Sites of action - Filtration - Reabsorption and Secretion - Loop of Henle

- Bowman’s capsule - Proximal tubule - Distal tubule Hormone controlled - Collecting ducts Creates osmotic gradient reabsorption

Urinary system Flashcards by kian colgate

Kidney
- Functions
- Parts

Excretion of wastes
H2O balance
* Plasma volume
Blood pressure control
* Renin
Acid-base balance
Blood Cell production
* erythropoietin
Vitamin D activation

Renal Calyces
Renal Cortex
- outer
Renal Medulla
-Inner
Renal Pelvis

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Urinary system
- consists of

Kidneys:
Blood supply
* 20% of total flow
Transport vessels
* Ureters
* Urinary bladder
* Urethra

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Nephron
- Functional unit of kidney, 2 types
- Tubule job
- vascular component

~ 1million / kidney
Two types
Cortical
* Shorter
* ~85%
Juxtamedullary
* Longer
* ~15%
* Osmotic gradient

Blood supply

Renal Artery
Afferent Arteriole
Glomerulus
* Ball-like tuft of capillaries
Efferent Arteriole
Peritubular capillaries
Renal vein

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Tubule
- parts

Bowman’s capsule
Proximal tubule
Loop of Henle
-Ascending
-descending
Distal tubule
Collecting duct

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Basic renal processes
- urine results from all three processes

Glomerular filtration
-Fluid into tubule

Tubular reabsorption
-From tubule into blood

Tubular secretion
- From blood into tubule

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Sites of action

Filtration
Reabsorption and Secretion
Loop of Henle

Bowman’s capsule
Proximal tubule
Distal tubule
Hormone controlled
Collecting ducts

Creates osmotic gradient
* reabsorption

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Substance fates
- substances can be

Filtered and secreted
* Some only secreted

Filtered and reabsorbed

Filtered and partially reabsorbed

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Kidney functions

Glomerular filtration
All but RBC’s and proteins
* Too big

Reabsorption
Na+, Cl-, Ca2+, PO4, water, glucose

Secretion
K+, H+, large organics

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Podocytes

-Glomerulus

Can change shape
- Control filtration
Renal failure
-Large slits
- Allows proteins and RBC’s in

Tuft of capillaries
Fenestrated
* More permeable
-Surrounded by Bowman’s capsule

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-Glomerulus filtration
- amount and what it moves

Across three layers of the glomerular membrane
-Glomerular capillary wall
-Basement membrane
* Acellular gelatinous layer
⬧ collagen and glycoproteins
-Inner layer of Bowman’s capsule
* Consists of podocytes that encircle the glomerulus tuft

~160-180 L / day (~125 mL/min)
-Moves electrolytes, water, glucose into tubules
- RBC’s and most proteins are too large to be filtered
- Urine, <1% of filtrate

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Forces Involved in Glomerular
Filtration
- Three main physical forces involved
- Favours vs opposes filtration

-Glomerular capillary blood pressure
- Plasma-colloid osmotic pressure
- Bowman’s capsule hydrostatic pressure (Bowman’s capsule osmotic pressure)

Favours filtration
- Glomerular blood pressure

Opposes Filtration
-Plasma-colloid osmotic pressure
- Bowman’s capsule hydrostatic pressure
- Net filtration of 10

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Glomerular Filtration Rate (GFR)
- Depends on
- GFR alters if
- Auto- Regulated

-Net filtration pressure
-How much glomerular surface area is available for penetration
- How permeable the glomerular membrane is
* Podocytes
* Slit size can change with infection

GFR will change if the blood hydrostatic
pressure changes

Tubuloglomerular feedback
* Local (paracrine) control
Hormones / Autonomic
* Change arteriole resistance

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Arterioles help control GFR
A higher/lower GFR if

Resistance changes in renal arterioles alter renal blood flow

A lower GFR if
-Afferent arteriole constricts OR efferent arteriole dilates

A higher GFR if
- Afferent arteriole dilates OR efferent
arteriole constricts

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Extrinsic Control on GFR
- Sympathetic control
- lower bp means

long-term regulation of arterial BP
-Input to afferent arterioles
Baroreceptor reflex
Lower blood pressure means lower GFR and retention of fluids

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Tubular reabsorption
- passive vs active reabsorption

Passive reabsorption
No energy is required
Down electrochemical or osmotic gradients

Active reabsorption
Requires energy
Moves against electrochemical gradient

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Sodium reabsorption

Active process
Na+/K+ pump creates Na+ gradients across membranes

-Na+ - K+ ATPase pump in basolateral membrane is essential for Na+
reabsorption
-Affects reabsorption of other substances

Facilitates Na+ reabsorption

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Reabsorption of other substances
- following Na reabsorption

Water reabsorption
* Via osmotic gradient created

Cl- reabsorption
* Via electrical gradient

Glucose – by carriers

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Glucose reabsorption
- sodium-linked
- tubular maximum
- renal threshold

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Sodium-linked glucose reabsorption in the proximal tubule
Point where all the glucose carriers are full
-excess glucose stays in the tubules and is lost in the urine
Blood glucose level where the carriers are full and glucose is seen in the urine
Eg. Diabetes Mellitus

Urea reabsorption
- urea
- passive process

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Urea - Small, diffusible

Passive process
To equilibrium, 50%

Reabsorbtion stats

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Na+ (99.9%) - Na+/K+ ATPase pump

Cl- (99%) - Electrical gradient

Water (99%) - Osmotic gradient

Glucose (100%) - Carrier-mediated

Urea (50%) - Passive

K+ (80-90%) - secreted and reabsorbed

Aldosterone
- what does it control and when released
- High aldosterone = ?

