renal fuction 4a Flashcards
what are the six sections the regulation of kidney can be divided into?
kidney function divided into six sections: regulation of extracellular fluid volume and blood pressure, regulation of osmolarity, maintenance of ion balance, homeostatic regulation of pH, excretion of waste and production of hormones
What is regulation of extracellular fluid volume and blood pressure?
:extracellular fluid decreases, blood pressure decreases, if ECF and BP fall to low body can’t maintain blood flow to the brain and other organs, works w/ cardiovascular system to ensure that blood pressure and tissue perfusions remain in a suitable range
what is regulation of osmolarity?
regulation of osmolarity: integrates kidney function with behavioral drives, such as thirst to maintain blood osmoalrity @ 290 mOsM
what is maintenance of ion balance?
Maintenance of ion balances: keep conc. of key ions within a normal range by balancing dietary intake with urinary loss. Na+ major ion involved in regulation of ECF and osmolarity K+ and Ca are also closely regulated
what is homeostatic regulation of pH?
Homeostatic regulation of pH: pH of plasma kept within a narrow range. If ECF to acidic, kidney remove H+ and conserves bicarbonate HCO3- , if the ECF is to alkaline it would remove HCO3- 0and conserves H+ , do not correct pH imbalances as rapid as the lungs do.
what is excretion of waste?
Excretion of waste: remove metabolic waste(creatinine and muscle metabolism), foreign substances, drugs, environmental toxins, nitrogenous waste (urea, uric acid), urobilinogen gives urine the yellow color
what is the production of hormones?
production of hormones: kidney play a role in three endocrine pathways, kidney cells synthesize erythropoietin- regulates red blood cell synthesis , also releases renin enzyme that regulates production of hormones involved in sodium balance and blood pressure homeostasis, renal enzymes help convert vitamin D3 into a hormone that regulates Ca2+ balance
what is the most important function of the kidney?
most important function of kidney is the homeostatic regulation of water and ion content of the blood
waste removal important but irregularities in water and ion levels cause serious medical conditions
what does the urinary system consist of (organs)?
urinary system consists of the kidneys, ureters, bladder and urethra
what is the route of water takes on its way from plasma to excretion in the urine (urine production)
- water and solutes move from plasma into the hollow tubules (nephrons) makes up the bulk of the paired kidney’s - modifies the composition of the fluid
- modified fluid leave the kidney and passed onto a hallow tube called the ureter, 2 ureters, 1 leading from each kidney to the urinary bladder
- the bladder expands and fills w/ urine until, by reflex action, it contacts and expels urine through a single tube, the urethra
what is micturition or urination?
process where urine is excreted
where does the kidney’s lie ?
kidney site of urine formation lies on the either side of the spine at the level of 11th and 12th rib
What is the purpose of the concave side of the kidney?
-concave surface of each kidney face the spine
- renal blood vessels, nerve, lymphatics, and ureters all emerge from the concave side
-renal arteries which branch of the abdominal artery supply blood to the kidney
Renal veins carry blood from the kidney to the inferior vena cava to the heart
what is a nephron ?
nephron functional unit- smallest structure that can perform all the functions of the organ
what does the cross-section of kidney look like?
what are the layers of the kidney?
the outer layer known as the cortex, inner layer known as medulla
the layer consists of organized microscopic hollow tubules known as a nephron
what are the two types of nephrons?
- cortical nephron, found in the cortex of kidney, 80% of all nephron found in the kidney
- juxtamedullary nephron, found in the medulla, 20% of all nephron found in the kidney
what is the conventional circulation?
artery –> capillary–> vein —>heart
what is the venous circulation ?
artery –> capillary–> vein —>capillary —> vein —>heart
renal circulation in the cortical nephron
abdominal aorta –> renal artery –> branches of smaller arteries –> afferent arteriole –> glomerulus (capillaries)
- -> efferent arteriole –> peritubular capillaries –> venules
- -> veins –> renal vein –> vena cava
renal circulation of the juxtamedullary nephron
abdominal aorta –> renal artery –> branches of smaller arteries –> afferent arteriole –> glomerulus (capillaries)
- -> efferent arteriole –> peritubular capillaries/Vasa Recta
- -> venules –> veins –> renal vein –> vena cava
what is the difference between juxtamedullary nephron and the cortical nephron?
juxtamedullary nephron has a long peritubular capillary that dips down and touches the medulla, called the vasa recta
What is the function of the renal portal system
- filter fluid out of the blood into the lumen of the nephron through the glomerulus capillaries
- reabsorb fluid from the tubule back into the blood at the peritubular nephron
what is the renal corpuscle?
