Urinary%20System%20Lecture%202,%20Q3%202011

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Urinary SystemLecture 2, Q3 2011
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Nephronfunctional unit of the kidney
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Parts of the nephron A normal kidney contains
800,000 to one million nephrons

• Renal corpuscle consists of
• Glomerulus a tuft of capillaries associated
  with a renal tubule
• Bowmans capsule a cup-like sac that houses the
  glomerulus

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Glomerulus inside Bowmans capsule together
called Renal Corpuscle
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Renal Tubule

• PCT - Proximal convoluted tubule reabsorbs
  water and solutes from filtrate secretes
  substances into it
• Loop of Henle part of the PCT that is hairpin
  shaped
• DCT - Distal convoluted tubule functions more
  for secretion than reabsorption

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Nephron types

• Cortical nephrons 85 of nephrons located in
  the renal cortex
• Juxtamedullary nephrons located at the
  cortex-medulla junction
• Loops of Henle deeply invade the medulla
• Extensive thin segments produce highly
  concentrated urine

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Vasa recta

• After the efferent arterioles descend into the
  medulla they divide into long thin STRAIGHT
  capillaries called the vasa recta (Latin for
  straight vessels)

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Urine formationThe 3 big-picture processes

• Glomerular filtration Tubular absorption
  Tubular secretion Excretion

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Glomerular filtration

• Separates plasma fluid and small solutes from
  larger proteins and blood cells
• High blood pressure in glomerular capillaries
  forces fluid through capillary walls into
  Bowmans capsule

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Tubular reabsorption

• Returns filtered water and nearly all major
  nutrients to the blood
• Primary active transport of Na across cell
  membrane drives diffusion of Cl- and water
  provides energy for reabsorption by secondary
  active transport or passive diffusion of other
  substances

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Tubular secretion

• Removes harmful or excess substances from blood
• Substances move by active transport or passive
  diffusion from capillaries into the tubule

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Filtrate contents glomerular filtrate

• Contains all plasma components except protein
• Loses water, nutrients, and essential ions to
  become urine
• The urine contains metabolic wastes and unneeded
  substances

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Countercurrent mechanism Tubes that interact to
make the excretory process work.

• Involves sodium pumps that create an area of high
  sodium concentration deep in the medulla, near
  the collecting duct
• This allows the kidneys to produce dilute or
  concentrated urine depending on your bodys needs
• Interaction between the flow of filtrate through
  the loop of Henle (countercurrent multiplier) and
  the flow of blood through the vasa recta blood
  vessels (countercurrent exchanger) allow this
  process to work

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Urinary infections UTIs

• Pyelitis - Acute inflammation of the pelvis of
  the kidney, caused by bacterial infection.
• the renal pelvis, the central part of the kidney
  is where urine accumulates before discharge.
• It is more common in women than in men.

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Pyelonephritis

• pyelonephritis is when a urinary tract infection
  has reached the pyelum (pelvis) of the kidney
• Symptoms include
• Loin pain, often severe
• Fever and shivers
• Blood-stained urine
• Foul-smelling and cloudy urine
• Painful and frequent urination
• Nausea and vomiting

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Volume of blood filtered daily

• 200 liters!
• The kidneys filter the bodys entire plasma
  volume 60 times each day