Excretory system for urine and the wastes it carries
Function of the urinary system
1. Extracts wastes from the bloodstream
2. Converts them to urine
3. Transports and eliminates urine
Kidneys
Bean-shaped organs located at the back of the abdominal cavity, lying on each side of the spinal column just above the waistline
Layers surrounding each kidney
True capsule (smooth, fibrous membrane adhering to the kidney surface)
Perirenal fat (adipose tissue surrounding each kidney)
Renal fascia (fibrous tissue that anchors the kidney to surrounding structures)
Hilum
Notch in the concave area of the kidney where the renal artery, renal vein, nerves, and lymphatic vessels enter and leave, and the ureter widens into the renal pelvis
Renal cortex
Outside portion of the kidney
Renal medulla
Inside portion of the kidney
Nephrons
Structural and functional units of the kidney, each containing a Bowman's capsule and a glomerulus
Each kidney contains about 1 million nephrons
Glomerulus
Part of the nephron that filters approximately 1,000 ml of blood per minute
The waste is mixed with water to create urine: 5% solids in 95% water
Substances removed by the nephron
Urea
Uric acid
Creatinine
Excess sodium
Excess chloride
Excess potassium ions
Ketone bodies
Ureter
Narrow, muscular tube about 11 inches in length and 3/8 inch in diameter, with 3 layers: inner mucous membrane, middle smooth muscle, and outer fibrous tissue
Bladder
Muscular, membranous sac that serves as a reservoir for urine, with an apex, neck, and triangular trigone near the base
An adult feels the need to void when the bladder contains about 300 ml or 1 ¼ cups
An average of 1,000 ml of urine is voided daily
Urine is clear to light yellow in color with a faint odor and slightly acidic pH
Bladder wall
Inner mucous layer, outside fibrous layer, and two inner muscle layers that thin and expand as the bladder fills with urine
Urethra
Extends from the bladder to the outside opening of the body, about 7.8" long in males and 1.2" long in females, transporting both urine and semen in males, only urine in females
Urinalysis
Laboratory procedure involving the physical, chemical and microscopic examination of a urine sample
Changes occur as urine is left standing, so the urinalysis is performed within one hour of voiding
Catheterization
Insertion of a plastic tube through the urethra into the bladder for free and complete drainage of urine, using a Robinson catheter for temporary placement or a Foley catheter with a balloon tip for longer-term use
Urinary incontinence
Loss of bladder control, ranging from leakage to uncontrollable wetting, becoming more common with age, caused by weak bladder muscles (stress incontinence) or overactive bladder, as well as prostate problems and nerve damage