| What is the kidney's function? (3) | Removes metabolic waste for excretion by removing nitrogenous wastes that could be toxic in large concentrations
And by removing excess water to maintain osmolarity within cells |
| What is excretion? | removal of waste products of metabolic activity such as (urea and co2) happens in both plants and animals |
| What is egestion? | undigested matter leftover frim digestion which is released as feces. Happens only in animals |
| What are the different excretory systems in animals and insects? (2) why? | insects have malphigian tubules which are connected to the digestive system
Mammals have kidneys which are separate from other systems |
| How is nitrogenous waste produced? | from the breakdown of amino acids and nucleotides |
| What and why are there different types of nitrogenous waste? (4) | type of nitrogenous waste in animals is linked with the evolutionary history of the animal and habitat
aquatic animals: ammonia (NH3) = toxic but water soluble
Birds, Reptiles, insects: uric acid (C5H4N4O3) = needs more energy but is non toxic and less concentrated
Mammals + amphibians: urea (CH4N2O) = non toxic and can be stored at higher concs |
| How do water levels in the body change? | water is produced by condensation reactions (anabolism)
Water is used in hydrolysis reactions (Catabolism) |
| What does conc of water affect? (2) | the osmolarity affects tissue viability |
| What is osmolarity? | the concentration of water in cells |
| What do nephrons do? | filter blood and remove metabolic wastes |
| What is the difference between osmoconformers and osmoregulators? | osmoconformers: match osmolarity to environment = needs less energy as it minimises water movement (jellyfish)
Osmoregulators: maintains a constant internal osmolarity + independent BUT needs more energy as the conditions are more controlled (mammals) |
| Draw and label a kidney (7) | cortex
medulla
renal artery and vein
renal pelvis
ureter
nephron |
| How does blood enters and exits the kidney? | enters the renal artery
exits the renal vein |
| What is produced with kidneys? (2) | urine is produced by the nephron
and transported out by the ureter and is stored in the bladder before excretion |
| How is the composition of blood in the renal artery is different from the renal vein blood? (4) | renal vein:
less urea bec large amounts is removed with the nephron to make urine
less water and solutes/ ions = the amount removed depends on the hydration levels
Less glucose and o2 because it is used to generate energy and fuel metabolic reactions
more co2 = produced in the kidneys as a byproduct of metabolic reactions
Renal artery:
more urea
more water and solutes
more glucose and o2
more co2 |
| explain how insects excrete nitrogenous wastes? (8) | insects have a circulating fluid system called hemolymph (blood system)
=nitrogenous waste build up in hemolymph
nitrogenous waste is absorbed by malpighian tubules
= high solute conc in malphigian tubules
ammonia is converted to uric acid which needs ATP
product combines with the digested food products later on and uric acid and undigested food material are excreted from the anus with feces (uric acid is nontoxic)
water absorbed by osmosis moves uric acid to hindgut
solutes, water and salts are reabsorbed in the hindgut returns to hemolymph = recycled |
| Explain how the structure of the nephron and its associated blood vessels enable the kidney to carry out its functions. (11) | excretion of nitrogenous waste is a function of the kidney with the use of processes like ultrafiltration, reabsorption and osmoregulation
Ultrafiltration occurs in the glomerulus which filters the blood entering the renal artery so that only the smaller molecules get filtered in not the larger molecules such as protein and blood cells = bec of basement membrane
the glomerulus has a high hydrostatic pressure within due to the wide afferent which the blood enters through and the narrow efferent whereby blood leaves. This forces the fluid into the capsule bec of the p gradient
Next in the proximal convulating tube useful materials such as ions, glucose and water is reabsorbed which has adaptations such as microvilli to aid it in reabsorbing
The water is reabsorbed in the descending limb of the loop of henle as it is permeable to water which creates a salt gradient in the medulla
the urine is passed out through the collecting duct to the ureter which stores the urine in the bladder
the water permeability varies depending on the ADH levels which depend on the person's hydration levels |
| Explain what ADH is and its effect on the body (8) | antidiuretic hormone is a peptide hormone that is produced in the hypothalamus and it regulated the blood solute levels in the collecting ducts of the kidney
hypothalamus detects solute concentration and if blood is too concentrates the pituitary gland releases ADH
ADH stimulates the water channels which increases permeability
Water moves through the aquaporins by osmosis into the blood which makes the urine more concentrated
if blood is hypotonic no ADH is released = water isn't reabsorbed from collecting duct = urine is more dilute |
| What is the circulating fluid system in insects called? | hemolymph |
| Where is the nitrogenous waste excreted from? | malpighian tubules which is connected to the digestive system |
| What is needed to convert ammonia to uric acid in insects? | ATP |
| How is uric acid excreted from insects? (3) | uric acid combines with the digested food products later on and are excreted from the anus with feces (uric acid is nontoxic)
water absorbed by osmosis moves uric acid to hindgut
solutes, water and salts are reabsorbed in the hindgut returns to hemolymph = recycled |
| What is ADH and what does it do? (5) | antidiuretic hormone is a peptide hormone produced in the hypothalamus and released by the pituitary gland to regulate blood solute concentrations |
| Where is ADH used? (2) | in the collecting ducts of the kidney
in the late distal convulating tubule |
| How is the release of ADH triggered? (5) | hypothalamus detects solute concentration and if blood is too concentrates the pituitary gland releases ADH
ADH stimulates the water channels which increases permeability
Water moves through the aquaporins by osmosis into the blood which makes the urine more concentrated
if blood is hypotonic no ADH is released = water isn't reabsorbed from collecting duct = urine is more dilute |
| Label and identify the functions of the different parts of the nephron (4) | Bowman's capsule: contains the glomerulus which filters the blood with hydrostatic pressure from the wide afferent and narrow efferent which creates a pressure gradient within. The basement membrane and podocytes filter out large molecules such as blood and proteins
Proximal convoluted tubule: folded structure connected to the bowman's capsule where selective reabsorption occurs.
