Malpighian Tubules. Malpighian tubules remove nitrogenous wastes (uric acid) from the hemocoel. Various ions are actively transported across the outer membrane of the tubule. Water follows these ions into the tubule and carries amino acids, sugars, and some nitrogenous wastes along passively. Some water, ions, and organic compounds are reabsorbed in the basal portion of the Malpighian tubules and the hindgut; the rest are reabsorbed in the rectum. Uric acid moves into the hindgut and is excreted in the feces. Coxal Glands in Arachnids. ( a ) The gut and excretory systems of a spider. The stercoral pocket is a diverticulum off the hindgut that stores waste prior to waste elimination. ( b ) Coxal gland muscles attach to the thin saccular fi ltration membrane. These muscles promote fi ltration and fl uid fl ow (black arrows) by contracting and relaxing along the tubular duct. Water and solutes are reabsorbed along the tubular duct.

1. Malpighian Tubules
and
Coxal Glands
Noshaba munawar

2. Malpighian Tubules
• Insects have an excretory system made up of the
• gut and Malpighian tubules
• (named after Marcello Malpighi, Italian anatomist,
• 1628–1694) attached to the gut (figure 28.13) .

3. Conti……….
 Excretion involves the active transport of potassium ions into the tubules
from the surrounding hemolymph
 And the osmotic movement of water that follows.
 Nitrogenous waste (uric acid) also enters the tubules.
 As fluid moves through the Malpighian tubules, some of
• the water and certain ions are recovered.
.
In cellular biology, active transport is the
movement of molecules across a cell
membrane from a region of lower
concentration to a region of higher
concentration—against the concentration
gradient

4. Conti……….
• All of the uric acid passes into the gut and out of the body in the feces.
• Because insects are capable of conserving water very effectively,
• the insect’s excretory system is a key adaptation contributing to these
animals’ tremendous success on land

6. Coxal Glands
• Coxal (L. coxa , hip) glands are common among arachnids (spiders,scorpions,
ticks, mites).
• These spherical sacs resemble annelid nephridia (figure 28.14) .
• Wastes are collected from the surrounding hemolymph of the hemocoel and
discharged through pores on one to several pairs of appendages near the
proximal segment(coxa) of the leg.
• .

7. Conti……….
• Evidence suggests that the coxal glands may also function in the release of
pheromones.
• Other arachnid species have Malpighian tubules instead of, or in addition to,
the coxal glands.
• In some of these species, however, Malpighian tubules seem to function in
silk production rather than in excretion