The urinary system

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The urinary system

• Functions
• Forms urine to excrete waste
• Regulates blood volume
• Regulates electrolytes
• Regulates acid-base balance

Structure 2 kidneys 2 ureters 1 bladder 1
urethra
In other words, the process of urine formation
helps maintain the normal composition, volume,
and pH of both blood and body fluids by removing
wastes and excess substances
http//www.healthtoolsonline.com/flash-img/urology
.swf
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Three Processes Occur

• Filtration Reabsorption Secretion

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Functionally, cortical and juxtamedullary
nephrons have distinct roles. Cortical nephrons
(85 of all nephrons in humans) mainly perform
excretory and regulatory functions, while
juxtamedullary nephrons (15 of nephrons in
humans) concentrate and dilute urine
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• Why the difference in cortical and juxtamedullary
  nephrons?
• In the descending limb (of the loop), water moves
  freely but salt cannot. Longer descending limbs
  make the filtrate more hypertonic than shorter
  limbs
• In the ascending loop, salt is actively pumped
  out (no water exchanges) which makes the filtrate
  hypotonic

http//www.youtube.com/watch?vSoilI_J0Vq0feature
related shows the medulla and cortex and
explains pyramids, calyces. 1.4 min
http//www.youtube.com/watch?v8TXXIJGz4F4feature
related diagram and explanation of nephron, show
cortex, medulla, and the two types of nephrons,
collecting ducts 1.35 min
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http//www.youtube.com/watch?v6Wc4f2KnbYofeature
related shows kidney cortex, medulla, nephron
function, chemistry, urine formation 8.5 min
http//faculty.southwest.tn.edu/rburkett/AP220ur
inary_system.htm nice site with lots of pictures
including scanning electron micrographs
http//video.google.com/videosearch?qcystoscopys
itesearch shows cystoscopy and biopsies. 4 min
- watch 1 min then go to about 3.5 for bx
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150-180 liters filtered
99 reabsorped
1 becomes urine
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Oh No! Not Hormones Again!!!

• ADH - Antidiuretic Hormone increases
  reabsorption of water from filtrate back to blood
  
• PTH - Parathyroid Hormone increases reabsorption
  of calcium from filtrate back to blood and
  excretes phosphate into filtrate
• Aldosterone increases reabsorption of sodium from
  filtrate back to blood and excretion of patassium
  into filtrate. Water follows sodium.
• ANP - Atrial Natriuretic Peptide decreases
  reabsorption of sodium, which remains in the
  filtrate. More sodium water are eliminated in
  urine

(Table 18-1, page 428 and Fig 18-5, page 429,
Scanlon text)
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Other Kidney FunctionsSecretion of
reninProduction of erythropoietinActivation of
vitamin D

When BP goes down, kidneys secrete renin and BP
goes up
The small print Renin converts angiotensin
(from lungs and blood vessels) to angiotensin II.
Angiotensin II causes blood vessels to constrict
and stimulates aldosterone (from adrenal glands)
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Other Kidney FunctionsSecretion of
reninProduction of erythropoietinActivation of
vitamin D

When blood oxygen goes down, kidneys produce
erythropoietin and RBC production goes up
The small print Erythropoietin causes bone
marrow to produce more red blood cells which can
carry more oxygen
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Other Kidney FunctionsSecretion of
reninProduction of erythropoietinActivation of
vitamin D

The kidneys activate vitamin D which increases
absorption of calcium and phosphate
The small print Vitamin D is converted to an
active form called calcitriol (D2) which causes
the small intestines to take up more calcium from
our food
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Finally, elimination! (sometimes called the home
stretch)
Rugae Detrusor muscles Internal and external
sphincters
Page 432 of Scanlon text
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urination
Urination is a spinal cord reflex over which
voluntary control may be exerted The bladder
stretches as it fills. The detrusor muscles are
sensitive to the stretching At about 300 ml, a
message is sent to the spinal cord A
parasympathetic nerve impulse is sent back to the
detrusor muscles to contract The internal
urethral sphincter relaxes If urination is
desired or required, the external urethral
sphincter is voluntarily relaxed and the bladder
empties
remember parasympathetic nerve pathways?
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So what is this stuff called urine?
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Review and Study Guide

• Be able to spell and define terms related to the
  urinary system
• Be able to label a diagram/picture of the kidney,
  the nephron, the urinary system, and the bladder
  as shown on these PPT slides
• Be able to clearly answer review questions on
  page 437 of your Scanlon text, specifically
  numbers 1, 3, 4, 7, 11, 12, 13, 14, 15
• Be able to fully explain filtration, reabsorption
  and secretion
• Be able to discuss 4 mechanisms of tubular
  reabsorption (425 427)

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Lets Review

1. name the three tubes that make up the urinary
   system
2. where are the kidneys located?
3. what is the functioning unit of the kidney
4. what is the name of the blood vessel the bring
   blood into the kidney?
5. what is the name of the cluster of blood vessels
   going into Bowmans capsule?
6. which arteriole enters Bowmans capsule?
7. Which exits?
8. what is the name of the convoluted tubule between
   Bowmans capsule and the loop?
9. What is the name of the loop?
10. what is the name of the twisted tubule after the
    loop?
11. what is the name of the structure that all the
    nephrons drain into?

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1. can you name the blood vessels from the abdominal
   aorta to the vena cava?
2. must be present for filtration to take place?
3. what happens in the loop of the cortical nephron?
4. what happens in the loop of the juxtamedullary
   nephron?
5. how much filtrate do we process each day?
6. how much urine do we secrete each day?
7. what is the first stimulus for urination?
8. list the structures from the glomerulus to the
   collecting duct
9. list the structures from the collecting duct to
   the urethra
10. what is meant by tubular threshold?
11. can you give an example of threshold?
12. what substances are secreted from the tubules?
13. name one hormone that influences reabsorption of
    water

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1. Name another hormone that influences the
   reabsorption of water
2. summarize the process of urine formation
3. what does renin do?
4. does the kidney have to do with vitamin D?
5. what is erythropoietin and what does it cause?
6. What is urine made of mostly?