11.3 The Kidney and Osmoregulation

Question 1

Osmolarity

Answer 1

the solute concentration of a solution

Question 2

Osmoregulators

Answer 2

animals that maintain a constant internal solute concentration even when living in marine environments with very different osmolarities (all terrestrial animals, freshwater animals and some marine organisms)

Question 3

Osmoconformers

Answer 3

animals whose internal solute concentration tends to be the same as the concentration of solutes in the environment

Question 4

Malpighian tubule system

Answer 4

carries out osmoregulation and the removal of nitrogenous wastes in insects
tubes that branch off from their intestinal tract
cells lining tubules actively transport ions and uric acid from the hemolymph (combines characteristics of tissue fluid and blood) into the lumen of the tubules
this draws water by osmosis from the hemolymph through the walls of the tubules into the lumen
the tubules empty their contents into the gut
in the hindgut most of the water and salts are reabsorbed while the nitrogenous waste is excreted with the feces

Question 5

Blood in Renal Vein vs. Blood in Renal Artery

Answer 5

substances present in higher amounts in renal artery:
- toxins and other substances that are ingested and absorbed but are not fully metabolized by the body
- excretory waste product including nitrogenous waste products mainly urea
- excess water
- excess salt
blood in renal vein is deoxygenated
renal vein also has a higher partial pressure of CO2 because its a waste product of metabolism
the concentration of glucose slightly lower in renal vein because some glucose is used by the metabolism of the kidney
plasma proteins same concentration in both because they are not filtered by the kidney

Question 6

Glomerular Filtrate

Answer 6

the fluid forced out in the capillaries in the glomerulus of the kidney (the pressure is high and the capillary wall is permeable) - nearly all proteins retained in capillaries so are not present as much in the filtrate

Question 7

Ultrafiltration

Answer 7

the separation of particles differing in size by a few nanometers - all particles with a relative molecular mass below 65,000 atomic mass units can pass through

Question 8

3 Parts of the Ultrafiltration System

Answer 8

1) Fenestrations between the cells in the wall of the capillaries (about 100nm in diameter) allow fluid to escape but not blood cells
2) The Basement Membrane that covers and supports the wall of the capillaries is made of negatively-charged glycoproteins which form a mesh that prevents plasma proteins from being filtered out due to their size and negative charges
3) Podocytes forming the inner wall of the Bowman’s capsule