Functions of Urinary System The urinary system produces urine The production of urine has three main functions Excretion of waste products of metabolism especially urea Osmoregulation control of the water salt and acidbase balance of the body ID: 775366
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Slide1
Urinary
System
28 April 2014
Slide2Functions of Urinary System
The urinary system produces urine. The production of urine has three main functions:Excretion of waste products of metabolism, especially ureaOsmoregulation – control of the water, salt, and acid-base balance of the bodyRemoval of drugs and toxinsOther functionsRegulation of blood pressure through production of enzyme reninStimulation of red blood cell production of hormone erythropoeitinConversion of vitamin D to active form
Fun fact: Urea is a nitrogenous compound produced by the liver when we digest proteins
Fun fact
: The two major places that remove or break down drugs and toxins are the liver and the kidney
Slide3Organs of the Urinary System
Slide4Kidney Structure
Urine is produced in the cortex by the nephrons. The nephrons are the functional unit of the kidney.Urine is concentrated in the medullaUrine collects in the calices, then flows into the renal pelvis then to the ureters
There are ~ 1 million nephrons in each kidney
Slide5Nephron Structure
A nephron consists of 4 main parts: Bowman’s capsuleProximal convoluted tubuleLoop of HenleDistal convoluted tubuleEach nephron empties into a collecting duct
Capillaries twine all around the nephron … why?
Most nephrons are entirely within the cortex; some have loops of Henle that extend into the medulla
The tubules of the nephron contain filtrate – the urine that is in process of being formed.
Slide6Nephrons & Urine Formation
There are three steps to urine formationFiltrationReabsorptionSecretion
Slide7Nephrons & Urine Formation
FiltrationBlood from the glomerular capillaries filters into the Bowman’s capsule due to extremely high pressure in capillariesFiltration is based on size only. Small items (everything in blood except the cells and most proteins) enter the Bowman’s capsule.Passive process
Fun Fact:
We produce ~180 L of filtrate a day … despite the fact that we have only about 5 L of blood. Nearly 99% of the water that is filtered out of the blood is reabsorbed the capillaries
.
Slide8Nephrons & Urine Formation
ReabsorptionReabsorption of important molecules (water, salts, amino acids, sugar, minerals) from tubules to capillariesSome reabsorption is passive, but most relies on active transportDifferent materials are reabsorbed in different sections (see diagram)
More on Loop of Henle!
Slide9Nephrons & Urine Formation
SecretionActive transport of unwanted materials from capillaries to filtrateUseful for larger molecules (some drugs and toxins) and for regulation of blood pHOccurs in convoluted tubules (esp. distal)
Slide10Loop of Henle
Responsible for most of the water and some salt reabsorptionUses a countercurrent multiplier mechanism by having the fluid flow in opposite direction, the exchange of materials can be maximized or minimizedThe loop dips into increasingly salty medulla to extract as much water as possible from the filtrate
passive
active
Slide11Loop of Henle
Descending loop of HenleDescending loop is permeable to water, but impermeable to saltSo, water passively diffuses from the loop of Henle into the interstitial fluid (and then into the peritubular capillaries)
passive
active
Slide12Loop of Henle
Ascending loop of HenleAscending loop is impermeable to water, but permeable to saltSo, water CANNOT re-enter the tubules, despite the fact that the filtrate is now more concentrated then the interstitial fluidNaCl first moves passively out of the loop, then is actively transported out. This both retains our salts and creates the salty medulla environment
passive
active
Slide13Collecting Duct Osmoregulation
The reabsorption of water in the collecting duct is controlled by hormones.If blood solute concentration is high, the pituitary releases antidiuretic hormone (ADH) which opens aquaporins in the collecting duct, making it permeable to water.If blood solute concentration is low, aquaporins are closed, making the duct impermeable to water
passive
active
Slide14Collecting Duct Osmoregulation
If you are dehydrated, will you produce ADH?Yes!If you produce ADH, will you produce a lot of urine, or a little urine?Little! Your body will produce a small amount of concentrated urine, retaining precious water in your blood.
passive
active
Slide15Collecting Duct Osmoregulation
With ADH
Without ADH
Slide16Comparison of Fluid Composition
Think, Pair, Share: Explain these values
SolutePlasma (mg/100 mL)Filtrate (mg/100 mL)Urine(mg/100 mL)Glucose9009000Urea30301200proteins74000
Review:
watch me!
Slide17You Do
Draw a nephron, labeling the parts and the major functions.
Draw a nephron, use different colored markers to show both the relative concentration (use dots!) of the each of the following chemicals within each region of the nephron and use arrows to show the flow of the substances in or out of the nephron.
water
salt
Sugar
Urea
Slide18Closure
What were our objectives, and what did you learn?
What was our learner profile, and how did we demonstrate it?
How does what we did today relate to our unit question?