Excretion (only key points so refer to notes) Flashcards
Excretion
removal of metabolic waste from the body
metabolic waste
substances produced in excess by metabolic processes in cells
main excretory products
carbon dioxide from respiration
nitrogen containing compounds like urea
bile pigments found in faeces
__________ is a substance that passes into _____ for excretion with faeces.
bilirubin
bile
what does the liver do?
converts excess amino acids to urea
what is the breakdown of amino acids called?
deamination
what substances does the skin excrete in sweat?
salts, urea, water, uric acid, ammonia
but water and salts are more to do with homeostasis not excretory products
how does carbon dioxide form hydrogen ion?
carbon dioxide + water ——> carbonic acid
carbonic acid dissociates to hydrogen ions and hydrogencarbonate ions
What do hydrogen ions affect?
what other substances reduce oxygen transport?
pH - bonds - haemoglobin shape - affinity for oxygen - oxygen transport
structure of other proteins that help transport substances
haemoglobinic acid
carbamonihaemoglobin
What does the body do to deal with H ions?
small change in pH - hydrogen ions detected by respiratory centre in medulla oblongata of brain - increases breathing rate to remove more carbon dioxide
respiratory acidosis
change in blood pressure by diseases, conditions that affect lungs
Briefly, what happens to excess amino acids?
toxic amino group removed (deamination)
amino group forms ammonia (very soluble, highly toxic)
amino acid + oxygen —–> ammonia + keto acid
ammonia + carbon dioxide —–> urea (less soluble, less toxic) + water
urea transported to kidneys for excretion
keto acid used in respiration or converted to carbohydrate/fat for storage
what does the hepatic artery do?
what does the hepatic portal vein do and what’s in the blood that is carries?
hepatic vein?
supplies oxygenated blood from aorta to liver for respiration
deoxygenated blood from digestive system, rich in products of digestion, blood contains toxic compounds absorbed from intestine so concentration of substances needs adjusting
blood leaves to vena cava to normal body circulation
Bile duct
bile function?
carries bile to gall bladder to be stored until required for digestion of fats in small intestine
bile contains excretory products - bile pigments like bilirubin that leaves in faeces
liver is divided into ________ which divided into __________.
lobes
lobules
inter-lobular vessels
smaller vessels from hepatic artery/hepatic portal vein
run between and parallel to lobules
what happens when blood enters lobules from inter-lobular vessels?
blood mixed passes to sinusoid (close contact with liver cells, they line it, remove/return substances from/to blood)
Kupffer cells
specialised macrophages that breakdown and recycle RBC
what is the product of haemoglobin breakdown?
bilirubin
features of hepatocytes
simple cuboidal shape
microvilli on surface
cytoplasm dense (many metabolic functions)
metabolic functions of liver
controls blood glucose levels, amino acid levels, lipid levels
synthesises bile, plasma proteins, cholesterol, RBC in fetus
stores vitamins, iron, glycogen
breaks down hormones
detoxifies alcohol and drugs
destroys RBC
how are toxins rendered harmless?
oxidation, reduction, methylation, combine with molecules
what does catalase do?
catalyses breakdown of hydrogen peroxide to oxygen and water
what does cytochrome P450 do?
breakdown drugs and in electron transport (respiration)
role in metabolising drugs can interfere with other metabolic roles which causes side effects
fatty liver
liver detoxify lots of alcohol, uses NAD so less to breakdown fatty acids so converted back to lipids and stored as fats in hepatocytes
renal artery
renal vein
supplies kidney with blood
drained out
nephrons
functional unit of kidney
tiny tubules
glomerulus
knot of capillaries in Bowman’s capsule
fluid from the blood passes into the Bowman’s capsule by___________________ which is…….
ultrafiltration
filtration of blood at molecular level under pressure
3 layers between blood in capillary and lumen of Bowman’s capsule
endothelium of capillary
basement membrane
epithelial cells of Bowman’s capsule (podocytes)
endothelium of capillary
narrow gaps between cells of endothelium of capillary walls
cells contain pores called fenestrations where blood plasma can pass out capillary
basement membrane
fine mesh of collagen fibres and glycoproteins
prevents molecules with relative molecular mass greater than 69000 passing
podocytes
finger-like projections (major processes) on each are minor/foot processes
hold cells away from endothelium of capillary
ensure gaps between cells so fluid can pass between to lumen on capsule
afferent arteriole is _______ than the efferent so ___________________
wider
ensures blood in capillaries of glomerulus maintains higher pressure than in Bowman’s capsule
pressure difference pushes fluid from blood to lumen
what happens at the proximal convoluted tubule?
selective reabsorption of 85%
reabsorb all sugars, most mineral ions, some water
how are cells lining the proximal convoluted tubule specialised?
cell surface membrane in contact with tubule fluid, highly folded (microvilli) so increase SA
membrane contains cotransporter proteins that transport glucose/amino acids in association with sodium ions from tubule into cells lining it.
opposite membrane close to tissue fluid and blood capillaries is also highly folded to increase SA
this membrane contains sodium/potassium pump to pump sodium ions out cell and potassium in
cytoplasm dense with many mitochondria
how does selective reabsorption occur?
sodium pumped out cells lining tubule so conc. decreases in cells and creates gradient
sodium ions from tubule associated with glucose/amino acids diffuse to cells through cotransporter proteins
water potential decreases in cells so water from tubule to cell by osmosis
glucose/amino acids diffuse into blood
osmoregulation
control of water potential in the body
ADH
antidiuretic hormone
invaginates
membrane folds inwards when low levels of ADH
so creates new vesicles that remove aquaporins from membrane
adjusting ADH
water potential low so osmoreceptors in hypothalamus lose water by osmosis and shrink, activate neurosecretory cells (nerve cells) in hypothalamus
neurosecretory cells produce and release ADH, moves down axon to terminal bulb in posterior pituitary gland
stored in vesicles
when cells stimulated, AP down axon and release ADH by exocytosis
ADH to capillaries act on collecting duct
glomerular filtration rate
rate fluid enters nephron
renal dialysis
artificially regulate concentrations of solutes in blood
blood passes over partially permeable dialysis membrane and exchange occurs between blood and dialysis fluid
haemodialysis
blood from artery/vein pass into machine artificial dialysis membrane shaped into capillaries heparin added to avoid clotting counter current flow blood returned to body via vein
peritoneal dialysis
dialysis membrane in own abdominal membrane (peritoneum)
permanent tube in abdomen, dialysis solution poured through, used solution drained out
hCG
human chorionic gonadotrophin
pregnancy tests use…..
monoclonal antibodies (made from 1 cell, specific to 1 molecule)