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-Controls Na+/K+ ATPase pumps
- Released if blood volume is low

High Aldosterone
↑ speed of pump
↑ Na+ reabsorption
↑ water reabsorption
* Decreased urine

Eg. Dehydration

Renin-Angiotensin-Aldosterone
System

Atrial Natriuretic Peptide (ANP)
- converts
- when secreted

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Regulates Na+ and blood pressure/volume

Antagonist to Aldosterone
- inactivates Na+/K+ pump
- Inhibits Na+ reabsorption

Secreted by atria with
↑ BP
↑ Na+
↑ Stretch of atria (↑ volume)

Secretion
- what is it and what kind of process
- Potassium
- Hydrogen
- Large organics

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Transfer of molecules from extracellular fluid into tubule
-Active process

K+
-Na+/K+ pump
-Later reabsorbed

H+
-Acid-base balance

Large Organics
biotransformed

Collecting ducts
- site of and controlled by
- Requires
- Loop of henle

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Site of water reabsorption
Controlled by ADH
Concentrates the urine

Requires osmotic gradient
-Loop of Henle

high solute concentration in renal medulla by selective reabsorption of salt and urea

Loop of henle - counter- current mechanism - descending loop - ascending hoop - Creates a large, vertical osmotic gradient in medulla

Descending loop: Permeable to water -Impermeable to salts - Filtrate becomes more concentrated Ascending: Permeable to salts * Actively reabsorbed NaCl - Impermeable to water - Filtrate becomes less concentrated - From 100 to 1200 mosm/litre

Water reabsorption - ADH causes - what is ADH - Low ADH - High ADH

- ADH causes insertion of water pores into the apical membrane - Anti-diuretic hormone that controls permeability of collecting ducts - Released if blood osmolarity high Impermeable to water, dilute urine * High volumes -Due to high blood osmolarity, makes collecting duct permeable to water -Concentrates urine * Lower volume, eg. Dehydration

Dehydration VS Water loading

↑ADH ↑Aldosterone ↓ ANP ↑ water reabsorption ↓ urine * More concentrated ↓ADH ↓Aldosterone ↑ANP ↓ Water reabsorption ↑ urine volume * More dilute

Behavioural mechanisms to dehydration

Drinking replaces fluid loss Low sodium stimulates salt appetite Avoidance behaviours help prevent dehydration - Desert animals avoid the heat

Proximal tubule

- 67% of Na, Cl, and water reabsorption - 100% glucose and amino acids are reabsorbed - K is secreted / reabsorbed (small amt) -Variable H secretion occurs -Organic ion secretion (not controlled) -Phosphate and electrolytes controlled, variable reabsorption -Urea reabsorption to equilibrium 50%

Distal tubule

Variable Na reabsorption - controlled by aldosterone and ANP Variable water reabsorption - controlled by aldosterone and ANP Variable K secretion / reabsorption -controlled by aldosterone Variable H secretion - depends on acid-base balance

Collecting ducts

Variable water reabsorption - controlled by ADH Variable H secretion Variable Urea reabsorption - related to loop of Henle

Micturition - the urination reflex -during

- Autonomic control of sphincters and detrusor muscle - CNS can over-ride or initiate -Stretch receptors increase their firing - Sphincters relax -Detrusor muscle contracts -Urine flows out of bladder

During filling of bladder

- Bladder (detrusor) muscle is relaxed - Sphincters are contracted

Renal failure, causes of renal failure - acute - chronic

Infections / Toxic agents Inappropriate immune responses Obstruction of urine flow An insufficient renal blood supply Hypertension Diabetes Chronic exposure to toxins / drugs

Renal failure, causes lead to - sickness - loss of minerals - affects nerves and organelles - low bp

Build-up of wastes to toxic levels - Vomiting, diarrhea, cellular necrosis -Loss of Calcium - Osteoporosis -Na+ and K+ imbalance Affects nerve and muscle Loss of proteins - Edema Loss of RBC’s - Anemia Low blood pressure (↓ renin) - Dizziness

Kidney stones - what it is - causes

- Crystallization of minerals in either the kidney, the ureters, or the bladder - Calcium - Oxalates -Veggies (spinach, beets) - Dehydration Binge drinking

Acid-base balance problems - acidosis -alkalosis - ph disturbance

Acidosis - neurons become less excitable and CNS depression Alkalosis - hyperexcitable pH disturbances - with K+ disturbances

Acidosis - metabolic acidosis - respiratory acidosis

Metabolic Acidosis - Metabolic organic acid production * Lactic acid (exercise) * Ketoacids ⬧ Diabetes -Diarrhea -Organic acids intake * Diet Respiratory Acidosis -Production of CO2 * Acid production

Alkalosis - metabolic alkalosis - respiratory alkalosis

Metabolic Alkalosis - Vomiting - Dietary sources of bases * Eg. Tums -Pyloric stenosis Respiratory Alkalosis Hyperventilation * (high altitude)

Respiratory compensations

-pH is adjusted by changing rate and depth of breathing -Response within minutes -CO2 + H20 ↔ H2CO3 ↔ H+ + HCO3-

Respiratory corrections - breathing

Reflex pathway for respiratory compensation of metabolic acidosis - Increased breathing

Body correction for acidosis

To raise body pH, buffers bind to H+ - Breathing increases * Decreases CO2 and H+ (via Carbonic Acid) - Kidney excrete H+ and keep Bicarbonate

Body correction for alkalosis

To lower pH, Buffers release H+ Breathing slows down * Retains CO2 and H+ Kidney retains H+ and secretes Bicarbonate

Intercalated cells -type A - type B

-Type A intercalated cells function in acidosis -Secrete H+, reabsorb bicarb - Type B intercalated cells function in alkalosis - Secrete bicarb, reabsorb H+

Urinary system Flashcards

(44 cards)