Kidney
Say it: KID-nee
The kidneys are two bean-shaped organs that filter the blood to make urine, balancing the body's water, salts and acid and helping set blood pressure.
Also: kidneys
Definition
What are the kidneys?
The kidneys are a pair of bean-shaped organs, each roughly the size of a fist, that sit against the back wall of the abdomen on either side of the spine, just below the rib cage. Each has an outer cortex, an inner medulla arranged in cone-shaped pyramids, and a funnel called the renal pelvis that drains urine into the ureter.
The working units are microscopic nephrons, about a million in each kidney. In every nephron a tuft of capillaries, the glomerulus, filters water and small molecules out of the blood, and a long tubule then reclaims what the body needs and adds further wastes. Only a small fraction of the filtered fluid leaves as urine. At rest, the kidneys receive about a quarter of all the blood the heart pumps.
Besides removing urea and other wastes, the kidneys keep sodium, potassium, calcium and acid levels steady. They also act as endocrine organs: they help regulate blood pressure, release erythropoietin, the hormone that prompts the marrow to produce red blood cells, and activate vitamin D for healthy bones. Clinicians track how well the kidneys work with the glomerular filtration rate.
Word parts
Where does the word “kidney” come from?
- nephr-
- kidney; used in words such as nephron and nephrologyGreek nephros
- ren-
- kidney; the source of the adjective renalLatin renes (kidneys)
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Terms that go with it
- NephronA nephron is the microscopic functional unit of the kidney, which filters blood and then adjusts the filtered fluid to form urine.
- Glomerular filtration rateGlomerular filtration rate is the volume of fluid both kidneys filter out of the blood each minute, the standard measure of kidney function.
- HomeostasisHomeostasis is the body's ability to keep internal conditions, such as temperature, blood glucose and pH, steady while conditions around it change.
- Blood pressureBlood pressure is the force that circulating blood exerts on the walls of the arteries, recorded as systolic over diastolic pressure in mm Hg.
- Red blood cellA red blood cell, or erythrocyte, is a disc-shaped blood cell without a nucleus that is packed with hemoglobin and carries oxygen around the body.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Anatomy and Physiology 2e, 25.3 Gross Anatomy of the Kidney
- NIDDK: Your Kidneys and How They Work
- NCI Dictionary of Cancer Terms: kidney
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