6. Proximal Convoluted Tubule (PCT) Explained | Renal Physiology | USMLE Step 1 | Dr. Sree Teja

𝐒𝐮𝐛𝐬𝐜𝐫𝐢𝐛𝐞 𝗙𝐨𝐫 𝗠𝐨𝐫𝐞 𝗜𝐧𝐟𝐨𝐫𝐦𝐚𝐭𝐢𝐨𝐧 𝐨𝐧 𝗛𝐞𝐚𝐥𝐭𝐡 👩‍⚕‍ 𝐚𝐧𝐝 𝗠𝐞𝐝𝐢𝐜𝐢𝐧𝐞💉🩺💊 📌𝗜𝗻𝘀𝘁𝗮𝗴𝗿𝗮𝗺 : https://www.instagram.com/clinical.learning/ Proximal Convoluted Tubule (PCT) Explained | Renal Physiology | USMLE Step 1 | Dr. Sree Teja The Proximal Convoluted Tubule (PCT) is the first and most metabolically active segment of the nephron 🌀 located in the renal cortex. It is responsible for the bulk of reabsorption — reclaiming about 65–70% of filtered sodium and water, along with glucose, amino acids, bicarbonate, chloride, and phosphate. Reabsorption here is powered by the Na⁺/K⁺ ATPase on the basolateral membrane, creating a gradient that drives secondary active transport (e.g., Na⁺/glucose cotransport via SGLT2, targeted by drugs like gliflozins 💊). The PCT also plays a key role in acid-base balance by reabsorbing HCO₃⁻ and secreting H⁺ ions via carbonic anhydrase-dependent mechanisms. Organic anions and cations (like creatinine, drugs, toxins) are secreted into the lumen here. It is also the site of isotonic reabsorption, meaning fluid reabsorbed has the same osmolality as plasma. The PCT is highly susceptible to ischemic injury due to its high ATP demand, and it's the initial site affected in conditions like acute tubular necrosis (ATN) 🔬. Understanding its transport mechanisms is essential for Step 1 questions involving diuretics, renal physiology, and metabolic disorders 🧠💧. #ProximalTubule #USMLEStep1 #RenalPhysiology #NephronFunction #DrSreeTeja #SGLT2 #AcidBaseBalance #MedicalEducation #HighYieldRenal #Step1Prep #TubularTransport #ATN #NaKATPase #PCTFunction #MedStudentNotes #BoardReview