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Digestive System

Digestive System. Chapter 14. The digestive system takes in food (ingests it), breaks it down physically and chemically into nutrient molecules (digests it), and absorbs the nutrients into the bloodstream. Then in rids the body of the indigestible remains (defecates).

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Digestive System

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  1. Digestive System Chapter 14

  2. The digestive system takes in food (ingests it), breaks it down physically and chemically into nutrient molecules (digests it), and absorbs the nutrients into the bloodstream. Then in rids the body of the indigestible remains (defecates). Overview of the Digestive System

  3. Separated into two groups: • Alimentary canal aka gastrointestinal (GI) tract • Performs the whole menu of digestive functions (ingests, digests, absorbs, and defecates) • Ex. Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus • Accessory digestive organs • Assist the process of digestive breakdown in various ways • Ex. Teeth, tongue, several large digestive glands Organs of Digestive System

  4. Mouth aka oral cavity • Food enters here • Mucous-membrane lined cavity • Lips for protection of opening • Cheeks form lateral walls • Hard palate forms anterior roof • maxillae and palatine bones • Soft palate forms posterior roof • Uvula is a fleshy fingerlike projection of the soft palate Parts of the mouth

  5. Tongue occupies the floor of the mouth • attached to the hyoid bone and styloid process of the skull • maneuvers food, forces food back for swallowing, speech • Lingual frenulum is a fold of mucous membrane that secures the tongue to the floor of the mouth and limits its posterior movements Tongue and parts

  6. Deciduous teeth erupt at 6 months of age—(20 teeth) • Replaced with permanent teeth from age 6—(32 teeth) • Incisors- chisel-shaped, cutting into food • Cuspids (canines)- 1 point, tearing and shredding • Premolars- 2 cusps, grinding • Molars- 3+ blunt cusps to crush and grind • Mastication- chewing; mechanical digestion Teeth

  7. The pharynx is subdivided into the nasopharynx(part of respiratory system), the oropharynx, and the laryngopharynx (continues to the esophagus) Parts of the pharynx

  8. The walls of the pharynx contain two skeletal muscle layers • Inner layer runs longitudinally • Outer layer runs circularly • Alternating contractions of these two muscle layers propel food through the pharynx into the esophagus aka peristalsis Pharynx

  9. Runs from pharynx through the diaphragm to the stomach • About 25 cm (10 inches) long • Conducts food to the stomach through peristalsis • The reason why food can get to your stomach even if you are hanging upside down. Esophagus aka gullet

  10. The walls of the alimentary organs from the esophagus to the large intestine are made up of the same four basic tissue layers (or tunics) • Mucosa (innermost layer)-lines the cavity • Submucosa-beneath the mucosa • Muscularisexterna-muscle layer • Serosa-(outermost layer) Tissue layers

  11. J-shaped, nearly heidden by the liver and diaphragm on the left side of the abdominal cavity Parts of stomach

  12. Top opening of stomach where food enters from esophagus is the cardioesophageal sphincter • The bottom opening of stomach where food continues to the small intestine is the pyloric sphincter or valve • Stomach varies from 15-25 cm (6-10 inches long) but diameter varies with amount of food contained • When full, can hold 4L (1 gallon) of food Stomach continued

  13. Stomach collapses when empty into large folds called rugae

  14. Divided into cardia, fundus, body, pylorus, separated from the duodenum by pyloric sphincter. • Gastric glands secrete acidic gastric juices. • Mixing waves- chyme forms and passes to duodenum • Protein digestion begins in the stomach with the enzyme pepsin, breaks peptide bonds- forming small strings of amino acids. Parts of stomach

  15. If your stomach didn't produce a new layer of mucous every two weeks, it would digest itself.

  16. Saliva -> Mouth -> Pharynx -> Esophagus -> Stomach -> Small intestine -> large intestine Pathway of food

  17. Ingestion-placing food in mouth • Propulsion-swallowing, peristalsis • Mechanical digestion-mixing in mouth, churning in stomach, segmentation in small intestine; physically breaking down into smaller particles • Chemical digestion-food broken down into building blocks by enzymes; water is necessary as dissolving medium and softening agent Functions of Digestive System

  18. Absorption-digested food must enter the mucosal cells by active or passive transport processes; mostly in small intestine • Defecation-elimination of indigestible residues from the GI tract vis the anus in the form of feces Functions of Digestive System

  19. Biochemistry macromolecules? • How specific?

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