EXCRETION Flashcards
what is excretion
the removal of waste product
what are some waste product?
co2, urea, nitrogen containing compounds, bile fragments
what are the excretory organs?
lungs, liver, kidney and skin
why is excretion important?
because otherwise toxic product will build up altering the ph and therefore preventing the normal functioning of enzymes which may lead to death
in which form is carbon dioxide transported after production?
as carbonic acid since co2+h20= h3co3
what happens to the carbonic acis (H3CO3)
it dissociated it=nto h ions and HCO-3
what happens with the H ions released afterwards?
1 Bind with haemoglobin = HAEMOGLOBINIC ACID
haemoglobin 3d SHAPE IS CHANGED REDUCING ITS AFFINITY FOR O2
- affect pH
what happens to co2 that is not converted into hydrogencarbonate?
it bind with haemoglobin to form carbaminohaemoglobin
what happens when there is excess H+?
what happens when excess H+ are detected?
how do cell resist to pH change?
it reduces the pH
it is detected by the respiratory system which leads to an increasing breathing rate in order to remove co2
proteins act a s abuffer to resist pH change.
deamination process and what is the formula
is the process by which the toxic amino group in amino acid is removed.
amino acid + oxygen –> keto acid and ammonia
what happens to the ammonia produced during deamination?
it is converted into urea.
ammonia + co2 = urea + water
describe the liver.
1.made of HEPATOCYTES
2.composed of HEPATIC LOBULES and divided into LUBULES
3. the liver is connected to the heart and small intestine
what are the veins/arteries that connects liver to heart?
hepatic artery -rich of O2 and poor in nutrients
hepatic vein - poor in o2
what is the vein that connects the liver with the small intestine?
hepatic portal vein - poor in 02 and rich in nutrients, waste products
explain what you can find in a lobule
1 hepatic artery
2 hepatic portal vein
3 bile duct
4 hepatic vein (at the centre)
5 Kupffer cells - kill and recycle old rbc
6 sinusoid - gap between hepatocytes where hepatic artery, hepatic portal vein blood is mixed
7 hepatocytes - liver cells that release waste product and intake nutrients from blood
what are the main liver functions?
- storage of glucose - in the form of glycogen
- detoxification of harmful substances
3 detoxification of alcohol
4 urea formation
5 fat metabolism - fat conversion into fatty acids
6 cholesterol production
7 bile production
8 vitamin storage
9 plasma protein synthesis
10 haemoglobin breakdown
how does detoxification of harmful substances occur?
how are toxins rendered less harmless?
what are some enzyme that render product less toxic ?
ethanol –> ethanal –> acetate + CoA
by oxidation, reduction and methylation process
CATALASE = Hydrogen peroxide into water and oxygen
CYTOCHROME P450 = breakdown drugs
how does detoxification of alcohol occur?
ethanol –> ethanal –> ethanoic acid –> acetylCoA
how is urine produced?
describe the 2 processes
by DEAMINATION (liver) and ORNITHINE CYCLE (liver)
DEAMINATION:
- removal of the amino group
- ammonia + keto acid produced
-ammonia enters the ornithine cycle
-keto acid broken down into lipids and cholesterol
ORNITHINE CYCLE:
- process by which ammonia is rendered less toxic
ammonia + co2 –> CITRULINE + H2O –> CITRULINE + ammonia –> ARGININE + H2O –> ARGININE + H2O = urea.
what is the kidney function?
blood filtration
kidney components
capsule
renal cortex
medulla (has pyramids)
pelvis
nephrons
ureter
renal artery
renal vein
what is the functional unit of kidney and does it do?
NEPHRONS - filters blood and reabsorb useful material before eliminating it in urine
nephrons structure
glomerulus
proximal convulated tubule
distal convulated tubule
Loop of Henle
descending limb
ascending limb
collecting duct
how does filtration occur?
ultrafiltration
selective reabsorption
reabsorption of water
osmoregulation
what is the glomerulus function and describe it
ultrafiltration - blood enters the glomerulus from the afferent arteriole at high hydrostatic pressure, which causes small molecules (amino acids and ions) to be pushed out of the capillaries through fenestration present in the endothelium, in the Bowman’s capsule.
what is the fluid created by the substances that are being pushed out?
