Flashcards in Renal Deck (197)
What must be transported with Na or K?
Cl-; to maintain electric neutrality
Where is the most Na absorbed in the tubular system?
the proximal convoluted tubule (65%)
Where do phosphate and ammonia buffer systems begin?
in the proximal convoluted tubule
What is the function of the phosphate and ammonia buffer system?
to help maintain normal acid-base balance
- bind with H+ ions
- generate new bicarbonate ions
What electrolyte is actively transported in the Loop of Henle?
What is passively transported in the Loop of Henle?
coupled with the active transport of Cl-, to maintain electrical neutrality, passive transport occurs with : Na, K, Ca and Mg
What is not absorbed in the Loop of Henle?
How do loop diuretics work?
they block Cl- and therefore, indirectly block the reabsorption of Na, K, Ca and Mg
What hormones function to "fine tune" the solutes reabsorbed in the distal convoluted tubule and collecting duct?
aldosterone, antidiuretic and parathyroid hormones
What electrolyte does aldosterone facilitate the reabsorption of?
Na in exchange for K and H
What does antidiuretic hormone facilitate the reabsorption of?
What electrolyte does parathyroid facilitate the reabsorption of?
Where is the juxtaglomerular apparatus found and what is it's function?
The juxtaglomerular apparatus is a specialized structure formed by the distal convoluted tubule and the glomerular afferent arteriole. It is located near the vascular pole of the glomerulus and its main function is to regulate blood pressure and the filtration rate of the glomerulus.
Where are the macula densa cells found and what are their function?
The macula densa is a collection of specialized epithelial cells in the distal convoluted tubule that detect sodium concentration of the fluid in the tubule.
What is the reaction of the macula densa cells to elevated sodium levels?
In response to elevated sodium, the macula densa cells trigger contraction of the afferent arteriole, reducing flow of blood to the glomerulus and the glomerular filtration rate. (decreasing hydrostatic pressure to "push" solutes out).
What is the reaction of the juxtaglomerular apparatus to hypotension?
The juxtaglomerular cells, derived from smooth muscle cells, of the afferent arteriole secrete renin when blood pressure in the arteriole falls. Renin increases blood pressure via the renin-angiotensin-aldosterone system.
Where is aldosterone manufactured?
is synthesized from cholesterol in the adrenal cortex
What triggers the release of aldosterone?
1) the presence of angiotensin II
2) elevated K serum levels
Where does aldosterone work in the tubular system?
late distal convoluted tubule and the collecting duct
How is the glomerulus affected by prematurity?
1) immature autoregulation of afferent arteriolar dilation and efferent arteriolar constriction
2) receptor site on afferent and efferent arteries (underdeveloped and hyporesponsive)
How is the proximal tubule affected by prematurity?
1) loss of Na, Ca, HCO3, glucose, protein
2) immature phosphate and ammonia buffer systems
30 delayed drug clearance
How is the distal tubule and collecting duct affected by prematurity?
1) hyporesponsiveness to aldosterone (leading to loss of Na, retention of K & H)
2) low circulating lveles of ADH
3) hyporesponsiveness to ADH (limited concentrating ability)
What is the indicated treatment for metabolic acidosis d/t renal immaturity?
1) art lines: use 1/2 Na ace instead of 1/4 NS
2) omit cysteine from TPN
3) add Na and K to TPN as acetate
When should cysteine be added to the TPN?
once pH balance is achieved
What is the benefit of keeping a preterm infant slightly alkalotic?
making a preterm slightly alkalotic will keep pH normal allowing for permissive hypercapnea
How long does it take for the neonatal kidney to renally compensate for respiratory acidosis?
as long as 3 days
How should a negative Na and H20 blanace in the 1st few days of life be interpreted in the preterm neonate?
- appropriate adaptation to extrauterine life
(we have no established optimal rate or extent of weight loss for preterm infants)
What pathologic conditions are a/w excessive fluid administration?
1) severe RDS
3) pulmonary edema
4) congestive heart failure
" a dry lung is a happy lung"
What do PT and FT infants have a limited ability to do as it relates to renal physiology?
excrete a large Na or H2O load