Slide Set 7 - The Urinary System - Kidney Flashcards
How does each system react to decreased blood pressure?
- Cardiovascular:
- Behavioral:
- Kidneys:
- increase cardiac output and vasoconstriction to increase blood pressure
- increase thirst - increase water intake which will increase extracellular and intracellular fluid volume to increase blood pressure
- kidneys conserve water to minimize further volume loss - so urine turns out more concentrated and smaller in volume
How does the cardiovascular system react to an increase in blood pressure? The kidney?
- decrease cardiac output and decreases vasodilation to decrease blood pressure
- The kidney excretes salts and water in urine - this decrease extracellular and intracellular volume of body, decreasing blood pressure
What are the 3 structures that carry urine from the kidneys to the outside for elimination from the body?
- uterers
- urinary bladder
- urethra
What are nephrons?
functional units of the kidney
Where does the urine travel to after the nephron?
calyx (which can be thought of as the start of the urinary plumbing) then to the ureter
What is the tube that leads urine from the kidney to the bladder?
ureter
What is the tube that leads the urine from the bladder to the exterior for excretion?
urethra
Size of urethra or women relative to men?
Men have a much longer urethra
What does the urethra of men pass through?
The prostate gland (site of passage of seminal fluid/semen)
How many nephrons can be found in a kidney?
~ 1 million
What are the two components of each nephron?
Tubular and vascular
The arrangement of the nephrons within the kidney gives rise to what two distinct regions?
renal cortex and renal medulla
Does the vascular or tubular component dominate the glomerulus?
vascular
What passes through the glomerulus?
water and solutes - kind of like plasma which is then transformed into urine
Discuss the vascular route of the kidney step by step
- The renal artery brings blood into the afferent arteriole which delivers blood to the glomerulus
- the blood that does not get filtered through the glomerulus leaves via the efferent arteriole
- efferent arteriole breaks down into peritubular capillaries which surround the tubular part of the nephron and supply the blood for exchange with the fluid in the tubular lumen
- Peritubular capillaries join into venules which transport blood into the renal vein which is the way by which blood leaves the kidney
What is filtered through the glomerulus?
all constituents within the blood except blood cells and proteins – non-discriminant
What is tubular reabsorption?
highly selective movement of filtered substances from the tubular lumen into the peritubular capillaries
What is tubular secretion? What does this provide?
selective movement of non-filtered substances from the peritubular capillaries into the tubular lumen for excretion. This provides a second chance for substances to enter the tubules for excretion after glomerulus filtration already occurred
How much of our blood passes through the glomerulus?
20%
What 3 things must substances pass through in order to be filtered and enter the lumen of bowman’s capsule?
- the pores between the endothelial cells of the glomerular capillary
- basement membrane
- Inner later of bowman’s capsule: the filtration slits between the foot processes of the podocytes of the inner layer of bowman’s capsule
What two forces are involved in filtration at the glomerulus? Which force favours and which force opposes filtration?
- Glomerular Capillary Blood Pressure (favours filtration)
- Plasma-colloid Osmotic Pressure (opposes filtration)
- Bowman’s capsule hydrostatic pressure (opposes filtration)
What is the magnitude of the Glomerular Capillary Blood Pressure, Plasma colloid osmotic pressure, and Bowman’s capsule hydrostatic pressure?
- 55 mm Hg out of glomerulus
- 30 mm Hg into glomerulus
- 15 mm Hg into glomerulus
What exerts the plasma-colloid osmotic pressure?
the unfiltered proteins on the filtered fluid that is in the bowman’s capsule
Under what circumstance can the Bowman’s Capsule Hydrostatic pressure increase?
in the case of a blockage
What happens at the proximal and distal tubules?
solutes are actively transported back into blood
What 3 things trigger vasopressin release?
- osmolarity of plasma > 280 mOsM (detected by hypothalamic osmoreceptors in the plasma - then in
- Decrease in atrial stretch due to low blood volume
- Decrease in blood pressure
What synthesizes vasopressin and what releases it?
Neurons that detect osmolarity, atrial stretch, and carotid/aortic baroreceptors send signals to the hypothalamus. Hypothalamic neurons then synthesize vasopressin. The posterior pituitary releases vasopressin
As plasma osmolarity ________, secretion of plasma vasopressin by the posterior pituitary _______. A graph representing this relationship is _______.
increases, increases
linear
What is myogenic regulation?
