8 - Renal Physiology and Renal Clearance PPT Flashcards
We leave GI and enter the KIDNEY. Name the functions of the kidney!
- Filters blood to remove junk
- Regulates blood pH, vol, pressure, osmolarity
- Produces hormones, namely 𝐫𝐞𝐧𝐢𝐧
Bonus points if you can name the cartoon this gif is from
What is the function of hormone 𝐫𝐞𝐧𝐢𝐧?
It works within the RAASystem to regulate blood pressure!
Review the general structure of the kidney.
- Renal Hilum
- Renal Cortex
- Renal Medulla
What’s the renal hilum?
It’s the indentation in the middle of each kidney and the entry and exit point for the ureter, arteries, veins, lymphatics and nerves
What’s the renal cortex?
Just the outer portion of the kidney
What’s the renal medulla?
It contains the renal pyramids, whose POINTY ENDS (also known as renal papilla) aim towards the center of the kidney
How many nephrons are in each kidney?
ONE MILLION NEPHRONS.
What’re the components of a nephron?
Renal corpuscle and renal tubule
Where does blood filtration start in the nephron?
Renal corpuscle
The renal corpuscle contains a glomerulus… what the bawa is that?
A tuft of capillary supplied by an afferent arteriole and Bowman’s capsule
How does blood enter the nephron?
- Blood flows into the glomerulus from the afferent arteriole
- Water and solutes pass through capillary endothelium into basement membrane/epithelium
- From basement membrane/epithelium into Bowman’s space
Where does blood exit the nephron?
Blood enters the efferent arteriole, dividing into the peritubular capillaries, and then to venules and larger veins
Filtered blood leaves Bowman’s capsule and enters the renal tubule. What is the renal tubule made up of?
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
- Collecting duct
Urine from the renal tubules enters ________ → ________ → ________ → ________
- Minor calyces
- Major calyces
- Renal pelvis
- Ureter
What’s a good way to remember which arterioles receive unfiltered/filtered blood?
Afferent=Unfiltered
Efferent=Filtered
Mnemonic: Arrive Ugly, Exit Fresh
Let me hear some functions of the Juxtaglomerular Complex!!!
- Allows for communication between the tubule and blood vessels entering the glomerulus
- Helps regulate blood pressure (BP) and glomerular filtration rate (GFR)
Where is the juxtaglomerular complex located?
Between the distal convoluted tubule and the afferent arteriole
What does juxtaglomerular mean?
“Next to the glomerulus”
What three types-a cells can one find within the juxtaglomerular complex?
- Macula densa cells
- Extraglomerular mesangial cells (say that three times fast)
- Juxtaglomerular cells
Macula densa cells are special, why?
They can sense a decrease in sodium/BP, they can then signal to juxtaglomerular cells to secrete renin, which increases sodium reabsorption and constricts blood vessels, thus increasing BP through the RAASystem!
What is renal clearance?
The rate at which the kidneys clear blood plasma of substances by excretion
(TRUE/FALSE): Medications are excreted by the kidneys after being removed from blood plasma.
(TRUE)
What does the rate of renal clearance depend on?
- Glomerular filtration rate (GFR)
- Tubular filtration rate
- Secretion rate
How can renal clearance rate be affected?
It can decrease gradually with age, and also experience acute changes due to pathology
To filter the blood and remove any unwanted substances from the body, the first step in blood filtration occurs at…
… the glomerulus
What is the glomerulus?
A tuft of capillaries surrounded by Bowman’s capsule
The glomerular filtration barrier is made up of how many layers, and what do they do?
3 layers, they separate the blood inside the glomerular capillaries from the fluid inside the Bowman’s capsule.
The slits within the barrier allow which solute from plasma to enter the Bowman’s space?
Sodium
Inversely, the barrier slits prevent which negatively-charged/large particles from entering?
Proteins and RBCs
After the fluid has been filtered, what is its name?
Pre-urine (the prequel to the hit series “Urine”)
What does our beloved pre-urine travel through after filtration?
It leaves the Bowman’s space and travels through the nephron
What are the two functions possible within the different nephron sections?
They either reabsorb substances back into systemic circulation OR actively secrete them into the nephron to be excreted in urine!
Good news, we don’t need to know the formula for calculating renal clearance. However, we must know these ratios!
Okay then, show me! Out with it man!
If urine concentration is high but plasma concentration is low, that means…
… a lot of stuff was removed from the blood and set to be excreted, leading to a 𝐡𝐢𝐠𝐡 𝐫𝐞𝐧𝐚𝐥 𝐜𝐥𝐞𝐚𝐫𝐚𝐧𝐜𝐞.
If the ratio (of urine concentration to blood plasma concentration) is 𝐞𝐪𝐮𝐚𝐥 𝐭𝐨 𝟏, what does that mean?
