urinary system Flashcards
excretion
removal of metabolic waste products produced by cell activity. metabolic waste is toxic and cannot be broken down by body eg urea and CO2
osmoregulation
the control of water and salt levels in the body which prevents problems with osmosis.
what happens if osmoregulation does not occur properly?
water could enter or leave cells causing cells to burst or crenate
fibrous capsule
outer membrane that protects the kidney
cortex
lighter coloured outer region made up of renal capsules, convoluted tubules and blood vessels
medulla
darker coloured inner region made up of loops of Henle, collecting ducts and blood vessels
renal pelvis
funnel shaped cavity that collects urine into ureter
renal artery
supplies the kidney with blood from the heart via the aorta
ureter
tube that transports the urine to bladder
renal vein
returns blood to the heart via the vena cava
nephrons
functional unit of a kidney each nephron includes a filter (glomerulus) and a tubule
what is water reabsorption of kidneys controlled by
ADH - antidiuretic hormone
what is the water potential in blood monitored by
osmoreceptors located in the hypothalamus
what occurs if the water potential of blood is low
water leaves the osmoreceptors by osmosis causing them to shrivel
this stimulates the hypothalamus to produce more ADH
what occurs if the water potential of blood is high
water enters the osmoreceptors by osmosis which stimulates the hypothalamus to produce less ADH from the posterior pituary gland
distal convoluted tubule and collecting duct become less permeable to water so less water is reabsorbed in the blood and more is lost in the urine - dilute
outline the route ADH takes
produced in the hypothalamus and ADH moves along the axon of the cell to the posterior pituitary gland and from here it is released into the capillaries and blood
what is the role of ADH
ADH hormone binds to the receptors in plasma membrane of cells lining the collecting duct which activates a phosphorylase enzyme causing vesicles containing water permeable channels called aquaporins to fuse with the plasma membrane
ADH eventually reaches the kidney and increases the permeability of the walls of collecting duct and distal convoluted tubule - water can move out of collecting duct by osmosis down a water potential gradient and into blood capillaries= water is retained so urine is more concentrated
what does the phosphorylase enzyme do in terms of permeability of membrane
causes vesicles containing water permeable channels called aquaporins to fuse with the plasma membrane
ADH reaches kidneys and increases the permeability of walls of collecting duct and distal convoluted tubule
explain the process of how the high water potential of blood is regulated
high water potential of blood is detected by osmoreceptors in the hypothalamus which stimulates less ADH to be released from the posterior pituitary gland
the walls of the collecting duct and distal convoluted tubule are less permeable so less water is reabsorbed and more is lost in urine increasing urine output (dilute urine)
explain the process of how low water potential of blood is regulated
low water potential of blood is detected by osmoreceptors in hypothalamus
water leaves osmoreceptors by osmosis causing them to shrivel
this stimulates the hypothalamus to produce more ADH which is released into blood via the posterior pituitary gland
ADH binds to receptors in plasma membrane of cells lining the collecting duct
activates a phosphorylase enzyme which causes vesicles with water permeable channels called aquaporins to fuse with the plasma membrane
DCT and collecting duct become more permeable to water
water moves out of CT and DCT by osmosis down potential gradient and blood capillaries
more water is reabsorbed and less is lost in urine ( decreased urine output & concentrated)
what is the role of kidneys
regulates the composition of blood
maintain water potential
remove urea
maintain mineral ion concentration
what is the two stage process to make urine called
ultrafiltration
selective reabsorption
what is the nephron made up of
renal (bowman’s) capsule
proximal convoluted tubule
loop of Henle
distal convoluted tubule
collecting duct
structure and function of renal bowman’s capsule
closed end of nephron
cup shaped and surrounds a mass of blood capillaries known as glomerulus
inner layer of renal capsule is made up of specialised cells called podocytes
basement membrane between capillaries and podocytes
structure and function of proximal convoluted tubule
a series of loops surrounded by blood capillaries
walls are made up of epithelial cells which have microvilli
structure and function loop of henle
a long hairpin loop that extends from the cortex into the medulla of the kidney and back again
surrounded by blood capillaries
structure and function of distal convoluted tubule
