Renal System Flashcards
renal capsule, adipose capsule and renal fascia are all what type of tissue?
connective tissue
renal capsule
- Physical barrier - protection against trauma
- maintains the SHAPE of the kidney
Adipose capsule
- padding - physical protection
- Maintains the POSITION
Renal fascia
- ANCHORS the kidneys to the surrounding structures
adipose capsule, renal capsule, and renal fascia in the order that you find them (moving in towards the kidney)
Renal fascia
adipose capsule
renal capsule
many __________ (of which there are around one million per kidney), feed into the _________ _________. Many of these lead into the __________ _______, which feeds into the ______ then the ________ _______ (“cups”). Finally entering the _______, before leaving the kidney via the _______ and entering the bladder.
many nephrons (of which there are around one million per kidney), feed into the collecting duct. Many of these lead into the papillary duct, which feeds into the minor then the major calyces (“cups”). Finally entering the pelvis, before leaving the kidney via the ureter and entering the bladder.
what constitutes a lobe?
Medullary pyramid + overlying cortex + 1/2 renal column from each side
how many lobes?
8-12 per kidney
where are renal corpuscles found
cortex only.
parenchyma
functional portion of the kidney
fenestration of the glomerular endothelium prevents…
blood cells being filtered out of the blood, but allows all plasma proteins to pass through
basal lamina of glomerulus
prevents filtration of larger proteins
slit membrane / diaphragm between __________. Prevents… ?
slit membrane between pedicels prevents medium-sized proteins from being filtered out of the blood plasma
parietal of the glomerular (Bowman’s) capsule
simple squamous epithelium forms the outer wall
visceral of the Bowman’s capsule
Podocytes (modified endothelium)
Glomerulus tissue
endothelium
Bowman’s capsule tissue
epithelium
glomerulus
specialised network / knot of capillaries
2 thing that make up the renal corpuscle
- Glomerulus
2. Glomerular capsule / Bowman’s capsule
what is the Basal lamina made up of?
the basement membranes of both the endothelium and the podocytes ‘crossing-over’
2 most Important functions of the kidney
- Regulation of water and electrolyte balance (osmolality)
- Regulation of arterial pressure
(other) functions of the kidney
- excretion of metabolic wastes or foreign chemicals
- Regulation of blood pH
- Regulation of erythrocyte production
- regulation of hormone production e.g. vitamin D
- regulating of blood glucose levels
Homeostasis
maintenance of a (nearly) constant internal environment
osmolality
measure of the effective water gradient, assuming that the solute is COMPLETELY IMPERMEANT.
It is simply a count of the number of dissolved particles
tonicity
tendency of a solution to resist expansion
isosmotic and isotonic
isosmotic when both solutions contain the same number of dissolved particles.
isotonic when there is no movement of water
cell placed in hypertonic solution will ______, whereas a cell placed in a hypotonic solution will ______.
cell placed in hypertonic solution will shrink, whereas a cell placed in a hypotonic solution will swell.
osmotic pressure
the pressure required to prevent net water movement
what percentage of males, females and infants are fluids?
males ~60%
females ~50%
infant ~65-75%
what makes up the body fluids?
2/3 Intracellular fluid
1/3 extracellular fluid
what makes up extracellular fluid?
20% plasma
80% interstitial fluid
what effect will an isotonic solution have on plasma osmolarity?
NO EFFECT
why are slightly hypertonic solutions used in an IV drip?
so that some water leaves the cells - boosting blood volume
how much water is lost and gained per day?
2500mL
total volume of fluid in a 70kg male
42L
which ions are in a higher concentration in the intracellular fluid vs. the extracellular fluid
K+
which ions are in a lower concentration in the intracellular fluid vs. the extracellular fluid
Na+, Cl-, Ca2+
what is responsible for the asymmetric distribution of ions ?
specialised transport properties
three processes involved in the formation of urine
- filtration at the glomerulus
- tubular reabsorption
- tubular secretion
excreted in urine =
filtered - reabsorbed + secreted
describe the initial glomerular filtration
same concentration as plasma, but it lacks proteins and other high molecular weight compounds and is free from blood cells
urine production proportional to…
renal pressure
how is GBHP tightly regulated?
by controlling the diameter of the afferent and efferent arteriole
net filtration pressure (NFP) =
Glomerular blood hydrostatic pressure (GBHP) - Capsular hydrostatic pressure (CHP) - Blood colloid osmotic pressure (BCOP)
= 10mmHg
what is blood colloid osmotic pressure - BCOP?
the osmotic force of the proteins left in the plasma, pulling back on the water in the filtrate = 25mmHg
what is capsular hydrostatic pressure - CHP?
pressure exerted on the filtrate by the ELASTIC properties of the glomerulus = 15mmHg
Glomerular blood hydrostatic pressure is the…
mechanical pressure within the glomerulus
2 things that are altered in regulation of the filtration rate
- surface area available
2. GHBP
2 forms of autoregulation of GFR
i. myogenic mechanism
ii. tubuloglomerular feedback
myogenic mechanism of regulation
When blood pressure increases, smooth muscle in the afferent arteriole stretches more. Therefore, it will contract and the lumen will narrow and GFR will decrease.
tuboglomerular feedback
macula densa receives rapid delivery Na+ due to high BP. This leads to a decrease in Nitric oxide (NO) by the juxtaglomerular apparatus. This causes the afferent arteriole to constrict and therefore the GFR decreases.
