excretion

excretion

toxic waste products of metabolism and substances in excess are removed from the body

carbon dioxide

decarboxylation of respiratory substrates in aerobic respiration
cells damaged if blood pH falls below normal → acidosis

ammonia

deamination of amino acids in hepatocytes. it increases cytoplasm pH and interferes with metabolic processes + receptors for neurotransmitters

urea

ornithine cycle in hepatocytes. readily diffuses into cells decreasing their water potential. causes them to absorb water by osmosis and expand until they burst

uric acid

breaking down of adenine and guanine in the liver (purines). can form crystals in joints, causing gout

bile pigments

breaking down of haem groups in liver cells. can accumulate in skin turning it yellow (jaundice)

bile

bile salts for lipid digestion, bile pigments from the breakdown of haemoglobin

hepatic artery

oxygenated blood from the heart is carried to the liver. provides oxygen for aerobic respiration, fuels metabolic activity of liver cells

hepatic portal vein

blood from digestive system - allows liver to absorb and metabolise nutrients that are absorbed into blood from small intestine

hepatic vein

deoxygenated blood exits the liver

gall bladder

stores bile, releases bile into duodenum via bile duct

sinusoids

where blood from hepatic artery and portal vein mixes within each lobule. wide capilleries

lobule

structures which the hepatocytes are arranged in. supplied with blood from hepatic artery and hepatic portal vein, also connected to a branch of hepatic vein which drains blood away into the main hepatic vein

liver functions

storage of glycogen, formation of urea, detoxification

formation of urea

deamination + ornithine cycle

deamination

NH2 is removed from each amino acid with an extra H+ atom. part of amino acid that remains is a keto acid. it can enter the Krebs cycle to be respired, be converted to glucose, be converted to glycogen, fat, storage

ornithine cycle

ammonia is converted into urea. ammonia + carbon dioxide → urea + water. it diffuses through plasma membrane of hepatocytes and transported to kidneys to be excreted

detoxification

breakdown of substances which are toxic / not required, such as alcohol, hydrogen peroxide, lactate, medicinal drugs

detoxification of alcohol

alcohol (ethanol) is absorbed in stomach and transported to hepatocytes. alcohol dehydrogenase converts ethanol into ethanal, then converted into other molecules that can be respired.

fatty liver

metabolis, of ethanol generates ATP - hepatocytes do not metabolise as much fat as usual but stores fat. causes reduces ability of hepatocytes to carry out other functions, can lead to cirrhosis (scarring of the liver)

liver histology

kidney function

osmoregulation, excretion

ureter

carries urine from kidneys to bladder

urethra

releases urine outside of body

kidney structure

surrounded by fibrous capsule. cortex contains glomerulus, bowman’s capsule, PCT, DCT. medulla contains loop of Henle + collecting duct. renal pelvis is where the ureter joins the kidney

afferent arteriole

carries blood from the renal artery to the glomerulus

efferent arteriole

leaves the glomerulus into a network of capillaries that run closely alongside rest of the nephron

ultrafiltration

small molecules (amino acids, water, glucose, urea, inorganic ions) are filtered out of the blood and into the Bowman’s capsule of the kidney nephron, forming glomerular filtrate

selective reabsorption

useful molecules are taken back from the filtrate and returned to the blood

features that aid ultrafiltration

capillary endothelium, basement membrane, epithelium of Bowman’s capsule

endothelium of capillary

gaos between the endothelial cells allow small molecules to pass

basement membrane

mesh of collagen and glycoproteins - small molecules can pass through holes in mesh

podocytes

has finger-like projections, gaps for small molecules to pass through

PCT adaptations

microvilli on luminal membrane (increases SA for reabsorption). many co transporter proteins in luminal membrane (each type of protein transports a specific solute across luminal membrane). many mitochondria (provides energy for sodium-potassium pump in basal membrane of cells). cells tightly packed together (no fluid can pass between cells)

selective reabsorption mechanism

1. Na+ are transported from PCT into surrounding tissue by active transport

2. creates electrical gradient , Cl- ions follow by diffusion

3. this lowers conc. of Na+ in epithelial cells, Na+ diffuse down conc gradient inot epithelial cells

4. Na+ move by co transporter proteins. the proteins also transport solute at the smae time

5. solutes diffuse down conc gradient into blood inside cells

6. water leaves PCT by osmosis due to reduced water potential

reabsorption of water + salts

1. sodium and chloride ions are pumped out of filtrate in ascending limb of loop of Henle into medulla, lowering water potential

2. ascending limb is IMPERMEABLE TO WATER. water is unable to leave by osmosis,

3. water potential of ascending limb increases as it rises back into cortex (removal of solutes, retention of water)

4. descending limb is PERMEABLE TO WATER. water moves out by osmosis, low permeability of ions. water potential of filtrate decreases due to loss of water, retention of ions

osmoregulation

control of water potential of body fluids. osmoreceptors detect water potential of blood.

1. decrease in water potential

2. impulse sent to posterior pituitary gland

3. releases ADH

4. ADH causes luminal membranes to become more permeable to water, increasees number of aquaporins

5. small vol of conc urine produced

kidney failure reasons

blood loss, high BP, diabetes, infections, drugs,

kidney failure consequences

GFR decreases, leads to a build up of toxins, electrolyte balance in blood is disrupted

excess potassium ions causes?

abdominal cramps, tiredness, muscle weakness, paralysis, continual increase causes frequency of SAN impulses to decrease, arrhythmia + cardiac arrest

build up of sodium causes?

disorientation, muscle spasms, higher blood pressure, general weakness

proteinuria

BP too high, kidney infection, blood filtration mechanism

glucouria

something wrong with functioning of insulin

ketones in urine

indicator of diabetes