Urinary Bladder Wall 3 layers total.
• Adventitia The superficial coat consisting of
  areolar connective tissue anchoring the urethra
  in place contains the blood vessels, lymphatic
  vessels, nerves that serve the muscularis and
  mucosa layers.
• Muscularis Two layers of smooth muscle (outer
  circular inner longitudinal) contract via
  peristaltic contraction to move urine.
• Mucosa The deepest coat made of transitional
  epithelium (that can change shape to expand!) and
  lamina propria (full of collagen elastic fibers
  lymphatic tissue).
• Goblet Cells Secrete mucous to prevent the
  bladder walls tissue from coming in contact with
  the acidic urine.

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Urethra

• Urethra The small tube that leads from the
  internal urethral orifice in the floor of the
  bladder to the exterior of the body.
• In Females 3-4 centimeters long, with the
  external urethral orifice (opening) lying between
  the opening of the vagina the clitoris.
• In Males 15-20 centimeters long 3 regions
• Prostatic Urethra Passes through the prostate.
• Membranous Urethra Passes through the urogenital
  diaphragm.
• Penile Urethra aka Spongy Urethra Passes through
  the penis.

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Urethra

• Mucosal Wall Consists of a deep mucosa layer a
  superficial muscularis layer.
• Internal Urethral Sphincter The circular muscle
  fibers around the opening from the bladder to the
  urethra provides involuntary control of
  urination.
• External Urethral Sphincter Inferior to the
  internal urethral sphincter circular muscle
  fibers close to the opening from the urethra to
  the outside provides voluntary control of
  urination.

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Micturition

• Micturition The discharge of urine from the
  urinary bladder.
• AKA urination or voiding.
• Micturition Reflex The reflexive muscular
  reactions that trigger micturition.
• Once the bladder exceeds 300-400mL, the pressure
  increases stretch receptors within the bladder
  walls transmit nerve impulses to the spinal cord.
  
• Micturition Center The section of the spinal
  cord between S2 S3 where stretch impulses are
  propagated trigger the micturition reflex.
• The micturition reflex sends parasympathetic
  impulses to the bladder wall the internal
  urethral sphincter.
• The sphincters open, the bladder wall detrusor
  muscles contract, micturition occurs.

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Micturition

• Potty Training The process of learning to
  control the micturition reflex!
• Fortunately for us, we learn this fairly easily
  during very early childhood.