Digestive system of Insects

Digestive system of Insects

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  DIGESTIVE SYSTEM Presented To: Dr. Asim Riaz Presented By : Muhammad Irfan Shan Rao Huraira Farooq
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  Digestive System ofInsects • Insects feed on a wide range of organic materials. • Almost 75% of all species of insects are phytophagous. • Insects may be:  Carnivorous  Entomophagous  Wood borers  Parasitic on other animals or insect species  Parastoids
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  Alimentary Canal • Along, muscular and an enclosed tube that extends from the mouth to the anus also called Digestive gut or Alimentary Canal
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  Alimentary Canal /Digestive gut • The alimentary canal in insects is divided in to three regions: • Foregut (stomodeum) of ectodemal origin  food is stored, filtered and partially digested. • Midgut (mesentron) of endodermal origin  primary site for digestion and aborption of food. • Hindgut (proctodeum) of ectodermal origin  some abosorption and feces formation occur
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  Structure of AlimentaryCanal
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  Foregut o Starts frommouth cavity to gizzard or proventriculus. o The mouth cavity: labrum as upper lip, labium as lower lip with mandibles and maxillae laterally and hypopharynx at the centre. o At the base of the hypopharynx, salivary glands open into the mouth cavity.
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  Salivary glands • Theglands are grape-like clusters called acinus. • Involved in the secretion of salivary juices into the salivary ducts. • The secretion of the glands contain: amylases, lipases, proteases etc.
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  Structure of Foregut Foregutis divided into:  Pharynx  Region between the mouth and oesophagus.  Oesophagus • It is a narrow part, food get transported from pharynx into the crop.  Crop • It is a sac like structure which is a dilated and store food material.  Gizzard/Proventriculus • A structure that contain sclerotized teeth-like denticles. These denticles grinding the food. (Lack in fluid feeding insects) • The junction of foregut and midgut is provided with a cardiac (oesophageal) valve also called Stomodeal valve (regulate flow of food)  The foregut is lined with chitinous protective layer called intima. Intima ptohibits the absroption of nutrients
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  Structure of Midgut •A short, cylindrical and straight tube. • Its anterior end arise six large, elongated sacs, the gastric caecae which consists of a longer anterior lobe and shorter posterior lobe. • The posterior lobes are filled with food whereas the anterior lobes have secretary function. • Gastric caecae which produce digestive enzymes and increase surface area. • The posterior end of the midgut is marked by the presence of malpighian tubules which absorb nuritients • At the junction of midgut and hindgut is a pyloric valve.
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  Midgut (Peritorphic membrane) •The midgut has a very thin and delicate layer called peritrophic membrane secreted by the epithelial cells. • The peritrophic membrane protects the tender epithelial cells / secretary cells of the midgut from friction by hard food particles. • It forms a coat over the food particles. • Midgut is not lined by intima and most of absoption of nutrients occurs here in ventriculus.
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  Hindgut  Malphagian tubulesattach to pylorus region of hindgut • Hindgut is divided into 3 regions: • Ileum (small intestine) is a thick and straight tube. • Colon (large intestine) is a short narrow tube which dilates posteriorly to merge into the rectum. • Rectum wider tube provided with six bands of longitudinal muscles alternating. These are involved in reabsorption of water and salts from the faecal matter. • The rectum ends in anus.
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  • Digestion takeplace in following 5 steps:  Ingestion  Transportation  Digestion  Absorption  Egestion Process of Digestion
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  Digestion take placein 5 steps 1. Ingestion • Food is partially digested in the oral cavity with the help of salivary enzymes. 2. Transportation • The food material entered in to the oesophagus is transported in to the crop by muscular activity. • From the crop, food enters in to the gizzard where it is still broken in to very minute particles with the help of denticles or the cuticular teeth.
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  Conti.. 3. Digestion • Fromgizzard food passes in to the midgut where actually digestion starts. • The epithelial cells produce enzymes i.e.  Proteases which break proteins in to aminoacids,  Carbohydrases breaking carbohydrates in to mono & disaccharides,  Lipases breaking lipids in to fatty acids and glycerol. 4. Absorption • Midgut epithelial cells absorb the nutrients from the digested food and pass on the faecal matter and undigested food material in to the hindgut. 5. Egestion: • The waste food material is discharged through the anus due to the action of the anal muscles.
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  Modifications
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