Key Terms
Osmosis
Water moves across a semi-permeable membrane in response to solute concentration differences. Water moves toward higher
Osmoregulation
Maintaining water and salt balance across membranes
Hypotonic environment (low solute outside)
Water enters the cell; cell swells. Hypertonic environment (high solute outside): water leaves the cell; cell shrinks.
Electrolyte
Dissolves into ions in water (ex: NaCl splits into Na+ and Cl-). Greater effect on osmotic pressure per unit mass.
Key ions tightly regulated in body fluids
Cations: Na+, K+, Ca2+, Mg2+
Anions
Cl-, carbonate, bicarbonate, phosphate
Passive diffusion
Water can cross freely; ions cannot rely on this.
Facilitated diffusion
Uses protein channels; moves solutes high to low concentration; no energy required. Active transport: moves ions AGAINST
Molarity
Moles of solute per liter of solution Molality: moles of solute per kilogram of solvent Milliequivalents per liter (mEq/
Osmoregulator
Actively maintains internal osmolarity regardless of environment. Most vertebrates, including humans.
Stenohaline
Tolerates only a narrow salinity range (ex: goldfish). About 90% of bony fish.
EXTERNAL LAYERS (outside to inside)
1. Renal fascia - tough connective tissue, outermost 2.
INTERNAL REGIONS (outside to inside)
1. Cortex - outer; contains nephrons; granular in appearance 2.
BLOOD SUPPLY PATH (artery side)
Aorta - renal artery - segmental arteries - interlobar arteries (through renal columns) - arcuate arteries (arch along b
After glomerulus
Efferent arterioles - peritubular capillary network (surrounds PCT and DCT in cortical nephrons) / vasa recta (surrounds