Renal System Flashcards
What is the renal system
Kidneys
What do the ureter, bladder and urethra do?
Store and carry urine
Primary function of kidneys
Make urine and filter waste
Blood sources to/from kidneys
Renal artery and renal vein
Where does renal artery branch from
Abdominal aorta
Where do renal vein drain filtered blood to
Abdominal vena cava
Outer region of the kidneys
Renal cortex
Inner region of the kidneys
Renal medulla
Area in kidneys where urine collects and is eventually drained via ureter
Renal pelvis
Groups of tubules in medulla that drain into renal pelvis
Renal Pyramids
True/false: kidneys are also endocrine producers (make hormones)
True
Hormone made by kidneys that acts on bone marrow to stimulate RBC production
Erythropoietin (EPO)
Are kidneys also metabolic organs?
Yes
What metabolic function do kidneys carry out?
Gluconeogenesis
What does the process of gluconeogenesis make glucose from?
Lactic acid and amino acids
Smallest functional unit of kidneys
Nephron
How many nephrons in each kidney
About 1 million
2 components of nephrons
Vascular and Tubular
Claw-shaped tubule that wraps around glomerulus
Bowman’s capsule
Tuft of capillaries where urine production starts
Glomerulus
Tubule that comes after Bowman’s capsule
Proximal
What tubule comes after proximal
Loop of Henle (descending and ascending)
What tubules comes after ascending
Distal
Where distal tubule goes to
Collecting duct
How many nephrons are typically attached to collecting ducts
8-10
Where are collecting ducts found?
Medullary pyramids
Where do collecting ducts drain to?
Renal pelvis
Smallest branch of renal artery that delivers blood to glomerulus
Afferent arterioles
Fluid moving from glomerulus to bowman’s capsule
Glomerular filtration
Fluid that goes from glomerular capillaries to bowman’s capsule is the same as plasma minus what?
Cells, proteins
Blood not filtered by glomerulus moves to where?
Efferent arterioles
Blood from efferent arterioles go to this mesh-like network of capillaries that surround the nephron
Peritubular capillaries
Where do peritubular capillaries drain blood to?
Abdominal Vena cava
Structure that is very important regulator of filtration
Juxtaglomerular apparatus
Where is juxtaglomerular apparatus located?
In distal tubule where a V is formed by afferent and efferent arterioles
What does juxtaglomerular apparatus measure in distal tubule?
BP, O2, fluid rate
Type of nephrons located in outer cortex
Superficial cortical
What percent of all nephrons are superficial cortical
80%
Nephrons located in inner cortex near medulla
Juxtamedullary
Percent of nephrons that are typically juxtamedullary
20%
Where are glomeruli of superficial cortical and juxtamedullary nephrons only found?
In the cortex
Superficial cortical nephrons have short loops of henle that extend to where?
Upper medulla
Juxtamedullary nephrons have long loops of henle that extend to where?
Deep in medulla with tip of loop next to renal pelvis
What kind of vessels do superficial cortical nephrons have?
Mesh of peritubular capillaries
What kind of vessels do Juxtamedullary nephrons have?
Single efferent loop that runs parallel to loop of henle
What is single efferent loop in Juxtamedullary nephrons called?
Vasa recta
What shape does vasa recta form after it leaves medulla?
Mesh
What is function of cortical nephrons?
Make urine
What is function of Juxtamedullary nephrons?
Concentrate urine and conserve water
3 processes of urine formation?
Glomerular filtration (GF)
Tubular reabsorption (TR)
Tubular secretion (TS)
How much of plasma is filtered at glomerulus?
20%
Where does the other 80% of plasma go that isn’t filtered by glomerulus
Efferent arterioles
At peritubular capillaries, what gets reabsorbed from filtered fluid?
Water and solutes
Glomerulus and bowman’s capsules together is called what?
Renal corpuscle
True/false: GF is both passive and non-selective
True
Name 3 layers of glomerular membrane
- Wall of glomerular capillaries
- Basement membrane
- Inner layer of bowman’s capsule
What are individual foot-like processes of bowman’s capsule inner layer called?
Podocytes
What is the main function of the 3 layers in glomerular membrane?
Prevent plasma proteins and cells from passing through
What is fluid that enters bowman’s capsule called?
Filtrate
Are forces of GF active or passive?
Passive
How much is glomerular capillary blood pressure?
55 mmHg
Is glomerular capillary blood pressure a push or pull force?
Push
How much is plasma colloid osmotic pressure?
30 mmHg
How much is bowman’s capsule hydrostatic pressure
15 mmHg
What force promotes GF and is most important?
Capillary blood pressure
How much is net filtration pressure?
10 mmHg
GF rate (GFR) is an indicator of what?
Number of functional nephrons and kidney health
What is GFR?
Volume of fluid filtered per minute
What 3 things does GFR depend on?
