Filter units

The idea

Kidneys remove nitrogenous wastes such as urea or uric acid from blood in nephrons, each a cluster of thin-walled capillaries associated with the cup-shaped Bowman's capsule of a coiled tube that collects the filtrate.

A coffee filter

A paper filter lets liquid through but keeps the solid bits back.

What do you think the kidney's filter units do to blood?

• Filter out wastes from blood
• Make new blood
• Digest food

One nephron

Press Next step.

The filter unit

The kidney removes nitrogenous wastes such as urea or uric acid from the blood, as the lungs remove carbon dioxide. Its basic filtration unit, the nephron, starts with a cluster of very thin-walled blood capillaries. Each cluster is linked with the cup-shaped end of a coiled tube, the Bowman's capsule, which collects the filtrate. Each kidney has large numbers of nephrons packed close together.

Kidneys remove nitrogenous wastes such as urea or uric acid from blood in nephrons, each a cluster of thin-walled capillaries associated with the cup-shaped Bowman's capsule of a coiled tube that collects the filtrate.

Notes

Nephrons in the kidneys filter nitrogenous wastes (urea, uric acid) from blood: a cluster of thin-walled capillaries with a cup-shaped Bowman's capsule on a coiled tube that collects the filtrate.

Check yourself

What do the kidneys remove from the blood?

What is the basic filtration unit of the kidney?

What collects the filtrate in a nephron?

What forms the filtering part of each nephron, like in the lungs?

• Oxygen. Oxygen is carried by the red blood corpuscles to the tissues.
• Carbon dioxide, as the lungs do. Carbon dioxide is removed from the blood in the lungs; the kidneys remove nitrogenous wastes.
• Nitrogenous wastes such as urea or uric acid — correct. Yes!
• The nephron — correct. Yes!
• The ureter. The ureter is a long tube that connects the kidney with the urinary bladder.
• The urinary bladder. The urinary bladder stores the urine until it is passed out.
• The villi. Villi are in the small intestine and absorb digested food.
• The cup-shaped Bowman's capsule at the end of a coiled tube — correct. Yes!
• The alveoli. Alveoli are balloon-like structures in the lungs.
• A thick-walled artery. The book describes a cluster of very thin-walled blood capillaries.
• A single valve. Valves keep blood flowing one way in veins and the heart; the filtering part is a capillary cluster.
• A cluster of very thin-walled blood capillaries — correct. Yes!