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34 Cards in this Set
- Front
- Back
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What is osmolality?
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The concentration of a solution expressed as the total number of solute particles per kilogram
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How much of body weight (BW) is comprised of total body water (TBW)?
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60%, 1 kg = 1 L
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What is the ratio of extracellular fluid (ECF) and intracellular fluid (ICF)?
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1/3 ECF : 2/3 ICF
20% body weight ECF : 40% body weight ICF |
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What is the 20-40-60 rule?
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ECF = 20% body weight
ICF = 40% body weight TBW = 60% body weight |
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What is the distribution of fluid outside the cells in interstitial spaces vs. fluid in plasma?
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75% ECF in interstitial fluid
25% ECF in plasma |
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What is plasma volume and how is it estimated?
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The volume of blood that is not occupied by cells
It is estimated by 1-hematocrit |
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What is hematocrit?
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The % of blood volume occupied by RBC that depends on the osmolality of plasma (not dependent on # of cells, but by volume)
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How does water move passively across cell membranes?
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Via membrane water channels called aquaporins (AQP)
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What is plasma osmolality indicative of at equilibrium?
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ECF osmolality and ICF osmolality are equal
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How do sodium and potassium concentrations differ in and out of cells?
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Sodium is the major extracellular osmole
Potassium is the major intracellular osmole |
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How is osmolality of a solution related to its water concentration?
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High osmolality = low water concentration
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What is reverse osmosis?
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Applying hydrostatic pressure to extrude water through a semipermeable membrane
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What is the reflection coefficient?
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The membrane permeability of solute particles, the greater the coefficient, the less permeable the membrane is to that particle
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How does Fick's principle apply to renal physiology?
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There is mass conservation of fluid flow to and from the kidney such that input = output
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What is renal clearance?
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The volume of plasma that is cleared of a substance per unit time to account for the amount of substance that has been excreted into the urine
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Where is EPO made and what does it do?
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Made by fibroblastic interstitial renal cells in response to reduced partial pressure of O2 in the kidneys
Stimulates red blood cell production by bone marrow |
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Where is calcitrol made and what does it do?
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Kidneys activate the vitamin D precursor
Promotes calcium absorption from the gut Regulates Calcium and Phosphate homeostasis |
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What does renin do?
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Activates angiotensin II that promotes tubular reabsorption of salt and water
Stimulates synthesis of adrenal aldosterone |
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What are prostaglandins and what do prostaglandins do?
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Adenosine, ATP, NO
Regulate vascular smooth muscle and control renal blood flow and glomerular filtration |
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What is glomerular filtration?
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The process by which water and solutes leave the vascular system through the glomerulus and enter Bowman's capsule
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What is reabsorption?
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The process that reclaims filtered substances
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What is secretion?
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The process by which non-filtered substances are added to tubular fluid
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What is excretion?
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Elimination of the tubular contents into urine
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What is the renal corpuscle and what takes place here?
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Glomerulus and Bowman's capsule
Filtration occurs here |
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What happens in the proximal tubule?
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Major site of water and salt reabsorption
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What happens in the loop of Henle?
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Descending (thin): Selective reabsorption of water
Ascending (thick and thin): Selective reabsorption of salt, impermeable to water. |
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What is the difference between cortical nephrons and juxtamedullary nephrons?
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Cortical nephrons have short loops of Henle that are confined to the cortex
Juxtamedullary nephrons have longer loops of Henle that enter the medulla |
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What is the macula densa in the nephron and what is so special about it?
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Specialized cells in distal convoluted tubule
Lays between afferent and efferent arterioles Provides feedback to parent glomerulus about flow and salt concentration |
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What happens in the distal and connecting tubules?
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Continued reabsorption of solutes
Impermeable to water |
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What happens in the cortical and inner medullary collecting ducts?
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Fine tuning of salt water reabsorption
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What are the three layers of the filtration barrier?
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1. fenestrated endothelium
2. negatively charged basement membrane 3. podocytes whose foot processes contribute to filtration slits |
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What are the Starling forces favoring and opposing glomerular filtration?
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Favoring filtration:
- Hydrostatic pressure of the glomerulus (PGC) - Oncotic pressure of Bowman's Capsule (πBC) Opposing filtration Oncotic pressure of the glomerulus (πGC) Hydrostatic pressure of Bowman's Capsule (PBC) |
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What are the different types of transport processes for reabsorption from tubular lumen back into the peritubular capillaries and how are they done?
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1. Uniporter/Channel: Carries a single type of molecule across
2. Diffusion 3. Paracellular diffusion: Movement between cells 4. Symport: Movement of two or more molecules in the same direction 5. Antiport: Movement of two or more molecules in opposite directions |
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What are the Starling forces favoring and opposing movement of water and solutes out of the tubule and into the interstitium/peritubular capillaries?
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Favoring reabsorption:
Hydrostatic pressure in the interstitium (Pi) Oncotic pressure of peritubular capillaries (πPC) Opposing Reabsorption Oncotic pressure in the interstitium (πi) Hydrostatic pressure of peritubular capillaries (Ppc) |
