Renal physiology

This filtrate then flows along the length of the nephron, which is a tubular structure lined by a single layer of specialized cells and surrounded by capillaries.

This is performed at the microscopic level by many hundreds of thousands of filtration units called renal corpuscles, each of which is composed of a glomerulus and a Bowman's capsule.

Substances, generally produced by body or the by-products of cell metabolism that can become toxic in high concentration, and some drugs (if taken).

Calcitriol, the activated form of vitamin D, promotes intestinal absorption of calcium and the renal reabsorption of phosphate.

Outside the range of pH that is compatible with life, proteins are denatured and digested, enzymes lose their ability to function, and the body is unable to sustain itself.

Abnormal ranges of the fractional excretion of sodium can imply acute tubular necrosis or glomerular dysfunction.

Two organ systems, the kidneys and lungs, maintain acid-base homeostasis, which is the maintenance of pH around a relatively stable value.

Any significant rise in plasma osmolality is detected by the hypothalamus, which communicates directly with the posterior pituitary gland.

There are two systems that create a hyperosmotic medulla and thus increase the body plasma volume: Urea recycling and the 'single effect.'

This allows urea to leave the collecting duct into the medulla, creating a hyperosmotic solution that "attracts" water.

This allows for a countercurrent exchange system whereby the medulla becomes increasingly concentrated, but at the same time setting up an osmotic gradient for water to follow should the aquaporins of the collecting duct be opened by ADH.

This primarily occurs through maintenance of the extracellular fluid compartment, the size of which depends on the plasma sodium concentration.

Each hormone acts via multiple mechanisms, but both increase the kidney's absorption of sodium chloride, thereby expanding the extracellular fluid compartment and raising blood pressure.

[15] A simple means of estimating renal function is to measure pH, blood urea nitrogen, creatinine, and basic electrolytes (including sodium, potassium, chloride, and bicarbonate).