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Function of kidneys

regulate the volume, composition, and pH of body fluids by managing blood plasma

The urinary system does what

removes metabolic wastes and substances in excess

The renal system consists of

pair of kidneys, pair of ureters, urinary bladder and urethra

Fibrous capsule

tough capsule that encloses the kidney

Kidneys are surrounded by a layer of

fat

Kidneys are located where

at the 12th rib in the retroperitoneal space. they are not abdominal

Which kidney is higher than the other

left is higher than the right

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

Flomelular capillary and bowmans capsule make up what

glomerulus

What is the site of filtration

Glomerulus

What is the site of most substance reabsorbtion

PCT (proximal convulated tubules)

Where is hydrogen pumped into the filtrate

PCT (proximal convulated tubules)

What is the site of water reabsorbtion

DCT (distal conulated tubules)

Where is the "first urine" found

as it exits the collecting duct into the minor calyx

If the molecule of urea were reasorbed from the DCT by active transport - what structures would it pass?

Paratubule capillaries

Where does most renal filtration occur and why

Glomulerus because of capillaries present

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

Filtration

occurs at the glomerulus. filters all particles small enough to be pushed through the fenestra of the glomerular capillaries

Reabsorption

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

Secretion

into the filtrate. the cuoidal epithelium that constitute the renal tubules (nephrons)use active transport to pump particles into the filtrate (hydrogen and penicillin)

What happens to particles secreted into the filtrate by active transport

the go out with the urine

Normal pH of urine

6. It's 10x's more acidic than blood plasma

Podocytes

highly modified epithelial cells that form a crucial part of flomerular capillary fenestrations. Responsible for renal filtration.

Juxaglomerular apparatus

where the DCT touches the afferent arteriole

The DCT touches the efferent and afferent arterioles as they enter and exit what?

the glomerulus

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 contains what?

wastes, excess water and excess electrolytes

Urine is the final product of the processes of what?

Glomerular filtration, tubular reabsorption, and tubular secretion

Glomerular filtration

substances move from the blood to the glomerular capsule

What is the main force that moves substances by filtration through the glomerular capillary wall

hydrostatic pressure of the blood

Normally, how much glucose is found in the blood plasma vs. the urine

plasma=100 urine=0

Normally, how much urea is found in the blood plasma vs. the urine

plasma=26; urine=1,820

Normally, how much uric acid is found in the blood plasma vs. the urine

plasma=4; urine=53

Normally, how much creatinine is found in the blood plasma vs. the urine

plasma=1; urine=196

What are the waste products of the urine

urea, uric acid, creatinine

A large net push of pressure produces alot/a little filtrate

alot

Glomerular filtration rate (GFR) is directly proportional to

the net filtration pressure

Net filtration pressure =

force favoring filtration (glomerular capillary hydrostatic pressure) - forces opposing filtration (capsular hydrostatic pressure and glomerular capillary osmotic pressure)

Normally, the glomerular net filtration pressure is

positive; which causes filtration.

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

Glomerular Filtration Rate remains relatively constant through a process called

autoregulation

What overrides autoregulation

when Glomerular Filtration Rate increases

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

What BP regulation system is important to heart patients

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

raise BP

The renal tubules use ___ to reabsorb particles that are not normally in urine

active transport

Substances move by ___ from the renal tubules into the interstitial fluid where they then diffuse into the ___ to ___

Active transport
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

Blood glucose is filtered into the filtrate at the

glomerular capillaries

The estimated Tmax for blood glucose in humans is

appx. 200mg/dl of whole blood

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

Explain a renal Tmax.

Cells can only do things so fast

What does a Tmax have to do with cells that form nephrons

There are only a certian number of receptors

Does the transport occur in both directions (in and out)?

yep

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

As hydrogen goes up, pH goes

down

Normal urine pH is

appx. 6 (acid)

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 ___

impermeable
dilute urine

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 the AP reaches the axon ending of the osmoreceptors, they release

ADH as a hormone

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

countercurrent multiplier

When (as) the body dehydrates it is detected by

osmoreceptors in the brain.

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 glomerulus

filtration of water and dissolved substances from plasma

function of the glomerular capsule

receives the glomerular filtrate

Function of the PCT

reabsorbtion of waste and secretion of hydrogen and pennicillin

function of the descending limb

reabsorption of water by osmosis

function of the ascending limb

reabsorption of sodium, potassium and chloride ions by active transport

function of the DCT

reabsorption of sodium and water
secretion of hydrogen and potassium

function of the collecting duct

reabsorption of water by osmosis

Urea is a waste product of

amino acid catabolism

the plasma concentration reflects what

the amoutn of protein in diet

Urea enters the renal tubules through

glomerular filtration

Urea is what % recycled

80%

If urea increases, what is happening to the kidneys

they are failing (BUN test-blood urea nitrogen)

uric acid is a waste product of what

nucleic acid (DNA-RNA) metabolism

Uric acid enters the renal turbules through

glomerular filtration

Some uric acid is reabsorbed by what

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 varies time to time due to what

dietary intake and physical activity

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

renal clearance

the rate at which a chemical is removed from the blood plasma which is aggressively filtered by the kidneys

renal clearance indicates what

kidney efficiency

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

the three openings in the urinary bladder is aka

trigone

urethra

a tube that conveys urine from the urinary bladder to the outside of the body

urine leaves the urinary bladder by...

micturition or urination reflex

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.

when kidneys fail, what molecules are abundant

urea, uric acid, creatinine

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