Excretory Systems Ch. 44 Regulating Water Loss and Solute Concentrations

Ch. 44 & 45 - Digestion & Fluid Balance 1.What organism is used by Dr. Carol Beuchat to illustrate how fluid is regulated and the role played by the urinary tract in maintaining homeostasis? (1st segment) 2.How is a complete digestive system different from an incomplete one? What function does each segment (region) of the digestive system have? 3.Name two enzymes mentioned by Dr. Sokolowski that play a role in the digestive system. How is the diet of a dog different from a cat? What are the nutritional needs for a cat and dog? What is the name of the café mentioned in the video? 4. The final segment discusses the role the kidneys play in maintaining homeostasis. What kind of machine is the patient connected to? **Write the title for each segment and FIVE statements for each segment.

Introductory Questions #7 1)How is an osmoconformer different from an osmoregulator? 2)Name a fish that is able to adjust to salt concentrations ranging from freshwater to 2,000mosm/L (twice that of sea water). 3)How do marine fishes (hyperosmotic to the water) adjust and balance their water loss? 4)Name the three types of nitrogenous waste products that are released fish, mammals, and reptiles. Which one is most toxic? Which one is a semi-solid form? Which one is made by combining ammonia and carbon dioxide? 5)Name the key excretory structures found in Flatworms (Platyhelminthes), Earthworms (annelids), and Insects (Arthropodds). 6)Name the two distinct regions of the mammalian kidney. Name the three regions of nephron starting from the Bowman’s capsule.

Nitrogen-containing wastes are toxic by- products of protein and nucleic acid breakdown –Ammonia is poisonous but soluble and easily disposed of –Urea is less toxic and easy to store and excrete –Some land animals save water by excreting a virtually dry waste Animals must dispose of nitrogenous wastes

Water Balance and waste disposal Osmoregulation: –management of the body’s water content and solute composition (hyper, iso, hypo tonic soln’s) Nitrogenous wastes: – breakdown products of proteins and nucleic acids; ammonia-very toxic Deamination –Ammonia: most aquatic animals, many fish –Urea: mammals, most amphibians, sharks, bony fish (in liver; combo of NH3 and CO2) –Uric acid: birds, insects, many reptiles, land snails

Water Balance and waste disposal

Osmoregulators Osmoconformer: no active adjustment of internal osmolarity ( marine animals); isoosmotic to environment Osmoregulator: adjust internal osmolarity (freshwater, marine, terrestrial) Freshwater fishes (hyperosmotic)- gains water, loses; excretes large amounts of urine salt vs. marine fishes (hypo-osmotic)- loses water, gains salt; drinks large amount of saltwater

Osmoregulators

Excretory Systems Production of urine by 2 steps: -Filtration (non-selective) -Reabsorption (secretion of solutes) Protonephridia ~ flatworms (“flame-bulb” systems) Metanephridia ~ annelids (ciliated funnel system) Malpighian tubules ~ insects (tubes in digestive tract) Kidneys ~ vertebrates

Excretory Systems

Kidney Functional Units Renal artery/vein: kidney blood flow Ureter: urine excretory duct Urinary bladder: urine storage Urethra: urine elimination tube Renal cortex (outer region) Renal medulla (inner region) Nephron: functional unit of kidney Cortical nephrons (cortex; 80%) Juxtamedullary nephrons (medulla; 20%)

Nephron Structure Afferent arteriole: supplies blood to nephron from renal artery Glomerulus: ball of capillaries Efferent arteriole: blood from glomerulus Bowman’s capsule: surrounds glomerulus Proximal tubule: secretion & reabsorption Peritubular capillaries: from efferent arteriole; surround proximal & distal tubules Loop of Henle: water & salt balance Distal tubule: secretion & reabsorption Collecting duct: carries filtrate to renal pelvis

