Exam 4 Flashcards
main functions of kidneys
- excretion of waste
- regulate blood volume, electrolyte (ions) composition, and ph of body fluid
- hormone and production of active agents
- other roles (gluconeogenosis)
what is the location of the kidneys?
they are just outside the abdominal cavity and sit on each side of the spine against the posterior wall
why are the kidneys heavily vascularized?
there needs to be capillaries running through the kidneys to allow for the filtration of blood
what is the typical filtration amount for the kidneys in one day?
about 180 L/day
How much of the filtration in the kidneys is reabsorbed back into the body?
about 179 L/day (only 1 L is lost to urine)
what are two parts of the blood that should not be in urine and are a sign of a disorder/illness?
- glucose
- proteins
what health condition will cause glucose to be excreted in urine?
diabetes
what health condition will cause proteins to be excreted in urine?
preeclampsia
what three parts of the blood are checked to ensure the kidneys are functioning properly?
- urea
- uric acid
- creatinine
what part of the blood, produced by muscles, should ALL be excreted in urine (0 reabsorbed)?
creatinine
3 layers of the kidneys
- renal cortex (outermost)
- renal medulla
- renal pelvis (innermost layer)
renal medulla
a set of cone shaped masses of tissue that secrete urine into sac-like tubules
renal pelvis
a funnel shape surrounded by smooth muscle that uses peristalsis to move urine out of the kidney into the ureter and to the bladder
ureters
aids in movement of urine to the bladder, even without aid of gravity
what is the purpose of the ureter having the muscular layer that consists of longitudinal and circular smooth muscles?
it creates peristaltic contractions that aids in the movement to the bladder, even without aid of gravity
what is transitional epithelium (urothelium)?
unique epithelium that is made up of several layers of cells that become flattened when stretched. It lines most of your urinary tract and allows your bladder to expand.
where is transitional epithelium found?
- ureter
- bladder
what does the transitional epithelium look like when the bladder is empty?
resembles columnar epithelia
what does the transitional epithelium look like when the bladder is full?
resembles a squamous appearance
what are the voluntary and involuntary muscles in the bladder?
- voluntary = detrusor muscle
- involuntary = external urethral sphincter
renal artery
brings in oxygenated blood from the heart to the kidney
renal vein
deoxygenated blood leaving the kidney
what is the order in which the renal artery will branch until reaching the capillaries?
- segmental artery
- interlobar artery
- arcuate artery
- interlobular artery
- afferent arteriole
(glomerulus) - efferent arteriole
afferent arterioles branch from interlobular arteries to the _______________ of the nephron
glomerulus
what is the functional unit of the kidney?
nephron
renal papilla
the openings of the the renal pyramid, where urine is transported from the nephrons to the collecting ducts
renal pyramids
where nephrons are
minor and major calyx
a minor calyx surrounds the renal papilla of each pyramid and collects urine from that pyramid. several minor calyxs converge to form the major calyx
ureter
takes urine to the bladder
what is the order in which the renal veins will branch after the capillaries?
- interlobular vein
- arcuate vein
- interlobar vein
- renal vein
glomerulus
fenestrated capillary network
Bowmans corpuscle
the outside shell around the glomerulus
convoluted tubules
names
- proximal tubule
- distal tubule
afferent arteriole
blood that comes in from the arcuate artery and into glomerulus
efferent arteriole
blood that comes out after the glomerulus and moves through the rest of the nephron and into the arcuate vein
renal corpuscle
the outside shell around the glomerulus
podocyte
a modified pericyte that covers the network or capillaries in the glomerulus, they intermesh to create the third layer in which the filtration of blood takes place
juxtaglomerular cells
synthesize, store and secrete the enzyme renin in response to a drop in blood pressure by stimulation from (nor)epinephrine
macula densa
cells specialized within the wall of the distal tubule that sense the salt content and the volume of fluid within the tubule, they will stimulate juxtaglomerular cells to release renin when they detect a drop in sodium concentration in the tubular fluid
2 types of nephrons
- cortical nephron
- juxtamedullary nephron
cortical nephron
glomerulus is located neared to the outer parts of the cortex and have short loops of Henle
juxtamedullary nephron
glomerulus is located near the junction on the cortex and medulla and have loops of Henle that penetrate deep into the medulla
Nephron function
nephrons filter blood and then reabsorb useful materials from the filtrate before eliminating the remainder as urine
3 key stages to nephron function
- ultrafiltration
- selective reabsorption (both tubules)
- osmoregulation (loop of Henle, collecting duct)
ultrafiltration
blood is filtered out of the glomerulus at the Bowmans capsule to form filtrate (nonselective)
selective reabsorption
materials are reabsorbed in convoluted tubules (both proximal and distal)
osmoregulation
the loop of Henle establishes a salt gradient which draws water out of the collecting duct
what is the purpose of microvilli in the tubules of the nephron?
