Flashcards in Renal System Deck (59)
What are the 6 functions of the kidney?
- Regulation of water and electrolyte balance
- Regulation of arterial pressure
- Excretion of metabolic waste products or foreign chemicals from the body
- Regulation of blood pH (e.g. via regulation of H+ and HCO3-)
- Regulation of erythrocyte production
- Regulation of hormone production e.g. calcitriol (vitamin D)
- Regulating blood glucose levels
What are 5 effects that failing kidneys can have on the body?
- High blood pressure
- Shortness of breath
The movement of water through a selectively permeable membrane from an area of lower solute concentration (high water concentration) to an area of higher solute concentration (low water concentration).
What is osmosis pressure?
The pressure required to prevent net water movement.
- A measure of the osmotic pressure exerted by a solution across a perfect semi-permeable membrane compared to pure water.
- Dependent on the number of particles in solution (but independent of the nature of the particles).
What is meant by hyperosmotic, isosmotic, and hyposmotic? Give examples of each.
- Hyperosmotic: a solution with a higher Osm than another (a 300mM/L NaCl vs 300mM/L urea)
- Isosmostic: two solutions with the same Osm (150mM/L NaCl vs 300mM/L urea)
- Hyposmotic: a solution with a lower Osm than another (150mM/L urea vs 150mM/L NaCl)
What is tonicity?
Takes into account the concentration of a solute and ability of the particle to cross a semi-permeable membrane.
Does NaCl have low or high permeability? What affect does a 150mM solution of NaCl have on a cell?
Cell neither shrinks or swells.
What is the osmolarity of cell cytosol?
Does urea have high or low permeability? What affect does a 300mM urea solution have on a cell?
Cell swells and will eventually burst, because the urea solution is hypotonic.
Distinguish between a hypertonic, isotonic, and hypotonic solution.
- Hypertonic: a solution with a higher POsm than other. Water will leave the cell, causing shrinkage.
- Isotonic: two solutions with the same POsm. No net water movement.
- Hypotonic: a solution with a lower POsm than another. Water will move into the cell causing swelling.
What are the 5 reasons for maintaining osmolarity?
- Setting the membrane potential
- Generating electrical acitivity in nerve and muscle
- Initiation of muscle contraction
- Providing energy for the uptake of nutrients and the expulsion of waste products
- Generation of intracellular signalling cascades
What percentage of a male's mass is fluid? What fraction of the fluid is extracellular? What percentage of that is plasma? What percentage of blood is plasma?
60% fluid = 42 L
1/3 extracellular = 14 L
20% plasma = 2.8 L
Blood is about 55% plasma.
Therefore 2.8 L of plasma = 5 L blood
What contributes to daily intake and output of fluids?
Intake: metabolism (8%), foods (28%), beverages (64%)
Output: faeces (4%), lungs (12%), skin (24%), urine (60%)
What ions have high extracellular concentrations? Which have high intracellular concentrations?
High E: Na+, Cl-, Ca2+
High I: K+
What are the three layers of the external anatomy of the kidneys?
1) Renal capsule: physical barrier, protection against trauma, maintains the shape of the kidneys.
2) Adipose capsule: padding, physical protection, maintains the position of the kidneys.
3) Renal fascia: anchors the kidneys to surrounding structures.
All are connective tissue
What is a lobe of a kidney made up of?
Medullary pyramid, overlapping cortex and half of each column.
What are the ion gradients in the body responsible for?
Responsible for the likes of setting the membrane potential, generating electrical activity in nerves and muscle, providing the energy for the uptake of nutrients and the expulsion of wastes.
What is responsible for the asymmetric distribution of ions between the intracellular and extracellular fluids?
Specialised transport properties of the cell membrane.
What is the equation for excretion?
Excretion = Filtration + Secretion - Reabsorption
What are the three basic processes involved in the formation of urine?
1) Filtration at the glomerulus
2) Tubular reabsorption
3) Tubular secretion
What is the glomerular filtration rate?
125mL/min (25% of the total renal plasma flow) = 180L/day
Describe the contents of glomerular filtrate.
Similar solute concentration (glucose, electrolytes etc.) to plasma. Lacks proteins and other high molecular weight compounds, and is free from blood cells.
Which capillary bed is the only one to have arterioles before and after it? What does this allow for?
Allows for tight regulation of pressure gradients to maintain near constant glomerular filtration rate. Increases in arterial pressure can be buffered by vasoconstriction of afferent arteriole whilst decreases in pressure can be buffered by vasoconstriction of efferent arteriole.
Why is glomerular filtration rate relatively constant? What is urine output directly proportional to?
Blood flow to the kidney is tightly regulated, thus glomerular filtration rate is relatively constant.
Urine output is directly proportional to renal pressure.
What does the equation P = QR mean?
Pressure = flow rate x resistance
What is net filtration pressure (NFP)? What is this value usually?
The pressure that determines how much water and small dissolved solutes leaves the blood (10mmHg)
What is glomerular filtration dependent on?
Net filtration pressure.
What is meant by glomerular blood hydrostatic pressure (GBHP)? What is this value usually?
The mechanical pressure between the afferent and efferent arterioles i.e. within the glomerulus: drives the plasma filtrate from the capillaries of the glomerulus into the capsular space (50mmHg).