Excretory System

Cellular Level  Involves transport of needed materials into and out of cells

Organ Level  Involves movement of materials through the kidneys  Consists of kidneys, ureters, urinary bladder, urethra  Eliminates waste products from the body in ways that maintain homeostasis

Kidneys  Kidneys remove waste products from the blood, maintain blood pH and regulate the water content of the blood  Kidneys are located near the lower back on either side of the spinal column

Kidneys  Kidneys filter the waste filled blood removing urea, excess water and other waste products  The clean blood returns through the renal vein and into circulation

Kidneys  As the kidney works, purified blood is returned to circulation while urine is collected in the urinary bladder  Urine is stored until it can be released from the body through a tube called the urethra

The Excretory System

Blood Purification  The mechanism of blood purification involves two distinct processes: Filtration Reabsorption

Filtration  Takes place in the glomerulus (small network of capillaries encased in the upper end of the nephron by a hollow, cup shaped structure called Bowman’s Capsule)  The materials that are filtered from the blood are called filtrate  The end filtrate contains water, urea, glucose, salts amino acids & some vitamins

Reabsorption  The process in which liquid is taken back into a vessel  Materials including amino acids, fats & glucose are removed from the filtrate by active transport & reabsorbed into the capillaries (water is returned by osmosis)