Body Fluid Regulation and Excretory System Body Fluid

Body Fluid Regulation and Excretory System

Body Fluid regulation n Retaining or eliminating certain ions (such as Na+, Cl-, K+, HCO 3 -) and water (in and out must be equal) n Osmosis – movement of water from greater concentration to less concentration (toward higher solutes!!)

Aquatic animals n Marine invertebrates (mollusks and arthropods) and cartilaginous fish (sharks) have body fluids isotonic to sea water n Bony fish – have some salt, prone to water loss n Salt water bony fish n n Drink water constantly Freshwater bony fish – hypertonic n Never drink water, constantly eliminate excess

Terrestrial animals n Lose water by evaporation, respiration, sweat and feces n Drink water occasionally to replace what is lost n Birds and reptiles can drink salt water because they have a salt gland near the eyes n Humans conserve water by producing a hypertonic urine

Nitrogenous waste products n Amino acid metabolism – broken down for energy or converted to fats, carbs for storage n amino groups are removed and excreted as ammonia, urea, or uric acid, depending on species n Ammonia – little or no energy needed in conversion by adding H (NH 3) Toxic and needs a lot of water to wash away n Excreted by bone fish, aquatic invertebrates, amphibians n

Nitrogenous waste continued n Urea – excreted by terrestrial amphibians and mammals n n n Less toxic than ammonia and needs less water to remove from body Requires energy Produced in liver n Uric acid – insects, reptiles and birds n Not very toxic, poorly soluble in water n Requires most energy, but conserves most water n White stuff in bird droppings

Excretory organs n Planarians n Excretory tubules n Flame cells – contain beating cilia, propels fluid through tubules and out of body n Earthworms n Nephridia – tubule with ciliated opening and excretory pore n Urine contains metabolic wastes, salts and water n Insects n Malpighian tubules – attached to gut n Uric acid flows from hemolymph into tubules n water flows from salt gradient but is usually reabsorbed

Urinary system in humans n Kidneys – size of fist, lower back, right slightly lower than left. n n Urine – product Kidney ureter urinary bladder urethra n In males, urethra also carries sperm n 3 parts n Renal cortex – outer region, nephrons n Renal medulla – renal pyramids n Renal pelvis – inner hollow changer, urine collects here and carried to bladder via ureter n Kidney stones (renal calculus), can block renal pelvis or ureter

Nephron n Over 1 million in each kidney n Produce urine n Primarily found in renal cortex n Structure: Glomerular capsule proximal convoluted tubule loop of the nephron distal convoluted tubule collecting duct (delivers urine to renal pelvis) n Glomerulus – capillary bed

Urine formation – 3 processes n Glomerular filtration at the glomerular capsule n Tubular reabsorption at the convoluted tubules n Tubular secretion at the convoluted tubules n Figure 38. 9

Urine formation and homeostasis n Hypertonic urine – more concentrated than blood n occurs as result of reabsorption of water n ADA – antidiruetic hormone – post. Pituitary n Water reabsorption at collecting duct n Aldosterone – adrenal glands n Excretion of K+, reabsorption of sodium n Renin – enzyme, stimulates adrenal gland to relsease aldosterone due to low blood volume n ANH – atrial natriuretic hormone – atria of heart due to increase in blood volume, blocks uptake of renin

Acid- base balance n Kidneys reabsorb bicarbonate ions and excrete hydrogen ions as need to maintain the normal p. H of the blood. n Urine p. H = 6 Excess of H+ excreted n Ammonia provides a buffer for H+ n