Bowman’s Capsule + Glomerulus
path of fluid in the nephron
from Bowman’s capsule filtered fluid flows into the proximal tubule, then to the loop of Henle ( hairpin- shaped segment that dips down toward the medulla and then back up) , fluid then passes the distal tubule, distal tubule of up to 8 nephrons drains into a single larger tube called the collecting ducts, collecting ducts pass from the cortex through the medulla and drain into the renal pelvis
what is the distal nephron?
distal tubule + its collecting duct
8 nephron for a collecting duct
what is a juxtaglomerular apparatus?
the nephron twists and folds back on itself so, final part of the ascending limb of the loop of Henle passes between the afferent and efferent arterioles. This region is known as the juxtaglomerular apparatus
the proximity of the ascending limb and the arterioles allow for paracrine communication b/w the two structures
what are the three processes that take place in the nephron
- filtration
- reabsorption
- secretion
what is filtration
- filtration the fluid from the body into the tubules
- filtration only takes place in the renal corpuscle, walls of the glomerular capillaries and Bowman’s capsule are modified to allow the bulk flow of fluid
- once the filtered fluid called filtrate, passes into the lumen of the nephron, it becomes part of the body’s external environment
- anything that filters into the nephron is destined for excretion unless it’s reabsorbed from the lumen of the nephron
what is reabsorption?
Reabsorption process of moving substances in the filtrate from the lumen of the nephron back into the blood flowing through peritubular capillaries
what is secretion?
- Secretion removes selected molecules from the blood and adds it to the filtrate in the tubule lumen
- secretion is more selective than filtration , usually uses membrane proteins to move molecules across the tubule epithelium
what is the fluid volume and osmolarity after leaving the Bowman’s capsule
180 L/day 100% volume 300 mOSM - same composition of plasma -isosmotic
what is the fluid volume and osmolarity after leaving the proximal tubule and before entering the loop of Henle
54 L/day 30% volume 300 mOsM - 70% reabsorbed - same osmolarity os filtrate entering the proximal tubule and exiting the promixal tubule
what is the fluid volume and osmolarity after leaving the loop of Henle before entering distal tubule + collecting ducts
18 L/day 10% volume 100 mOsM - site of the creation of dilute urine -more solute absorbed than water - fluid hypo-osomtic relative to plasma
what is the fluid volume and osmolarity after leaving distal tubule + collecting ducts
1.5 L/day
1% volume
50–1200 mOsM
- the salt and water balance are regulated through several hormones
Equation for fluid amount excreted
Amount filtered - Amount reabsorbed + Amount secreted = amount excreted
what is filtration fraction
percentage of plasma that flows into the kidney and filters in the nephron
what are the three filtration barriers plasma has to go through before entering the lumen of the tubule
three filtration barriers before entering the tubule lumen: the glomerular capillary endothelium, a basal lamina (basement membrane), and the epithelium of Bowman’s capsule
what is the glomerular capillary endothelium?
