Excretion Flashcards
Excretion
removing metabolic waste from the body
metabolic waste
waste produce from metabolism
Carbon dioxide form respiration and urea from deamination
egestion
removal of undigested waste by defamation
deamination
removal of ammonia from amino acids
Respiratory acidosis
Effect of lowered blood pH (excess CO2)
Why must nitrogenous compounds be removed from the body
This is because the body cannot store amino acids, but it would be toxic to excrete them
amino acids store lots of energy
Hepatic Artery
brings oxygenated blood from aorta
25%
Hepatic Portal Vein
Carries blood loaded with the products of digestion straight from the intestine to the liver (75% of the blood)
Hepatic Vein
Connects to inferior vena cava and carries deoxygenated blood back to heart
Sinusoids
connects the hepatic artery to the hepatic vein allowing hepatocytes to remove harmful substances from the blood
Kuppfer cells
Hepatic macrophages that are attached to the walls of the sinusoids
Ingest foreign particles
Recycle old RBC’s
What do hepatocytes do
Relatively unspecialised to carry out many functions
Synthesise proteins (enzymes and hormones)
Transform and store carbs (glycogen)
Synthesise cholesterol and bile salts
Form bile and secrete into bile canaliculi
Absorb substances from blood and also secrete products
Shape of hepatocytes
Cuboidal w/ many microvilli (increases SA for contact w/ sinusoids)
Role of the liver in excretion
Break down excess amino acids and haemoglobin
Detoxifies alcohol
Produces urea
Basic functional unit of liver
Lobule
Protein metabolism in the liver
Protein synthesis of plasma proteins
Deamination to form keto acid and NH2
Transamination to make new amino acids
F ate of keto acids
Kreb’s cycle (respration)
Where does deamination occur
In hepatocytes
Equation of deamination
Amino acid + oxygen —> keto acid + ammonia
Ornithine cycle
2NH3 + ornithine + CO2 (from respiration) —> H2O + urea (circulates in blood until filtered by kidney)
Detoxification of alcohol
Alcohol is broken down by hepatocytes by alcohol dehydrogenase to make ethanal which is further dehydrogenated by ethanal dehydrogenase to make ethanoate
NAD is needed to oxidise and breakdown fatty acids
Uses of ethanoate
Build up fatty acids
Cellular respiration
Ultrafiltration
Afferent arteriole has larger diameter then efferent arteriole
high hydrostatic pressure is generated
endothelium wall of capillary has small pores/ fenestrations
Pressure is higher in the glomerulus then the Bowman’s capsule so fluid is pushed out
3 layers between glomerulus and bowman’s capsule
endothelium: fenestrations
Basement membrane- stops removal of large substances
epithelium of Bowman’s capsule- Podocytes- finger like projections to ensure the passage of substances
glomeruls filtrate
The fluid that filters through from the blood into the Bowman’s capsule
selective reabsorption in PCT
membrane of epithelial cells in PCT actively transports sodium ions out of cytoplasm into the blood via the sodium potassium pump
this lowers the concentration of sodium ions in the epithelial cells so sodium ions diffuse down concentration gradient back into cytoplasm passing through co transporter proteins
each type of the co transporter proteins transports a sodium ion and another substance like glucose or amino acids
which molecules are reabsorbed in the pct
All glucose in the glomerular filtrate is reabsorbed into the blood
This means no glucose should be present in the urine
Amino acids, vitamins and inorganic ions are reabsorbed
The movement of all these solutes from the proximal convoluted tubule into the capillaries increases the water potential of the filtrate and decreases the water potential of the blood in the capillaries
This creates a steep water potential gradient and causes water to move into the blood by osmosis
A significant amount of urea is reabsorbed too
The concentration of urea in the filtrate is higher than in the capillaries, causing urea to diffuse from the filtrate back into the blood
reabsorption of water in the Loop of Henle and other
Descending limb permeable to water
water is removed by osmosis into surrounding tissue
bottom of loop of henle
sodium and chloride ions diffuse out of loop of henley reducing water potential of surrounding tissue
Ascending limb impermeable to water
sodium and chloride ions are actively transported out of loop of henle decreasing water potential of surround tissue in the medulla.
water is removed from urine in collecting duct
water is reabsorbed in the DCT
Haemodialysis
Heparin- stops blood clotting
air bubbles removed before reentering the body
blood form the patients vein is passed through tubes made from partially permeable membranes
on the outside of the tube dialysis fluid flows in the opposite direction which contains same concentration of ions and glucose that the patients blood has
peritoneal dialysis
a peritoneal layers of tissue that lies in abdominal cavity
a catheter is inserted into the peritoneal cavity
dialysis fluid is passed in and left there
remaining fluid is drained of and replaced
kidney transplant negatives and positives
new kidney not recognised as self
different antigens present in kidney causing rejection by immune system
immunosuppressant drugs required
invasive procedure
no longer needs dialysis
all surgeries come wiv risks
osmoregulation
osmoreceptors in hypothalamus detect low concentration of water in blood
ADH is released from posterior pituitary gland
transported to kidney in blood
receptors on collecting duct are complementary to and specific to ADH so bind together
this triggers a cascade of enzyme controlled reactions. whereby water channels called aqua potions form and fuse to membrane
this removed water out of collecting duct and is reabsorbed by the blood
low levels of ADH
cell membrane folds inwards creating new vesicles
these remove aquaporins
urine becomes more dilute
pregnancy test
hCG is complementary shape to monoclonal antibodies
hCG binds to them to form hCG antibody complex which moves up the stick wiv the urine
excess antibodies are carried up with urine and bind to immobilise enzymes in the upper band - control
hCG complex bind to immobilised enzymes in the lower band
how to test for anabolic steroids
using gas chromatography
