View
7
Download
0
Category
Preview:
Citation preview
water balancechapter 42
maintaining water balance• osmoregulation
• water and dissolved solutes• metabolic wastes (nitrogen)• excess water / homeostasis
• adjusting the composition of internal body fluids• in arthropods -- hemolymph• in vertebrates -- interstitial fluid / blood
maintaining water balance• transport epithelia
• extensive surface area• water balance and excretory• examples
• marine birds like albatross• drink seawater
Ducts
Nostrilwith salt
secretions
Nasal saltgland
nitrogenous wastes• ammonia
• many aquatic invertebrates • highly soluble, but very toxic -- requires lots of water
• ammonium -- NH4+
• common in freshwater fish... • exchanged for Na+ in freshwater fish
• urea• mammals, adult amphibians, many marine fishes, and turtles -- • low toxicity, can be concentrated• requires much less water than ammonia• requires energy to produce from ammonia
nitrogenous wastes• uric acid
• Land snails, insects, spiders, birds, and many reptiles
• relatively nontoxic.• largely insoluble in water • more expensive• related to mode of reproduction
• amniotic eggs
osmosis• central problem of osmoregulation --
• how to balance uptake and outflow of water?• osmosis• osmolarity • human blood is about 300 mosm/L• seawater is about 1,000 mosm/L.
• hypertonic = hyperosmotic; hypotonic = hypoosmotic
homeostasis• marine
• hypoosmotic regulators -- • problems • retaining water • getting rid of salt
• isoosmotic conformers.• fresh
• hyperosmotic regulators -- • problems • removing excess water • acquiring salt
• variability• anadromy/catadromy• stenohaline/euryhaline
Excretion of salt ions from
gills
Gain of water and salt ions from food
Osmotic water loss through gills and other parts of body
surface
Excretion of salt ions and small amounts of water in scanty urine from
kidneys
Gain of water and salt ions from
drinking seawater(a) Osmoregulation in a saltwater fish
Uptake of water and some ions in food Uptake of salt
ions by gills Osmotic water gain through gills and other parts of body
surface
Excretion of large amounts of water in dilute
urine from kidneys(b) Osmoregulation in a freshwater fish
terrestrial concerns• dessication?• adaptations to prevent water loss:
• anhydrobiosis• nocturnal activity• waxy cuticle in arthropods...• keratin • many desert animals can reabsorb water from bladder
excretory organs• specilized organs (comparative anatomy)
• general scheme for filtration• blood or hemolymph or coelomic fluid
collected• filtration
• composition of filtrate is changed
organs• protonephridia
• network of branching tubules• flame cell
• or solenocyte• nephridiopores• osmoregulation
Tubule
Tubules of protonephridia
Cilia
Interstitial fluid flow
Opening in body wall
Nucleus of cap cell
Flame bulb
Tubule cell
organs• metanephridia
• nephrostome• capillaries surrounding tubules• nephridiopore
nephrostomenephridiopore
bladder
organs• malpighian tubules
• connected to digestive tract• tips immersed in hemolymph• water, various solutes reabsorbed in
rectum
Rectum
Digestive tract
HindgutIntestine
Malpighiantubules
Rectum
Feces and urine
HEMOLYMPH
Reabsorption
Midgut(stomach)
Salt, water, and nitrogenous
wastes
organs• Vertebrate kidneys
• profused by renal artery and renal vein
• nephron• glomerulus
• afferent arteriole• efferent arteriole• bowman’s capsule
• proximal tubule• loop of henle• distal tubule
• two distinct regions• renal cortex and renal medulla
• cortical nephrons• juxtamedullary nephrons
Corticalnephron
Juxtamedullarynephron
Collectingduct
Torenalpelvis
Renalmedulla
Renalcortex
Posteriorvena cava
Renal arteryand vein
Urinarybladder
Ureter
Urethra
Kidney
Aorta
Renalcortex
Renalmedulla
Renalpelvis
• homeostatic control mechanisms • antidiuretic hormone - osmolarity• blood pressure
• renin - angiotensin II - aldosterone• atrial natriuretic factor -
• opposes RAAS• reduces blood pressure
Renin
Distal
tubule
Juxtaglomerular
apparatus (JGA)
STIMULUS:
Low blood volume
or blood pressure
Homeostasis:
Blood pressure,
volume
Liver
Angiotensinogen
Angiotensin I
ACEAngiotensin II
Adrenal gland
Aldosterone
Arteriole
constriction
Increased Na+
and H2O reab-
sorption in
distal tubules
PSA about next slide
Kidneys
Recommended