When arteriole pressure increases the renal afferent arterial is stretched. The vascular smooth muscle responds by contracting thus increasing resistance.
Where does tubuloglomerular feedback occur?
Juxtaglomerular apparatus
What is the juxtaglomerular apparatus?
The fork made by the afferent and efferent arteriole that surround the distal tubule
There are specialized __________ cells in the wall of the afferent arteriole which are called __________ cells. There are also specialized ________ cells in this region called ________.
smooth muscle
granular
tubular
macula densa
What happens when more fluid passes through the distal tubule at the juxtaglomerular apparatus?
More fluid means a higher salt level. Macula densa cells act to detect changes in salt levels in the distal tubule. In turn, they release adenosine which acts as a paracrine regulator and causes vasoconstriction at adjacent granular cells.
What are the 4 kidney functions?
- Filtration: blood to lumen
- Reabsorption: lumen to blood
- Secretion: blood to lumen
- Excretion: lumen to external environment
Adenosine acts as what type of regulator? What does it cause?
Acts as a paracrine regulator and causes vasoconstriction at adjacent granular cells
Once the glomerulus filtration rate increases, what auto regulatory process occurs to decrease the GFR back to normal levels?
GFR increase –> flow through tubule increases –> NaCl flow past macula densa increases
- Macula densa cells release adenosine (acts as a paracrine regulator and causes vasoconstriction)
- Afferent arteriole constricts
- resistance in afferent arteriole increases
- hydrostatic pressure in glomerulus decreases
- GFR decreases
How does counter current exchange occur in the medulla of the kidney?
The filtrate passing through the distal tubule is flowing the opposite direction as the blood in the vasa recta
How does the presence of ADH affect the urine?
small volume of concentrated urine
What happens when the body needs salt? (5 steps)
- aldosterone combines with a cytoplasmic receptor
- hormone-receptor complex initiates transcription in the nucleus
- new protein channels and pumps are made & there is also an increase in Na and K channel open times
- Na ATPase pump speeds up
- Increased Na absorption into vasa recta and K secretion into the lumen of the distal tubule
When is the renin-angiotensin-aldosterone system initiated?
when there is low blood pressure
RAAS:
- What does the liver normally constantly produce for the plasma?
- How does a decrease in blood pressure affect this molecule?
- How does the production of ANG-2 affect the arterioles, the cardiovascular control centre in medulla oblongata, the hypothalamus, and the adrenal cortex in order to increase blood pressure back to normal?
- angiotensin
- Causes granular cells to produce renin. Renin converts angiotensin to ANG-1 in plasma. ACE enzyme converts ANG-1 to ANG-2 in plasma
- Arterioles vasoconstrict. There is an increased cardiovascular response. The hypothalamus increases vasopressin and increases thirst meanwhile the adrenal cortex increases aldosterone which increases Na absorption – both these things together increase volume and maintain osmolarity. All of this together works to increase blood pressure
What is produced in the case of high blood pressure? It is secreted as a response to what 3 things?
Atrial Natriuretic Peptide (ANP)
Secreted by atria in response to:
- being stretched by Na+ retention
- expansion of ECF volume
- increase in arterial pressure
What does the release of Atrial Natriuretic Peptide inhibit? What 3 things does this result in?
Na reabsorption in the distal tubule which increases Na output in urine
- increases Na output in uine
- increase GFR - more water loss
- Inhibits renin secretion by the kidneys
these are all hypotensive effects to help correct the original stimulus that brought about release of ANP
What are 5 causes of Renal Failure?
- infectious organism
- Toxic agents
- Inappropriate immune response
- obstruction of urine flow
- insufficient renal blood supply
What are 10 of the kidneys functions?
- Mantain H2O balance in the body
- Maintain proper osmolarity of body fluids, primarily through regulating H2O balance
- Regulate the quantity and concentration of most ECF ions
- Maintain proper plasma volume
- Help maintain proper acid-base balance in the body
- Excreting the wastes of bodily metabolism
- Excreting many foreign compounds
- Producing erythropoietin
- Producing renin
- Converting vitamin D into its active form
