Title: Oct 12 3:37 PM (1 of 39) Ch 44 Osmoregulation and Excretion

Title: Oct 12 3:37 PM (1 of 39) Ch 44 Osmoregulation and Excretion

Water Balance and Waste Disposal osmoregulation managing water content and solute composition based on movements of solutes excretion of metabolic wastes regulates bathing fluid of cells in excretory organs maintain water balance and dispose of wastes Title: Oct 12 3:38 PM (2 of 39)

Excretion process that rids the body of nitrogenous metabolites and other waste products What organic compounds produce nitogenous wastes? Title: Oct 12 3:41 PM (3 of 39)

How do organisms balance water gain and loss? osmoconformer being isoosmotic to surroundings will not gain or lose water live in water with consistant osmolarity osmoregulator an animal that must control its internal osmoregularity in hypoosmotic gets rid of water in hyperosmotic gains water Title: Oct 12 3:42 PM (4 of 39)

stenohaline animals that cannot tolerate large changes in external osmolarity euryhaline animals that can tolerate large changes ex. salmon Title: Oct 12 5:37 PM (5 of 39)

Osmolarity solute concentration expressed as molarity isoosmotic if two solutions separated by a selectively permeable membrane have the same osmolarity When two solutions differ in osmolarity, the one with the greater solute concentration is hyperosmotic and the one with the lower solute concentration is the hypoosmotic. Water flows from hypoosmotic to hyperosmotic. Title: Oct 12 3:58 PM (6 of 39)

hypoosmotic to seawater, loses water by osmosis, gains salt by diffusion Title: Oct 12 3:43 PM (7 of 39)

Title: Oct 12 3:43 PM (8 of 39) constantly gains water and loses salt

anhydrobiosis adaptations for animals that live in water temporaril tardigrades water bears Hydrated 85% water Dehydrated 2% water Title: Oct 12 3:44 PM (9 of 39)

Land animals have body coverings that prevent dehydration keratinized skin lose water from skin, urine, feces, respiration have to rehydrate regularly Title: Oct 12 3:46 PM (10 of 39)

transport epitheliumhelps regulate solute movements move solutes in specific directions form a barrier at tissue environment boundary in animals arranged in tubes with high surface area ex. Salt glands in marine birds remove excess sodium chloride from blood Title: Oct 12 3:47 PM (11 of 39)

So why can't humans drink salt water like a seagull can? bird gets rid of extra salt through a salt gland if humans drink salt water, they need a greater amount of water to excrete the salt load using their kidneys therefore: become dehydrated Title: Oct 12 3:56 PM (12 of 39)

Metabolic wastes dissolved in water (except carbon dioxide) nitrogenous wastes (breakdown products of proteins and nucleic acids) ammonia toxic molecule common in aquatic species diffuse easily in invertebrates diffuses through body fish lost as ammonium ions form gills can be excreted directly or as urea must be very dilute in land animals or toxic Title: Oct 12 3:48 PM (13 of 39)

Urea used for land animals (mammals, most adult amphibians, marine fish, turtles produced by liver that combines ammonia with carbon dioxide, then carried to excretory system by blood low toxicity (100,000 x less than ammonia) reduces need for water for excretion disadvantage must expend energy to make form ammonia Title: Oct 12 3:49 PM (14 of 39)

Uric Acid land snails, insects, birds and many reptiles nontoxic insoluble in water, excreted as semisolid paste advantage if little water is around, but takes lots of energy to produce uric acid is favored for egg layers because it can be stored within the egg without harming the embryo Title: Oct 12 5:42 PM (15 of 39)

Title: Oct 12 3:49 PM (16 of 39)

Diversity of excretory systems regulate solute movement between internal fluids and the external environment the filtrate produced by the system is from body fluids Based on four processes: filtration reabsorption secretion excretion Title: Oct 12 3:49 PM (17 of 39)

Capillary Filtration Reabsorption Secretion Excretion Filtration collects filtrate from blood; water/ solutes forced by blood pressure across selectively permeable membrane Reabsorption transport epithelium reclaims valuable substances from filtrate puts back in body Secretion toxins and ions are extracted from body fluids and added to excretory tube Excretion fitrate (urine) leaves system and body Title: Oct 12 4:06 PM (18 of 39)