a series of loops surrounded by blood capillaries
walls are made up of epithelial cells and are surrounded by less capillaries than the proximal tubule
collecting duct
a tube into which a number of distal convoluted tubules from a number of nephrons empty
lined by epithelial cells and becomes increasingly wide as it empties into the pelvis of the kidney
what are the blood vessels associated with each nephron
afferent arteriole
efferent arteriole
glomerulus
blood capillaries
afferent arteriole
a tiny vessel that rises from the renal artery and supplies the nephron with blood
enters the renal capsule of the nephron where it forms the glomerulus
efferent arteriole
a tiny vessel that leaves the renal capsule and later branches to form the blood capillaries
glomerulus
filtering unit of kidney
highly branched knot of capillaries from which fluid is forced out of the blood
glomerulus capillaries recombine to form the efferent arteriole
blood capillaries
concentrated network of capillaries - peritubular capillaries
surrounds PCT and where they reabsorb mineral salts, glucose and water
capillaries merge together into venules (tiny veins) which further merge to form the renal vein
structure and function of podocytes
finger like projections called major processes
makes up the wall of renal capsule and have gaps between cells to allow passage of substances into the renal lumen of the renal capsule
structure and function of proximal convoluted tubule
convoluted (coiled ) region of nephron found after the renal capsule in cortex
surrounded by dense network of capillaries branching from efferent arteriole
walls are made up of cubodial epithelial cells
plasma membrane of cells in contact with lumen of tubule is highly folded to form microvilli
basal membrane is folded
many mitochondria to provide energy for active transport as PCT reabsorbs glucose, nutrients and ions
what does the proximal convoluted tubule reabsorb
water
sodium ions
electrolytes
mineral ions
glucose
why does urea need to be removed from the body
urea is toxic metabolic waste and can cause damage to tissues and organs
how does the structure of the glomerulus and the renal capsule allow ultrafiltration to take place
glomerulus has a higher hydrostatic pressure than the lumen of bowman’s renal capsule
causes the blood plasma and smaller molecules dissolved in it eg glucose to be forced out of capillaries and into the lumen of renal capsule forming a filtrate
filtrate flows along the nephron
explain the process of ultrafiltration
blood enters the kidneys through the renal artery which branches into tiny arterioles which enters the bownman’s capsule of nephron
afferent arterioles splits into complex of capillaries known as glomerulus
glomerular capillaries later merge to form the efferent arteriole
What is the basement membrane made out of
Fine mesh of collagen fibres and glycoproteins
What is the role of basement membrane
Acts as filter and stops the removal of large molecules such as plasma proteins & cells from blood
How does the blood plasma and small molecules dissolved in enter the bow mans renal capsule
Gaps between major processes (finger like projections) of podocytes allow plasma and small molecules to leave the blood and enter the capsule
Gaps reduce resistance to movement of these fluids as it passes between podocytes and not through them
Results in water, glucose urea and mineral ions to be squeezed out of capillaries to form the glomerular filtrate in Bowmans capsule
Why is there high hydrostatic pressure in glomerulus
Diameter of afferent arteriolar is wider than the efferent arteriole
Why can’t plasma proteins leave the blood in the glomerulus
Too large to leave the blood and basement membrane acts a filter and blocks removal of large molecules
adaptations of PCT
adapted to reabsorb useful substances from filtrate
1. infoldings at basal membrane which allows large surface area to reabsorb substances from filtrate
2. epithelial cells which have microvilli to provide large surface to reabsorb from filtrate
3. high density of mitochondria for ATP to carry out active transport
RAAM
renin-angiotensin-aldosterone mechanism
role of RAAM
acts as a homeostatic negative feedback system in body that regulates blood pressure, blood volume and sodium levels
process of RAAM
if blood pressure or blood volume drops, the kidney is stimulated to produce renin
1. renin is released from the kidney to bloodstream.
2. renin acts on the angiotensinogen which is produced in the liver - forms angiotensin 1
3. ACE (angiotensin converting enzyme) is released by the lungs
4. ACE converts angiotensin 1 to angiotensin 2.
5.angiotensin 2 stimulates adrenal glands to release aldosterone which stimulates the kidney to reabsorb more salts and water
6. this increases blood pressure and fluid volume
also causes vasoconstriction to increase blood pressure