Overview of Mammalian Nephron Function

Figure Bowman’s capsule Blood Proximal tubule NaCl HCO 3 – H2OH2OGlucose and amino acids Some drugs and poisons NH 3 H+H+ CORTEX MEDULLA Filtrate H2OH2O Salts (NaCl, etc.) HCO 3 – H+H+ Urea Glucose Amino acids Some drugs Reabsorption Active transport Passive transport Secretion (active transport) Distal tubule H2OH2O HCO 3 – NaCl K+K+ H+H+ Collecting duct NaCl Urea H2OH2ONaCl H2OH2O Urine (to renal pelvis) Loop of Henle

The Human Kidney & Nephron

Kidney regulation: hormones Antidiuretic hormone (ADH) ~ secretion increases permeability of distal tubules and collecting ducts to water (H2O back to body); inhibited by alcohol and coffee Juxtaglomerular apparatus (JGA) ~ reduced salt intake--->enzyme renin initiates conversion of angiotension (plasma protein) to angiotension II (peptide); increase blood pressure and blood volume by constricting capillaries Angiotension II also stimulates adrenal glands to secrete aldosterone; acts on distal tubules to reabsorb more sodium, thereby increasing blood pressure (renin-angiotension- aldosterone system; RAAS) Atrial natriuretic factor (ANF) ~ walls of atria; inhibits release of renin, salt reabsorption, and aldosterone release

Basking in the sun Sitting in the shade Bathing Burrowing or huddling Migrating Behavior often affects body temperature Figure 25.3

Torpor is a state of reduced activity and lowered metabolic rate –Hibernation in cold weather –Estivation in warm weather Reducing the metabolic rate saves energy Figure 25.4

Land animals gain water by drinking and eating –They lose water and solutes by evaporation and waste disposal –Their kidneys, behavior, and waterproof skin conserve water

Water lost in thermoregulation can cause osmoregulatory problems –Drinking water is the best way to prevent dehydration during exercise Sweating can produce serious water loss Figure 25.6

Many small invertebrates can dehydrate and become dormant when their environment dries up Some animals face seasonal dehydration Figure 25.7

Each nephron consists of a folded tubule and associated blood vessels –The nephrons extract a filtrate from the blood –They refine the filtrate into a much smaller amount of urine Figure 25.9D Bowman’s capsule Arteriole from renal artery Arteriole from glomerulus Branch of renal vein Glomerulus Capillaries From another nephron Collecting duct 1 Proximal tubule 2 Loop of Henle with capillary network 3 Distal tubule D. DETAILED STRUCTURE OF A NEPHRON

Filtration –Blood pressure forces water and many solutes from the blood into the nephron Reabsorption –The nephron tubule reclaims valuable solutes The key functions of the excretory system are filtration, reabsorption, secretion, and excretion

Secretion –The nephron removes substances and adds them to the filtrate The product of all of the above processes is urine, which is excreted Figure Nephron tubule FILTRATION H 2 O, other small molecules REABSORPTION SECRETION EXCRETION Capillary Urine

The proximal tubule reabsorbs –nutrients –salts –water Antidiuretic hormone and other hormones regulate the amount of salt and water the kidneys excrete From blood to filtrate to urine: A closer look

Controlled secretion of H + and reabsorption of bicarbonate ions help regulate blood pH Secretion also includes the active transport of drugs and poisons Reabsorption of salts and urea promote the osmotic reabsorption of water

A dialysis machine compensates for kidney failure –It performs the function of the nephrons by removing wastes from the blood and maintaining its solute concentration Kidney dialysis can be a lifesaver

Line from artery to apparatus Pump Line from apparatus to vein Fresh dialyzing solution Dialyzing solution Used dialyzing solution (with urea and excess salts) Tubing made of a selectively permeable membrane Figure 25.12

It assists the kidneys by –making urea from ammonia –breaking down toxic chemicals The liver is vital in homeostasis

Blood from the intestines flows through the liver before distribution to the rest of the body –This allows the liver to adjust the blood’s chemical content Figure Inferior vena cava Hepatic vein Liver Hepatic portal vessel Intestines