Flashcards in Test 1 (Renal, Obesity, Coags, hepatic, gallbladder...) Deck (313)
What is the % of CO that is partitioned to renal blood flow?
20-25% via the renal artery
The renal cortex gets what % of the RBF?
80% (extracts very little O2)
The renal juxtamedullary gets what % of the RBF?
What area of the renal system is most sensitive to ischemia?
The medulla: which uses high metabolic activity for solute absorption and requires low blood flow to maintain osmotic gradients.
What MAP is appropriate to maintain autoregulation in the kidneys?
MAP of 75-160mmHg
A MAP below _____ % can be associated with impaired filtration.
Filtration ceases at a MAP less than ______%.
Your 2 kidneys are comprised of 2 regions called the _______ and the ________.
cortex and medulla
What is the functional unit of the kidney? How many are there?
nephron; approx. 1.25 million per kidney
What is the function of the nephron?
functional unit of the kidney; it holds filtrate that is filtered by blood, excretes waste, and absorbs important substances such as water and bicarbonate
What does renal fraction mean?
renal fraction is the portion of the blood that passes through the kidney
What is the renal fraction of the CO? and in mL?
20-25%; 1100-1200mL per minute
What is the glomerulus?
It is a high pressure capillary bed formed by the afferent arterioles.
In what two ways is RBF regulated?
intrinsic autoregulation and neural regulation
What is neural regulation and the effect of SNS stimulation on the RBF?
afferent and efferent arterioles are innervated by the sympathetic nervous system, stimulation of the SNS causes vasoconstriction..... and thus a decrease in RBF
What are the main functions of the kidney?
maintenance of ECF composition and volume, endocrine functions (erythropoietin, RAA system, vitamin D), regulation of arterial BP
What is the significance of erythropoietin, the RAA, and vitamin D?
erythropoietin stimulates the production of RBCs; RAA regulates BP, K, and Na excretion; kidney converts vitamin D into its active form to absorb Ca from the intestine... so a deficiency in vitamin D results in hypocalcemia
What does one nephron consist of and what are its 4 main functions?
consists of the glomerulus (bowmans capsule), proximal and distal convoluted tubule (in the cortex), and the loop of henle and collecting tubule (in the medulla); functions include glomerular filtration, tubular reabsorption, tubular secretion, and excretion (byproduct of the previous 3 functions)
What are the 2 types of nephrons? Describe.
cortical nephrons (extend only partially into the medulla) and juxtamedullary (lie deep in the cortex and extend deep into the medulla); 1/5 to 1/3 are juxtamedullary---> play an important role in the concentration of urine.
What is the name of the peritubular capillaries of the loop of Henle?
What is the difference between reabsorption and secretion?
reabsorption is when a substance is transported from the tubule to the capillary..... secretion is when a substance is transported from the capillary to the tubule
What part of the medulla is most vulnerable to ischemia?
outer medulla (top of the loop of Henle)
What is the % and mL/min value for GFR?
20% RBF (125mL/min)
The release of what substance causes RAA activation?
What % of the approximately 125mL/min of filtrate is reabsorbed from the renal tubules while the remainder is excreted as urine?
Why does glucose get excreted in urine when past a certain concentration?
some substances like glucose have a maximum reabsorption value after which the remainder is excreted.
What factors can increase the GFR?
increased renal blood flow, dilation of the afferent arteriole, and increased resistance in the efferent arteriole increases GFR
Describe the activation and process of the RAA.
SNS stimulation and decreased delivery of sodium and chloride to the macula densa cause the juxtaglomerular cells to release renin---> renin clears angiotensinogen from the liver to form angiotensin I---> in the lung, angiotensin I is changed into angiotensin II under the influence of a converting enzyme---> in addition to having a generalized vasoconstriction effect, angiotensin II causes constriction of the efferent arteriole---> this causes pressure in the glomerulus to increase and the GFR to return to normal
What is the short description for the proximal tubule?
"coarse control": reabsorbs the bulk of glomerular filtrate (65-75%); NaCl, water, bicarb, glucose, protein, amino acids, potassium, magnesium, calcium, phosphates, uric acid, urea; also produces ammonia; has active (at the cost of metabolic energy d\t electrochemical gradient) and passive (movement of substances across concentration gradients) transport