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Understanding the Upper Digestive Tract and Swallowing Process

Explore the anatomy and functions of the oral cavity, teeth, tongue, palate, and salivary glands in Chapter 23 of Marieb’s Human Anatomy and Physiology. Learn about the mechanisms of ingestion, mechanical digestion, and chemical digestion as the food travels through the upper digestive tract. Enhance your knowledge of the swallowing reflex and the three phases involved in the process. Dive into the intricate details of saliva composition, teeth structures, and the coordination of muscles during swallowing.

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Understanding the Upper Digestive Tract and Swallowing Process

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  1. Marieb’s Human Anatomy and Physiology Marieb w Hoehn Chapter 23 Digestive System Lectures 9 & 10 Part 2: Upper Digestive Tract & Swallowing

  2. Mouth (Oral or Buccal cavity) (Labium) • ingestion • mechanical digestion (mastication) • prepares food for further chemical digestion (Labium) Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

  3. Tongue Very muscular; muscles run in several directionsCovered by mucous membranes Blast from the past - Root of tongue is anchored to the hyoid bone • Tastebuds • Friction for food handling • Secretes lingual lipase

  4. Palate • roof of oral cavity (adenoids) Important in separating the nasopharynx from the pharynx during swallowing

  5. Secondary (Permanent) Teeth Total of 32 secondary (permanent) teeth 1 16 Watch for incoming ICBMs!!! – Or - I ‘C’ Big/Pretty Molars 32 17 Know the order of these

  6. Primary (Deciduous, Baby, Milk) Teeth (Mastication = chewing) • 8 incisors • 4 cuspids • 8 molars • 20 total All primary teeth are lost, generally between ages 6 and 12

  7. Section of a Tooth Oh no! Not again! What type of articulation is this? Know this diagram for exam

  8. Functions of Saliva • Moistens food • Binds food particles • Dissolves food for tasting • Begins chemical digestion of complex CHO (amylase) • Cleans teeth and mouth (pH = 6.5 – 7.5) • Anti-microbial (IgA and lysozyme)

  9. Salivary Glands

  10. Secretions of Salivary Glands Secretions are about neutral pH and continual due to basal parasympathetic stimulation, but increase after - presence, or anticipation of, food; - parasympathetic stimulation (watery, large volume) - sympathetic stimulation (viscous, small volume) • Parotid glands • clear • primarily water, serous fluid • rich in amylase • mumps virus typically attacks here • Submandibular glands • primarily serous fluid • some mucus, amylase • Sublingual glands • primarily mucus • most viscous

  11. Pharynx Pharynx aids swallowing by grasping food and moving it toward the esophagus.

  12. Three Phases of the Swallowing Reflex Only voluntary phase is the buccal (oral) phase, i.e., the initiation of swallowing, then… • soft palate and uvula raise • hyoid bone and larynx elevate Pharyngeal phase • epiglottis closes off top of trachea • longitudinal muscles of pharynx contract reflexive • inferior constrictor muscles relax and esophagus opens Esophageal phase • peristaltic waves push food through pharynx

  13. Swallowing Mechanism

  14. Review • Tongue • Lined by mucous membranes • Thick, skeletal muscle • Papillae function in food handling and taste • Lingual frenulum • Lingual tonsils • Lingual glands secrete lingual lipase • Palate (roof of oral cavity) • Hard palate (Palatine proc. of maxillary bones) • Soft palate • Uvula is suspended from this • Uvula closes opening to nasal cavity (nasopharynx)

  15. Review • Tonsils • Lingual (back of tongue) • Palatine (lateral to tongue) • Pharyngeal (posterior wall of pharynx; adenoids) • Teeth • Primary teeth (deciduous teeth; baby teeth) • 6 months to 2-4 years • 20 total • Secondary (permanent teeth) • 6 yrs to 17-25 years • 32 total

  16. Review • Teeth (continued) • Incisors – sharp for biting • Cuspids (canine) – for grasping/tearing • Bicuspids and molars – grinding • Structure • Crown – above gum line • Root – below gum line • Outer covering is enamel • hardest substance in body • NOT replaceable • Inner substance is dentin (alive) • Pulp cavity • Periodontal ligament

  17. Review • Salivary glands produce saliva which • Moistens food • Binds food particles • Begins chemical digestion of CHO • Dissolves food (for taste) • Cleanses mouth and teeth; antibacterial • Three pairs of salivary glands • Parotid; front of ear, watery fluid rich in amylase • Submandibular; floor of mouth, viscous fluid • Sublingual; below tongue, thick, stringy secretion

  18. Review • Salivary glands • Sympathetic stimulation – small quantity of viscous saliva • Parasympathetic stimulation – large volume of watery saliva • Pharynx • Cavity connecting mouth with esophagus • Nasopharynx, oropharynx, laryngopharynx • Muscles • Inner circular – constriction • Outer longitudinal – movement of food bolus

  19. Review • Swallowing • Initiation is voluntary; act of swallowing is NOT – it’s a reflex • Three stages • Chewing and rolling of food into oropharynx (voluntary, buccal) • Swallowing reflex (pharyngeal) • Epiglottis closes over larynx • Muscles in lower pharynx relax • Esophagus opens and food moves in • Peristalsis in esophagus transports food to stomach (esophageal) • Esophagus • Muscular tube connects to cardiac region of stomach • Esophageal hiatus • Lower esophageal (cardiac) sphincter

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