excretion in humans

• Excreted through the lungs and dissolved in the blood plasma

• Urine passes from the kidneys, to the ureters and to the bladder where it is stored temporarily • When the bladder becomes full, the urethra carries the urine from the bladder to outside the body

• Composed of urea, excess water and ions excreted by the kidneys

• Assists the body in taking up amino acids for cellular use • The liver can convert amino acids into fibrinogen and other plasma proteins • Breaking down excess amino acids • Excess amino acids are converted into urea in the liver (deamination)

cortex renal vein renal artery medulla ureter

outer part where blood is filtered and some selective reabsorption happens

inner part where some selective reabsorption happens and fluid is collected to form urine

carries urine to the bladder

• Main functional unit of the kidney • Filters the blood - separating waste and returning substances that are needed back to the bloodstream • Consists of the glomerulus and the tubule

Glomerulus: - Network of capillaries - Place where blood is filtered under pressure (called ultrafiltration) - Water, glucose and ions leave the capillaries and enter the tubule. Protein molecules are too big so they stay in the blood.

Tubule: - Where selective reabsorption of substances occurs - Substances such as: - All of the glucose - Most of the water - Some ions