L14- Urinary Flashcards
Function of the urinary system
Regulates extracellular fluid (plasma +ISF)
By filtering blood of wastes ➡️ urine
Result(s) of kidneys regulating extracellular fluid
- waste concentration
- pH (H+ & Hco3)
- water
Electrolyte concentration
What are the organs found in the urinary system
Kidneys, ureters, bladder, urethra
Kidneys
Filters blood of wastes to produce urine
Ureter
Transports urine to urinary bladder
Urinary bladder
Stores urine
Urethra
Excretes urine
Renal pelvis of kidneys
Collects urine before it leaves ureter
Nephron (of kidneys)
Functional unit
- forms filtrate and dumps into collecting duct
What are the 4 parts of a Nephron
Glomerular capsule, proximal convoluted tubule, distal convoluted tubule, the loop of Henle (ascending & descending)
Vascular supply of nephron includes
Glomerulus, efferent arteriole , afferent arteriole, peritubular capillaries & vasa recta
What structures make up a renal corpuscle
Glomerular capsule, glomerulus
Fluid flow in kidneys
Plasma ➡️ pre-urine filtrate ➡️ urine
(Glomerous). (Nephron). (Leaves collecting duct)
Filtration membrane includes
- Capillary fenestrations
- Basement membrane
- filtration slits
Filtration membrane is
Filtration of blood that produces pre-urine filtrate in glomerular capsule
Juxtaglomerular apparatus (JGA) includes
Juxtaglomerular cells & macula dense cells
- is the triangle area b/w afferent and efferent arterioles
What are the 2 types of nephrons
Cortical nephron & juxtamedullary nephron
Juxtamedullary nephron
- less numerous (20%)
- long loop of henle = goes into medulla & cortex
2nd capillary bed= peritubular capillaries & vasa recta
Cortical nephron
- more numerous (80%)
- short loop of henle ( mostly in cortex of kidney)
2nd capillary bed = peritubular capillaries
What are the steps of urine formation
- Filtration
- Reabsorption
- Secretion
- Concentration
- Excretion
Filtration
Blood ➡️ tubule
- filtrates everything in the blood but cells & proteins ( too big)
- occurs at renal corpuscle= glomerular corpuscle
Filtrate =
Plasma - cells & proteins
What percent of filtrate is reabsorbed regardless of a persons state of hydration
99% of filtrate reabsorbed & 1% excreted as urine
What is the total blood volume of an average adult?
5.5 liters of blood
How much blood is filtered a day?
180L of filtrate / day
Reabsorption
Tubule ➡️ blood
- reabsorbed what we want to keep
Where does reabsorption occur and what is absorbed?
65% at proximal convoluted tubule
20% at descending loop of henle
- na+, cl, h2o
What percentage of glucose and amino acids is reabsorbed and where are they reabsorbed at?
100% reabsorbed at proximal convoluted tubule
- Cotransport w/ Na+
Why is glucose found in urine for individuals with diabetes?
They reach the glucose transport maximum, meaning they have too much glucose in the blood therefore some needs to be excreted out through urine
Secretion ( active process)
Blood ➡️ tubule
@ distal convoluted tubule
- fine tunes blood removing excess H+ , K+ & xenobiotics, metabolites
Removal of excess h+ maintains ______
Ph
Removal of excess k+ maintains _________________
Electrophysiology
How does our body remove chemicals that it’s never seen before?
Go to liver ➡️ converting it to soluble form then removed by “multi-specific” transporters in kidneys
Concentrating urine is important
To maintain blood osmolarity
How do we concentrate urine
Pulling water out of collecting duct by osmosis ( na+ goes h2o follows)
Driving force for osmosis is
Salt gradient in the renal medulla interstitial fluid
What is the osmolarity of the renal cortex? What is the osmolarity of the renal medulla?
Cortex = 300
Medulla = 600-1200
Loop of Henle _______ salt gradient
Creates
Vasa recta ___________ salt gradient by taking in h2o
Maintains
Collecting duct _________ salt gradient to concentrate urine
Uses
How does ADH Concentrate urine
Antidiuretic hormone (ADH) inserts aquaporins into collecting duct
+ ADH = concentrated urine up to 1200mOm
- ADH = dilate urine @ 100mOsm
Counter current multiplier
Mechanism used to create salt gradient - loop of henle
Counter current exchanger
Mechanism that maintains salt gradient - Vasa recta
Why must we concentration urine?
Prevent dehydration
Counter current means
Ascending and descending limb moves in opposite directions
The descending limb of Henle
- is passive
- it must lose water to assist in formation of salt gradient in Medulla
Ascending loop of Henle
Is active
- forms salt gradient in renal medulla
What is the problem of water leaving desending loop of
Henle? How is this solved?
Water dilutes gradient in renal Medulla
Solution = water is picked up in the ascending vasa recta
The descending vasa recta
Picks up salt from gradient in medulla ➡️ creating salt gradient in vasa recta
Ascending vasa recta
Uses the salt gradient to pick up water from medulla preventing dilution of salt gradient ➡️ returning salt to medulla to maintain salt gradient
In the complete absence of ADH, what will the osmolarity of urine be?
100mOm - filtrate enters collecting duct @ 100mOm therefore when we are over hydrated no ADH with be present to help retain water
In the Presence of ADH, what is the maximal osmolarity that the urine can achieve?
1200 mOm - it enters collecting duct at 100, but as it passes through the more dehydrated the person is the more ADH present inserting more Aquaporins to retain water
What causes ADH to stimulate the insertion of aquaporins
Exocytosis
What removes aquaporins
Endocytosis
What are the 2 causes of increased osmolarity?
- Dehydration
- Increased salt intake
What are the two ways to fix osmolarity?
- drink water
- hold on to water by concentrating urine
NFL for dehydration
Low water intake = stimulus
➡️ increase osmolarity ➡️ osmoreceptors shrink in hypothalamus ➡️ posterior pituitary increase ADH (aquaporins) ➡️ kidneys increase h2o reabsorption ➡️ less water excreted in urine
