DIGESTIVE SYSTEM

• one end of the tube is the mouth and the other end is the anus. This

  tube—called the alimentary canal or gastrointestinal tract
• Mechanical digestion is the breakdown of large pieces of

  complex molecules to smaller pieces of complex molecules
• CHEMICAL digestion is the breakdown of complex molecules to their building blocks so that they

  can be absorbed.
• hard palate, formed by the maxilla and palatine bones
• soft

  palate, composed of soft tissue
• uvula, a posterior projection that

  directs materials downward to the pharynx

  so that they do not travel to the nose
• The baby’s first set of teeth—the

  deciduous teeth
• a tooth is held in its bony socket (alveolus) in the jaw by

  periodontal ligaments.
• The tissue surrounding a tooth is the gingiva
• portion of the tooth emerging from the gingiva is

  called the crown.
• crown is covered by a very hard, smooth, white layer called

  enamel.
• The enamel’s function is to protect the underlying layer, the dentin.
• The

  root of the tooth, below the gum line, is not covered by enamel
• Deep to the dentin is

  a pulp cavity that contains the blood vessels and nerve for the tooth.
• the oral cavity by a medial fold called the lingual frenulum
• The salivary glands, which produce about 1.0 to 1.5 liters (L) of

  saliva a day,
• parotid glands (anterior to the ears)
• submandibular

  glands (inferior to the angle of the mandible on each side)
• sublingual glands

  (below the tongue)
• The saliva, which is mostly water, also contains the

  enzymes amylase and lingual lipase,
• The

  process of chewing, called mastication
• The saliva’s pH is 6.8 to 7.0.
• The mucus in the saliva moistens the bite of food (now called a bolus)
• The nasopharynx leads from the nasal cavity

  to the oropharynx.
• he oropharynx is a funnel leading from the oral cavity to the

  laryngopharynx.
• The laryngopharynx leads to the trachea and the esophagus.
• The epiglottis is made of elastic cartilage connective tissue.
• The esophagus is a straight, muscular tube that extends from the laryngopharynx,

  travels through the mediastinum, penetrates the diaphragm, and connects to the

  stomach
• The upper one-third of the esophagus has skeletal muscle
• the middle one-third has a mixture of skeletal and smooth muscle
• lower

  one-third has just smooth muscle
• Swallowing,

  called deglutition
• the muscular walls move the bolus along its length in wavelike contractions called peristalsis
• The stomach is a J-shaped organ found in the upper left quadrant of the abdomen,

  immediately inferior to the diaphragm.
• muscular sac capable of holding 1.0 to

  1.5 L after a meal, but it can stretch to hold up to 4 L when extremely full.
• cardiac sphincter (lower esophageal sphincter) controls the opening to the

  stomach from the esophagus.
• lesser curvature on the inside of the J
• greater

  curvature on the outer side of the J;
• Fundus, superior to the cardiac sphincter
• body, making up the majority of the stomach