Renal Flashcards
Posterior pituitary stores and releases what two hormones?
- ADH
- Oxytocin
- released when needed
ADH is significant why?
- primary role is to stimulate water retention by kidneys
- secondary role is to cause a rise in blood pressure via vasoconstriction
Osmolality
- concentration of solution (how “substancey” something is)
Brattleboro rats
Mutated ADH gene
- exhibit excessive thirst and frequent urination
- kidneys can’t retain water
Human water content varies with age and gender - give some examples
- babies ~75% water
- women ~50%
- men ~60%
- elderly ~45%
What happens when blood osmolality goes up?
- osmoreceptors in hypothalamus signal to posterior pituitary to release ADH into blood stream
- ADH tells kidneys to resorb water (pee less)
- Blood volume goes up and blood osmolality decreases
Sources of water intake
- fluids and food (2250 mL)
- metabolism (250 mL)
Sources of water loss
- urine (1500 mL)
- lungs (700 mL)
- sweat (200 mL)
- feces (100 mL)
Where is all the water in our bodies?
2/3 is intracellular
1/3 is extracellular
* interstitial fluid
* blood plasma
Human urine is ___ times more ______ than blood
4.6; concentrated
Arabian camel water regulation
Can’t avoid hot dry dessert and could go days without water - even active
- can’t close kidneys down! so instead
- lipid stored in hump because lipid metabolism provides lots of energy
- dry food provides some water
- kidney is very efficient
- thermoregulates by panting but shuts down when dehydrated
- urine to blood ratio is 7
Kangaroo rat water regulation
Never drinks water and has high respiratory water loss!
- obtains water from dry food and metabolic water
- moist air in burrows
- nocturnal
- very dry fees
- urine to blood ratio is 14
Marine mammal water regulation
No access to fresh water and seawater has a salt concentration of 3.5%
- obtain water from food (krill)
- produce very concentrated urine
- ratio of 5 to 6
Water regulation hibernating bears
Hibernate at half the year without eating drinking or excreting
- reduce BT
- reduce heart rate
- metabolic water from lipids balances respiratory water loss
- special mechanism for eliminating urea without urinating
3 main functions of the kidney
- excrete metabolic waste products
- involved in water and electrolyte regulation
- balance pH
Functional unit of kidney
NEPHRON
- 80% cortisol
- 20% dip into medulla
4 regions of nephron
- Bowman’s capsule
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
Bowman’s capsule
Contains glomerulus
- porous epithelial lining allows for filtration
- podocytes (holey cells)
PCT
Located in renal cortex
- lots of mitochondria to make ATP to power pumps that pull lots of sodium ions from filtrate
- large surface area
Loop of Henle
Starts in cortex, dips into medulla, and comes back up
- Drives reabsorption by creating a salt concentration gradient
- actively pumps out salt in ascending limb
- passively pumps out water in defending limb
DCT
Renal cortex
- filtrate runs out of loop and into collecting duct
Urine is formed by 3 basic steps
- Filtration
- Reabsorption
- Secretion
Glomerulus
Tangle of capillaries (like a ball of yarn)
- blood flows in afferent arteriole
- blood exits efferent arteriole
- filtering occurs thanks to hydrostatic blood pressure
Glomerular filtration rate
Myogenic autoregulation of filtration so that nothing changes with blood pressure
- increase in bp causes afferent to constrict and efferent to dilate
- decrease in bp causes afferent to dilate and efferent to restrict
Juxtaglomerular apparatus
Assists with constricting and dilating in myogenic autoregulation
Juxtaglomerular cells
Smooth muscle cells in afferent arteriole
Macula densa cells
Sensory cells in region of distal convoluted tubule that send message about what is happening and what needs to be corrected
Mesangial cells
Connect JG and MD cells via gap junctions
Sympathetic Nerve Fibres
Are associated with afferent arterioles
- redirect blood from kidneys to other organ systems
GFR is relatively constant at?
125 ml/min to ensure constant flow of filtrate for reabsorption and elimination
Renin-Angiotensin system @__________
level of body - not glomerulus!
When blood pressure falls RAAS…
- JG cells secrete renin into blood
- Renin acts on angiotensinogen to produce ANG1
- ANG1 is converted into ANG2 by ACE
- ANG2 is a potent vasoconstrictor
- causing increase in bp
When blood volume is low RAAS…
- ANG2 stimulates aldosterone secretion from adrenal cortex
- together they increase salt and water retention in kidneys and blood volume increases
Peritubular capillaries
Surround nephron
- sends more water/solutes into nephron and drawing out more water/solutes from nephron
Ascending limb
- thick wall
- impermeable to water
- permeable to salt
Descending limb
- thin wall
- permeable to water
- impermeable to salt
- deepest region reaches 1200-1400 mOsmol
Collecting ducts
Nephron drainage site
- more water is drawn out by osmosis from medullary concentration difference and reabsorbed into blood
- ADH must be present to make urine hyperosmotic
Vasa recta
Blood vessels wrapped around loop of henle
- maintain standing osmotic gradient
- countercurrent exchange takes up water
Countercurrent multiplier system set up by?
Ascending and descending limbs @ loop of henle
