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