Tubules

Nephrons consist of tubules (very narrow tubes) that take waste substances, including urea, away from the blood, but put the substances needed by the body back into the blood.

The comparison of a tuba horn and tubule in a nephron are very similar indeed

Think of a tuba (the brass wind instrument) as being like a tubule.

The tubule story

This is the story of the tubule – what it does, from start to finish

Bowman’s capsule

Each tubule begins at a point called Bowman’s capsule. (This is where some substances are filtered out of the blood into the tubule – see Blood flow through the kidneys below for further details).

The bowman's capsule is the first part of nephron and tubule

The bowman's capsule filters most of the substances directly from the blood stream into the tubule

Imagine a tuba player with a big bow in his cap (Bowman’s capsule).

Proximal tubule

At various points along the tubule, glucose, water and salts needed by the body are selectively reabsorbed – taken back in – by the blood system via capillaries – very fine blood vessels. This process starts at the proximal tubule, a series of bends in the tubule.

The proximal tubule is the first bend in the filtration system and where the separation of substances begin

At the proximal bend salt, water, glucose needed by the body are reabsorbed into the blood through tiny capillaries

The tuba player takes off his cap so a hairdresser can apply cream from peroxide tubes (proximal tubule) to his hair.

Loop of Henle

More substances transfer back into the capillaries along the loop of Henle.

The Henle loop is where substances from the previous bends are reabsorbed back into the blood stream

This section is a very narrow section of tubule with capillaries surrounding it

The hairdresser who dyed the tuba player’s hair is in fact a loopy hen (loop of Henle).

Distal tubule

Next along the tubule comes the distal tubule, another series of bends in the tube, where again substances needed by the body are reabsorbed into the blood vessels from the tubule.

The distal tubule is an other series of bends where substances are absorbed back into the blood

The finest substances needed are reabsorbed back into the body reaching the end of filtration

The reason the loopy hen is off her trolley is that she’s been distilling alcohol through a bendy tube (distal tubule) and sampling the results.

Collecting duct

The filtrate that now remains in the tubule, plus the materials secreted from the blood, is urine, which continues to the collecting duct.

The filtrate that remains in the tubule enters the collecting duct

Material secreted by the blood, urine also continues to the collecting duct

The loopy hen had been drinking all afternoon with her mates, a collection of ducks (collecting ducts).