UoB Medicine

Glomerular Filtration 180L (plasma) filtered but 175L reabsorbed. Governed by GFR. GFR: the speed at which the filtrate passes across the 3 barriers. Usually 100ml/min which is fixed in healthy individuals.  3 barriers involved in filtration: Fenestrations - filters by size Basement membrane- filters by charge as it's -vely charged (MAIN BARRIER) Podocytes - 3rd back up component  Glomerular Filtrate contains: No cells Trace amount of proteins Ions and small organic substances in the same conc. as plasma  The rate of filtration depends on: Molecular weight - inversely proportional Charge - positively charged >> neutral >> negatively charged Shape - long, thin molecules are filtered more easily than spherical molecules of the same MW Glomerular and Peritubular Capillary Beds Blood supply is via 2 capillary beds formed from the efferent arteriole.    Peritubular capillary bed - supplies to cortex. Intertwined around PCT/DCT -

Introduction Kidney - organ of excretion and body fluid regulation Produces urine dependent on the condition of the body Regulation of EC fluid - osmolarity/ plasma blood volume Production of hormones eg. renin (regulates blood volume) In the body - 14L Interstitial fluid 28L Intracellular fluid H2O is lost and gained from the body in a variety of ways.  However, this can vary in a number of ways and the kidney must adapt to support this, H2O intake: type of food, water availability H2O output: lactation, exercise, environmental conditions, disease The most common causes of fluid loss are: Sweating Diarrhoea Vomiting Hyperventilation Fever Hyponatremia: low Na+ therefore plasma is too dilute and H2O moves into cells causing them to swell. Leads to a person becoming irrational/comatose  Low K+ : cardiac arrhythmia Low Ca2+ : Fatigue/weakened + can soften bones/rickets/osteomalacia   Low Mg2+: Causes muscles to twitch uncomfort