Kidney

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The kidneys are bodily organs with two functions - to filter wastes from the bloodstream and to regulate the acidity of the blood.

In humans the kidneys are the two organs that are located in the posterior part of the abdomen, on either side of the spine.

Each kidney is about 11 cm long and about 5 cm thick, weighing 150 grams in the human adult.

The basic anatomy of the kidney

On the medial aspect of each kidney is an opening, called the hilus, which admits the renal artery, the renal vein, nerves, and the ureter. Within the kidney is a cavity named the renal sinus. Within the renal sinus are the filtration organs called nephrons (containing the filtering unit (glomerulus), its tubule and duct), of which there are more than a million within each kidney. At the top of each kidney is an adrenal gland (also called suprarenal gland).

renal capsule - The membranous covering of the kidney.

cortex - The outer layer over the internal medulla. It contains blood vessels, glomeruli (which are the kidneys' "filters") and urine tubes and is supported by a fibrous matrix.

hilus - The opening in the middle of the concave medial border for nerves and blood vessels to pass into the renal sinus.

renal column - The structures which support the cortex. They consist of lines of blood vessels and urinary tubes and a fibrous material.

renal sinus - The cavity which houses the renal pyramid.

calyces - The recesses in the internal medulla which hold the pyramids. They are used to subdivide the sections of the kidney. (singular - calyx)

papillae - The small conical projections along the wall of the renal sinus. They have openings through which urine passes into the calyces. (singular - papilla)

pyramids - The conical segments within the internal medulla. They contain the secreting apparatus and tubules and are also called malphighian pyramids.

renal artery - Two renal arteries come from the aorta, each connecting to a kidney. The artery divides into five branches, each of which leads to a ball of capillaries. The arteries supplie (unfiltered) blood to the kidneys. The left kidney receives about 60% of the renal bloodflow.

renal vein - The filtered blood returns to circulation through the renal veins which join into the vena cava.

renal pelvis - Basically just a funnel, the renal pelvis accepts the urine and channels it out of the hilus into the ureter.

ureter - A narrow tube 40 cm long and 4 mm in diameter. Passing from the renal pelvis out of the hilus and down to the bladder. The ureter carries urine from the kidneys to the bladder.

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