Proximal tubule
Proximal Tubule
The Proximal Tubule (pronounced: prox-i-mal too-bule) is a segment of the nephron in the kidney that plays a crucial role in the reabsorption of water, ions, and all organic nutrients.
Etymology
The term "Proximal Tubule" is derived from the Latin word 'proximus' meaning 'nearest' and the Latin word 'tubulus' meaning 'small tube'. It is named so because it is the nearest tubule to the glomerulus in the nephron.
Function
The primary function of the Proximal Tubule is to reabsorb about 65% of the glomerular filtrate back into the bloodstream. This includes water, glucose, amino acids, and ions such as sodium, potassium, and chloride. It also secretes substances such as hydrogen ions, creatinine, and drugs into the filtrate.
Structure
The Proximal Tubule is made up of a single layer of cuboidal cells with microvilli, which increase the surface area for reabsorption. It is divided into two parts: the proximal convoluted tubule (PCT) and the proximal straight tubule (PST). The PCT is closer to the glomerulus and has a twisted structure, while the PST is further away and has a straight structure.
Related Terms
- Nephron: The functional unit of the kidney, consisting of the glomerulus, proximal tubule, loop of Henle, distal tubule, and collecting duct.
- Glomerulus: A network of tiny blood vessels in the kidney where the filtration of blood takes place.
- Distal Tubule: The portion of the nephron that is furthest from the glomerulus, involved in the reabsorption of sodium and secretion of potassium.
- Loop of Henle: The U-shaped part of the nephron that plays a key role in concentrating the urine.
- Collecting Duct: The final part of the nephron that collects urine from multiple nephrons and transports it to the renal pelvis.
External links
- Medical encyclopedia article on Proximal tubule
- Wikipedia's article - Proximal tubule
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