Nephron

Nephrons are tiny tubules (miniature tubes) which are the smallest working part of the kidney. This is where the kidney removes waste, excess salt and excess water.

Nephron
Diagram (left) of a long juxtamedullary nephron and (right) of a short cortical nephron. The left nephron is labelled with six named nephron segments. Also labelled is the collecting duct, mislabelled the "collection duct"; it is the last part of the nephron.
Latin	Nephroneum
System	Urinary system
Precursor	Metanephric blastema (intermediate mesoderm)

Each nephron starts in the cortex of the kidney, then goes into the medulla of the kidney, before coming back to the cortex, then goes through the medulla into the pelvis of the kidney. In the pelvis, the nephrons join up with the ureter.

In humans, a normal kidney has between 800,000 and 1.5 million nephrons.

Each nephron consists of a cup-shaped structure at one end called the Bowman's capsule. It extends into a long urinary tubule,that is surrounded by a network of renal capillaries. The urinary tubules of nephrons in each kidney join to form a common tube called the ureter.

Inside the Bowman's capsule is a network of blood capillaries, the glomerulus. The Bowman's capsule and glomerulus together form the Malphigian capsule or Malphigian body.

Liquid passes through the segments of the nephron in this order:

1. Bowman's capsule (including glomerulus)
2. Proximal convoluted tubule
3. Descending loop of Henle
4. Ascending loop of Henle
5. Distal convoluted tubule
6. Collecting duct

Nephron Media

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  Fig.1) Schematic diagram of the nephron (yellow), relevant circulation (red/blue), and the four methods of altering the filtrate.

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  Fig.2) Schematic of the glomerular filtration barrier (GFB).*A. The endothelial cells of the glomerulus; 1. endothelial pore (fenestra). B. Glomerular basement membrane: 1. lamina rara interna 2. lamina densa 3. lamina rara externa *C. Podocytes: 1. enzymatic and structural proteins 2. filtration slit 3. diaphragm

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  Fig.3) Secretion and reabsorption of various substances throughout the nephron.

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  Fig.4) Diagram outlining movement of ions in nephron, with the collecting ducts on the right.

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  Fig.5) Proximal tubule cell showing pumps involved in acid base balance, left is the lumen of tubule

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  Fig.6) Cross-sectional histologic preparation showing (b)small connecting tubules with simple columnar epithelium and (a) large connecting tubules with simple cuboidal epithelium.

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  Fig.7)*Cross-sectional diagram of the juxtaglomerular apparatus and adjacent structures: 1) top, yellow - distal convoluted tubule; 2) top, brown -macula densa cuboidal cells surrounding arterioles; 3) small blue cells - juxtaglomerular cells; 4) large blue cells - mesangial cells; 5) tan - podocytes lining Bowman's capsule adjacent to capillaries, and parietal layer of capsule, 6)center - five glomerular capillaries, and the 6)bottom, purple - exiting tubule. Structures (2), (3), and (4) constitute the juxtaglomerular apparatus.

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  Distribution of blood vessels in cortex of kidney. (Although the figure labels the efferent vessel as a vein, it is actually an arteriole.)

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  Glomerulus is red; Bowman's capsule is white.

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  Microscopy of kidney tissue showing tubules. One tubule is highlighted to show epithelial cells (blue), cell nuclei (green) and the tubule lumen (dark center).