Function of kidneys
regulate the volume, composition, and pH of body fluids by managing blood plasma
List structures that a molecule of urea must pass in order to go from the afferent arteriole to the toilet
Afferent arteriole-glomelular capillary-bowmans capsule-PCT-descending loop of henley-ascending loop of henley-DCT-collecting duct-minor calyx-major calyx-renal pelvis-ureter-bladder-urethra-toilet
If the molecule of urea were reasorbed from the DCT by active transport - what structures would it pass?
The kidneys remove metabolic wastes from the blood and excrete them to the outside of the body including what
nitrogenous and sulfur containing products of protein metabolism
The kidneys also help control what
rate of RBC production (erythropoeitin), regulates blood pressure, and regulates various ions concentrations
The kidneys accomplish their functions by what three main activities?
Filtration, Reabsorbtion, secretion
occurs at the glomerulus. filters all particles small enough to be pushed through the fenestra of the glomerular capillaries
from the filtrate. important molecules get pushed into the filtrate and are reabsorbed by active transport into the peritubular capillaries, back into circulation. What's not reabsobed goes out with the urine
into the filtrate. the cuoidal epithelium that constitute the renal tubules (nephrons)use active transport to pump particles into the filtrate (hydrogen and penicillin)
highly modified epithelial cells that form a crucial part of flomerular capillary fenestrations. Responsible for renal filtration.
The DCT touches the efferent and afferent arterioles at the gloerulus allowing the nephron to do what? This is similar to what
to react to changes in blood pressure by secreting renin
it's similar to nephrons deep in the kidney that are close to the medula that react to changes in blood tone
What is the main function of the nephrons and collecting ducts?
to control the composition of body fluids and remove metabolic wastes from blood
Urine is the final product of the processes of what?
Glomerular filtration, tubular reabsorption, and tubular secretion
What is the main force that moves substances by filtration through the glomerular capillary wall
hydrostatic pressure of the blood
Net filtration pressure =
force favoring filtration (glomerular capillary hydrostatic pressure) - forces opposing filtration (capsular hydrostatic pressure and glomerular capillary osmotic pressure)
The forces responsible for filtration pressure are
hydrostatic pressure and osmotic pressure of plasma and the hydrostatic pressure of the fluid in the glomerular capsule
What three mechanisms are responsible for keeping the glomerular filtration rate constant
Autoregulation; Increased sympathetic impulses that decrease GFR by causing afferent arterioles to constrict; the hormone-like renin-angiotensin system
Summarize the renin-angiotensin system
the liver makes and releases a zymogen called angiotensinogen. when the kidney detects low BP it releases renin. renin immediately converts angiotensinogen to angiotensin I. Angiotensin I is converted to angiotensin II by cells (especially in the lungs) They use ACE. ACE causes BP to increase
Cardiac patients often have fluid retention problems and low BP so the renin-angiotensin system works to do what
Substances move by ___ from the renal tubules into the interstitial fluid where they then diffuse into the ___ to ___
peritubular capillaries to the general circulation
The proximal convoluted tubule (PCTs) reabsorb most __
Glucose, water, proteins, and vitamins
Amino, lactic, citric, acids
Phosphate, sulfate, calcium, potassium, and sodium ions
When glucose remains in the filtrate because it is in high concentrations, what stays with it?
water stays with it. (Isotonic)
when high blood sugars 'spill into the urine' a person makes a lot of urine because?
when glucose is absorbed, water stays with it
Define the renal transport max of glucose
the maximum blood glucose level at which a person can remove all of the glucose from the filtrate.
The Tmax is reached when
all intramembranous glucose carriers are saturated with glucose transport and can operate no faster.
"High blood sugars spill into the urine" Why?
The kidneys can only absorb so much (they are rate limited) and when you are beyond the max (transport max) the excess goes out with the urine
What does a Tmax have to do with cells that form nephrons
There are only a certian number of receptors
Probenecid, is a commonly used drug that inhibits secretion of certain compounds by interfering with?
the "renal transport mechanism"
What is probenecid used for
It is used to keep penicillin at high blood concentration. (keep penicillin out of the urine/stop the secretion of penicillin into the filtrate.)
In tubular secretion, substances move from the plasma of the peritubular capillaries into
into the fluid of the renal tubules
In tubular secretion, what is pumped into the filtrate and how?
Waste molecules such as drugs and ions are pumped into the filtrate by active transport
what hormones affect the solute concentration of urine, particularly sodium.
Hormones such as aldosterone and ANP (Atrial Natriuretic Peptide)
The ability of the kidneys to maintain the internal environment rests on their ability to concentrate urine by
reabsorbing large volumes of water
The distal convoluted tubule and the collecting duct are ___ to water, so water may be excreted as ___
When a patient is dehydrated, the hypertonic blood plasma is detected by
osmoreceptors in the hypothalamus
The osmoreceptors experience an AP and their peripheral process terminate where?
in the posterior pituitary. (Neurohypophysis)
When ADH is present, the cells of the DCT and collecting duct become ___, and water is reabsorbed by osmosis into the ___
permeable to water
extremely hypertonic medullary interstitial fluid
A countercurrent mechanism in the nephron loops ensures that the medullary interstitial fluid becomes hypertonic. This is known as
Function of the counter-current mechanism
The function of the counter-current mechanism is to keep the medulla hypertonic.
Summarize the kidneys abilitly to concentrate urine
1. When (as) the body dehydrates it is detected by osmoreceptors in the brain.
2. They detect hypertonic blood and experience an AP.
3. The AP causes the release of anti-diuretic hormone from the post-pit.
4. The DLLH and the ALLH treat Na+ differently so that the adrenal medulla is hypertonic as compared to fluid in the collecting ducts. (counter-current mechanism)
5. The function of the counter-current mechanism is to keep the medulla hypertonic.
6. ADH reaches the renal medulla by the general circulation.
7. When ADH is present (Patient is dehydrated) water exits the DCT and returns to the general circulation.
8. Urine volume produced per unit time drops.
9. Water is saved. (Return to isotonic.)
function of the ascending limb
reabsorption of sodium, potassium and chloride ions by active transport
urine composition reflects what
the volumes of water and solutes that the kidneys must eliminate from the body or retain in the internal environment to maintain homeostasis
urine composition typically contains...
95% water, high concentrations of urea, uric acid and creatinine (the 3 nitrogen wastes) and may contain trace amounts of amino acids and varying amounts of electrolytes
the rate at which a chemical is removed from the blood plasma which is aggressively filtered by the kidneys
How is urine eliminated?
passes the collecting ducts to the openings of the renal papillae, enters the minor and major calayces, passes through the renal pelvis, enters into the ureters, enters the urinary bladder, urethra carries urine out of the body
events of micturition
urinary bladder distends as is it fills with urine, stretch receptors in the bladder wall are stimulated, signaling the micturition center in the sacral spinal cord, parasympathetic nerve inpulses travel to the detrusor muscle which responds by contracting, neet to urinate is urgent, voluntary contraction of the external urethral sphincter and inhibition of the micturition reflex by impulses from teh brainstem prevent urination, following the decision to urinate, the external urethral sphincer is relaxed and facilitate the micturition reflex, the detrusor muscle contracts and urine is expelled, neurons of the micturition reflex center fatigue, the muscle relaxes and the bladder fills again.