BMS2031 Lecture 8: Week 3. Renal physiology and Urine formation
Week 3. Renal physiology and Urine formation
RENAL PHYSIOLOGY
• Location of the kidneys and urinary system:
• Functions of the kidney: regulates body fluid volume and osmolarity
o regulation of water and electrolyte volume and osmolarity
-arterial BP, sodium, potassium, calcium etc.
o regulation of acid-base balance
-hydrogen ions (pH)
o excretion of metabolic waste products and foreign chemicals
-nitrogen (urea, ammonium) and drugs
o endocrine organ
-renin, erythropoietin and 1,25-dihydroxy vitamin D3
o glucogenesis
• Osmolarity: a measure of the number of particles present in solution thus takes into account
dissociated anions and cations in solution
-> solute concentration in a solution
eg. 1 mole of NaCl has an osmolarity of 2 (Na and Cl)
• Symptoms associated with non-functioning kidneys:
o Hypertension
o Oedema (fluid accumulation)
o Metabolic acidosis (acid out of balance)
o Anaemia
o Osteoporosis
o Thirst
o Malnutrition
o Hyperkalaemia (high plasma potassium levels)
o Cognitive impairment
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• There is ~42 litres of water in the body (45% to 75% of body weight)
Adipose tissue = 10% water
Other tissues = 65% water
Total body water content hardly changes from day to day in a healthy person
• Body fluid compartments:
o Intracellular fluid (ICF) = fluid within cells
o Extracellular fluid (ECF) = fluid outside cells (plasma, interstitial fluid, lymph)
o Transcellular fluid = contained within cell layers (cerebrospinal, peritoneal, pericardial)
-separated from the rest of the ECF by both and endothelial and epithelial cell layer
• Electrolytes dissociate in water into ions and are the most abundant solutes in body fluids
• Intracellular fluids are separated from extracellular fluids by a selective cell membrane that is
highly permeable to water but not to most electrolytes
• Osmotic pressure is normally the same in ICF and ECF
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• Extracellular and intracellular fluids:
Extracellular fluid
Intracellular fluid
o Major cation = Na+
o Major anion = Cl-
o Major cation = K+
o Major anion = PO43-
o Intracellular = interstitial = plasma
• What happens to the volumes and osmolarity of your body fluids if you drink 1.5 L of water?
o Immediate effect: increase in ECF (decreased ECF osmolarity)
o Eventually reaches equilibrium: increase in volume and decrease in osmolarity in both
ICF and ECF
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Location of the kidneys and urinary system: functions of the kidney: regulates body fluid volume and osmolarity regulation of water and electrolyte volume and osmolarity. Arterial bp, sodium, potassium, calcium etc. regulation of acid-base balance. Hydrogen ions (ph: excretion of metabolic waste products and foreign chemicals. Nitrogen (urea, ammonium) and drugs: endocrine organ. Renin, erythropoietin and 1,25-dihydroxy vitamin d3: glucogenesis, osmolarity: a measure of the number of particles present in solution thus takes into account dissociated anions and cations in solution. Total body water content hardly changes from day to day in a healthy person: body fluid compartments: Intracellular fluid (icf) = fluid within cells: extracellular fluid (ecf) = fluid outside cells (plasma, interstitial fluid, lymph, transcellular fluid = contained within cell layers (cerebrospinal, peritoneal, pericardial) Separated from the rest of the ecf by both and endothelial and epithelial cell layer: electrolytes dissociate in water into ions and are the most abundant solutes in body fluids.