renal system Flashcards
Where is ADH/vasopressin synthesized and stored?
hypothalamus ; posterior pituitary
How is plasma osmolality affected by dehydration?
increases ; stimulates an increase in water reabsorption in the kidneys (more H2O in blood, less in urine)
How does over-hydration affect plasma osmolality?
decreases ; stimulates decrease in water reabsorption in the kidneys (less H2O in blood, more H2O in urine)
What happens in Brattleboro rats?
- mutation in ADH gene ; no ADH production
- excessive thirst
- excess dilute urine
- diabetes insipidus (kidneys cannot conserve water)
What rhythm does ADH follow in children?
- circadian
- ASH levels increase at night (increased absorption of H2O, decreased production of urine)
How much H2O is intracellular and how much is extracellular?
2/3 - intracellular
1/3 - extracellular
How is H2O intaken?
- drinking fluid and H2O in food
- Water produced by metabolism
What is the rule of 3s?
- A human can survive for 3mins w/o air
- A human can survive for 3hrs w/o shelter (in harsh environment)
- A human can survive for 3 days w/o water
- A human can survive for 3 days w/o food
What is special about water regulation in the Arabian Camel?
- Can survive for days w/o H2O in hot and dry environment
- lipid metabolism of lipid stored in hump provides a significant amount of metabolic H2O
- dry food provides some H2O
- cannot halt the function of the kidneys but they are efficient at H2O recovery
- When Hydrated: thermoregulate by panting
- When Dehydrated: no panting
- thermoregulation turned off for water conservation (supercooling at night, overheating during day)
Describe the functioning of the Renin-Angiotensin System (RAAS)
1. Blood pressure falls
2. Juxtaglomerular cells secrete renin into the blood
3. Renin acts on angiotensinogen to produce angiotensin I (ANGI)
4. ANGI is converted into ANGII by angiotensin converting enzyme (ACE)
5. ANGII is a vasoconstrictor
6. Blood pressure increases
What is the function of Angiotensin II?
- Stimulates aldosterone secretion from adrenal cortex
- Acts with aldosterone to increase salt & water retention by kidneys (increases blood volume)
Waht is special about water regulation in the Kangaroo Rat?
- high oxygen consumption and respiratory water loss
- survive w/o drinking H2O (even when available)
- maintain body temp.
- obtain H2O from dry food and metabolism
- moist air in burrows reduces respiratory H2O loss
- nocturnal (avoid heat of the day)
- produce very dry feces
What happens when humans drink salt water?
become dehydrated
What happens to the blood after it travels through the glomerulus?
It continues winding around the nephron:
- Blood vessels send more water/solutes into the nephron as needed
- Blood vessels draw water/solutes out of the nephron as needed
What is Secretion?
- Opposite of reabsorption
- Active transport of substances from the peritubular capillaries into the tubular fluid
Excess K+ from glomerular filtrate is returned/reabsorbed into peritubular capillaries (blood) in proximal convoluted tubule – where does most of this filtrate go? Where does the rest go?
-
~65% of salt & water in original glomerular ultrafiltrate reabsorbed across proximal tubule & returned to
vascular system - ~20% returned to vascular system by reabsorption through descending limb of loop of Henle
How do marine mammals that have no access to fresh water survive?
- obtain water from food (krill, fish, plankton
- obtain water from metabolism
- produce very concentrated urine
How do grizzly bears survive during hibernation?
- live off stored fat reserves - metabolic water from lipids balance respiratory water loss
- do not eat, defecate, drink or urinate
- reduce their metabolix rate and heart rate
- urea recycled to produce protein
- water reabsorbed from bladder
What is paracellular transport?
reabsorbtion due to tight junctions of the proximal convoluted
tubule cells being leaky
What is transcellular transport?
reabsorbtion through the cell
What are teh functions of the kidneys
- essential organs for life
- excrete metabolic waste products
- involved in other homeostatic processes (H2O and electrolyte regulation, pH balance
- Major blood vessels associated (renal artery and vein)
Desrcibe the steps of secretion (3)
1. Filtration:
- Fluid & solutes leave glomerulus & enter Bowman’s capsule
2. Tubular reabsorption:
- Returns useful solutes & water to bloodstream
3. Tubular secretion:
- Returns selected solutes & water to tubules; eliminates wastes from blood
End result is filtered blood & waste removal (concentrated
urine)
What drains the urine from the kidneys?
ureters ; by peristalsis
What stores urine?
the bladder
What drains the bladder?
Urethra
What is the function of the The Loop of Henle?
Sets up hyperosmotic environment in renal medulla (juxtamedullary nephrons) so that urine concentration can occur
What are the components of the kidneys?
