Saturday, June 30, 2012

Class XI, BIOLOGY, "Digestive System of Cockroach"

Digestive System of Cockroach

NUTRITION
OMNIVOROUS, i.e. It can eat any kind of organic matter. They search their food by antennae.
TYPE OF DIGESTIVE SYSTEM
TABULAR DIGESTIVE SYSTEM, i.e. straight slightly coiled dig tube, open at both ends, complete dig. system.
ORGANS OF DIGESTIVE SYSTEM
+ ALIMENTARY CANAL
It is divisible into 3 parts
1. FORE GUT / STOMODAEUM
  • MOUTH
  • BUCCAL CAVITY
  • OESOPHAGUS
  • CROP
  • GIZZARD
2. MIDGUT / MESENTERON / VENTRICULUS
  • HEPATIC CAECA
3. HIND GUT / PROCTODAEUM
  • ILEUM
  • COLON
  • RECTUM
  • ANUS
+ ASSOCIATED GLAND
  • SALIVARY GLANDS
1.FORE GUT
MOUTH
It lies at base of pre-oval cavity which is bounded by mouth part.
LABRUM / UPPER LIP
Appendage of 3rd head segment.
MANDIBLES
Appendage of 4th head segment. They help in mastication
MAXILLAE
Appendages of 5th head segment. They pick up and bring food.
LABIUM / LOWER LIP
Appendages of 6th head segment.
BUCCAL CAVITY
The mouth opens into buccal cavity which is short and receives the common duct of salivary glands.
Saliva cantain ‘AMYLASE’ which act upon carbohydrates.
OESOPHAGUS
Buccal cavity opens into pharynx which in turn opens into oesophagus which is a long and thin tube lying in thorax.
CROP
It is a large thin walled and pear shaped structure meant for storing food.
GIZZARD
Crop opens into thick walled, rounded gizzard with muscular chitins lining which is internally produced six teeth for grinding and straining the food.
2. MID-GUT
It is narrow, short and tubular portion originate from gizzard. At beginning it receives eight hepatic caeca hanging in haemocoel (body cavity filled with white colour blood), ending blindly but opening in gut.
ENZYMES FROM HEPATIC CAECA
They are lined by glandular cells, which secrete enzymes.
Enzymes from hepatic caeca and mid-gut flow back into crop where digestion takes place.
ENZYMES
1. PEDTIDASES AND TRYPSIN LIKE ENZYME -> digest proteins.
2. AMYLASES -> complete digestion of starches
3. LIPASE -> digestion of fats.
Digested food form a bolus and enclosed in a thin chitinous tube secreted by stomodael valve of gizzard. This covering is called PERITROPHIC MEMBRANE.
It is permeable to enzymes and digested food. This membrane protects the lining of mid gut from damage by hard indigestible components of food.
Digested food is absorbed in mid gut.
3. HIND-GUT
It has a cuticular ectodermal lining.
ILEUM
Short, narrow and muscular ileum. The beginning of ileum is marked by 60-70 fine and long, greenish yellow MALPHIGIAN TUBULES. (excretory in function)
COLON
Colon is long, wider and coiled portion of hind gut
RECTUM
Rectum is broad last part of hind gut. It absorbs H2O and conserves the much needed H2O from undigested food before expelling out the faeces.
ANUS
Anus is the last opening of digestive system by which hind gut opens to outside.
SALIVARY GLANDS
Salivary glands are 2 in number. each present on the sides of oesophagus. Saliva contain amylase for digestion of carbohydrates.

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