Nephron — filtration, reabsorption and secretion
One nephron from afferent arteriole to collecting duct, with the Starling pressures that drive filtration (55 − 30 − 15 = 10 mmHg), a GFR of 125 mL min⁻¹ = 180 L a day, segment-by-segment reabsorption from the proximal tubule's 65% of sodium to ADH-controlled water recovery, and the 1.5 L that finally leaves.
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{
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{ "id": "barrier", "type": "layers", "label": "Fenestrae, basement membrane, podocytes", "x": 215, "y": 200, "width": 150, "height": 104, "fill": "#e0f2fe", "stroke": "#0369a1", "bold": true },
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{ "id": "glucose", "type": "target", "label": "Glucose Tm 375 mg min⁻¹ — all recovered", "x": 740, "y": 200, "width": 150, "height": 104, "fill": "#fef3c7", "stroke": "#b45309", "bold": true },
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{ "id": "ascending", "type": "cone", "label": "Thick ascending limb — NKCC2 pumps NaCl", "x": 390, "y": 360, "width": 150, "height": 104, "fill": "#fef3c7", "stroke": "#b45309", "bold": true },
{ "id": "gradient", "type": "mountain", "label": "Medullary gradient — 300 to 1200 mOsm", "x": 565, "y": 360, "width": 150, "height": 104, "fill": "#ccfbf1", "stroke": "#0f766e", "bold": true },
{ "id": "spillover", "type": "cross", "label": "Above 11 mmol L⁻¹ glucose spills over", "x": 740, "y": 360, "width": 150, "height": 104, "fill": "#fee2e2", "stroke": "#b91c1c", "bold": true },
{ "id": "distal", "type": "valve", "label": "Distal tubule — aldosterone tunes Na⁺", "x": 40, "y": 520, "width": 150, "height": 104, "fill": "#e0f2fe", "stroke": "#0369a1", "bold": true },
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{ "id": "secretion", "type": "syringe", "label": "Secreted: H⁺, K⁺, creatinine, many drugs", "x": 390, "y": 520, "width": 150, "height": 104, "fill": "#fef3c7", "stroke": "#b45309" },
{ "id": "urine", "type": "bottle", "label": "Urine — 1.5 L a day, 99% reabsorbed", "x": 565, "y": 520, "width": 150, "height": 104, "fill": "#fce7f3", "stroke": "#be185d", "bold": true },
{ "id": "furosemide", "type": "first-aid", "label": "Furosemide blocks NKCC2 — big diuresis", "x": 740, "y": 520, "width": 150, "height": 104, "fill": "#f1f5f9", "stroke": "#475569" }
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{ "id": "e4", "source": "barrier", "target": "retained", "label": "anything above 70 kDa" },
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{ "id": "e15", "source": "ascending", "target": "gradient", "label": "builds the countercurrent" },
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{ "id": "e19", "source": "collecting", "target": "urine", "thickness": 2.5 },
{ "id": "e20", "source": "distal", "target": "secretion" },
{ "id": "e21", "source": "secretion", "target": "urine" },
{ "id": "e22", "source": "collecting", "target": "peritubular", "label": "recovered water rejoins the blood" },
{ "id": "e23", "source": "furosemide", "target": "ascending", "label": "the loop diuretic target", "style": "dashed" }
]
}