- Net filtration
- Surface area
- Permeability of membranes
What is Filtration Coefficient (Kf)
Surface area x permeability
True/false: Kf should be a constant value in a healthy person
True
What is equation for GFR
Kf x net filtration
Why is GFR so important?
It is 1st step in urine formation
2 mechanisms of GFR
- Auto regulation
- Extrinsic sympathetic control
What mechanism controls GFR most of the time?
Auto regulation
How does auto regulation control GFR?
By preventing GFR change with normal BP changes
What does auto regulation change when BP fluctuates to maintain a constant GFR?
Diameter of afferent arteriole
What does auto regulation constrict or dilate to change afferent arteriole diameter?
Smooth muscle lining of vessel
What does extrinsic sympathetic control do?
Alters GFR to control blood volume
In what structure does GFR happen?
Juxtaglomerular Apparatus (JXA)
What are 2 special cells in JXA?
Granular (afferent)
Macula densa cells (distal)
What do macula densa cells constantly sense?
Fluid rate through distal tubule
If macula densa senses fluid change, what cells get a message to release vaso dilators or constrictors?
Granular cells in afferent arterioles
Can extrinsic sympathetic control override auto regulation?
Yes
What is released by sympathetic nerves in extrinsic control?
Epi and norepinephrine
What does epinephrine and norepinephrine attach to in afferent and efferent vessels?
Alpha adrenergic receptors
Is tubular reabsorption always selective?
Yes
Can tubular reabsorption (TR) be active or passive?
Either
How much of H2O filtered at capsule is reabsorbed?
99%
How much of glucose is reabsorbed
100%
How much sodium is reabsorbed
99.5%
How much of energy requirements of the kidneys is spent on Na+ reabsorption?
80%
What is only area where sodium is NOT reabsorbed?
Descending loop
What does sodium help reabsorb in proximal tubule?
Glucose
Aminos
H2O
Urea
What does reabsorption of sodium in ascending loop help?
Concentrate urine
Conserve H2O
What does sodium reabsorption in distal tubule and collecting duct regulate?
ECF volume and BP
How does sodium cross lumenal membrane
Passive channel or cotransporter
How does sodium leave basal membrane
ATP pump
Does ATP pump at basal membrane require energy?
Yes
Where in tubule does a lot happen in terms of sodium reabsorption
Proximal tubule
How does sodium cross lumenal membrane in proximal tubule?
Co-transporters for glucose, aminos or vitamins (each has specific one)
How do glucose, aminos, water soluble vitamins leave basal membrane
Passive facilitated diffusion carriers
Where is glucose filtered?
Glomerulus
What is max rate of reabsorption based on # of available transporters called?
Tubular maximum
What is amount of any substance filtered by kidneys per minute called?
Filtered load
What is normal plasma glucose level?
100mg/100ml
What is amount of glucose filtered per minute?
125mg/min
What is tubular maximum for glucose
375mg/min
What is term for maximum plasma concentration reached for any organic nutrient before it will show in urine
Renal threshold
What is renal threshold for glucose
300mg/ml
How does sodium reabsorb in ascending loop at lumenal membrane?
K+ and Cl- cotransporters
How does K and Cl cross basal membrane in ascending loop
Passive channel
How does sodium cross basal membrane in ascending loop
ATP Pump
What is sodium always coupled with?
Passive H2O reabsorption
H20 reabsorption is always active or passive?
Passive
What does H2O need for reabsorption
Osmotic gradient
Where does 80% of water reabsorption take place
Proximal tubule
What are 2 mechanisms of water reabsorption
Paracellular and trans cellular
Where are tight junctions most leaky for water to reabsorb
Proximal tubule and descending loop
How does sodium aid paracellular water reabsorption
Sodium pushed out along lateral wall attracts water
T/F: Water always moves from low to high Osmolarity
True
When sodium moves through a cell to interstitial space, what happens to osmolarity of interstitial space?
Increases
What structures help move water through membranes
Aquaporins
Aquaporins are always along basal membranes but only on lumenal in these parts
Proximal
Descending loop
Only place where water is NOT reabsorbed
Ascending loop
What 2 things are needed for water to reabsorb?
- Osmotic gradient
- Permeability (Aquaporins or leaky junctions)
3 substances that are secreted
H ions
K ions
Organic cations and anions (drugs, etc)
Where are H ions mostly secreted
Collecting duct and proximal tubule
How do H ions cross basal lateral membrane
ATPase pump
How do H ions cross lumenal membrane in proximal tubule
Sodium antiporter
How do H ions cross lumenal membrane in collecting duct and ascending loop
Facilitated diffusion
How much of filtered K is reabsorbed through passive diffusion in proximal
50%
How is K secreted in distal and collecting basal membrane
ATP Pump
T/F K reabsorption is unregulated but secretion is regulated
True
Why is K only secreted in distal and collecting
Only places with passive K channels on lumenal membrane
