Refresher of M1 Renal Physiology Flashcards
(36 cards)
What are some functions of the kidney? (7)
- Excretion of metabolic waste products
- Water and Electrolyte balance
- Regulation of body fluid osmolality and electrolyte concentrations
- Regulation of arterial pressure
- Regulation of acid-base balance
- Secretion, metabolism, and excretion of hormones
- Gluconeogenesis
The central physiologic role of the kidneys is to control the ______ and ________ of the body fluids
Volume; composition
Intracellular fluid = __ of total body water
Extracellular fluid = __ of total body water
2/3
1/3
The average 70 kg man will have ____ liters of total body water
____ liters will be in th ECF and ____ will be in the ICF
42 liters
ECF: 14 Liters
ICF: 28 Liters
What is osmolarity?
The concentration of osmotically active particles in total solution expressed in terms of mOsm/liter of water
What is the average osmolarity of the ECF and ICF?
280-300 mOsm/liter
What are the units of osmolality?
When does osmolality = osmolarity?
Osmolality: mOsm/kg of solvent (water)
In relatively dilute solutions such as those found in the body, osmolality = osmolarity
Describe the changes in volume and osmolarity upon adding solutions of…
Isotonic NaCl
Hypotonic NaCl
Hypertonic NaCl
- Isotonic NaCl
- Volume of extracellular compartment increases
- No change in osmolarity
- Hypotonic NaCl:
- Volume of extracellular and intracellular compartments increase
- Osmolarity decreases in both comparments
- Hypertonic NaCl:
- Extracellular volume increases, intracellular volume decreases
- Osmolarity increases in both
What four kidney processes determine the composition of urine?
- Filtration
- Reabsorption
- Secretion
- Excretion
What is the glomerular filtrate?
What is filtered and excluded from this filtrate?
The glomerular filtrate is an ultrafiltrate of plasma formed by the net effect of Starling Forces to move (filter) fluid out of the glomerular capillaries and into Bowman’s space
Most large proteins, substances bound to protein, and cellular elements are excluded from glomerular filtrate
What are the physical forces causing filtration by glomerular capillaries and what are their average values?
Glomerular hydrostatic pressure (60 mmHg)
Glomerular Colloid Osmotic Pressure (32 mmHg)
Bowman’s capsule pressure (18 mmHg)
Normal values for…
Renal plasma flow:
Glomerular Filtration Rate:
Efferent Plasma Flow:
Renal plasma flow: 700 ml/min
Glomerular Filtration Rate: 125 ml/min
Efferent Plasma Flow: 575 ml/min
GFR = Kf x [(PGC + πBS) - (πGC + PBS)]
What do these terms mean?
- Kf = ultrafiltration coefficient (product of hydraulic permeability)
- PGC = Glomerular Capillary Hydrostatic Pressure
- πGC = Glomerular Capillary Oncotic Pressure
- PBS = Bowman’s Space Hydrostatic Pressure
- πBS = Bowman’s Space Oncotic Pressure
Which of the following is more associated with a change in urine output?
Renal blood flow
Arterial Pressure
Glomerular Filtration Rate
Arterial Pressure
What is the myogenic autoregulation mechanism?
Intrinsic property of blood vessels
Stretch of vascular smooth muscle, as experienced during an increase in arterial pressure, elicits a contraction which elevates vascular resistance and maintain blood flow (and GFR) constant
How does tubuloglomerular feedback affect GFR and RBF autoregulation?
In response to an elevation of perfusion pressure, increased fluid is filtered leading to increased delivery of NaCl to the macula densa. This increased delivery elicits an increase in vascular resistance
Angiotensin II preferentially constricts the _______ arteriole
efferent
How do the following hormones affect GFR?
Norepinephrine/Epinephrine:
Endothelin:
Angiotensin II:
Endothelial Derived Nitric Oxide:
Prostaglandins:
Norepinephrine/Epinephrine: Decrease
Endothelin: Decrease
Angiotensin II: Decrease or no change
Endothelial Derived Nitric Oxide: Increase
Prostaglandins: Increase
What are the 3 layers that make up the filtration barrier?
Capillary wall (fenestrated)
Basement membrane
Podocytes
What is the main determinant of filtration barrier permeability?
Podocytes
What types of selection are associated with the filtration barrier?
Size-selection: more permeable to small molecules
Charge selective: more permeable to positively charged molecules
What are the components of the podocyte foot process contractile system which are linked to the slit diaphragm
Nephrin (N) and P-cadherin (P-C)
What is the function of the thin descending loop of henle?
Reabsorption of water secondary to cortical-medullary osmotic gradient
What is the function of the thin ascending loop of Henle?
- Impermeable to water
- Passive reabsorption of sodium, dilution of tubular fluid
- Permeable to urea, urea is secreted
