The nephron
The nephron is the functional unit of the kidney. There are 2 basic types of nephron:
Cortical nephrons have glomeruli in the outer 70% of the cortex and have short loops of Henle whereas juxtamedullary nephrons have glomeruli close to the cortex-medullary boundary and long loops of Henle.
The basic structure of the nephron is shown below.
The first component of the nephron is Bowman's capsule which surrounds glomerular capillaries and collects the filtrate that passes through them. Bowman's capsule and the glomerulus are collectively known as the renal corpuscle.
Once collected by the Bowman's capsule plasma filtrate moves into the proximal convoluted tubule (PCT) before entering the loop of Henle. Filtrate moves from the ascending loop of Henle into the distal convoluted tubule (DCT) and eventually passes via a connecting tubule into the collecting duct. Note the collecting duct is not considered part of the nephron. The PCT, loop of Henle and DCT are collectively referred to as the renal tubule.
- Cortical nephrons, comprise ~85% of the total number of nephrons
- Juxtamedullary nephrons, comprise ~15% of the total number of nephrons
Cortical nephrons have glomeruli in the outer 70% of the cortex and have short loops of Henle whereas juxtamedullary nephrons have glomeruli close to the cortex-medullary boundary and long loops of Henle.
The basic structure of the nephron is shown below.
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The nephron. click on image to enlarge
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Cortical vs juxtamedullary nephrons. click on image to enlarge
The first component of the nephron is Bowman's capsule which surrounds glomerular capillaries and collects the filtrate that passes through them. Bowman's capsule and the glomerulus are collectively known as the renal corpuscle.
Once collected by the Bowman's capsule plasma filtrate moves into the proximal convoluted tubule (PCT) before entering the loop of Henle. Filtrate moves from the ascending loop of Henle into the distal convoluted tubule (DCT) and eventually passes via a connecting tubule into the collecting duct. Note the collecting duct is not considered part of the nephron. The PCT, loop of Henle and DCT are collectively referred to as the renal tubule.
Functions of nephron components
| Component | Function |
|---|---|
| Bowman's capsule | Collect filtrate generated by the glomerulus |
| PCT | Resorption of water and solutes Secretion of drugs and toxins |
| Loop of Henle | Reabsorption of water Concentration of urine |
| DCT | Tubuloglomerular feedback via the macula densa Resorption of ions Acid-base control |