Organisms Response to Change - Kidneys Flashcards
what are the roles of the kidneys?
osmoregulation
excretion
how do the kidneys carry out osmoregulation?
by controlling the volume and concentration of urine produced
how do the kidneys carry out excretion?
by removing waste products from the metabolism
what is a nephron?
the functional unit of a kidney
what is the fibrous capsule?
the outer membrane that protects the kidney
what is the cortex?
the lighter coloured outer region consisting of renal capsules, convulated tubules and blood vessels
what is the medulla?
darker coloured inner region of the kidney consisting of the loops of henle, collecting ducts and blood vessels
what is the renal pelvis?
a funnel-shaped cavity that collects urine into the ureter
what is the ureter?
a tube that carries urine to the bladder
what is the renal artery?
the artery that supplies the kidney with blood
what is the renal vein?
the vein that returns blood to the heart from the kidney
what are the main components of a nephron?
renal capsule
proximal convulated tubule
loop of henle
distal convulated tubule
collecting duct
what is the renal capsule?
closed end at the start of the nephron
what is the structure of the renal capsule?
cup-shaped and surrounds the glomerulus
inner layer consists of podocytes - specialised cells
what is the proximal convulated tubule?
series of loops surrounded by blood capillaries
what is the structure of proximal convulated tubule?
walls consist of epithelial cells containing microvilli
what is the loop of henle?
long, hairpin loop extending from the cortex into the medulla and back again
surrounded by blood capillaries
what is the distal convulated tubule?
series of loops surrounded by blood capillaries, but less than proximal convulated tubule
what is the collecting duct?
tube that distal convulated tubules empty into
becomes increasingly wide as it empties into pelvis of kidney
what is the structure of the collecting duct?
lined with epithelial cells
becomes wider as it empties into pelvis of the kidney
what are the different blood vessels present in a nephron?
afferent and efferent arterioles
glomerulus
blood capillaries
what is the afferent arteriole?
vessel from the renal artery that supplies the nephron and glomerulus with blood
what is the glomerulus?
branched knot of capillaries between the afferent and efferent arterioles
what is the efferent arteriole?
blood vessel attached to the glomerulus, carrying blood away from the renal capsule
describe the blood capillaries present in a nephron
concentrated network surrounding:
distal/proximated convulated tubules
loop of henle
they merge to form the renal vein
what are the 2 processes involved in the production of urine?
ultrafiltration
selective readsorption
label this diagram of a nephron

A - afferent arteriole
B - glomerulus
C - efferent arteriole
D - distal convulated tubule
E - renal capsule
F - proximal convulated tubule
G - ascending loop of henle
H - descending loop of henle
I - collecting duct
describe the process of ultrafiltration
high pressure created in glomerulus
water and small molecules are forced out of the blood and into renal capsule
how is a high pressure created in the glomerulus?
efferent arteriole has a narrower diameter than the afferent arteriole
coiling of capillaries in the glomerulus restricts blood flow
what is the pathway for filtration in the renal capsule?
glomerular capillary endothelium
basement membrane
renal capsule epithelium / podocytes
what components of the filtrate cannot pass through the glomerular capillary endothelium in ultrafiltration?
red blood cells
which components of the filtrate cannot pass through the basement membrane in ultrafiltration?
plasma proteins
which components of the filtrate can pass through the filtration pathway in ultrafiltration?
water
glucose
electrolytes
amino acids
fatty acids
nitrogenous wastes
what components of the nephron are involved in selective readsorption?
proximal convulated tubule
loop of henle
distal convulated tubule
collecting duct
how much of the filtrate is readsorbed in the proximal convulated tubule?
85%
what is the role of the loop of henle in selective readsorption?
allows water to be readsorbed from collecting duct
what is the role of the distal convulated tubule in selective readsorption?
makes final adjustments
toxic substances are secreted into the filtrate
water readsorption
what is the role of the collecting duct in selective readsorption?
water readsorption
what is readsorbed in the proximal convulated tubule?
water
ions
glucose
amino acids + small proteins
urea
which substances are readsorbed through facilitated diffusion / active transport in the PCT?
ions
glucose
amino acids
how is water readsorbed in the PCT?
osmosis
how is urea readsorbed in the PCT?
passively due to the movement of water by osmosis
what are the adaptations of the PCT for selective readsorption?
microvilli and infoldings to increase surface area
mitochondria for active transport/facilitated diffusion
which substances are readsorbed by co-transport in the PCT?
glucose
amino acids
describe how glucose and amino acids are readsorbed by co-transport in the PCT
- Na+ actively transported from PCT into blood and are carried away
- Na+ diffuse into PCT cells from lumen of PCT by facilitated diffusion
- glucose or amino acid carried with the ion
- glucose/amino acid and Na+ then diffuses into blood from PCT
what % of water and ions have been readsorbed at the end of the proximal convulated tubule?
65%
what % of glucose and amino acids have been readsorbed at the end of the proximal convulated tubule?
100%
what change is there to the concentration of urea at the end of the proximal convulated tubule?
conc will have increased
how does the loop of henle allow water to be readsorbed in the collecting duct?
makes the medulla concentrated with ions, lowering water potential, promoting readsorption by osmosis
why is the water potential high at the start of the loop of henle?
all of the glucose and amino acids were readsorbed in the PCT so the filtrate is less concentrated
what are the 2 regions of the loop of henle?
descending limb
ascending limb
what are the differences between the descending and ascending limbs of the loop of henle?
descending: narrow, thin walls that are highly permeable to water
ascending: wider, thick walls impermeable to water
describe what happens in the descending limb of the loop of henle
water potential lowered so water diffuses out of descending limb and into blood capillaries
filtrate moves along descending limb, becoming more concentrated
how is the water potential lowered in the descending limb of the loop of henle?
Na+ actively transported out of ascending limb, some passively diffuse into the descending limb, but most accumulate in interstitial region
what is the interstitial region?
region between the cortex and medulla of the kidney
describe what happens in the ascending limb of the loop of henle
at bottom of the limb - sodium ions diffuse out
as filtrate moves along limb, sodium ions actively transported out
filtrate becomes less concentrated and water potential increases
what is the countercurrent multiplier?
filtrate in collecting duct with a low water potential meets interstitial fluid with lower water potential
ensures water potential gradient exists for entire length of collecting duct
where is ADH produced?
hypothalamus
where is ADH stored and secreted from?
posterior pituitary
how does the hypothalamus detect low water potential in the blood?
osmoreceptors in the hypothalamus shrink
describe what happens when low water potential is detected in the hypothalamus
impulses sent to posterior pituitary
ADH released into blood and travels to kidneys
how does ADH cause the kidneys to change the water potential of the blood?
ADH binds to receptors of distal convulated tubule and collecting duct, activating phosphorlyase
phosphorylase causes vesicles in the cells to move and fuse will cell membrane, inserting aquaporins into the membrane
permeability to water + urea of collecting duct increased
more water passes into medulla fluid and blood vessels
urea passes into medulla fluid, lowering water potential
how do osmoreceptors respond to thirst?
impulses sent to thirst centre of the brain increasing intake of water