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HUMAN ANATOMY - 8 Digestive system Primery Purpose of Digestive System • Breaking down nutrients to the degree to be absorbed, distributed and used by the body. • Scince, dealing with digestive system is call gastro-enterology. Functions of digerstive system • Digestion - mechanical & chemical • Absorbtion - uptake of digested nutrients into blood vessels within the wall of digestive tract • Elimination – of waste substances out of the body Basic anatomy of digestive system (p.955, fig. 25.1) The system consists of 2 major subdivisions • Digestive tract : mouth – pharynx – esophagus – stomach – small intestine – large intestine • Accessory organs: salivary glands, liver, pancreas Mouth (pp.958-959) • Teeth & tongue provied with mechanical digestion • Salivary glands (parotid is the largest) provide with chemical digestion • Salivary amylase digest carbs and salivary lipase starts digest fats Pharynx & esophagus • Pharynx is muscular funnel, connecting mouth with esophagus. • Esophagus is 30 cm muscular tube, which passes thorax, penetrates diaphagm and enters stomach. • Stomach is J-shaped muscular organ, which spreads from esophagus to small intestine. Stomach (p.966, fig. 25.12) • Apart from mechanical digestion, stomach provides with chemical digestion of the following enzymes – Pepsin – digests proteins – Gatric Lipase – digests 10-15% of fats • Stomach secrets also hydrocloric acid, which activates these enzymes . • Stomach secrets Intrinsic factor, which binds vit.B12 for its further absorbtion in small intestine (without vit.B12 hemoglobin can’t be synthesized, and anemia develops) Functions of hydrochloric acid • Activates gastric enzymes • Destroys connective tissues • Converts ferric ions into absorbable ferrous (Fe2+) ions for hemoglobin synthesis • Destroys many pathogens Small intestine (p.980, fig.25.24) • Consists of 3 parts – Duodenum (lat. “12”) 25 cm length, gets bile & pancreatic content – Jejunum (lat. “empty”)– 1.5 m length, major part of digestion & absorbtion – Ileum (lat. “twisted”)– 2.5 length, has thinner walls, rich in lymphatic nodes. Large intestine (p.991, fig. 25.31) • It consists of the following parts: – Ascending colon – Transverse colon – Descending colon – Sigmoid colon – Rectum • It function to reabsorb water & NaCl and form feces Accessory organs • Liver (p.975) • Pancreas (p.977)