Eating.2C digestion.2C and excretion Mollusca

snail radula @ work

  = food       = radula

  = muscles

  = odontophore belt

members of mollusc family use intracellular digestion function. molluscs have muscular mouths radulae, tongues , bearing many rows of chitinous teeth, replaced rear wear out. radula functions scrape bacteria , algae off rocks, , associated odontophore, cartilaginous supporting organ. radula unique molluscs , has no equivalent in other animal.

molluscs mouths contain glands secrete slimy mucus, food sticks. beating cilia (tiny hairs ) drive mucus towards stomach, mucus forms long string called food string .

at tapered rear end of stomach , projecting hindgut prostyle, backward-pointing cone of feces , mucus, rotated further cilia acts bobbin, winding mucus string onto itself. before mucus string reaches prostyle, acidity of stomach makes mucus less sticky , frees particles it.

the particles sorted yet group of cilia, send smaller particles, minerals, prostyle excreted, while larger ones, food, sent stomach s cecum (a pouch no other exit) digested. sorting process no means perfect.

periodically, circular muscles @ hindgut s entrance pinch off , excrete piece of prostyle, preventing prostyle growing large. anus, in part of mantle cavity, swept outgoing lane of current created gills. carnivorous molluscs have simpler digestive systems.

as head has largely disappeared in bivalves, mouth has been equipped labial palps (two on each side of mouth) collect detritus mucus.