BIOL 2420 Lecture Notes - Lecture 1: Extracellular Fluid, Metabolic Waste, Urobilinogen
26 Apr 2018
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Unit 7 – Lecture 1
Functions of The Kidneys
- The most important function of the kidney is the homeostatic regulation of the water and ion
content of the blood
o Salt and water balance
o Fluid and electrolyte balance
- waste removal is important but disturbances in the blood volume or ion levels cause serious
medical problems before the accumulation of waste reaches toxic levels
- kidneys maintain normal blood concentrations of ions and water
o they balance intake of those substances with their excretion in the urine
o they obey the principle of mass balance
o 6 general areas of kidney function
1. regulation of extracellular fluid volume and blood pressure
▪ ECF volume decreases, blood pressure also decreases
▪ If ECF volume and blood pressure fall too low, the body cannot maintain
adequate blood flow to the brain and other essential organs
▪ Kidneys work in an integrated fashion with the cardiovascular system to ensure
that blood pressure and tissue perfusion remain within an acceptable range
2. regulation of osmolarity
▪ body integrates kidney function with behavioural drives like thirst to maintain
blood osmolarity at a value close to 290 mOsM
3. maintenance of ion balance
▪ keeps concentrations of key ions within a normal range by balancing dietary
intake with urinary loss
▪ sodium
• major ion involved in the regulation of extracellular fluid volume and
osmolarity
▪ potassium and calcium
• concentrations are closely regulated
4. homeostatic regulation of pH
▪ pH of plasma is kept in a normal narrow range
▪ if ECF becomes too acidic, kidneys remove H+ and conserve bicarbonate ions
• bicarbonate acts as a buffer
▪ if ECF becomes too basic, kidneys remove bicarbonate and conserve H+
▪ kidneys play a huge role in pH homeostasis
• but they DO NOT correct pH disturbances as rapidly as the lungs can
5. excretion of wastes
▪ remove metabolic waste products and xenobiotics, foreign substances (drugs
and environmental toxins)
• creatine – muscle metabolism
• nitrogenous wastes – urea and uric acid
• urobilinogen – hemoglobin metabolite
o yellow color of urine
• hormones – endogenous substance removed from blood by kidneys
▪ foreign substances
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Document Summary
The most important function of the kidney is the homeostatic regulation of the water and ion content of the blood: salt and water balance, fluid and electrolyte balance. Urinary system: composed of kidneys and accessory structures renal physiology: the study of kidney function. The urinary system consists of kidneys, ureters, bladder, and urethra. Begins when water and solutes move from plasma into the hollow tubules (nephrons) that make up the bulk of the paired kidneys. Nephrons modify the composition of the fluid as it passes through them. E. coli is the most common cause of urinary tract infections. It is a normal inhabitant of the human large intestine: not harmful when restricted to the lumen, however it becomes pathogenic when present in the urethra. Increased frequency of urination: urine samples contain red and white blood cells in those with a uti, no cells are found in normal urine samples.
