Urinary 1-6 Flashcards
What is the main function of the urinary system?
Control concentrations of key substances in extracellular fluid - homeostasis
What results from failure to control ECF volume?
Changes in blood pressure, tissue fluid and cell function
What reults from failure to control ECF osmolarity?
Cells shrink or swell
What are membranes permeable to?
Very permeable to water, selective to other types of molecules and electrolytes
What is osmolality?
Solute per kg of solvent - functionally the same as osmolarity.
What is osmolarity?
Number of osmoles of solute per litre - total concentration of substances which do not cross the membrane freely
Is potassium concentration higher intra cellularly or extra cellularly?
Intracellularly (sodium opposite)
What are the main anions extra cellularly?
Cl- and HCO3-
What controls the pH of extra cellular fluid?
HCO3
How do the kidneys control homeostasis?
Control volume
Control osmolarity
help to control pH
Excrete some waste products
What substances are 100% reabsorbed?
HCO3, glucose and amino acids
What % of cardiac output goes to the kidneys? (at rest)
25%
What is the functional unit of the kidney?
Nephron - filter unit connected to a long tube for reabsorption
In order, what are the regions of the nephron?
Prox. con. tubule (cortex) -> loop of henle (into and out of medulla) -> dist. con. tubule (cortex) -> collecting duct (passes through the medulla to pelvis)
What is the glomerulus?
Highly specialised filter.
What is filtered through the glomerulus?
Water, electrolytes and small molecules - NOT large proteins
What causes filtration through the glomerulus?
Pressure from the capillaries to the afferent arterioles.
Where is the major site of reabsorption in the kidneys?
Proximal convoluted tubule -
60-70% Na and water
80-90% K
90% HCO3
100% glucose and aa (usually)
reabsorbed materials leave by peritubular capillaries
What are the 2 membranes lining the tubular cell?
Luminal (luminal side)
Basolateral (ECF side)
POLARISED
allow transport across the epithelium
What controls tranport across the tubular cell membranes?
Na-K pump - couple other substances to energy from sodium movement. Water follows osmotically
What is the main function of the loop of henle?
Create a gradient oof increading osmolarity in the medulla by counter-current multiplication - produces concentrated urine as water is reabsorbed
How is the distal convoluted tubule different to the prox.?
Variable reabsorption of electrolytes and water.
What is the function of the dis. con. tubule?
Removes more Na and Cl and actively secretes H ions
What is diluresis?
large volumes of dilute urine