Glomerular capillaries are fenestrated capillaries, with large pores that allow most components of plasma to filter through endothelium
- pores are small enough prevent blood cells from leaving the capillaries
- negatively charged proteins on the pore surface repel negatively charges plasma proteins
what is the basal lamina (basement membrane)
it’s acellular layer of extracellular matrix that separates the capillary endothelium from the epithelial lining of Bowman’s Capsule
- consists of negatively charged glycoproteins, collagen, and other proteins
- acts as coarse sieve, keeping most proteins in plasma
what is the epithelium of the Bowman’s capsule
- capsule epithelium that surrounds each glomerular capillary consists of specialized cell called podocytes
- podocytes have long cytoplasmic extensions called foot processes that extend from the main cell body
- foot processes wrap around the glomerular capillaries and interlace with one another, leaving narrow filtration slits closed by a semiporous membrane
- filtration slit membrane contains several unique proteins: nephrin and podocin
- in these diseases, where nephrin or podocin are absent or abnormal, proteins leak across the glomerular filtration into the urine
what are three pressure that influence glomerular filtration
- The hydrostatic pressure
- colloid osmotic pressure
- fluid pressure created by fluid in Bowman’s capsule
of blood flowing through the glomerular capillaries force fluid through the leaky endothelium
- capillary blood pressure averages around 55 mm Hg and favors filtration into Bowman’s capsule
- filtration takes place along nearly the entire length of the glomerular capillaries
what is hyrdrostatic pressure
the hydrostatic pressure of blood flowing through the glomerular capillaries force fluid through the leaky endothelium
- capillary blood pressure averages around 55 mm Hg and favors filtration into Bowman’s capsule
- filtration takes place along nearly the entire length of the glomerular capillaries
what is colloid osmotic pressure
The colloid osmotic pressure (π) inside the glomerular capillaries is higher than that of the fluid in the bowman’s capsule
- gradient is due to the proteins present in the plasma
- osmotic pressure gradient averages 30 mm Hg and favors fluid movement back into the capillaries
what is the fluid pressure found in the Bowman’s capsule
Bowman’s capsule is an enclosed space, so the presence of fluid in the capsule created a hydrostatic fluid pressure Fluid that opposes fluid movement in to the capsule
- fluid filtering out of the capillaries must displace the fluid already in the capsule lumen
- the net driving force is 10 mm Hg in the direction of filtration, not very high but with a very leaky nature and fenestrated capillaries, it results in rapid fluid filtration into the tubules
what is GFR?
- the fluid volume that filters into the Bowman’s capsule per unit of time
- 180L/day, 125ml/min
- 60 times a day, 2.5 times per hour
What influences GFR ?
- net filtration pressure: the three pressure hydrostatic pressure, colloid osmotic pressure + fluid pressure created by fluid in Bowman’s capsule
- Filtration coefficient - 2 factors:
the surface area of the glomerular capillary
permeability of interface between capillary + capsule
blood pressure provides hydrostatic pressure that drives glomerular filtration true or false
True
increase in resistance in the afferent arteriole
decrease in renal blood flow
decrease in hydrostatic pressure
decrease in GFR
increase in resistance in the efferent arteriole
decrease in renal blood flow
increase in hydrostatic pressure
increase in GFR
what is the main role of autoregulation of GFR
protect the filtration barrier from high blood pressure that can damage it
what are two mechanisms of autoregulation if GFR
myogenic response- intrinsic ability of vascular smooth muscle to respond to blood pressure BP
-Vasoconstriction in response to high BP is more effective in normalizing GFR than vasodilation in response to low blood pressure
tubuloglomerular feedback- paracrine signaling mechanism through which fluid flows through the loop of henle influences GFR
-invovles juxtaglomerular apparatus
juxtaglomerular apparatus
modification on both the tubule and wall of arterioles.
- mascula densa on the epithelium if the tubule
-granules (GF cells) on the arteriole walls
-mascula densa walls- paracrine factors that act of the smooth muscle on the ateriole walls
granules- secrete renin, an enzyme that regulates Na and water balance
juxtaglomerular apparatus
- increase in GFR
- increase in flow in tubules
- increase in flow of NaCl past macula densa
- paracrine signals from macula densa acts of the arteriole walls
- arteriole walls comstrict
- decrease renal flow in the tubules
- decrease hydrostatic pressure
- decrease in GFR
Hormones and the autonomic nervous system alter glomerular filtration rate in two way:
by changing resistance in the arterioles and by altering the filtration coefficient.
