renal physiology Flashcards
- describe in a single sentence the role of the kidney in total body homeostasis.
the maintenance of the composition and volume of the extracellular fluid!
- state the volume of each of the major body compartments in a standard-sized, healthy, adult individual.
For a body mass of 70kg (154lbs): Intracellular fluid is 27L (non circulating cell volume is 24L and blood cells are 3L), and extracellular fluid is 15L (interstitial fluid is 12L and plasma is 3L)
- describe the major components and volumes of daily water intake and loss.
Input (2.5L): 2.0L of fluid and food are ingested and 0.5L are added from metabolic processes. Output (2.5L): 0.1L is lost from sweat and feces, 0.9L is lost from respiration and skin leaks, 1.5L is lost from urine. The overall ECF volume does not change
- identify the processes of water intake and output that are regulated to achieve extracellular fluid homeostasis.
Regulation of urinary output: this regulates volume, osmolarity, electrolyte composition, pH, metabolic wastes and foreign substances (ie. Drugs)
- identify the basic functional structures of the nephron.
Epithelial tubule, glomerular and peritubular capillaries
- describe the basic glomerular and tubular processes and how they interact to achieve ECF homeostasis.
1) Glomerular Filtration: filter the plasma into the initial part of the tubule. This process of filtration allows the free passage of water and solutes into the tubule, but retains larger colloids (i.e. proteins, lipid aggregates, etc.) and RBCs. 2) Tubular Reabsorption: Once in the tubule, the kidney can recapture the filtered components that it wishes to regulate. 3) Excretion: Regulated substances in excess of those required to maintain ECF balance simply pass through the tubule and are excreted as part of the urinary output. 4) Tubular secretion: Movement of substances from blood into the tubule via pumps or channels
- for a normal sized healthy individual, to state the magnitude of renal blood flow, renal plasma flow, glomerular filtration rate, filtration fraction, and urine flow rate.
Renal blood flow is 1.3L/min (25% of cardiac output), Rnal plasma flow is 0.65L/min, Filtration fraction is 0.2 (20% of the plasma flow undergoes glomerular filtration), glomerular filtration rate is 130ml/min (0.2 x 650), urine flow rate is 1.5L/day
How much of the bodies daily energy is used by kidneys
10%
What other functions does the kidney have (other than regulation of ECF?
kidneys produce erythropoetin (EPO) from its precursor synthesized in the liver, contribute to gluconeogenesis, and play a role in renin-angiotensin axis
- describe regulation of vascular resistance by angiotensin II via the baroreceptor-mediated renin/angiotensin axis.
Decreased blood pressure triggers the baroreceptor reflex which increases renin production by kidney. Renin cleaves angiotensiogen from liver into angiotensin I, then Angiotensin I is cleaved into angiotensin II by ACE. Angiotensin II leads to vasoconstriction and increased blood pressure.
What is rate limiting in the renin-angiotensin axis
Renin production
