Digestive System PDF
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This document provides a comprehensive overview of different digestive systems found in various animal types, from Protozoa to Arthropoda. It details the processes involved, such as ingestion, digestion, absorption, assimilation, and egestion, highlighting the structural and functional adaptations in different organisms. The document also explains characteristics and examples of various invertebrates' digestive systems.
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Digestion – a physical as well as a chemical process of changing food from insoluble to soluble form. Food must be changed into a simple liquid form to facilitate its transport by the blood. FUNCTIONS – primarily for digestion The process of digestion includes several processes like: 1. Ingestion –...
Digestion – a physical as well as a chemical process of changing food from insoluble to soluble form. Food must be changed into a simple liquid form to facilitate its transport by the blood. FUNCTIONS – primarily for digestion The process of digestion includes several processes like: 1. Ingestion – taking in of food through the mouth. 2. Digestion – changing of food from solid to liquid state. 3. Absorption – passage of simple food from the digestive tract to the blood and lymph. 4. Circulation – transport of the absorbed food to the tissues of the body. 5. Assimilation – incorporation of absorbed simple food as part of the protoplasm. 6. Egestion – passing out of the undigested food or residue through the anus. Invertebrate Digestive System 1. Protozoa – provided with organelle, the food vacuole, which serves as an organ for digestion. Digestion is intercellular ( takes place within the cells ) 2. Porifera – with schizocoel and choanocytes - digestion is intracellular. 3. Coelenterata – with gastrovascular cavity, which serves as an incomplete digestive tube ( a type of digestive tube with only one opening which serves for both entrance and exit; with a mouth but no anus ). Digestion is both intracellular and extracellular ( type of digestion that takes place outside the cell, usually within the digestive cavity ). a. Intracellular – smaller food particles are absorbed into the vacuoles of the cell of the gastrodermis. b. Extracellular – the glandular cells of the gastrodermis secrete enzymes into the gastrovascular cavity where the digestion of the large particles takes place. Platyhelminthes – has an incomplete, branched digestive tube; an exception is the tapeworm which has no digestive tract. ▪ Tapeworm have no digestive tract and absorb food directly through their body walls ▪ The head of the tapeworm is called scolex – structure that contain suckers and hooks ▪ The scolex is used to attached their bodies into the intestinal wall of their host ▪ Diphylobothrium lutum (fish tapeworm) Hymenolopis Nana (dwarf tapeworm) ▪ Taenia Saginata (beef tapeworm) Taenia solium (pork tapeworm) ▪ Echinococcus granulosus (hydatid cyst disease) Echinococcus Multicularis (alveolar cyst disease) Nemathelminthes – has complete digestive tube ( type of digestive tube with a mouth for entrance and anus for exit. ▪ Nemathelminthes – roundworms like ascaris ▪ Annelida – a typical example of an invertebrate with a complete digestive tube. - digestion is extracellular. Parts of the digestive tube of the earthworm: 1. Mouth – the anterior opening which is provided with prostomium or lips used for grasping the food. 2. Buccal cavity- 3. Pharynx muscular structure which facilitates sucking in of food. 4. Crop – an expanded portion of the esophagus which serve for temporary storage of food. 5. Gizzard – very muscular structure which through its grinding motion with bits of sand present in it that act as an abrasive material ( aids in cutting the food into smaller bits ). 6. Intestine – place where digestion of food takes place; digestion is hastened by the secretion of enzymes secreted by the intestinal glands. Enzymes present: a. amylopsin – acts on carbohydrates b. pepsin – acts on protein c. lipase – acts on fats d. cellulase – acts of cellulose 7. Anus – the terminal opening of the digestive tube, an exit of digestive waste products Mollusca – with a complete digestive tube in some the mouth is provided with horny teeth that rasp off food particles. - digestion takes place in the stomach - absorption takes place in the intestine and residue exit through the anus. Echinodermata – with complete digestive tube ( incomplete in some )- the stomach is usually everted on the food, mucus is secreted, then the stomach with its contents is withdrawn into the body.- large bits are cast out through the mouth.- the intestines is mainly for excretion Arthropoda – with a complete digestive tube - mouth parts are modified appendages and are specialized for various purposes depending upon the feeding habits of the animal ( chewing, piercing, lapping, sucking) Enzymes present: a. amylopsin – acts on carbohydrates b. pepsin – acts on protein c. lipase – acts on fats d. cellulase – acts of cellulose