The gastrointestinal system #1


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The gastrointestinal system #1

  1. 1. System Overview The digestive tract, often called the alimentary tract or canal, is a muscular tube that contains the organs of digestion  The tube begins with the mouth and ends at the anus In between these two points are the pharynx, esophagus, stomach, small intestines, and large intestines Accessory organs, such as teeth, salivary glands, liver, pancreas, and gallbladder, are necessary for processing materials into useable substances
  2. 2. System Overview The components of the digestive system work together to perform the following general steps: 1. Ingestion 2. Mastication 3. Digestion 4. Secretion 5. Absorption 6. Excretion (defecation)
  3. 3. System Overview Food first enters the mouth, an activity called ingestion Once food is ingested, the tongue and teeth work together to mechanically process the food by physically breaking it down The chewing process is called mastication Digestion is the chemical process of breaking down food into small molecules  This is necessary so nutrients can be absorbed by the lining of the digestive tract
  4. 4. System Overview The secretion of acids, buffers, enzymes, and water aid in the breakdown of food Once the food is broken down both physically and chemically, it is ready for absorption through the lining of the digestive tract for use by the body Finally, waste products and unusable materials are prepared for excretion and are eliminated by the body through defecation
  5. 5. The Mouth and Oral Cavity Your mouth is the opening that leads to the oral cavity, also called the buccal cavity Your lips, or labia, act as the door to this cavity The hard and soft palates create the roof of the cavity while the tongue acts as the floor The tongues base (area of attachment) and the uvula (dangles from the soft palate) act as a boundary between the oral cavity and the pharynx  The uvula aids in swallowing , it helps direct food toward the pharynx and helps block food from coming out your nose
  6. 6. The Mouth and Oral Cavity The lingual tonsils are at the back of the cavity  They aren’t important for digestion, they help fight infection as part of the lymphatic system The sides of the cavity are created by your cheeks The mouth receives, tastes, mechanically breaks down, and begins the process of chemical breakdown of food, adding saliva
  7. 7. Tongue Your tongue is a muscle that provides taste stimuli to your brain, senses temperature and texture, manipulates food while chewing, and aids in swallowing As the tongue moves food around in the oral cavity, saliva is added to moisten and soften it, while teeth crush the food until it reaches the right consistency
  8. 8. Tongue The tongue pushes the food into a ball-like mass, called a bolus, so it may be swallowed and passed to the pharynx The lingual frenulum, a membrane under the tongue, keeps you from swallowing your tongue and aids in speaking  An abnormally short frenulum prevents clear speech= tongue-tied The area under the tongue has many blood vessels  This sublingual blood vessel network readily absorbs substances and is a rapid means of administering medication
  9. 9. Salivary Glands There are three pairs of salivary glands, which are controlled by the autonomic nervous system A large parotid salivary gland is found slightly inferior and anterior to each ear  These are the ones that swell when you get mumps The ducts from these glands empty into the upper portion of the oral cavity
  10. 10. Salivary Glands The smallest of the salivary glands, the sublingual salivary glands are found under the tongue The submandibular salivary glands are located along both sides of the inner surface of the mandible, or lower jaw On average, the salivary glands produce 1–1.5 liters of saliva daily Small amounts of saliva keep the mouth moist, but the idea or presence of food increase production significantly
  11. 11. Salivary Glands Although saliva is almost totally water (99.4%), it also contains antibodies, buffers, ions, waste products, and enzymes Enzymes are formed by cells Enzymes act as organic catalysts to speed up chemical reactions  One enzyme, salivary amylase, speeds up the chemical activity of breaking down carbohydrates into smaller molecules that are more easily absorbed by the digestive tract After eating, saliva cleans the oral surfaces, reducing the amount of bacteria that grows in your mouth
  12. 12. Teeth You will only have two sets of teeth in your lifetime The first set, are called baby teeth, or deciduous teeth  They will eventually fall out The 1st tooth appears around 6 months of age The lower central incisors appear first, with all 20 teeth in place by age 2½ Between 6 and 12 years these teeth fall out and are replaced by your second set of 32 permanent teeth  The exception to this are the wisdom teeth which may not appear until an individual is as old as 21
  13. 13. Tooth Types Incisors are located at the front of the mouth  Blade shaped, and are used to cut food Canine teeth are for holding, tearing, or slashing food  They are also known as eyeteeth or cuspids, and are located next to incisors Bicuspids, or premolars, are transitional teeth Molars are the final type of teeth and have flattened tops  Both bicuspids and molars are responsible for crushing and grinding food
  14. 14. Tooth Structure Each tooth has a crown, neck, and root The crown is the visible part of the tooth  It is covered by the hardest biologically manufactured substance, enamel The neck is the transitional section that leads to the root Internally, most teeth are made up of dentin, a mineralized bone-like substance The next layer is connective tissue called pulp, located in the pulp cavity The pulp cavity contains blood vessels and nerves providing nutrients and sensation  The nerves and blood vessels get to the pulp cavity via the root canal
  15. 15. Tooth Structure The root is nestled in a bony socket and is held in place by fibers of the periodontal ligament In addition, cementum covers the dentin of the root, aiding in securing the periodontal ligament Cementum is a soft version of bone Healthy gums, or gingiva, also help hold the teeth in place Epithelial cells form a tight seal around the tooth to prevent bacteria from coming into contact with the tooth’s cementum