help with reabsorption, increase surface area, have active transporters on their surface
urine formation is accomplished by 4 principal functions:
- filtration (blood to lumen)
- reabsorption (lumen to blood)
- secretion (blood to lumen)
- osmoconcentration
three barriers of ultrafiltration in the glomerulus
- endothelium
- glomerular basement membrane
- podocytes
endothelium of the glomerulus
- fenestrated
- plasma is able to move out, RBC and proteins remain in the capillary
glomerulus basement membrane
- negatively charged
- repels negatively charged ions and proteins
- attracts positive ions
podocytes
- specialized epithelial calls that cover the network of capillaries in the glomerulus
- form a slit diaphragm
GFR
- glomerular filtration rate
- amount of plasma that is passed through glomerulus per minute (avg = 125 ml/ min)
glomerular filtration is directly proportional to _________ __________ _____________
net filtration pressure
3 factors of net filtration pressure
- glomerular (blood) hydrostatic pressure
- blood colloid osmotic pressure
- capsular hydrostatic pressure
glomerular (blood) hydrostatic pressure
blood moving into the capillary
blood colloid osmotic pressure
pressure pushing in on the glomerulus
capsular hydrostatic pressure
pressure pushing in on glomerulus
net __________ pressure on the glomerulus creating a net outward pressure of 10 mmHg
positive
high blood pressure __________ hydrostatic pressure
increases
filtration is regulated by:
- fenestrations in capillary endothelial cells
- podocytes with filtration slits
- membrane charge
- basement membrane with capillary cells
filtration results in filtrate _________ blood cells or large proteins and predominance of ____________ charged substances
without, positively
how can filtration be regulated?
- neural inputs
- sympathetic inputs
most of reabsorption occurs within the __________ ____________ __________
proximal convoluted tubule (using concentration gradients and transporters are used for reabsorption)
how does K move through the proximal convoluted tubule?
through channels
how does Na move through the proximal convoluted tubule?
cotransporter, countertransporter, Na/K ATPase pump
how does glucose move through the proximal convoluted tubule?
facilitated diffusion and cotransporter
how does bicarbonate move through the proximal convoluted tubule?
transports from CO2 and H2O and exits through a cotransporter
how does H+ move through the proximal convoluted tubule?
(made due to carbonic acid) counter transporter
how does Cl move through the proximal convoluted tubule?
move through without help
bicarbonate is unable to move through the proximal tubule wall in order to go back into the bloodstream, so what does it have to do?
bicarbonate is changed into carbonic acid and carbonic anhydrase enzyme turns into CO2 and H2O, CO2 can move into the proximal tubule cell where it can turn back into bicarbonate and move into the bloodstream
aquaporins
lots of aquaporins in the proximal tubules to allow movement of water across the lipid rich hydrophobic membrane (most water is reabsorbed)
the main site for bulk reabsorption
proximal convoluted tubule
bulk reabsorption is achieved by the proximal convoluted tubule because of primary and secondary ________ ___________
active transport
active transport
involves movement of materials against a concentration gradient and requires an expenditure of energy
primary active transport
hydrolysis of ATP
secondary active transport
coupling with the transport of another molecule along its electrochemical gradient
symporter
2 molecules in the same direction
antiporter
2 molecules in different directions
most of water is reabsorbed in this part of the loop of Henle because it has a lot of aquaporins
descending loop of henle
what occurs to osmolarity during the descending loop of henle?
