Digestive System Functions of the Digestive system 1

Digestive System Functions of the Digestive system: 1. Intake and digestion of food 2. Absorption of nutrients from digested food 3. Elimination of solid waste products Accessory Organs of Digestion: Include the liver, gallbladder, and pancreas Gastrointestinal (gastr/o + intestin/o = -al)

Anatomy Structures are divided into two sections: 1. Upper GI tract – mouth, esophagus, stomach 2. Lower GI tract – small intestine, large intestine, rectum, anus Oral Cavity (mouth) 1. Lips – form opening to the mouth 2. Hard palate – anterior portion of roof of mouth 3. Soft palate – posterior portion of roof of mouth, closes off nasal passage during swallowing 4. Uvula – helps in producing sound and speech

Upper GI tract Cont’d. Tongue – strong and flexible, aids in speech and moves food during chewing and swallowing, contains papillae which are also known as taste buds. Teeth – 20 baby teeth, 32 permanent teeth; four kinds: 1. Incisors 2. Canines 3. Premolars (bicuspids) 4. Molars

Upper GI tract Cont’d. Parts of a tooth 1. Crown – the part of the tooth that is visible, covered with enamel 2. Root – holds the tooth securely in the dental arch 3. Dentin – makes up the bulk of the tooth Gingiva (gums) – surrounds teeth, covers the bone of the dental arches, forms the lining of cheeks Salivary Glands – secretes saliva to moisten food, begins digestive process, cleanses the mouth

Upper GI tract Cont’d. Pharynx (also known as the throat) • common passageway for food and air • during swallowing, food is prevented from moving from the pharynx into the lungs by the epiglottis. Esophagus • collapsible tube that leads from the pharynx to the stomach • the lower esophageal sphincter is a muscle that controls the flow between the esophagus and the stomach.

Upper GI tract Cont’d. Stomach • has 3 sections: fundus, body, and the antrum • the pyloric sphincter controls flow from stomach into the duodenum of the small intestine.

Lower GI tract Small Intestine – extends from pyloric sphincter to the large intestine; in the small intestine is where nutrients are absorbed into bloodstream; 20 feet in length; has three sections: 1. Duodenum – first section, closest to the stomach 2. Jejunum – middle section, between duodenum and ileum 3. Ileum – last section, closest to the large intestine

Lower GI tract Cont’d. Large Intestine – waste products of digestion are processed in the large intestine and excreted through the anus; has 6 sections : 1. Cecum – pouch that extends from the ileum to the beginning of the colon 2. Ascending colon – travels upward from cecum 3. Transverse colon – passes right to left toward the spleen 4. Descending colon – travels down the left side of abdominal cavity 5. Sigmoid colon – joins descending colon with the rectum 6. Rectum – last division of the large intestine Anus – solid waste is passed out of the body through the anus

Accessory Organs of Digestion Liver (located in the right upper quadrant) • removes excess glucose from the bloodstream • destroys old red blood cells • removes poisons from blood • makes some blood proteins • secretes bile to break down fat Gallbladder (cholecyst/o) • stores and concentrates bile for later use Pancreas located posterior to the stomach, creates pancreatic juices to neutralize stomach acids and digestive enzymes to process protein, carbohydrates, and fat.

Flow through the Digestive System You will need to know the order of flow for food moving through the digestive system on your next test. The Language of Medicine, 7 th Edition; Chabner, Davi-Ellen; Saunders, 2004

Definitions Digestion – process by which complex foods are broken down into nutrients that the body can use Metabolism – all of the processes involved in the body’s use of these nutrients(building up and breaking down of body cells) Absorption – process where digested nutrients are taken into the circulatory system

Definitions Cont’d Mastication – also known as chewing, breaks down food into smaller pieces Peristalsis – series of wavelike contractions of smooth muscles in a single direction. Chyme – semi-fluid mass of partially digested food that passes from stomach into small intestine Defecation – evacuation or emptying of the large intestine