Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
The proximal convoluted tubule (PCT) is a segment of the nephron in the kidney where reabsorption of water, ions, and nutrients from the filtrate occurs. It plays a crucial role in maintaining osmotic balance and excreting waste products.
5 Must Know Facts For Your Next Test
Approximately 65% of the glomerular filtrate is reabsorbed in the PCT.
The PCT has microvilli lining its luminal surface to increase surface area for reabsorption.
Substances such as glucose, amino acids, bicarbonate, sodium, chloride, and water are actively reabsorbed here.
The PCT is involved in the secretion of substances like hydrogen ions and certain drugs into the filtrate.
Reabsorption in the PCT is driven by both active transport mechanisms and passive diffusion.
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Related terms
Nephron: The functional unit of the kidney responsible for filtering blood and forming urine.
Glomerulus: A network of capillaries located at the beginning of a nephron that filters blood to form filtrate.
Distal Convoluted Tubule (DCT): A segment of the nephron that further modifies filtrate through selective secretion and absorption after it passes through the loop of Henle.