WEEK 11 - EXCRETION + OSMOREGULATION Osmotic Pressure: !!!!!!!!!!!!!!!!!! Excretion: Process by which organisms eliminate substances in excess of need ➔ Functions: ◆ Maintain proper ion concentrations ◆ Maintain proper water content ◆ Remove toxic products ➔ Examples of excretion products: ◆ Carbon Dioxide ◆ Water ◆ Ammonia Too much water can also be toxic, as cells can burst, and it would dilute important elements and nutrients. ➔ Plants: ◆ CO2 and H2O are used in photosynthesis ◆ Nitrogen compounds are not toxic to plants ◆ Some waste products are stored in vacuoles and deciduous leaves ➔ Animals: ◆ Consume complex diets with excess of certain elements ◆ Require excretory systems Diffusion: solute molecules move from an area of high concentration to an area of low concentration Osmosis: diffusion of water; water moves from a region with less solute concentration, to a region with more solute concentration. It requires a semipermeable membrane. It always occurs in cellular environments. ➔ Hypotonic: (cell gets thick) outside the cell has less solute than the inside of the cell ➔ Isotonic: (cell’s chillin) outside the cell has equal solute to the inside of the cell ➔ Hypertonic: (cell’s a skinny not so legend) outside cell has more solute than the inside of the cell Osmoregulation: regulation of water content and ion concentrations in the body ➔ Saltwater Fish: live in a hypertonic environment (water’s salty af yo) ◆ Water moves outward via osmosis ◆ Salts tend to move inward constantly by diffusion ● Major challenges: 1. Excess salts: ○ Gills have special cells that pump out excess salts out via active transport 2. Loss of Water ○ Drinks seawater ○ Makes small amount of concentrated urine ➔ Freshwater Fish: live in a hypotonic (the fish be saltier af) The complex diets of animals and toxic effect of some nitrogenous waste compounds on animals make excretory systems more important in animals than in plants. Main Nitrogenous Waste Products in ANimals: 1. Ammonia (Most aquatic animals) - Least amount of energy 2. Urea (mammals, most amphibians, sharks, and some bony fishes) - HOOMANS 3. Uric Acid (Many Reptiles, Birds, Insects, and Land Snails) - Requires more energy - It takes 5 Excretory Mechanisms - Contractile Vacuoles in Freshwater Unicellular Organisms - Humans use kidneys THE NEPHRON Water Balance in Terrestrial and Aquatic Vertebrates: - Freshwater: doesn’t drink water, pee a lot of diluted pee - Saltwater fish: drinks lotsa water, pees a little concentrated pee - Terrestrial Vertebrate: salt and water are both taken in by mouth, and often pees moderately concentrated pee Human Excretory System: - Two Kidneys (left + right) - Contains almost a million nephron - Nephron is a functional unit of a kidney - Nephron makes pee and empties into renal pelvis, - Each kidney (renal pelvis) empties into a ureter - Ureter empties into bladder - Urine leaves via urethra What goes into making your urine, comes from your blood. Urine Formation: 1. Glomerular Filtration: blood enters glomerulus and acts as a filter (RBCS, WBCs, large proteins cannot pass - Glomerulus (big mass of glomerular capillaries) - Bowman’s Capsule (part of nephron): captures the filtrate (NOT RBCS, etc.) 2. Proximal Convoluted Tubule: reabsorption of 80% of the filtrate (H2O, NaCl, Nutrients) (material moves from filtrate back to plasma) - Secretion of H+ and NH3 (from blood to nephron tubules) - Adding H+ controls pH Acidity 3. Descending limb of the loop of Henle: reabsorption of water (urine concentrates) 4. Ascending limb of the loop of Henle: Reabsorption of NaCl (urine dilutes) 5. Distal Convoluted Tubule: reabsorption of 9% of the filtrate (H2O, NaCl, HCO3) - Secretion of K+ and H+ 6. Collecting Duct: reabsorption of 4% of the filtrate (H2O, NaCl, Urea) Blood Plasma Vs. Urine: Compared to blood plasma, urine has: - Nil or very low concentration of proteins, amino acids and glucose - Similar or slightly higher concentration of sodium ions - Slightly higher concentrations of chloride ions - Much higher concentrations of urea and uric acid Hormonal Control of Urine Production: 1. Antidiuretic Hormone: direct anti-urine, makes less urine, more concentrated. Made by hypothalamus and stored in the posterior pituitary gland until it is needed. - ADH is released by posterior pituitary gland in response to being thirsty, and travels via bloodstream to the nephron tubules, which causes an increased water permeability (water moves inward, from nephron to plasma) Purpose: water moves inward from nephron to plasma 2. Aldosterone: made when you have low blood volume or pressure, caused by low salts/ions; increase sodium absorption. - Increase in sodium absorption will cause lower volume of urine as water follows the solute concentrations - Released by adrenal glands Purpose: to increase sodium absorption All hormones travel via blood.
