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56 Cards in this Set

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renal cortex
outer region of kidney, where renal artery divides into many branches, supplying blood to nephrons located in the cortex- nephrons in the renal cortex means that this is where the majority of renal filtration takes place
renal medulla
location of the collecting ducts, where nephrons empty their contents
nephron
tubular structures within kidney that are specialized for transport of water and solutes between interstitial fluid and urinary filtrate
glomerulus
large tuft of specialized capillaries specialized for fluid filtration. glomerulus is located within bowmans capule of each nephron.
podocyte
octopus-like large structures surrounding the glomerular capillary basement membrane and serving as a barrier to large molecular solutes - part of the filtration structure of the glomerulus.
bowmans capsule
interior of the cuplike structure surrounding the glomerulus at the end of each tubular membrane.
proximal tubule
FUNCTION: ABSORPTION
tubule closest to the glomerulus, responsible for reabsroption of low molecular weight molecules important to metabolism, and water.
distal tubule
FUNCTION - SECRETION
major regulator of Na+ and water excretion, and K+.
afferent arteriole
carries arterial blood to glomerulus
efferent arteriole
carries blood flowing from the glomerulus to the peritubular capillary.
peritubular capillaries
surround the tubular portions of the nephron and are important in reabsorbing and excreting products from and to the interstitial space to assist the nephron in carrying out its function
Loops of henle
concentrates urine through a counter-current multiplier system - concentrated at tip, dilute at base.
proximal convoluted tubule
completely reabsorbs metabolically useful molecules, secretes others (urea, creatinine, histamine, penicillin)
collecting duct
where nephrons merge to carry end products of tubules via the ureter, to the bladder
ureter
tubes leading from kidneys to bladder which carry waste products to be expelled from the body
bladder
temporary storage point for urinary waste products before urination
urethra
tube runs from bladder --> outside, through which urine is expelled.
How much fluid is reabsorbed, and at what rate?
99% is reabsorbed:
110ml of water in = 1 ml of urine out.
rate of bloodflow through organs expressed how?
pressure in - pressure out/resistance = blood flow.
glomerular filtration rate
volume of fluid filtered in one minute through the glomerulus. on average, about 20% of the total volume of plasma passing through the glomerulus.

Glomerular filtration is because of fluid pressure differentials, forcing blood plasma out of the capillaries of the glomerulus and into bowman’s capsule
tubular reabsorption
tubular cells taking filtered molecules from tubular fluid and placing them back into the interstitial fluid
tubular secretion
tubular cells carry molecules that have diffused out of the peri-tubular capillaries INTO renal tubular fluid.
excretion
total filtration, less reabsorption, PLUS secretion = excretion.

Filtration = about 20% of blood going through glomerulus.

Less reabsorption = molecules that are sent back into interstitial space and reabsorbed into the blood via the peritubular capillaries.

Plus secretion = molecules that pass from blood TO urine (creatinine, penicillin, histamine, urea, etc.)
plasma colloid pressure
inherent pressure of the plasma due to the continued presence of large ions, proteins and other molecules that can't readily diffuse out.
hydrostatic pressure
effected by arteriole pressure (both efferent and afferent) hydrostatic pressure in the glomerulus effects glomerular filtration rates. The pressure exerted by the blood plasma. This pressure assists in forcing the filtration of plasma through the glomerular capillaries. At about 60mg Hg, this is much higher within the kidneys than in any other somatic capillary
net filtration pressure
Within the glomerulus, net filtration pressure is the resultant pressure through the capillaries, taking the gross input pressure minus the opposing forces. The opposing pressure forces are the colloid osmotic pressure of the plasma, plus the inherent hydrostatic pressure of the bowman’s capsule
renal blood flow
fluid filtered through the glomerular capillaries- helps to determine renal function
inulin
- polysaccharide
-not normally found in plasma
- used as a way of measuring glomerular filtration rates
- nontoxic
-Filters through the glomerulus and is neither absorbed nor secreted
- THEREFORE, 100% of inulin filtered = GFR.
Na+ K+ pump
maintains Na+ K+ concentrations in proximal tubular cells which allows reabsorption of metabolic products from glomerular filtrate.
glucose reabsorption
1mg/ml = 100 mg glucose filtered / minute. Usually ALL glucose is reabsorbed.
renal threshold
plasma glucose level at which glucose begins to escape complete reabsorption and enter urine. (as in diabetes.)
osmotic diuresis
increases in solute concentration necessitates additional water to carry solutes away. Increases in solute excretion causing additional water and diuresis is osmotic diuresis.
urea
solute normally found in plasma which is filtered and mostly reabsorbed.
acidosis
if GFR falls to below normal rates, kidneys ability to secrete acid is reduced. Acid is retained, body pH fluid falls, body functions may not work properly.
vasopressin / antidiuretic hormone (ADH)
hormone inhibits diuresis
synthesized by hypothalamus.
stored in posterior pituitary.
aldosterone
secreted by cortical layer of adrenal gland
stimulates activity of Na+K+ transport --> important regulator of BLOOD PRESSURE
renin
protein which initiates reactions in renin-angiotensin system. Causes the formation of angiotensin I from angiotensinogen, secreted by the liver.
Angiotensin converting enzyme: ACE
ACE, angiotensin converting enzyme has an important role in determining blood pressure, as it splits angiotensin I to produce angiotensin II, which increases blood pressure by constricting small vessels. The lungs contain the highest concentration of ACE in the body and it is here that the majority of angiotensin is converted by ACE, however ACE is also present in most other cells of the body
renin angiotensin system
REGULATES BLOOD PRESSURE.
1. Kidney senses low blood pressure or reduced Na+ filtration of glomerulus
2. kidney secretes renin
3. liver continuously secretes angiotensinogen to blood.
4. renin contacts angiotensinogen in blood, it becomes angiotensin I
5. Angiotensin I contacting ACE (present in most cells, but highest concentration in lungs) converts it to Angiotensin II
6. Angiotensin II causes:
- vasoconstriction of small vessels (rise in blood pressure)
- Increased ADH secretion by posterior pituitary = increased thirst --> increased thirst = increased: drinking + fluids --> increased blood pressure
- increased ALDOSTERONE secretion by Adrenal gland --> SALT reabsorption and potassium secretion increase by KIDNEY--> INCREASES BLOOD PRESSURE.
diabetes insipidus
causes high volumes of urine production - can't drink enough to keep up -> this causes LOW blood pressure. No irregularity of glucose in blood plasma, urine, nor any impairment of insulin secretion.
CAUSED BY LACK OF ADH (ANTI-DIURETIC HORMONE) production by hypothalamus, so PREVENTION of urination doesn't happen.
osmoreceptors
receptors in brain which sense osmolality of plasma, which serves as information which influences secretion rates of ADH.

