physiology kidneys

What are the Function of the Kidneys

Regulation of the extracellular fluid

How is the Regulation of the extracellular fluid accomplished

urine formation

Detrusor muscle = innervated by

parasympathetic nervous system

Internal urethral sphincter is what type of muscle

smooth muscle

External urethral sphincter is what type of muscle

skeletal

Guarding reflex

parasympathetic nerves are inhibited while striated muscles are stimulated by somatic motor neurons

parasympathetic nerves are inhibited while striated muscles are stimulated by

somatic motor neurons

Voiding reflex =

sensory neuron stimulation activates parasympathetic nervous system when bladder is sufficiently stretched

sensory neuron stimulation activates

parasympathetic nervous system

sensory neuron stimulation activates parasympathetic nervous system when

bladder is full

Where are Cortical nephrons located

in the cortex

Juxtamedullary nephrons have

long nephron loops

Juxtamedullary nephrons play an important role in what

concentrating urine

Glomerulus

capillary network that produces filtrate

What does Glomerular capsule (Bowman’s capsule) surround

glomerulus

Glomerulus + glomerular capsule makes what

renal corpuscle

Proximal convoluted tubule

single cuboidal layer with microvilli

Nephron loop (Loop of Henle)

mix of simple squamous and simple cuboidal

Distal convoluted tubule

simple cuboidal, and very few microvilli

Collecting duct

many distal tubules come together

Filtration occurs where

from blood to glomerular capsule

reabsorption occurs where

from renal tubules to blood

secretion occurs where

from blood to renal tubules

excretion occurs where

from bladder to exterior of body

cells called podocytes wrap around

glomerular capillaries

Parietal layer is what kind of tissue

simple squamous epithelium

Afferent arteriole supplies blood where

blood to glomerulus

Fenestrae

first filtration barrier

Glomerular basement membrane

second filtration barrier

Podocytes

foot processes interdigitate and act as third filtration barrier

What does the Efferent arteriole drain

glomerulus

Formed under pressure =

hydrostatic pressure of blood

What are the 3 forces that affect ultrafiltrate production

Glomerular (capillary) hydrostatic pressure, osmotic pressure, Capsular hydrostatic pressure

GFR stands for what

Glomerular Filtration Rate

Glomerular Filtration Rate

volume of ultrafiltrate produced by the kidneys/minute

Total blood volume (5.5 L) is filtered how often

every 40 minutes

how much do you pee a day

7.5 L per hour or ~ 180 L/day

Most of the filtrate is returned where

vascular system

Average urine production/day

1-2L

Extrinsic (Sympathetic nervous system) affects

the diameter of the afferent arterioles

Increased sympathetic stimulation causes

vasoconstriction

Increased sympathetic stimulation causes vasoconstriction which leads to

decreased GFR (urine production) and conserves H2O

Myogenic constriction of afferent arterioles due to

increased blood pressure

Macula densa monitors flow of

filtrate in ascending Loop of Henle

Macula densa monitors flow of filtrate in ascending Loop of Henle which affects

vasoconstriction and vasodilation of afferent arteriole

99% of filtered NaCl and H2O is reabsorbed into

the blood

99% of filtered NaCl and H2O is reabsorbed into the blood

Most of this occurs in the

proximal convoluted tubules

What remains in the nephrons is the

filtrate

Na+ that passively enters the proximal convoluted tubule cells is actively pumped to the

interstitial space

Na+ that passively enters the proximal convoluted tubule cells is actively pumped to the interstitial space, creating a gradient for what to occur

osmosis

Na+ that passively enters the proximal convoluted tubule cells is actively pumped to the interstitial space, creating a gradient for osmosis to occur

This Is part of what mechanism

countercurrent multiplier mechanism

Countercurrent multiplier system creates

osmotic gradient

Countercurrent multiplier system creates osmotic gradient to reabsorb

water and concentrate urine

The ascending limb is not permeable to

H2o

The ascending limb is not permeable to H2O but actively transports what

Na+ to the interstitial space

The descending limb of the nephron loop is permeable to only

H2O (osmosis)

The concentrated interstitial fluid in medulla causes remaining H2O to be passively drawn out of the descending limb and enters

peritubular capillaries (vasa recta)

Substances are removed from and returned to the interstitial fluid =

countercurrent exchange (fluid moves in opposite directions)

Substances are removed from and returned to the interstitial fluid = countercurrent exchange (fluid moves in opposite directions) this maintains

hypertonicity or saltiness of the interstitial fluid

Urea leaves ascending limb and collecting duct and contributes to

the osmotic pressure in the medulla

About ½ of the urea that enters the filtrate ends up being

secreted

Plasma [K+] indirectly affects what

H+] and vice versa

K+ and H+ are secreted in response to

Na+ reabsorption

K+ and H+ are secreted in response to Na+ reabsorption via

K+/H+ pumps in the late distal tubule

When is ADH is released

the osmotic pressure of blood increases

ADH makes the collecting duct more permeable to

H2o

ADH makes the collecting duct more permeable to H2O via

activation of aquaporins

Aldosterone stimulates

Na+ reabsorption

K+ is secreted into the

renal tubules and lost in urine

Renin-angiotensin-aldosterone System

decreased blood volume detected by juxtaglomerular apparatus and renin is released

Renin causes a cascade of events which lead to

Na+ reabsorption H2O retention

Where is Juxtaglomerular apparatus located

the junction of the distal convoluted tubule and the efferent and afferent arterioles

What does the Juxtaglomerular apparatus monitor

flow rate of blood and NaCl concentration in ultrafiltrate

How does Juxtaglomerular apparatus react

via controlling renin release and afferent arteriole diameter

Atrial natriuretic factor (ANF)

secreted by the atria of the heart in response to increased stretch (increased blood volume)

ANF cause increased excretion of

of Na+ and H2O and decreased H2O volume in blood

The kidneys will secrete

secrete H+ and conserve HCO3-

blood pH can be maintained within

narrow limits

Urine cannot fall much below what pH

4.5

In order to purge more H+ they must combine with

urinary buffers

Ammonia and various phosphates act as what

urinary buffers

Acute renal failure

reduced blood flow through kidneys

Glomerulonephritis

= inflammation of glomeruli

Renal insufficiency

Can lead to hypertension, which chronically

hypertension can result in

hemodialysis