osmolarity increases from about 300 to 1200
the increased osmolarity in the descending loop of henle results in reabsorption of up to ____% of the water filtrate from the nephron
15%
site of NaCl reabsorption
ascending loop of henle
what is reabsorbed in the ascending loop of henle?
ions, mainly Na+, are actively pumped out of the loop by large numbers of Na/K ATPase pumps
2 significant effects of NaCl being reabsorbed
- hypo-osmotic filtrate in the distal tubule decreasing osmolarity
- pumping Na+ in the interstitial space contributes to a hyper osmotic environment in the kidney medulla
are there aquaporins in the ascending loop of henle?
- NO
- it released NaCl NOT H2O, the descending loop of henle is the part that has aquaporins
countercurrent multiplier system
the structure of the loop of henle and its associated capillary network
what does “multiplier” mean in the countercurrent multiplier system?
due to the solute pumps that increase (multiply) the concentrations of Na+ (and urea) deep in the medulla
what does “countercurrent” mean in the countercurrent multiplier system?
ascending and descending loops are next to each other and their fluid flows in opposite directions
descending loop of henle = loses ______
water
ascending loop of henle = loses ______
NaCl
the terminal portion of the distal tubules (from multiple nephrons) empty into a straight __________ ______
collecting duct
what hormone is the collecting duct system controlled by?
antidiuretic hormone
when ADH is present, the collecting duct becomes _____________ to water
permeable
what is the function of the antidiuretic hormone?
antidiuretic hormone draw out water from the collecting duct decreasing urination
what molecules are reabsorbed by nephron tubules?
Ca2+, Na+, glucose, and AA
what molecules are secreted into the filtrate and waste products?
urea, K, ammonia, creatinine and some drugs
what cells secrete renin?
juxtaglomerular cells
signals to release renin
- fall in blood pressure in the afferent arteriole
- macula densa cells respond to a fall in Na
- the baroreceptors respond to a decline in sympathetic blood pressure
steps of the RAAS
- macula densa cells in the DCT detect the low Na and alert the JG cells
- JG cells secrete renin into blood
- the liver is constantly producing angiotensinogen into the blood and when renin is released an enzyme reaction occurs breaking angiotensinogen into angiotensin 1
- angiotensin 1 has and enzymatic reaction with ACE that is in pulmonary blood and breaks down into angiotensin 2
- angiotensin 2 stimulates vasoconstriction and the adrenal cortex to secrete aldosterone
- aldosterone stimulates Na uptake on the apical cell membrane in the DCT and collecting ducts (increase H2O and Na+ reabsorption)
aldosterone
increases the amount of Na/K ATPase in the basal membrane of the DCT and the collecting duct
antidiuretic hormone function
reabsorption of H2O by activating the aquaporin channels
most Ca2+ is absorbed by the _______ and _____________
PCT and ascending loop of henle
Ca2+ remaining in the tubule moves through Ca2+ channels that are activated by ____________ and _____________
parathyroid hormone and Ca2+ binding protein
what is micturition?
urination
urination is the result of _______ _________ in the bladder wall that transmit nerve impulses to the spinal cord to generate a spinal reflex
stretch receptors
when stretch is detected in the bladder, the resulting parasympathetic neural outflow causes contraction of the _________ ________ and relaxation of the ___________ _________ ___________
detrusor muscles and relaxation of the internal urethral sphincter
at the same time the detrusor muscles relax and relaxation of the internal urethral sphincter what does the spinal cord have to inhibit?
somatic motor neurons resulting in the relaxation of the skeletal muscle of the external urethral sphincter
is the opening of the external urethral sphincter voluntary or involuntary?
voluntary
