Excretion: is the removal of waste products of metabolism formed inside cells WASTE
What happens if wastes remain inside a cell? Accumulation ofWASTE wastes leads to death.
Animals excrete:1. Carbon dioxide + water from: respiration2. Urea, uric acid or ammonia from: deamination In which organ does deamination occur? Liver Which material is broken down to produce urea? Excess proteins
Deamination: breaking down excess amino acids AMINO ACID is broken into two: Part with The rest isnitrogen forms: used for energy AMMONIA UREA
Animals excrete:3. Bile pigments from: decomposition of old and worn out red blood cells Iron in haemoglobin is stored Remaining part of haemoglobin = bile pigments
Plants excrete:1. CO2 and H2O from: respiration2. O2 from: photosynthesis3. Various wastes: when leaves or bark are shed Bark peels off
Four mammalian excretory organs:1. LUNGS excrete CO2 lose water vapour2. KIDNEYS excrete salts, water and nitrogenous products
Four mammalian excretory organs:3. SKIN excretes salts, some urea and water4. LIVER excretes bile pigments
Functions of the kidney1. excretion removes urea2. osmoregulation keeps the blood at a constant concentration
Kidneys have a homeostatic functionHomeostasis – keeping a constant internal environment
Question: SEP, 2012The kidneys play an important role inhomeostasis. Explain this homeostatic roleplayed by the kidneys. (3)Remove urea from the blood. Urea is a waste ofmetabolism that must be eliminated from thebody.Help keep a constant concentration in the bloodby controlling the amounts of water and salts.
Fig. 2 Vertical section through a kidney. Cortex Medulla Renal artery Renal vein Pelvis Ureter
Give six differences betweencomponents found in the renal artery and the renal vein.Renal artery Renal vein188.8.131.52.5.6.
Give six differences betweencomponents found in the renal artery and the renal vein.Renal artery Renal vein1. More O2 Less2. Less CO2 More3. More urea Less4. More glucose Less5. More salts Less6. More water Less
Section through a kidney Renal artery branches into many arteriolesPelvis: urinecollects here; thenflows into ureter
Arterioles continue to branch inside a kidney to form capillariesAORTA A knot of capillaries = glomerulus pelvis
Microscopic slice of kidney tissueBlood pressure forces tissue fluid out of a clumpof narrow capillariesThe fluid contains urea, salts, glucose and othersoluble substancesThe fluid trickles down this tubule and the usefulsubstances such as glucose are reabsorbed into theblood In this tubule more or less water is reabsorbed to maintain the blood concentration Excess water, some salts and urea collect here before passing to the bladder as urine
QUESTION: SEP, 2012The nephron plays an important role inosmoregulation in humans. The following are themain parts of the nephron.Bowman’s capsule; proximal convoluted tubule; Loopof Henle’; distal convoluted tubule and collectingduct.a) Draw a labelled diagram to show the structure of the nephron. Label the main parts clearly. (4)b) Give the function of the Bowman’s capsule and the Loop of Henle’. (4)
What must a person do ifhe/she suffers from kidney failure?
Explain why total kidney failure is fatal if left untreated.The kidney filters wastes like urea from thebloodstream.If wastes remains in the blood, they build upand disturb the internal balance.Death results as accumulated wastes act aspoisons.
Question:A kidney transplant is a more permanenttreatment for kidney failure. Give TWO reasonswhy a patient may be treated with dialysisinstead of a transplant.i) No compatible kidney available / waiting list is longii) Not strong enough for operation / operation has its risks
Water Balance LOSS GAIN1. Sweating 20% 1. In Drinks 60%2. Breathing 16% 2. In Food 28% out3. In faeces 4% 3. Metabolic 12% water4. In urine 60% metabolic water is water formed by chemical reactions such as respiration
A kangaroo rat lives in the desertand never drinks water. List two ways of how it can get water.
Mention three ways how the valuesshown would change on a hot day.