Transcript الشريحة 1

Syllabus
 Filter Feeding
 In Polychetes
 In Molluscs
 In Deuterosmia
 In Crustaceans
 Respiration
 Physical factors
 Pigments
 Gills and Lophophores in Polychetes
 Gills and Lungs in Molluscs
 Gills and Trachea in Arthropods
Filter Feeding
Remember
 This type is found only in aquatic animals
 It is disappeared from the terrestrial animals due
to the lower density of air
 It is occurred in small aquatic animals
 It takes place through special organs
Digestion in Molluscs
 The ingestion of small particles probably determined the
retention of the:
 Intracellular method of digestion .
 The alimentary system adapted for microphagy.
 The stomach is a characteristic part in the alimentary tract.
 This type of digestion requires a large area of phagocytic epithelium
 The food must be delayed in its passage through the alimentary tract and
distributed over the epithelium.
Digestion in Molluscs
 The structure of the stomach In
bivalves:
 A long crystalline style and flexible rod
projects into the lumen of the stomach.
 This rod is composed of layers of
mucoprotein
 This rod is secreted by a style sac which is
an extension of the stomach.
 The style sac contains cilia causing the
style to rotate, and to drive it forwards into
the stomach.
 The free end of the style is worn away by
friction against the gastric shield, which is
a thickening of the cuticular lining of the
stomach wall.
 This causes dissolving of the style
substance containing a digestive amylase
 This substance is added to the contents of
the gastric lumen.
Digestion in Molluscs
 The sorting mechanism in the
stomach of bivalves:
 Food particles enter the stomach with
strands of mucus, are mixed with the
digestive secretion by the rotation of
the style , so that the extracellular
digestion of carbohydrate is initiated.
 Particles of food are continually
broken off and sorted by the stomach
wall.
 The stomach wall is lined with ciliated
ridges and grooves that have an action
similar to that of the labial palps.
 The larger and heavier particles enter
the deeper grooves and are transported
by cilia into the intestine and the effect
of more alkaline pH forming them into
faecal pellets that extruded through
the anus.
Filter Feeding in Molluscs
 The fine particles are borne over the cilia on the ridges of the
stomach wall towards the opening of the digestive diverticula
or glands.
 There are two diverticula, each consisting of a highly branched
system of blined tubules opening into the stomach by ciliated
duct. The epithelium of these tubules are also ciliated and is
composed of highly vacuolated cells. These cells are highly
phagocytic, capable of ingesting fine particles into food
vacuoles and the digestion is completed inside the vacuoles.
 The intracellular digestion takes place.