excretion

definition of excretion

excretion is the removal of metabolic waste products from the body

importance of excretion

to prevent accumulation of metabolic waste products that can be toxic to the body in high concentrations

examples of metabolic waste products

carbon dioxide, urea and water

which reaction produces carbon dioxide, which organ removes it, and how is it excreted?

aerobic respiration, lungs, gas in expired air

which reaction produces urea, which organ removes it, and how is it excreted?

deamination, kidney, component of urine

which reaction produces water, which organ removes it, and how is it excreted?

aerobic respiration, kidney, main component of urine. OR skin, main component of sweat. OR lungs, water vapor in expired air.

parts of the human urinary system

renal artery, renal vein, kidney, ureter, bladder, urethra

what is urea?

urea is a metabolic waste product that is produced by the liver though the process of deamination.

how is urea formed?

proteins we eat in food are digested as amino acids, which is being used by the body to grow and repair body tissue. excess amino acids are transported to the liver where they undergo a process called deamination (removal of nitrogen groups) to form urea. urea is a metabolic waste product produced in the liver and removed by the kidneys.

what is the pathway taken by urea?

urea produced by the liver is released into the blood, which travels through the hepatic vein and the vena cava to reach the heart, it then travels through the right atrium to the right ventricle to the pulmonary artery, then through the pulmonary vein to the left atrium to the left ventricle to the aorta. it is pumped of the heart into the renal artery of the kidneys

what 2 processes are involved in urine formation?

ultrafiltration and selective reabsorption

ultrafiltration process?

ultrafiltration occurs at the Bowman’s Capsule, where the afferent arteriole is wider than the efferent arteriole, causing higher blood pressure in the glomerulus, which causes high hydrostatic pressure which forces water and other small molecules through the partially permeable glomerular capillary wall and basement membrane into the Bowman’s Capsule. filtrate is formed in the Bowman’s Capsule.

what are these small molecules involved in ultrafiltration?

glucose, amino acids, excess mineral salt ions and metabolic waste products (urea!). all these are passed out in the filtrate

what are these larger molecules involved in ultrafiltration?

plasma proteins, blood cells. they cannot pass through the glomerulus and remains in the blood in the glomerular capillaries.

selective reabsorption process?

selective reabsorption occurs at the proximal convoluted tubule, where useful substances are reabsorbed from the FILTRATE into the blood and the remaining fluid passes out of the collecting duct as urine.

what are the useful substances involved in the selective reabsorption?

glucose, amino acids, some mineral salt ions and some water. all glucose, amino acids and some mineral salt ions are reabsorbed via diffusion and active transport (requiring energy!). some water are reabsorbed via osmosis.

what item is not filtered out of blood during ultrafiltration?

proteins!