-->Plasma osmolality up, ADH up, Urine down.

more concentrated urine = more diluted bodily fluids = plasma osmolality down to normal.
Atrial natriuretic peptide (ANP)
released when atrial stretch-receptors sense too much blood volume. Causes kidney to excrete more Na+, and therefore more H2O, bringing blood volume back down to normal.
countercurrent multiplier system
system in the nephrons which concentrates urine through the exchange of ion back and forth across the interstitial space between close together parallel tubules.
dialysis
separating fluids by a selectively permeable membrane which is bathed in an ideal plasma substitute so that water and small solutes pass across the membrane, thus filtering out. Filters out K+, urea, etc.
diuretics
class of drugs which, through the inhibition of Na+ transport through renal tubules, cause increased natriuresis (salt excretion) as well as increased overall urine excretion by the kidneys. The resultant decrease in blood volume is effective for lowering blood pressure. Thus, diuretics are used to treat both hypertension and heart disorders
mechanism which maintains acid-base balance in the body
kidneys secrete acid into tubules along the length of the nephron.
hypertension effects on urine production
increased pressure = increased fluid volume = atrial release of atrial natriuretic peptide = increased excretion of Na+, H2O, i.e. MORE urine production.

Hypotension = opposite effect.
GLOMERULAR FILTRATE COMPONENTS
Albumin
glucose
amino acids
urea
sodium
potassium
creatinine
H+
Nephron components
Afferent arteriole
efferent arteriole
glomerulus
bowmans capsule
proximal tubule
peritubular capillaries
distal tubule
loop of henle
collecting duct
Structural factors which allow filtration through glomerulus
1. glomerulus being served not by one but by TWO arterioles, resulting in a HIGHER than normal pressure going into the glomerulus.
2. despite the thickness of the filtration barrier made up of the:
- podocytes which restrict cell filtration
- basement membrane which blocks proteins and large solutes, and
- the interdigitating foot processes of the podocytes, this barrier remains PERMEABLE, physically allowing filtration
Pressure gradients which allow glomerular filtration
pressure of the arterial blood coming in does so at a higher pressure, of about 60 mm Hg. There are inherent pressures within the structure of the glomerulus, however. The bowmans’ capsule has an inherent pressure of about 20 mm Hg, while the colloid osmotic process creates an opposing force of about 30 mm Hg. The incoming pressure of 60 mm Hg, versus the 50 mm Hg of opposing pressures, means that there is still a net pressure of 10 mm Hg which is forcing the capillary filtration of the glomerulus
Diabetes mellitus symptoms
sugary urine
high urine flow
can't drink enough
improper insulin levels
too much glucose for kidney to reabsorb
trouble maintaining plasma osmolality
Diabetes insipidus
NOT sugary urine
high urine flow
have trouble drinking enough
INSULIN FINE
glucose uptake fine
VERY LOW blood pressure
ADH levels low --> urination not being prevented by hypothalamus hormone.
How glucose absorbed out of proximal tubule?
Na+ concentration HIGHER in tubular fluid than in cells lining tubule --> allows glucose transport via facilitated diffusion of Na+ with Na+'s carrier molecule.

glucose then goes into interstitial fluid, and into peritubular capillaries (blood) --> is completely reabsorbed.
decrease in aldosterone affect water reabsorption and sodium reabsorption how?
decreased Na+ reabsorption, increased K+ absorption. Decreased Na+ = decreased H2O. If 20% of water is lost, death results.
Increased Aldosterone production causes?
increased Na+ retention
increased H2O retention
increased fluid/blood volume
increased blood pressure - hypertension.