The substance is 𝐟𝐫𝐞𝐞𝐥𝐲 𝐟𝐢𝐥𝐭𝐞𝐫𝐞𝐝 𝐛𝐮𝐭 𝐧𝐨𝐭 𝐬𝐞𝐜𝐫𝐞𝐭𝐞𝐝.
If the ratio is 𝐠𝐫𝐞𝐚𝐭𝐞𝐫 𝐭𝐡𝐚𝐧 𝟏, what does that mean?
The substance is 𝐟𝐫𝐞𝐞𝐥𝐲 𝐟𝐢𝐥𝐭𝐞𝐫𝐞𝐝 𝐚𝐧𝐝 𝐬𝐞𝐜𝐫𝐞𝐭𝐞𝐝.
If the ratio is 𝐥𝐞𝐬𝐬 𝐭𝐡𝐚𝐧 𝟏, what does that mean?
The substance is 𝐧𝐨𝐭 𝐟𝐫𝐞𝐞𝐥𝐲 𝐟𝐢𝐥𝐭𝐞𝐫𝐞𝐝 𝐚𝐧𝐝/𝐨𝐫 𝐢𝐬 𝐫𝐞𝐚𝐛𝐬𝐨𝐫𝐛𝐞𝐝.
What is Osmoregulation?
The regulation of body fluid solute concentration!
What are the main components of blood plasma osmolarity?
Sodium, glucose and urea
(TRUE/FALSE): Changes in hydration affect plasma osmolarity and blood pressure.
(TRUE)
Which receptor detects changes in plasma osmolarity, and where is it located?
Osmoreceptors, they’re located in supraoptic nuclei of the anterior hypothalamus
Which receptor detects changes in blood pressure, and where is it located?
Baroreceptors, they’re located in the cardiovascular system
Osmo/baroreceptors regulate production of which hormone in the hypothalamus?
Antidiuretic hormone (ADH)
How does overhydration affect osmoregulation?
- Plasma osmolarity decreases, blood pressure increases
- Osmo/baroreceptors fire less and less ADH is produced
- Little to no water is reabsorbed
How does dehydration affect osmoregulation?
- Plasma osmolarity increases, blood pressure decreases
- Osmo/baroreceptors fire more, more ADH is produced
- More water is reabsorbed from kidney
What is antidiuretic hormone (ADH)?
It’s a peptide hormone that prevents excessive urine production by reabsorbing more water from kidneys… duh
What does ADH allow the body to do?
Control the amount of fluid retained
What is ADH’s alter ego called, since it causes smooth muscle cells in arteries to constrict?
Vasopressin
Where is ADH stored?
Posterior pituitary gland
Where does ADH bind after its released to the kidneys?
V2 Receptors (aka AVPR2) on principle cells in the collecting duct within the nephron
What does AVPR2 convert ATP to?
cAMP
This cAMP conversion opens __________ to pull water from the lumen of the ducts into the interstitium for reabsorption into circulation
aquaporin channels
What are some causes of a large decrease in blood volume that would result in a large drop in blood pressure?
- Massive hemorrhage
- Third degree burn
What receptors detect this huge change and signal the hypothalamus to increase ADH secretion?
Baroreceptors
Where are baroreceptors located?
Specifically, in the carotid artery and the arch of the aorta
Where else might we find the beloved baroreceptors?
Within the afferent artery under the name “juxtaglomerular cells”
What’s the function of juxtaglomerular cells?
They detect the changes in blood pressure and signal to the kidneys to secrete renin
What is renin and what is its relation to angiotensinogen, a secretion of the liver?
Renin is an enzyme that enters the blood plasma and binds to angiotensinogen, where it just hacks off a chunk of angio-T, leaving behind ANGIOTENSIN-I!!
Angiotensin-I floats around until it reaches various ___________ in the body.
capillaries
What enzyme do endothelial cells in the lungs have particularly for angiotensin?
Angiotensin converting enzyme (ACE) (get whoever named that one a promotion)
What is the product after angiotensin converting enzyme (ACE) cleaves two amino acids off angiotensin-I?
Angiotensin-II (crazy!!!)
What is the function of angiotensin-II?
It stimulates the hypothalamus to make more ADH
Angiotensin-II also acts directly on blood vessels to do what?
Stimulate vasoconstriction
Angiotensin-II also acts on the adrenal gland to stimulate the release of what?
Aldosterone
What are the two ways ADH can increase blood pressure?
- ADH increases # of aquaporin 2 in the distal tubule/collecting duct, which reabsorbs water from urine and replenishes plasma vol.
- ADH acts on smooth muscle cells in the arteries causing them to constrict, increasing peripheral vascular resistance and BP.
- When that happens, baroreceptors detect the BP change and tell the hypothalamus to stop ADH secretion!