BLOOD PLASMA / glomerular filtrate which contains: water amino acids vitamins and inorganic minerals
what is the barrier that enables filtration? what are the components?
the endothelium of the capillary - presence of fenestration which allows small molecules to pass out of the capillary
the basement membrane - consist of a fine mesh of collagen fibres and glycoproteins, acts as a filter to prevent the passage of big molecules
the epithelial cells of Bowman’s capsule - podocytes (finger like projections called major processes on which minor processes can be found), projections ensures that there r gaps between cells.
where does selective reabsorption occur?
in the proximal and distal convulated tubule
what increases the efficiency of selective reabsorption of cells in PCT?
microvili of cells
highly folded
cotransport protein
mithocondria
walls of PCT are 1 cell thick to allow short diffusion distance
how does selective reabsorption occur?
Na+ ion are actively transported out of the epithelial cell into the capillary, this causes a concentration gradient between epithelial cell and tubule lumen.
Due to this concentration gradient, Na+ diffuse in the epithelial cell via CO-TRANSPORT protein, Na+ enters the epithelial cell in addition to glucose and amino acids.
Finally, glucose can diffuse from PCT to capillary and blood stream.
where does water reabsorption occur?
loop of Henle
how does reabsorption of water occur?
Na+ and Cl- are actively pumped out the ascending limb increasing the ions concentration in the tissue fluid and lowering the water potential.
This causes water to diffuse out by osmosis from the descending limb
Ions concentration in the limb decrease as we go down the loop.
what are the properties of the ascending and descending limb
descending limb = permeable to water and impermeable to ions
ascending limb = impermeable to water and permeable to ions
what happens after the loop of henle process?
tissue fluid goes in the distal convulated tubule and here mineral ions adjusment occurs through active transport and then goes in the collecting duct.
what happens in the collecting duct?
osmoregulation
desscribe osmoregulation
is the regulation of water and salt level in the body
what is the kidney capable to do based on water concentration/demand in the body?
alter the permeability of the collecting duct so:
less water demand –> less water conservation –> less permeable wall –> less reabsorption –> more urine produced and less concentrated
how is the permeability controlled ?
by the hormone ADH
how does ADH affect permeability of collecting duct?
by inserting more aquaporins into the membrane of the collecting duct. These aquaporins allow water to be reabsorbed into the capillaries. As a result the urine passed out increases in concentration
Collecting duct cells contain vesicles, the membranes of which contain many aquaporins
ADH molecules bind to receptor proteins, activating a signalling cascade that leads to the phosphorylation of the aquaporin molecules
This activates the aquaporins, causing the vesicles to fuse with the luminal membranes of the collecting duct cells
This increases the permeability of the membrane to water
describe the process of osmoregulation?
osmoreceptors detects changes in the water potential.
if low water potential –> osmorecetors loose water and shrink –> detected by neurosecretory cell and causes their stimulation IN THE HYPOTHALAMUS –> causes release of ADH –> act on the collecting duct increasing its permeability to allow more reasorption of water
pregnancy test
urine passes through the reaction centre
reaction site contains free antibodies with dye enzymes attaches
hCG hormone from urine binds to free antibody with dye enzyme attached in the reaction centre
free antibody which has formed a complex with hCG binds to fixed hCG in the test site
free antibodies which have not formed a complex with hCG bind to fixed antibodies in the control site
blue dye appears in the control and test sites, which shows positive result
what happens to ADH after its function?
ADH is ultra filtrates from blood since it s small molecule, Ash is not completely reabsorbed therefore is excreted in urine
longer loops of henle
- more water reabsorption form collecting duct
- more Na+ and K+ pumped out of ascending limbs
