The Kidney and Osmoregulation

1. The Kidney and Osmoregulation First a few terms you will need to know before we start discussing the kidney the essential regulation of water and ion levels in the blood osmoregulation solute a substance dissolved within another substance solvent the liquid within which a solute is dissolved solution the homogeneous mixture of two or more substances where you can not distunguish between the substances osmotic pressure the created by water hyper = abundance tonic = salt therefore low in water = hypo osmotic Hypertonic Hypotonic hypo = low tonic = salt therefore lots of water = hyperosmotic Isotonic iso = same tonic = salt therefore also same water = iso osmotic the solution is isotonic with respect to the cell the solution is hypotonic with respect to the cell the solution is hypertonic with respect to the cell Movement of Molecules across the cell membrane when molecules move across the membrane against the concentration gradient (low to high) and cellular energy (ATP) is used to do so Active Transport when molecules move across the membrane along the concentration gradient (high to low), no cellular energy is used Passive Transport

2. Each kidney has 3 distinct zones 1st The outer RenalCortex, is the thick outer layering where the initial blood filtering takes place. 2nd The RenalMedulla. The medulla is divided into a number of fan shaped regions and helps to conserve water and valuable salts. 3rd The RenalPelvis is inside of these two zones, it is the funnel shaped, hollow inner compartment, or, where urine is stored before it passes into the ureter. The functional units of the kidney, twisted tubules called Nephrons reach from the cortex down into the medulla and empty in the pelvis. Each kidney is approximately the size of an adult fist and is located high in the abdominal cavity behind the lungs and liver. For each kidney to carry out its vital function of filtering blood it must have a steady flow of blood that enters the kidney under high pressure. Two renal arteries branch off of the aorta (largest artery of the body) to supply each kidney with a constant fresh source of blood. Once the blood has been filtered it is transported via the renal veins back to the heart so that the blood may begin its cycle all over again. Renal Renal Renal Pelvis

3. FUNCTIONS OF THE KIDNEY There are a number of kidney functions but here are the most important: 1.Toxin Removal 2. Drug Removal 3.Fluid Balance 4.Electrolyte Balance: In order for cells to function properly, the concentration of electrolytes in the blood need to be tightly controlled. Here are the most important electrolytes: Sodium (Na) Potassium (K) Calcium (Ca) Magnesium (Mg) Phosphorus (PO3) 5. Acid-Base Balance 6.Blood Pressure Control The kidneys are responsible for regulating blood volume which has a direct impact on blood pressure. 7. Hormone Production: Vitamin D - Used to harden or mineralize bone in addition to calcium and phosphorous balance. Erythropoietin (EPO) - Tells the bone marrow to make more red blood cells. THE NEPHRON The functional unit of the human kidney is the nephron. Each nephron extend from the outer cortex through the medulla and drain into the renal pelvis. Each human kidney contains ~ 1 000 000 nephrons. * UBI #1 - if all of the nephrons in an adult’s kidney were stretched out and placed end to end, they would form a line ~ 80 km long or ~50 miles long UBI #2 a human can survive with only 1/10 of their nephrons

4. 3 Basic Processes of the Nephron There are 3 basic processes involved in the kidneys “cleansing” action: Filtration:Movement of molecules from the blood into the nephron at the glomerulus. Tubular Reabsorption:Movement of molecules from the nephron back into the blood. Tubular Secretion:Movement of molecules from the blood back into the nephron at any point along the nephron other than the glomerulus. Bowman's Capsule AKA Glomerular Capsule (sight of filtration)

5. Diagram of the Nephron f a g d h j j