51.
Salt and Water Balance and Nitrogen Excretion 1092
51.1
What Roles Do Excretory Organs Play
in Maintaining Homeostasis? 1093
Water enters or leaves cells by osmosis
1093
Excretory organs control extracellular
fluid osmolarity by filtration, secretion,
and reabsorption 1094
Animals can be osmoconformers or osmoregulators
1094
Animals can be ionic conformers or
ionic regulators 1095
51.2 How Do Animals Excrete Toxic
Wastes from Nitrogen Metabolism? 1095
Animals excrete nitrogen in a number
of forms 1095
Most species produce more than one
nitrogenous waste 1096
51.3 How Do Invertebrate Excretory
Systems Work? 1097
The protonephridia of flatworms excrete
water and conserve salts 1097
The metanephridia of annelids process
coelomic fluid 1097
The Malpighian tubules of insects
depend on active transport 1098
51.4 How Do Vertebrates Maintain Salt
and Water Balance? 1098
Marine fishes must conserve water
1099
Terrestrial amphibians and reptiles
must avoid desiccation 1099
Birds and mammals can produce highly
concentrated urine 1099
The nephron is the functional unit
of the vertebrate kidney 1099
Blood is filtered in the glomerulus
1100
The renal tubules convert glomerular
filtrate to urine 1101
51.5 How Does the Mammalian Kidney
Produce Concentrated Urine? 1101
Kidneys produce urine and the bladder
stores it 1101
Nephrons have a regular arrangement
in the kidney 1101
Most of the glomerular filtrate is
reabsorbed by the proximal convoluted
tubule 1103
The loop of Henle creates a concentration
gradient in the surrounding tissue
1103
Water permeability of kidney tubules
depends on water channels 1104
Water reabsorption begins in the distal
convoluted tubule 1104
Urine is concentrated in the collecting
duct 1104
The kidneys help regulate acid–base
balance 1105
Kidney failure is treated with dialysis
1105
51.6
What Mechanisms Regulate Kidney Function?
1107
The kidneys maintain the glomerular
filtration rate 1107
Blood osmolarity and blood pressure
are regulated by ADH 1107
The heart produces a hormone that
influences kidney function 1108
