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Urinary System
Anatomy and Physiology
Functions of Urinary System
• Regulate the volume, composition, and pH of body fluids
• Remove or add substances to the blood
• Form urine
Organs of the Urinary System
• Two kidneys• Two ureters• Bladder• urethra
Kidneys
• Reddish brown; bean shaped on the posterior wall of the abdomen
• Inner region is the medulla; outer region is the cortex
• Nephrons are the working units
Ureters
• Tubes which drain the urine from the kidneys to the bladder
• Peristalsis moves the urine from the kidney to the bladder
• Can become inflamed in a urinary tract infection
ureter
Bladder
• Hollow muscular organ
• Stores urine• At the neck is the
internal urethral sphincter muscle
• Can become inflamed in a urinary tract infection
Urethra
• Tube that takes the urine from the bladder to the outside
• Can become inflamed in a urinary tract infection
• Delivers both urine and semen in males
Urethra
Regulating substances and forming urine
• The nephrons of the kidneys filter the blood
• This means they remove substances from the blood
• The removed substances are called filtrate
• If these substances stay in the tubes of the urinary structures, they will be part of the urine and excreted
Regulating substances and forming urine
• The nephrons filter out some things we still need
• Part of the nephron’s job, then, is to put these wanted substances back into the blood
• Putting them back into the blood is called reabsorption
• This happens as the filtrate moves through the nephron structure
Nephron
Nephron
One million nephrons in each kidney
Glomerulus
Glomerulus:
This is the filter.
Reabsorption
• Different substances are reabsorbed back into the bloodstream at specific locations along the nephron tubules.
• Some areas of the wall are more permeable to certain substances
Secretion
• Sometimes, to adjust the blood and the filtrate for homeostasis, certain substances are added back into the tubule
• This is called secretion
Dilute versus Concentrated
• Dilute urine contains lots of water, and not many dissolved particles. Light color
• Concentrated urine contains very little water, and lots of dissolved particles. Dark in color. Dehydrated!
• Kidneys make adjustments to the blood, which results in the composition of urine