Functions of Digestive System U.4 L.2

  • monomer : small molecules that groups together to create a saccharide

  • Components of digestion : Ingestion (taking in nutrients), Digestion (break down complex molecules into smaller ones), absorption (transport of nutrients to body’s tissues), Egestion (removal of waste)

  • ingestion : mouth

  • digestion : small/large intestine, stomach, mouth

  • absorption : small intestine

  • egestion : anus, rectum

  • Digestion is started in the mouth, mechanically

  • mechanical digestion : physically break food into smaller pieces, used by teeth, tongue, palate, cheeks and gizzard in some animals

  • chemical digestion : when enzymes in saliva, stomach and small intestine break down larger molecules

  • enzymes are proteins which can help break down protein into amino acids where they can help to create new enzymes

  • prefix “ase” indicates an enzyme (ex. lipase, protease)

  • The mouth has ingestion, mechanical digestion (mastication aka. chewing) and chemical digestion (salivary amylase breaks down starch)

  • lipids start digestion in the small intestine

  • carbs start digestion in the mouth

  • proteins start digestion in the stomach

  • the mouth contains accessory organs, (salivary glands, mucus and bolus)

  • salivary glands triggered by the smell of food or presence in the mouth

  • saliva contains mucus that acts like a lubricant and helps food stick together in a bolus

  • bolus : once food is mixed with saliva its called a bolus, no longer their original state, become chyme in the stomach and then feces

  • three pairs salivary glands, parotid glands 2 in the cheeks, sublingual glands 2 under the tongue, and submandibular glands 2 under jaw

  • The tongue positions the food for teeth, tastes, taste buds in papillae, taste buds (rough projections of your tongue) are scattered around the tongue

  • the taste buds evolved over time because poisonous foods or the nutritional advantages caused the taste to evolve

  • adult humans (omnivores) have incisors (specialized for cutting), canines (dagger shaped for tearing) and pre-molar and molars

  • mouth’s palates are both soft and hard (palate : the top/roof of your mouth)

  • Hard palate contains bone at the top and front of the mouth (helps with chewing)

  • Soft palate is at the back of the mouth and contains the uvula (prevents food from going up the nose)

  • When swallowing food is pushed to the back of the mouth, so that it can be swallowed, bolus of food passes through the pharynx to the esophagus

  • pharynx : common path of food and air

  • epiglottis : covers the opening of the trachea while swallowing

  • soft palate/uvula : cover the opening to the nasal passages during swallowing

  • bolus of food is moved through the digestive system by peristalsis

  • peristalsis : rhythmic, wavelike contractions of smooth muscle (circular and longitudinal muscles that surround the digestive tract)

  • peristalsis : when you swallow and feel your throat that is peristalsis

  • The stomach is a bag shaped structure

  • food enters through the cardiac sphincter leaves by the pyloric sphincter

  • muscular walls and rugae (ridges inside of the stomach) churn the food

  • food is mixed with gastric juices (enzymes and acid) into the stomach and form a “milky” chyme

  • lipids and carbs are not primarily digested in the stomach, mostly proteins are

  • gastric secretions are juices that include mucus, hydrochloric acid (HCI), enzymes and pepsinogen

  • mucus : provides a protective coat for the stomach lining

  • HCI : kills harmful substances that are ingested with food, converts pepsiongen to their active form (pepsin)

  • pepsin : protein digesting enzyme that breaks the longer amino acid chains in proteins to shorter chains

  • chyme is very acidic and you neutralize it by adding a base