Neural regulation of the GFR
Sympathetic nerves release norepinephrine which causes constriction of afferent arterioles and increased renin release. therefore the GFR decreases
2 hormones that are used to regulate GFR
- Angiotensin II - released when blood volume or blood pressure drops. Causes constriction of afferent and efferent arterioles – decreased GFR
- ANP - secreted when the atria of the heart stretch too much. Causes the relaxation of the mesangial cells in the glomerulus, which increases the capillary surface area of the glomerulus – increased GFR
proximal convoluted tubule
- largest ammount of solute and water reabsorption
- 100% of glucose reabsorbed
- 60% of glomerular filtrate and NaCl and water
- Na+ reabsorbed through glucose/Na+ symporters and Na+/H+ antiporters
- water movement via osmosis
- osmolarity similar to plasma
- highly developed brush border
descending loop of Henle
- water reabsorbed by osmosis
- impermeable to NaCl
- interstitial fluid in renal medulla becomes 2-4x more concentrated
- filtrate ~1200mOsmol/L at the bottom
Ascending loop of Henle
- NaCl actively absorbed by symporter
- impermeable to water (therefore filtrate becomes more dilute)
- content becomes ~100mOsmol/L as it enters the distal tubule
Late distal tube and collecting duct
- additional reabsorption of NaCl
- impermeable to water (in the absence of ADH)
vasopressin also called…?
Antidiuretic hormone (ADH)
No ADH =
no reabsorption of water = dilute urine
alcohol effect on ADH
inhibits production = no ADH = dilute piss
cortical nephrons
production of dilute urine
juxtamedullary neurons
production of concentrated urine
vasa recta
carries away the reabsorbed filtrates
what is the main solute at the top of the ascending loop?
urea
why is the loop of henle described as a countercurrent mechanism?
the descending loop is impermeable to NaCl and the ascending loop is impermeable to water
__________ in the ___________ detect changes in osmolarity. The ADH precursor is synthesised in the __________ and stored in vesicles in the _______ ________. When osmolarity increases, the ________ sends a signal to the __________ __________ to release ADH into the _______.
osmoreceptors in the hypothalamus detect changes in osmolarity. The ADH precursor is synthesised in the hypothalamus and stored in vesicles in the posterior pituitary. When osmolarity increases, the hypothalamus sends a signal to the posterior pituitary to release ADH into the blood.
action of ADH
stimulates the insertion of aquaporin-2 containing vesicles into the apical membrane of the collecting duct epithelia. water can then be absorbed through these water channels
how do osmoreceptors work?
they contain stretch-inhibited cation channels which open when the cells are exposed to hypertonic stimulus. Na+ enters and triggers an AP which travels to the posterior pituitary. ADH is released
threshold for ADH release
280 mOsmol/L plasma osmolarity
thirst felt when …
plasma osmolarity is greater than 290 mOsmol/L
BP drop effect on ADH levels
baroreceptors stretch less - ADH released - Water retained - BP returns to normal
most important hormones in regulating SODIUM reabsorption
- Angiotensin
- Aldosterone
what is renin and what does it do?
renin is an enzyme released in the juxtaglomerular cells which ultimately leads to an increase in levels of angiotensin II
3 triggers for renin release from granular cells in the juxtaglomerular apparatus
- low Na+
- Low BP in afferent arteriole
- low blood volume (decreased renal perfusion)
4 effects of Angiotensin II
- potent vasoconstrictor - decreases GFR
- small direct effect on reabsorption in proximal tubule
- stimulates release of Aldosterone
- stimulates thirst and salt intake - release ADH
aldosterone
released from the adrenal cortex. Aldosterone acts on the collecting ducts to increase transcription of Na+/K+ATPase pumps and therefore reabsorb more water and NaCl
function of Renin-angiotensin-aldosterone system
retention of sodium and water and thus blood volume
How do the macula densa cells in the juxtaglomerular apparatus respond to a decrease in NaCl?
release prostaglandins which act on granular cells in the afferent arteriole which release RENIN.
which is the first response when the BP changes?
autonomic nervous response
