Excretion and osmoregulation

Universal needs All cells need aqueous environment Problems: Balance water and solutes= osmoregulation Nitrogenous waste (from proteins) very toxic Osmolarity: blood: 300 milliosmoles/L Seawater: 1,000 milliosmoles/L

Bioenergetics Osmoconformers: must live in stable environment Osmoregulators: use energy to maintain homeostasis

Adaptations: salt water Ocean fish: Gills get rid of NaCl. Active pump Cl- Na+ follows Kidneys get rid of Nitrogenous waste as ammonia with very little water Shark: keeps high concentration of urea (to balance water loss thru osmosis) Will actually take on water and have to urinate Must soak shark meat in fresh water before eat it

Adaptations: fresh water Fresh water animals: Constantly gain water and lose salts Make large amounts of dilute urine Gills actively transport Cl Anhydrobiosis: life without water: some critters do this in times of dehydration: go into dormant state

Adaptations: land Land animals shell or fur or skin: waxy coat to decrease water loss by evaporation Eat and drink water Kidneys make concentrated urine

Circulation Insects and others: open circulation. Hemolymph baths all cells Closed circulation: cells bathed in interstitial fluid: controlled indirectly by composition of blood.

Transport epithelium May face the outside environment directly OR may line channels and tubes. Control movement of solutes.

Nitrogenous waste Ammonia: aquatic animals… flush it away Very soluble Very toxic Urea: land animals, sharks, some fish 100,000 times less toxic Produced in LIVER from ammonia, requires energy Uric acid: insects, snails, birds Paste, insoluble in water Most energy to produce

Making urine Filtration of blood Selective reabsoption of water Secretion of solute

Taxonomy Flatworms: flame bulb system: protonephridia: tubules throughout body (filtration happens at the ends) Earthworms (annelids): metanephredia: have 2: have osmoregulation and excretory functions

Mammalian kidney Liver: makes urea, from ammonia Kidney – ureter - bladder – urethra Kidney: filters blood, excretes solutes, reabsorb water Creates hyperosmotic urine

The Sodium-Potassium pump represents a common mechanism in maintenance of water and electrolyte balance Shark Rectal Gland and NaCl SecretionOsmoregulatory Activity in Marine and Freshwater Fish Gill Mammalian Kidney Function

The ability to form a concentrated urine is critical to the success of animals in terrestrial habitats The countercurrent multiplier activity of the loop of Henle in the mammalian nephron creates an osmotic gradient for water reabsorption and production of a concentrated urine.Regulation of water and electrolyte balance is energetically demanding.

Water Conservation Terrestrial animals must always be concerned with conserving water The skin is one of the primary water conservation organs - it keeps the water in and prevents evaporation The kidney, however, also prevents water loss while still filtering the blood

Regulation of Blood Volume and Concentration The total volume of blood plasma and interstitial fluid is regulated by the degree of filtration and reabsorption in the kidney The solute concentration and many nutrient levels are also regulated by the excretory system

The loop of Henle has three distinct regions Descending limb: thin wall the thin-walled: highly permeable to water. Impermeable to solutes As the filtrate travels down the descending loop, water will flow from the loop into the surrounding medium via osmosis. When the filtrate reaches the hairpin turn Lower portion of the ascending limb: highly permeable to NaCl Ascending Limb As it travels up into the less-concentrated regions of the medulla, Na+ and Cl- will passively diffuse across the membrane. As the filtrate continues up the thick portion of the loop of Henle, Na+ and Cl- are actively pumped out of the filtrate into the surrounding medium. This requires energy, but helps to maintain the osmotic concentration gradient in the medulla.1200 mosm/L)

Controls: Anti diuretic Hormone ADH Present – Made in Hypothalamus Stored in posterior pituitary Duct is VERY permeable to water SMALL volume of urine is produced

Controls: renin - angiotensin Also ANTI diuretic! Conserve water Renin is secreted by kidneys when blood pressure is Low Stimulates: Angiotensin release 1. constrict blood vessels 2. stimulate aldosterone release from adrenal cortex Reabsorb sodium and water from kidney