- cortex
- renal medulla
- major arteries/veins
- paillae of the renal medulla (renal pyramids)
- renal pelvis connected to ureter
What is the nephron?
- functional unit of the kidney
- blind-ended microscopic tubules
- lost with age, cannot be replaced
- associated with networks of peritubular capillary vessels
What is the function of the Descending Loop of Henle?
- Thin-walled
- Filtrate becomes very concentrated (from 300 to 1200 mosm/L as it reaches loop turn)
- Allows water to be drawn out i.e. impermeable to salt & permeable to water
What is the function of the Ascending Loop of Henle?
- Thick-walled
- Rich in mitochondria
- Salt actively extruded & sent back into interstitial fluid i.e. permeable to salt & impermeable to water
- Concentration (osmolality) decreases from 1200 back to 300 mosm/L
What does it mean when a nephron is juxtamedullary?
they dip into the medulla
What is the Countercurrent Multiplier System?
- Descending limb is passively permeable to water, making
the concentration in the tubule more concentrated - Extrusion of salt from ascending limb makes the
surrounding interstitial fluid more concentrated
What are the four regions of the nephron?
1.Bowman’s/glomerular capsule (where blood enters)
2.Proximal convoluted tubule
3.Loop of Henle
4.Distal convoluted tubule
note: collecting ducts olay an essential role in water retention but not typically considered a part of the nephron
──── must be present
to make urine
hyperosmotic (more
concentrated than blood)
ADH
What are the three steps of urine formation?
- filtration - movement of fluid from blood -> lumen of nephron ; only takes place in “renal corpuscle” where glomeruli and Bowman’s capsule allow for bulk flow of fluid
- Reabsorption - after filtrate leaves Bowman’s capsule, it is modified by reabsorption ; substances in the nephron tubules flow back into blood
- secretion: select molecules are removed from the blood and added back into the nephron tubule filtrate
What is the fucntion of the collecting ducts?
Under influence of ADH, water drawn out of filtrate by osmosis from medullary collecting duct into blood (to make urine
hyperosmotic)
Describe the steps needed to make urine hyperosmotic in the collecting ducts
(i think the collecting ducts?? These slides are very confusing lolol)
- ADH is secreted from the posterior pituitary
- ADH/vasopressin binds receptor
- Signals cAMP
- Inserts AQP2 on apical side
- Water absorbed by osmosis into blood
What are the risk factors for chronic kidney disease?
- 20+ yrs. old
- female
- diabeters
- hypertension
How does filtration occur in the kidneys?
- inner layer of Bowman’s capsule made up of podocytes
- intricate interdigitation of pedicels
- filtration slits/diaphragms - act as filters, negatively charged, major barrier to proteins, smaller plasma solutes easily enter glomerular filtrate
- proteinuria - mutations in slit proteins causing protein in urine
How is blood plasma forced out of the glomerulus into the Bowman’s capsule?
Blood hydrostatic pressure
What is the role of the Vasa Recta?
- Acts as counter current exchange system
- Diffusion of salt & water changes the salt concentration of the interstitial fluid in the renal medulla (therefore maintains standing osmotic gradient)
is the daily glomerular filtrate production higher in women or men?
Men - 180L/day
Women - 150L/day
How often is the entire blood volume filtered?
every 40 mins ; most of it is recovered
What is the role of the Ureters?
- Urine moves from renal pelvis to ureter
- Smooth muscle in walls carry out peristalsis
- Peristalsis waves move urine toward bladder
What is the Glomerular Filtration Rate?
- determined by glomerular blood hydrostatic pressure in the glomerular capillaries
- Increased blood pressure: afferent arteriole constricts ; efferent arteriole dilates
- Decreased blood pressure: afferent arteriole dilates ; efferent arteriole constricts
What prevents backflow of urine from the bladder back into the ureters?
flap valve
What happens to GFR when blood hydrostatic pressure changes?
stays constant at 125mL/min
What are some characteristics of Hyperosmotic Urine?
- Sterile
- Pale to dark yellow
- Rapidly populated by bacteria
What are some substances that if found in urine, insidcate disease (5)?
- Protein
- Glucose
- Blood cells
- Hemoglobin
- Bile
What does a relatively stable GFR ensure?
constant flow of glomerular filtrate ; allowing reabsoprtion to occur and waste to be eliminated
What are Juxtaglomerular cells?
smooth muscle cells in the afferent
arteriole
What are Macula densa cells?
sensory cells in a region of the distal
convoluted tubule
What are Mesangial cells?
connect juxtaglomerular & macula densa cells (i.e. communication)
What are Sympathetic nerve fibres?
associated with afferent arterioles; redirect blood from kidney to other organ system
