Excretion 5.2 Flashcards
why is excretion important?
important in maintaining metabolism
what is excretion?
process by which excess toxic waste products of metabolism are removed from the body
give examples of excretory organs
lungs,kidney,liver and skin
what is metabolic waste made of?
carbon dioxide
nitrogenous waste
urea
water
salts
ammonia
mammals produce urea, fish and birds/insects produce..?
fish- ammonia
birds and insects- uric acid
what is bile pigments?
breakdown of haemoglobin from old red blood cells in the liver
they colour the faeces
what is urea made of?
undigested food and fibre
how does the skin act as an excretory organ?
sweat contains salts, urea, water, uric acid and ammonia
what happens if products of metabolism build up in the body?
build up of CO2 and NH3 is toxic
this can interfere by altering the pH or act as inhibitors and reduce the activity of enzymes
what is the role of the liver
breakdown of unwanted or toxic substances and the production of excretory waste,
what are hepatocytes?
liver cells
contains a nuclei, golgi apparatus, folded membrane and mitochondria
what is the difference between the hepatic artery and hepatic vein
hepatic a - receives oxygenated blood from the heart ( smaller than v bcs carries only 30% blood)
hepatic v - brings deoxygenated blood back to heart (bigger bcs carries 70%)
describe the internal structure of the liver
. hepatocytes
. lobes -> lobules (connective tissue)
. sinusoids ( wide capillaries)
. branch of hepatic vein ( drains blood away from lobule)
. kupffer cells
. bile caniculli
function of the bile caniculli?
where bile is produced and secreted
drains it into the bile duct which then brings it to the gall bladder to be stored
why might blood in the hepatic portal vein contain toxins
after digestion of alcohol, blood from the intestine contains toxins
what are the functions of liver
storage of glycogen
detoxification
formation of urea
explain the role of the liver in storing glycogen
hepatocytes are involved in converting glucose into glycogen
glycogen can be broken down to release glucose into the blood
explain how detoxification works on hydrogen peroxide (substance in the liver)
catalase breaks down hydrogen peroxide into oxygen and water (by-product)
what happens when too much alcohol is taken
cirrhosis
explain how detoxification works on alcohol
ethanol, broken down by hepatocytes into ethanal then to acetic acid which is less harmful
what does NAD do
breakdown fatty acids used in respiration
what happens if NAD is used up
breakdown of fatty acids is no longer possible
FA converted back to lipids
builds up in liver and can cause hepatitis or cirrhosis
describe AA in the liver
excess amino acids cant be stored in the body as their amino group make them toxic
they cant also be excreted as a whole because theyre full of lots of energy
so, excreted via deamination
what is deamination
removal of an amino group from the amino acid leaving ammonia
describe ammonia in the liver
very toxic and insoluble , quickly converted in to urea which is less soluble and less toxic
what are the products of deamination?
ammonia and keto acid
function of kupffer cells
attached to the walls of the sinusoids, remove bacteria and break down old RBC​
what is the function of the hepatic portal vein
brings products of digestion from small intestine to liver so that any harmful substances can be filtered out and destroyed before digestion
what are the kidney tubules called
nephron
what does the nephron consist of
- bowman’s capsule
- glomerulus
- proximal and distal convoluted tubule
-loop of henle - collecting duct
what does the filter barrier consist of
endothelial and epithelial cells
basement membrane
function of bowman’s capsule
contains the glomerulus and where ultrafiltration takes place
function of glomerulus
knot of capillaries where pressure forces all the solutes in the blood plasma to the Bowman’s capsule
function of endothelium cells of filter barrier
gaps, allow dissolved substances/ blood plasma to pass capillary
function of basement membrane of filter barrier
prevents large molecules and proteins from entering
function of epithelial cells of filter barrier
podocytes, gaps between cells to let blood pass through lumen of Bowman’s capsule
what is ADH?
hormone
constricts blood vessles
helps the kidneys control the amount of water and salt in the body
what is ultrafiltration
the process of filtration of blood from the glomerulus into the Bowman’s capsule because of increased glomerular blood pressure
describe the process of ultrafiltration (6 marks)
- Blood flows into glomerulus through the afferent arteriole, that carries the blood away​
- The afferent arteriole is wider than the efferent arteriole ​
- The difference in diameter ensure that blood in the capillaries of glomerulus maintains a pressure higher than the Bowman’s capsule​
- This pressure difference pushes fluid from the blood into the Bowman’s capsule​
what is filtered out of the blood
?
Water​
Amino acids​
Glucose ​
Urea​
Ions
describe the process of selective reabsorption (6 marks)
- Na+ ions are pumped out of the cells actively
- conc. of Na+ ions in cytoplasm decreases creating a concentration gradient
- Na+ ions diffuse into cell through a cotransport protein - carrying glucose or an AA at the same time
- Water moves into cell by osmosis
- Glucose/AA diffuse into blood
how are the cells needed in reabsorption specialised? (4 marks)
microvilli – increases surface area for reabsorption
Cytoplasm, lots of mitochondria to release ATP ​
What is osmoregulation
the control of water potential in the blood​
how does ADH change the water content of the blood when it is too low or high?
: Blood ADH levels rises when dehydrated​
water potential​drops
Detected by osmoreceptors in the hypothalamus ​
The posterior pituitary gland is stimulated to release ADH into the blood​
DCT walls and collecting duct walls are more permeable, so more water is reabsorbed into the blood by osmosis​
highly concentrated urine produced so less water lost​
: When blood ADH levels fall when hydrated, vice versa occurs​
state 2 things that lead to kidney failure
(4 marks)
infections
high blood pressure
describe what could happen to the body due to kidney failure
3 things
.Waste products to build up - weight loss and vomiting​
. Anemia
. Imbalance of electrolytes - brittle bones​
what is renal dialysis?
when the patient’s blood is filtered
what is a kidney transplant? ( 4 marks )
new kidney to replace damaged kidney.​
New kidney must have same blood and tissue type​
Y: cheaper than dialysis​
N: organ rejection
what are steroids and what are the negatives?
Anabolic steroids are drugs that builds up muscle tissue​
Athletes are banned from taking these, as it is unfair and has dangerous side effects like liver damage
