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19 Cards in this Set
- Front
- Back
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What is the GFR in an average size normal man is app....
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125ml/min. Values in women are 10% lower. This turns out to be app. 180L/day. Thus, 99% of filtrate is absorbed.
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The permeability of the glomerular capillaries is about 50X that of the capillaries in skeletal muscle. TRUE/FALSE
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TRUE.
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What is the neutral filtrable size of most substances?
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Neutral substances with effective molecular diameters of less than 4nm are freely filtered, and those with diameters of more than 8nm approaches zero.
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What is the charge on silaoproteins?
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These proteins in the glomerular capillary wall are negatively charged.
Studies with anionically charged and cationically charged dextrans indicate that the negative charges repel negatively charged substances in blood, with the result that filtration of anionic substances 4nm in diameter is less than half that of neutral substances of the same size. |
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How much protein is normally found in the urine?
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It is normally less than 100mg/dl and most of this is not filtered but comes from shed tubular cells.
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What happens to the negative charges in nephritis?
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The negative charges in the glomerular wall are dissipated, and albuminuria can occur for this reason without an increase in the size of the pores in the membrane.
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Can the capillary bed(K(f) be altered by the mesangial cells?
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Yes. These cells produce a decrease in K(f) that is largely due to a reduction in the area available for filtration.
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Angiotensin 11 is an imporatant regulator of mesangial contraction, and there are angiotensin 11 receptors in the glomeruli. TRUE/FALSE
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TRUE.
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The pressure in the glomerular capillaries is higher than that in other capillary beds bcause the afferent arterioles, are short straight branches of the interlobular arteries. TRUE/FALSE
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TRUE.
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Does mean systemic arterial pressure affect autoregulation of glomeruli?
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Yes. The GFR tends to be maintained when efferent arteriolar constriction is greater than afferent constriction.
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What is filtration fraction?
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It is the ratio of the GFR to the renal plasma flow(RPF). It is normally 0.16-0.20. The GFR varies less than the RPF. When there is a fall in systemic blood pressure, the GFR falls less than the RPF because of efferent arteriolar constriction, and the filtration fraction rises.
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Small proteins and some peptide hormones are reabsorbed in the proximal tubules by endocytosis. TRUE/FALSE
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TRUE. Movement is by way of ion channels, exchangers, cotransporters and pumps.
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Name some syndromes that are associated with mutations of individual genes regarding tubular secretion and absorption.
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Dent's disease/Bartters syndrome and Liddle'syndrome.
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Give some examples of proteins involved?
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Polycystin-1(PKD-1) and Polycystin-2(PKD-2). PKD-1 appears to be a calcium receptor that activates a non specific ion channel associated with PKD-2.
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What is the function of PKD-2?
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Its function is unknown, but both proteins are abnormal in autosomal dominant polycystic kidney disease, in which renal parenchyma is progressively replaced by fluid filled cysts until there is complete renal failure.
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What is transport maximum?
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Transport maximum(Tm), Renal active transport systems have a maximal rate, at which they can transport a particular solute.
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How does transport maximum relate to a particular solute?
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The amount of a particular solute transported is proportionate to the amount present up to the Tm for the solute, but at higher concentrations, the Tm is saturated and there is no appreciable increment in the amount transported.
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Is tubular epithelium a "leaky epithelium"?
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Yes. The tight junctions between cells permit the passage of some water and electrolytes.
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Give an example of a protein localized to tight junctions?
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Paracellin-1, a protein localized to tight junctions is related to Mg+ reabsorption, and a loss of function mutation of its gene causes severe Mg+2 and Ca+2 loss in the urine.
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