Digestive System

• Functions:

  1. ingestion and mastication
  2. propulsion and mixing
  3. digestion and secretion
  4. absorption
  5. elimination
• digestive tract:

  1. oral cavity
  2. pharynx
  3. esophagus
  4. stomach
  5. small and large intestines
  6. anus
• associated organs:

  1. salivary glands
  2. liver
  3. pancreas
  4. gallbladder
• the liver and pancreas empty into the small intestine
• 4 major tunics:

  1. mucosa
  2. submucosa
  3. muscularis
  4. serosa
• mucosa: innermost tunic
• mucosa: muscous epithelium is the innermost
• mucosa: lamina propria is the loose connective tissue
• mucosa: muscularis mucosae is the thin outer layer of smooth muscle
• submucosa: thick layer of loose connective tissue containing nerves, BVs, and small glands
• mucularis: consists of circular (inner) and longitudinal (outer) smooth muscle
• serosa: outermost layer
• serosa: peritoneum is the smooth epithelial layer
• serosa: the underlying connective tissue is called adventitia, which is a connective tissue layer found in the digestive tract that is not covered by a peritoneum
• processes:

  1. ingestion
  2. propulsion
  3. mechanical digestion
  4. chemical digestion
  5. absorption
  6. defecation
• peristalsis still occurs until the large intestine
• surrounding ms. of lips: orbicularis oris
• surrounding muscle of cheeks: buccinator
• 32 teeth for normal adult
• palate: roof of oral cavity
• tonsils: palatine, pharyngeal, lingual
• pairs of salivary glands:

  1. parotid glands
  2. submandibular glands
  3. sublingual glands
• parotid glands: largest salivary glands
• parotid gland: serous gland
• submandibular glands: produce more serous than mucous secretions
• sublingual glands: smallest salivary gland
• sublingual gland: produces primarily mucous secretions
• saliva: 99% water
• salivary amylase: digestive enzyme that breaks down starch
• lysozyme: mild antibacterial enzyme found in saliva
• normally, only the oropharynx and laryngopharynx carry food to the esophagus
• Swallowed food from oral cavity are prevented from entering the nasal cavity by the soft palate, and kept out of the lower respiratory tract by the epiglottis and vestibular folds.
• esophagus: upper 1 / 3 is skeletal muscle
• esophagus: middle 3rd is a mix of smooth and skeletal muscle
• esophagus: lower 1 / 3 is smooth muscle
• upper and lower esophageal sphincter regulate the movement of food into and out of the esophagus
• mucus protects the inferior esophagus from stomach acid
• anatomy of stomach:

  1. cardiac part
  2. body
  3. pyloric part
  4. muscularis layer
  5. rugae
• cardiac part: fundus is superior to the cardiac opening
• body: creates the greater curvature and lesser curvature