Renal system

BruceBlaus / CC BY-SA

The renal system works with the urinary system to collect the body’s waste products and expel them as urine. The renal system includes:
• kidneys
• ureters
• urinary bladder
• urethra.

Kidneys
• Located on each side of the abdomen near the lower back
• Work with the urinary system to collect the body’s waste products and expel them as urine
• Filter about 45 gallons of fluid each day

Ureters
• Muscular tubes that contract rhythmically to transport urine from each kidney to the bladder

Urinary bladder
• A sac with muscular walls that collects and holds urine that’s expelled from the ureters every few seconds

Urethra
• A narrow passageway from the bladder to the outside of the body through which urine is excreted

How the kidneys perform
Vital functions that the kidneys perform include:
• maintaining fluid and acid-base balance and regulating electrolyte concentration
• detoxifying the blood and eliminating wastes
• regulating blood pressure
• aiding red blood cell (RBC) production
• regulating vitamin D and calcium formation.

Controlling fluid balance
• Antidiuretic hormone, produced by the pituitary gland, controls the concentration of body fluids by altering the permeability of the kidneys.
• Aldosterone, produced by the adrenal cortex, regulates water reabsorption by the distal tubules by increasing sodium reabsorption.

Regulating acid-base balance
To regulate acid-base balance, the kidneys:
• secrete hydrogen ions
• reabsorb sodium and bicarbonate ions
• acidify phosphate salts
• produce ammonia.

Collecting and eliminating waste
The kidneys collect and eliminate wastes from the body by:
• filtering blood flowing through the glomeruli
• reabsorbing filtered fluid through the tubules
• releasing the filtered substance from the tubules.

Regulating blood pressure
The kidneys help regulate blood pressure by:
• producing and secreting renin in response to a decline (actual or perceived) in extracellular fluid volume.

Producing RBCs
The kidneys aid in the production of RBCs by:
• secreting erythropoietin (a hormone that prompts increased RBC production) when the oxygen supply in tissue blood drops
• producing active vitamin D and regulating calcium balance and bone metabolism.

How renal disorders develop
• Acute renal failure — sudden interruption of renal function caused by obstruction, poor circulation, or kidney disease.
• Acute tubular necrosis — destruction of the tubular segment of the nephron, causing renal failure and uremia.
• Benign prostatic hyperplasia — enlarged prostate gland that compresses the urethra and causes urinary obstruction.
• Chronic renal failure — irreversible deterioration of tissue and eventual loss of kidney function. • Glomerulonephritis — bilateral inflammation of the glomeruli, commonly following a streptococcal infection.
• Hydronephrosis — abnormal dilation of the renal pelvis and the calyces of one or both kidneys.
• Prostatitis — inflammation of the prostate gland.
• Renal calculi — substances that normally dissolve in the urine precipitate to form “kidney stones.”