2.1 The Glomerulus And Glomerlar Injury Flashcards
What is reabsorption?
the movement of a substance from the tubular fluid back into the circulation
What is secretion?
the movement of substances from the blood into the tubular fluid via tubular cells (active transport) or intracellular spaces (passive transport)
What is excretion?
the removal of waste products from the blood and the net result of filtration, secretion and reabsorption of a substance
What 2 ways can solutes be transported across cells?
- Paracellular movement – across the tight junctions connecting the cells. Down concentration gradient
2 Transcellular movement – through the cell. May be down or against concentration gradient. Water follows movement of solutes by osmosis
What is diffusion?
The movement of a substance down their electrochemical gradient. Passive. Must be lipid soluble
What is facilitated diffusion?
The movement of a substance down their electrochemical gradient, relies on a carrier molecule to transport substances across the membrane. Passive. Faster than diffusion. Relies on a pore, channel or carrier protein.
What is primary active transport?
energy dependent process in which substances cross the cell membrane against their concentration and electrochemical gradients.
How is energy for primary active transport attained?
hydrolysis of ATP to ADP and Pi to provide chemical energy for the transport mechanism.
What is the most important primary active transporter?
Na +/K+ ATPase pump. Found on the basal and basolateral membranes of the tubular cells
What are tubular cells?
Cells that line the convoluted tubule
Give examples of primary active transporters?
Na+/K+ ATPase
Ca 2+ ATPase
H+/K+ ATPase
H+ ATPase
What is secondary active transport?
Transport that uses the energy produced from another process for transporting molecules.
What is a symporter?
A membrane channel protein that is a secondary active transporter. Moves a molecule in the same direction as Na + gradient
e.g. Na+/K+ cotransporter or Na+/glucose
What is an antiporter?
A membrane channel that is a secondary active transporter. Move ions against electrochemical gradient, opposite to Na+ gradient
e.g. Ca2+/Na+ and the H+/Na+ exchangers
Give examples of primary active transporters?
- H+/K ATPase
- Proton pump
- Ca2+ ATPase
- Na+/K+ ATPase
What are ion channels?
Protein pores found on the epithelial cell membranes.
What ion channels are found in the kidney?
Channels specific to Cl -, Na+ and K+ are found on apical membrane of tubular cells.
How many L a day are excreted?
1.5L
How can we work out the total body fluid?
60% of weight (42L in average 70kg man)
Describe the distribution of total body water
1/3 is extracellular fluid - 3/4 is interstitial fluid - 1/4 intravascular/plasma 2/3 is intracellular fluid - 2L in RBC
Describe the composition of blood?
5.5L of blood
2L of water in RBC
3.5L of plasma
Describe the intracellular composition of ions
high K+, low Na+, many large organic anions
Describe the composition of extracellular fluid
low K+, high Na+, main anion Cl- and HCO3-
How is the difference in ion composition of intracellular and extracellular fluid maintained?
By active transport (Na+/K+ ATPase)
What is osmolality?
is solute per kilogram of solvent
What is osmolarity?
number of osmoles of solute per litre
What is oncotic pressure?
osmotic force due to proteins
In what units are oncotic pressures measured?
In milli-osmoles
What cannot be filtered out of the glomerulus normally?
blood cells and platelets
proteins
Where is the glomerulus found?
In the cortex
What is the normal GFR?
90 - 120 ml/min
What is the renal plasma flow?
800mL/min