Chapter 44: Osmoregulation and Excretion Flashcards
Excretion
How the body rids itself of nitrogenous metabolizes and metabolic waste products
Osmoregulation
How animals control solute concentrations and balance water gain or loss
Osmoconformer
To be isoosmotic with surroundings: always marine animals
Osmoregulator
Control internal osmolarity independent of that of its environment
Stenohaline
Cannot tolerate substantial changes in external osmolarity
Euryhaline
Can survive large fluctuations in external osmolarity
How do osmoregulating marine fish balance water loss from the hyper osmotic salt water?
Drink excess water, rid selves of salts through gills and kidneys
Hemolymph
Fluid surrounding cells in an open circulatory system like insects
Interstitial fluid
Fluid surrounding cells in closed circulatory system, like vertebrates
Transport epithelia
One or more layers of epithelial cells specialized for moving particular solutes in controlled amounts in specific directions
Ammonia
Very toxic, usually excreted very dilutely, eg fish across gills
Urea
Slightly toxic, less water loss, humans, etc.
Uric acid
Nontoxic, guano, solid paste
Filtration
Driven by hydrostatic pressure, drives water, small solutes, etc across membranes to form filtrate
Excretory system in flatworms aka Platyhelminthes
Protonephridia: dead end tubules ending in flame bulbs, connected to external openings
Excretory system of annelids
Metanephridia: collect fluid directly from coelom, enveloped in capillary network, cilia
Excretory system of insects
Malpighian tubules: dead end tips immersed in hemolymph, connect to digestive tract
Where does blood come to the kidneys from?
Renal artery: to outer renal cortex and inner renal medulla
Describe flow in nephrons
Glomerulus in Bowman’s capsule, to proximal tubule, to loop of Henle, to distal tubule, to collecting duct
What is reabsorbed in the proximal tubule?
Ions, water, nutrients: NaCl moves from filtrate to interstitial fluid, water follows by osmosis int peri tubular capillaries
What happens in the descending limb of the loop of Henle?
More reabsorption of water through aquaporin-protein-formed channels
What happens in the ascending loop of Henle?
Not permeable to water, only ions: NaCl diffuses out in lower, thinner segment, and actively transported out at thicker top segment to make the filtrate more dilute
What happens in the distal tubule?
K+ secreted into filtrate, NaCl reabsorbed
What two substances help control pH in kidneys?
Secretion of H+ and reabsorption of HCO3-
Where is there the highest filtrate concentration in nephrons?
Bottom of loop of Henle
Countercurrent multiplier system
Countercurrent systems that expend energ to create condensation gradients
Vasa recta
Hair pin shaped capillaries that serve the renal medulla
