3.4 digestive system in animals

• Digestive System


  The system in animals responsible for breaking down macromolecules into smaller sub-units that can be absorbed and used for energy production, growth, maintenance, and repair
• Macromolecules


  Large molecules such as proteins, carbohydrates, and lipids (fats) that need to be broken down into smaller sub-units or monomers before they can be absorbed into an animal's body for various functions
• Alimentary Canal


  The passage from the mouth to the anus in animals, also known as the gastrointestinal tract, where digestion and absorption of nutrients take place
• Enzymes


  Biological molecules that catalyze chemical reactions in the body, aiding in the breakdown of macromolecules during digestion for easier absorption and utilization
• Ingestion


  The process of taking food into the mouth
• Mechanical digestion


  The physical breakdown of food, starting in the mouth and continuing in the stomach
• Chemical digestion


  The breakdown of macromolecules of food into smaller sub-units through the action of enzymes, starting in the mouth and continuing in the stomach and small intestine
• Absorption


  The process in the small intestine where end products of digestion cross the tissue layer lining the gut and enter the body's internal environment
• Elimination


  The process of storing and eliminating undigested wastes as feces, occurring in the rectum and anus
• Mucosa


  The innermost lining of the digestive system
• Sub-mucosa


  Connective tissue forming the second layer of the gut lining
• Muscularis


  Muscle tissue of the gut
• Serosa


  Outer connective tissue that encloses the gut
• Epithelial tissue


  Forms the innermost lining of the digestive system, part of the mucosa layer
• Connective tissue


  Forms the second layer of the gut lining, including blood vessels, lymphatic vessels, and nerves
• Muscle tissue


  Forms the third layer of the gut wall, known as the muscularis
• Villi


  Outfoldings in the small intestine that increase surface area for absorption
• Crypts


  Infoldings in the small intestine that aid in absorption and secretion
• Glandular epithelium


  Epithelial tissue that forms glands and secretes substances, like the gastric glands in the stomach
• Epithelial tissue


  Tissue that functions in the digestive system, providing protection, absorption, and secretion in the alimentary canal
• Protection


  The function of epithelial tissue that prevents physical or chemical damage to tissues, such as the stratified squamous epithelium lining the gut
• Absorption


  The process where end products of digestion are taken up from the gut lumen and transferred across the epithelial tissue of the mucosa to blood and lymph vessels for distribution
• Secretion


  The function of glandular epithelial tissue in releasing substances into the lumen of the gut, such as mucus from goblet cells
• Connective tissue


  Forms the second layer of the gut wall (sub-mucosa) and the outermost layer (serosa) in the digestive system, providing structural support and metabolic support
• Muscles


  Tissues in the body that have the ability to contract and relax, responsible for various movements in the alimentary canal
• Sphincters


  Thickened rings of muscle that control the opening and closing of tubes in the alimentary canal
• Pyloric sphincter


  A sphincter located at the join of the stomach and the duodenum of the small intestine, controlling the flow of acidic chyme into the alkaline duodenum
• Chyme


  A slurry of partially digested food produced in the stomach that passes into the small intestine
• Peristaltic movement


  Coordinated contraction of muscles in the alimentary canal to propel digested food through the gut and cause mixing
• Lower oesophageal sphincter


  A sphincter located at the junction of the lower end of the esophagus and the upper region of the stomach, preventing stomach acid from moving up into the esophagus
• Enzymes


  Proteins that act as biological catalysts, aiding in the breakdown of large complex nutrients in food to small monomers or components that can be absorbed by the body cells
• Enterocytes


  Cells lining the small intestine responsible for absorbing nutrients from the digested food
• Salivary amylase


  Enzyme produced in the salivary glands that begins the digestion of carbohydrates such as starch in the mouth
• Lingual lipase


  Enzyme produced by glandular cells of the tongue that starts the digestion of lipids in the mouth and stomach
• Oesophagus


  A narrow tube about 25 centimetres long responsible for transporting food into the stomach
• Peristalsis


  The involuntary constriction and relaxation of muscles in the alimentary canal to push food to the stomach
• Gastric juice


  Acid fluid secreted by the stomach glands for digestion in the stomach
• Proenzyme


  A precursor of an enzyme that must be activated to form the functional enzyme
• Chief cells


  Secretory cells in the parathyroid gland that produce parathyroid hormone (PTH) or in the gastric pits of the stomach, secreting gastric lipase and the inactive proenzyme, pepsinogen
• Pyloric sphincter


  Controls the passage of chyme from the stomach into the small intestine (duodenum)