Ions are actively transported with protein pumps
Amino acids and glucose are transported with Na+
and H2O passively moves through with the movement of the ions with osmosis
Loop Of Henle: a selective permeable loop that goes down to the medulla and creates a salt gradient to draw water out of the collecting duct. it does this by creating more solute in the medulla.
The descending loop is permeable to water but not salts which makes the curve in the medulla very hypertonic
Distal convoluted tube: more reabsorption occurs here (ADH is released here) |
| What are the 3 processes nephrons carry out? | ultrafiltration: blood is filtered out of the glomerulus at the bowman's capsule to make a filtrate
selective reabsorption: usable materials are reabsorbed in convoluted tubules (proximal and distal)
Osmoregulation: loop of Henle creates a salt gradient which draws water out of the collecting duct |
| Describe the process of ultrafiltration and the parts of the nephron used (3) | Blood enter from the renal artery into the glomerulus through the wide afferent and leaves through the narrow efferent arteriole
1) Hydrostatic pressure: This increases the pressure within which forces the fluid into the bowman's capsule = filtrate = lacks protein and blood (large molecules)
2) basement membrane and podocytes stops large molecules from entering (size selective) = proteins and blood |
| Describe the process of selective reabsorption and the parts of the nephron used (9) | reuptakes useful materials from filtrate in the convoluted tubes
reabsorbs ions, amino acids, glucose, H2O, hormones, vitamins
the tubule has:
microvilli: increase SA for absorption from filtrate
single cell thick and tight junction = thin surface
Lots of mitochondria: active transport
Substances are actively transported across the apical membrane and then passively diffuse across basolateral membrane
Ions + vitamins = actively transported w protein pumps + carrier proteins
Glucose + amino acids co transported across apical w Na+ (symport)
water follows the movement of ions passively w osmosis |
| What is osmoregulation? (3) | controls the water balance of the blood which happens in the medulla due to:
the loop of Henle making a salt gradient (hypertonicity)
ADH regulating water level reabsorption in the collecting duct |
| How is a salt gradient established in the loop of Henle? (5) | descending limb = water permeable
ascending limb: salt permeable
so when the loop descends into medulla the fluid becomes salty (hypertonic)
the vasa recta surrounding the loop flows in the opposite direction (counter-current)
= so salt absorbed in ascending limb is also drawn down into medulla = bigger salt gradient |
| How is water drawn out of the collecting duct? | hypertonic conditions draws water out by osmosis in the collecting duct
amount released to be retained is controlled by the ADH
ADH is released by the posterior pituitary when the solute conc is high which is detected by the hypothalamus
ADH increases permeability of collecting duct which upregulates the production of aquaporins (water channels)
less water = concentrated urine
WHen hydrates = less AH = less water is reabsorbed = dilute urine
ADH = Are DeHydrated |
| What can not maintaining water balance lead to? | dehydration / overhydration |
| What happens when you're dehydrated(7) | water loss from body so the fluid become hypertonic
thirst and excrete less concentrated urine
BP drops because of less water in plasma
Hear rate increases
Tired + can't lower body temp (lack of sweat)
severe cases = seizures, brain damage, death |
| What happens when you're over hydrated? (5) | makes fluids hypotonic
excess clear urine to remove the water
causes cells to swell due to osmotic movement = tissue damage
headaches , blurred vision, seizures, death |
| How is the length of the loop of Henle positively correlated with the need for water conservation? | Arid desert animals will need a more efficient water conservation than animals in moist, mesic places = longer loop increases salt gradient in medulla
- more water is reabsorbed = concentrated urine
Moist, animals = short loops
Desert animals = long loops |
| What are kidney diseases? | conditions which stop the ability to filter waste products from the blood = reduced glomerular filtration rate (gfr) = can lead to kidney failure |
| What is used as indicator to kidney disease and why? (5) | blood cells, glucose, proteins and drugs detected in urinary tests bec kidneys normally prevent excretion of blood and protein and glucose during ultrafiltration and reabsorption
Glucose: diabetes (incomplete reabsorption)
Proteins: disease (PKU ) or hormonal conditions (pregnancy)
blood cells: diseases like cancer
Drugs: can be detected in urine like performance enhancing drugs |
| What is a treatment for kidney failure? (6) | hemodialysis
external filtering to remove metabolic wastes
blood is removed and pumped through with a dialyzer which has:
semi permeable membrane and introduces fresh dialysis and removes waste to maintain conc g
4 hours / 3 x a week |
| What is the best long term treatment for kidney failure? (3) | kidney transplants
donors have to be a close genetic match to minimise rejection
transplanted kidney is grafted into abdomen with arteries veins and ureter connected to vessels |
