chapter 13 Flashcards
Describe excretion and organs involved in it
The removal of waste substances of metabolic reactions, toxic materials and substances in excess of requirements
Organs:
lungs : excrete carbon dioxide, water vapour
Kidney : excrete urea, excess water and ions
Liver: produces urea
Why is excretion needed , in terms of carbon dioxide ad urea
Carbon dioxide :
easily dissolves in water to form acidic solution, which lowers pH of cells, reducing enzyme activity that are essential
Urea also very toxic in high concentrations
State and describe the main structures involved in the excretory system a
Kidney - two bean shape that filters blood to remove toxic waste
Renal artery - carry oxygenated blood to kidney , contains high concentration of waste and urea
Renal vein - Carry deoxygenated blood, contains low concentration of waste and urea
Ureter- tube connecting kidney to bladder
Bladder- organ that stores urine
Urethra - tube that connect bladder to exterior, where urine and semen released
Describe the parts of the kidney and its functions
Cortex
Medulla
Functions:
- regulate water content of the blood for maintaining blood pressure
- excrete toxic waste products of metabolism and substances in excess
Outline the structure and functions of nephrons and its blood vessels
Nephron starts in cortex, loops down into medulla and back up
Process 1 : Ultrafiltration
Glomerulus inside Bowman’s capsule . Smaller molecules are forced out of the capillaries and into Bowman’s capsule
Capillaries get narrow which increases blood pressure forcing small molecules out.
E.g : Glucose, water, salt, urea, amino acids
Process 2: Selective Reabsorption
1. Glucose only reabsorbed at proximal convoluted tubule by active transport ( nephrons adapted by having a lot of mitochondria
- Salts reabsorbed at Loop of Henle by diffusion and active transport
- Water reabsorbed at Loop of Henle and collecting duct by osmosis
- urea not reabsorbed , but excreted
Describe the role of liver in excretion and assimilation
Excess amino acids cannot be stored, so broken down by process , deamination ( removal of nitrogen containing part of amino acids to form urea )
Enzymes in liver split up amino acid molecules ( carbon into glycogen and stored. Nitrogen into ammonia and then urea )
Urea dissolved in blood and taken to kidney to be excreted
state the consequences of high urea levels
- cell death
- reduced response to insulin, leading to diabetics
- deposits inside blood vessels