WK 12 - Urinary System And Renal Physiology Flashcards
What are the primary roles of the kidney
• Excretes waste products of metabolism
• Excretes foreign chemicals/ substances
• H2O and electrolyte balance (osmoregulation)
• Body fluid makeup/ concentration
• Arterial pressure
• Acid-base balance
• Endocrine: Secretion, metabolism and excretion of hormones
• Gluconeogenesis
• Erythrocyte production
What is the primary functions of the urinary system
- H+/pH concentration regulation
- acid-base regulation
- this precise H+ regulation is essential as most of the activities of enzymes in the body are influenced by [H+]. Therefore, changes in [H+] alter all the cell and body functions
What is the gross organisation of the urinary system
• Kidneys are positioned on the posterior abdominal wall
• Indented medially – renal a, renal v, ureter, nerve supply, lymphatics
• Ureters – final urine passage to the bladder
• Bladder – urine storage until it is emptied
What is the structure of a kidney
What is the key functions of kidneys
- Metabolic waste product excretion
- Excretion of foreign substances and chemicals
- Regulating H2O and electrolyte balance (‘osmoregulation’)
- Body fluid makeup/ concentrations of other substances and molecules
- Arterial blood pressure (BP) regulation
- Regulation of acid-base balance (pH) within the body fluids
- Has endocrine functions as well, as mentioned in W10: Secretion, metabolism and excretion of
hormones - Gluconeogenesis: “glucose formatio
What are the key features of a nephron
- The kidney’s smallest functional unit – 800k to 1 million
- Components of the nephron = Glomerulus and Tubule
What are the key roles of the nephron and how does it support the role of kidneys
Each nephron can form urine
Glomerulus
→ ‘tuft’ of glomerular capillaries.
→Allows blood filtration to remove wastes and substances/fluid is filtered from the blood
→the ↑ relative pressure within the glomerular capillaries permits this to occur rapidly
Tubule
→Lengthy tube
→There is reabsorption of substances from the tubules and into the blood (peritubular capillaries)
→There is also secretion of substances from the peritubular capillaries and into the tubules
→Filtered fluid is converted to urine for excretion
What is the role of renal function in acid-base regulation
Renal control – acid-base regulation (pH)
- Net Result – excretion of urine that is high acidity or high alkalinity
- HCO3- ions are filled in the kidney tubules +++
- Excretion of these will remove the base/net loss of base
- Loss of base and buffer would result in an increase to extracellular fluid (ECF) [H+]
What is the role of renal function in blood pressure regulation
Kidney function – arterial blood pressure (BP)
- Long-term regulation/maintenance ++
- Principally via H2O and Na excretion – this will impact the cardiovascular (CV) parameters
- Plays an acute role in BP regulation
- Hormonal and ‘vasoactive’ factor secretion
- Vasoactive = affecting the diameter of blood vessels. E.g., renin-angiotensin II system
- The renin-angiotensis vasoconstrictor mechanism for arterial pressure control
What are the key steps of urine formation
Begins with glomerular filtration
Kidney-led determinats
1- glomerular filtration
2- reabsorption of substances from the tubules and into the blood
3- secretion of substances from the blood and into the tubules
4- excretion
Renal handling of substances
- Urinary excretion rate of a substance is equal to the rate at which the substance is filled minus its reabsoprtion rate plus the rate at which it is secreted from the peritubular capillary blood into the tubules
What are the typical renal response to alkalosis
- There will be a decrease in ECF [H+]
- Kidneys will secrete less H+
- Kidneys will not reabsorb all of the filtered HCO3-
- An increase [HCO3-] will be excreted
- There is less buffer available for H+ therefore the pH will decrease
- Renal correction of alkalosis – decreased tubular secretion of H+ And increased excretion of HCO3-
What are the typical renal responses to acidosis
- There’s an increase in ECF [H+]
- Kidneys secrete more H+
- Kidneys reabsorb all of the filtered HCO3- (and not excrete it in the urine)
- More HCO3- is produced
- There is more buffer available for H+ therefore, the pH will increase
Renal correction of acidosis – increased excretion of H+ and addition of HCO3- to the extracellular fluid
What are the causes of skeletal muscle acidosis
1- production of CO2 and carbonic acid in working muscle
- Product of CHO, PROTEIN and FAT oxidation for ENERGY
- Readily forms carbonic acid
- Carbonic acid dissociates into H+ and HCO3-
2- Production of lactate
- Lactate = lactic acid
- Product of anaerobic energy
- Accuamlation argued to decrease msucel pH
3- adenosine tri phosphate (ATP) breakdown
- H+ ions are produced when ATP is cloven for energy
What changes lead to metabolic acid-base disturbances (acidosis), and consider ways that compensation might occur to respond to this disturbance - therefore what are the general lines of defence against acidosis
• There will be a ↑ECF [H+]
• The kidneys will secrete more H+
• The kidneys will reabsorb all of the filtered HCO3
(and not excrete it in the urine)
• More HCO3
- is produced
• There is more buffer available for H+ →pH will ↑
What are the acute mechanisms that are capable of buffering against acidosis (include where they occur and the role of renal function)
How kidneys regulate buffer availability
A modest short-term role – which is mostly about time
The way kidney can affect [H+] is by increase or decrease of bicarbonate excretion
When the pH decreases
- The kidneys will decrease the rate of HCO3- excretion
When the pH increases
- The kidneys will increase the rate of HCO3- excretion
