Organ
Proximal convoluted tubule
A brush-bordered epithelium for bulk recovery
High-yield
The proximal tubule recovers roughly two thirds of filtered sodium and water. Glucose and amino acids are normally almost completely reclaimed, provided transporter capacity is not exceeded or inhibited.
Overview
Filtrate leaving the corpuscle enters a coiled cortical tubule whose cells have dense apical microvilli and abundant mitochondria. This large transport surface recovers much of the filtered water and solute load. The proximal tubule then straightens before continuing into the thin limb.
Reference facts
- Location
- The convoluted portion lies in the cortical labyrinth near its corpuscle and continues toward a medullary ray.
- Parts
- The proximal tubule has coiled and straight portions; its cuboidal epithelial cells bear a prominent brush border.
- Blood supply
- Cortical peritubular vessels and medullary microvessels around the straight segment support exchange and oxygen delivery.
- Innervation
- Renal sympathetic input can promote proximal sodium reabsorption alongside hormonal and local regulation.
- Function
- Recovers water and solutes approximately isosmotically, including much bicarbonate and normally nearly all filtered nutrients; secretes organic ions and numerous drugs.
Clinical correlation
Generalized proximal dysfunction causes Fanconi syndrome, with urinary losses of glucose, phosphate, amino acids and bicarbonate. High transport demand makes proximal cells, particularly the straight S3 segment, vulnerable to ischemic and toxic injury.
Frequently asked questions
Where is the proximal convoluted tubule located?
The convoluted portion lies in the cortical labyrinth near its corpuscle and continues toward a medullary ray.
What does the proximal convoluted tubule do?
Recovers water and solutes approximately isosmotically, including much bicarbonate and normally nearly all filtered nutrients; secretes organic ions and numerous drugs.
What are the parts of the proximal convoluted tubule?
The proximal tubule has coiled and straight portions; its cuboidal epithelial cells bear a prominent brush border.
What is the blood supply of the proximal convoluted tubule?
Cortical peritubular vessels and medullary microvessels around the straight segment support exchange and oxygen delivery.