Excretory systems in other organisms Protonephridia network of dead end tubules connected to external openings flame bulb is the cap end excrete dilute fluid nitrogenous waste (Ex parasitic flatworms); involved in osmoregulation (other flatworms found in flatworms (phylum Platyhelminthes), rotifers, mollusc larvae and lancelets Title: Oct 12 4:13 PM (19 of 39)

Title: Oct 12 5:47 PM (20 of 39)

Metanephridia consist of tubules that collect coelomic fluid and produce dilute urine for excretion Title: Oct 12 4:19 PM (21 of 39)

Malpighian Tubules remove nitrogenous from hemolymph and used in osmoregulation in insects and other terrestrial arthropods Title: Oct 12 5:56 PM (22 of 39)

Title: Oct 12 6:00 PM (23 of 39) Kidneys excretory organ for vertebrates

Title: Oct 12 6:04 PM (24 of 39) Cross Section of Kidney

Title: Oct 12 6:03 PM (25 of 39)

only mammals and some birds have loops of Henle In human 85% of nephrons have short loops of Henle and are in renal cortex 15% are juxtamedullary nephrons have loops of Henle that go deep into the renal medulla 1,600L of blood flows through pair of kidneys/day but only 1.5L leaves body as urine Title: Oct 12 6:08 PM (26 of 39)

How is blood filtered? 1. blood pressure forces fluid from blood into glomerulus contains salts, glucose, amino acids, vitamins, nitrogenous wastes, water and other small molecules 2. From Bowman's Capsule passes through three regions of nephron proximal tubule loop of Henle diatal tubule Title: Oct 12 6:13 PM (27 of 39)

In the proximal tubule: get reabsorption of ions, water and nutrients molecules are transported actively and passively some toxic materials are secreted into the filtrate fitrate volume decreases Title: Oct 12 6:18 PM (28 of 39)

In Loop of Henle: Descending part reabsorption of water contiues through aquaporins movement driven by high osmolarity of interstitial fluid (hyperosmotic to filtrate) filtrate becomes more concentrated Title: Oct 12 6:20 PM (29 of 39)

Loop of Henle continued: Ascending part salt, not water diffuses from tubule to interstitial fluid filtrate gets more dilute Title: Oct 12 6:23 PM (30 of 39)

Distal Tubule: regulates potassium and NaCl concentrations ion movement controls ph level Collecting duct: filtrate goes from medulla to renal pelvis water, salt and some urea is lost filtrate gets more concentrated Title: Oct 12 6:25 PM (31 of 39)

Title: Oct 12 6:29 PM (32 of 39) Filtering process

Osmolarity of interstitial fluid depends on NaCl and urea as filtrate flows in collecting duct past interstitial fluid of increasing osmolarity, more water moves out = concentrated urine Title: Oct 12 6:31 PM (33 of 39)

How do hormones regulate the blood osmolarity? Antidiuretic hormone (ADH) increases water reabsorption in the distal tubule and collecting ducts an increase in osmolarity triggers release of ADH helps conserve water Title: Oct 12 6:39 PM (34 of 39)

ADH allows aquaporins to be inserted into the membrane lining the lumen. Aquaporin channels allow water to be reabsorbed from the collecting duct and put back into the body Title: Oct 12 6:42 PM (35 of 39)

Mutation in ADH production causes severe dehydration and results in diabetes insipidus Alcohol is a diuretic as it inhibits the release of ADH Title: Oct 12 6:48 PM (36 of 39)

How is blood pressure regulated by the kidneys? Renin Angiotensin Aldosterone System (RAAS) 1. Renin is released by the kidney when blood pressure drops 2. Renin cleaves angiotensinogen (plasma protein) into angiotensin II (functions as a hormone) 3.Angiotensin II increases the blood pressure by constricting capillaries; also signals adrenal glands to release aldosterone 4. Aldosterone acts on nephrons' distal tubules makes them reabsorb sodium and water which increases blood volume and pressure Title: Oct 12 6:49 PM (37 of 39)

So what if you have high blood pressure? drugs that block angiotensin II are used to treat hypertension inhibit angiotensin converting enzyme (ACE) which catalyzes the 2nd step on production of angiotensin II Title: Oct 12 6:58 PM (38 of 39)

So... ADH and RAAS are partners in homeostasis ADH and RAAS both increase water reabsorption, but only RAAS will respond to a decrease in blood volume Another hormone, atrial natriuretic peptide (ANP), opposes the RAAS ANP is released in response to an increase in blood volume and pressure and inhibits the release of renin Title: Oct 12 7:03 PM (39 of 39)