Bsci202 final The Digestive System Functions Ingestion is taking in food another Propulsion is moving foods from one region of the digestive system to o peristalsis are alternating waves of contraction and relaxation that squeezes food along GI tract o segmentation moves material back and forth to aid with mixing in the digestion is breaking food down both physically mechanically and small intestine chemically absorption is movement of nutrients into the bloodstream o end products of digestion are absorbed in the blood or lymph o food must enter mucosal cells and the into blood or lymph capillaries defecation rids body of indigestible waste Functions of the Digestive System food breakdown as mechanical digestion o examples mixing food in mouth by the tongue churning food in stomach segmentation in small intestine o mechanical digestion prepares food for further degradation by enzymes food breakdown as chemical digestion o enzymes break down food molecules into their building blocks o each major food group uses different enzymes carbohydrates are broken to simple sugars by enzymes such as amylase lactase fructose proteins are broken to amino acids by proteases such as trypsin fats are broke to fatty acids and glycerol alcohols by lipases nucleic acids are broken down into nucleotides by nucleases Organs of the Digestive System 2 main groups o alimentary canal gastrointestinal or GI tract is a continuous coiled hollow tube mouth pharynx esophagus stomach small intestine large intestine anus o accessory digestive organs layers of alimentary canal organs 1 4 layers o mucosa o submucosa o muscularis externa o serosa visceral peritoneum layers of alimentary canal organs mucosa o innermost moist membrane consisting of surface epithelium small amount of connective tissue lamina propria small smooth muscle layer submucosa o o soft connective tissue with blood vessels nerve endings and just beneath the mucosa lymphatic s layers of alimentary canal organs o circular layer o outer longitudinal layer muscularis externa is composed of smooth muscle which has a serosa is the outermost layer of the wall contains fluid producing cells o visceral peritoneum is the innermost layer that wraps the canal o parietal peritoneum is the outer layer that lines the abdominopelvic Accessory Digestive Organs consists of the organs cavity teeth salivary glands pancreas liver gallbladder Movement of Digestive Materials visceral smooth muscle shows rhythmic cycles of activity caused by pacemaker cells peristalsis causes waves that move a bolus segmentation churns and fragments a bolus Control of the Digestive System movements of materials along digestive tract is highly regulated and controlled by o 1 neural mechanisms parasympathetic and local reflexes o 2 Hormonal mechanisms enhance or inhibit smooth muscle o contraction local mechanisms coordinate response to changes in pH or chemical stimuli Control of Digestive Activity mostly controlled by reflexes via the parasympathetic division 2 o neural and hormonal mechanisms coordinate glands o GI activity stimulated by parasympathetic innervation o Inhibited by sympathetic innervation Chemical and mechanical receptors are located in organ walls that trigger reflexes Stimuli include o of the organ o pH of the contents o presence of breakdown products reflexes include o activation or inhibition of glandular secretions o smooth muscle activity Mouth oral cavity anatomy lips labia protects the anterior opening cheeks form the lateral walls uvula is the fleshy projection of the soft palate speech and direct food Hard palate forms the anterior roof Soft palate form the posterior roof Mouth anatomy Vestibule is the space between lips externally and teeth and gums internally Oral cavity proper is the area contained by the teeth Tongue is attached at hyoid bone and styloid processes of the skill and by the lingual frenulum to the floor of the mouth o Tongue s primary functions include o Mechanical processing o Assistance in chewing and swallowing o Sensory analyiss by touch temperature and taste receptors tonsils o palatine o lingual Digestive Activities of the Mouth the mouth open into the oral buccal cavity mouth functions include o analysis of material before swallowing o mechanical processing by the teeth tongue and palatal surfaces o o lubrication limited digestion mechanical breakdown o mastication chewing of food food is physically broken down by chewing o mixing masticated food with saliva o initiation of swallowing by tongue o allows for the sense of taste works with smell chemical digestion food is mixed with saliva o o starch is broken down into maltose by salivary amylase 3 Teeth humans have 2 sets of teeth function is to masticate chew food o deciduous baby or milk teeth o 20 teeth are fully formed by age 2 permanent teeth classification of teeth incisors used for cutting o o canines used for tearing or piercing o premolars used for grinding o molars used for grinding Regions of a Tooth crown is the exposed part o replace deciduous teeth between ages of 6 12 o a full set is 32 teeth but some people do not have wisdom teeth 3rd molars if they do emerge the wisdom teeth appear between ages 17 25 o o enamel is the hardest substance in the body o dentin is found deep to the enamel and forms the bulk of the tooth o pulp cavity contains connective tissue blood vessels and nerve fibers o root canal is where the pulp cavity extends into the root neck root o region in contact with the gum o connects crown to root o cementum covers outer surface and attaches tooth to periodontal 3 pairs of salivary glands empty secretions into mouth membrane salivary glands o parotid glands o submandibular glands o sublingual glands saliva o mixture of mucus and serous fluids o helps to form a food bolus o contains salivary amylase to begin starch digestion o dissolves chemicals so they can be tastes pharynx anatomy nasopharynx is not part of the digestive system oropharynx is posterior to oral cavity laryngopharynx is below the oropharynx and connected to the esophagus pharynx physiology serves as a passageway for air and food common passageway for food liquids and air line with stratified squamous epithelium pharyngeal muscles assist in swallowing 4 o pharyngeal constrictor muscles o palatal muscles food is propelled to the esophagus by 2 muscle layers longitudinal inner layer o o circular outer layer food movement is by alternating contractions of the muscle layers peristalsis
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