Lec 28 - Tongue and Salivary glands

• Label the areas of the tongue

  A) terminal sulcus

  B) median sulcus

  C) posterior 1/3

  D) anterior 2/3

  E) palatine tonsils

  F) lingual tonsil

  G) epiglottis

  
• The terminal sulcus divides the tongue into anterior 2/3 and posterior 1/3. These two areas also have different embryological origins
• The tongue has 4 different types of lingual papillae

  • filiform papillae (scattered throughout anterior tongue)
  • fungiform papillae (scattered and concentrated at tip)
  • foliate papillae (lateral aspects of tongue)
  • circumvallate papillae (large circular papillae that trace terminal sulcus)
• The histology of the tongue

  • oral mucosa - stratified squamous epithelium (sometimes keratinized, sometimes not depending on where the section is)
  • connective tissue (LCT and DCT)
  • skeletal muscle (longitudinal, transverse, and oblique)
• This is a section of skeletal muscle from the tongue

  A) longitudinal

  B) transverse

  C) oblique

  
• Filiform papillae are for mechanical grip. They are highly keratinized and cone shaped. They do not contain tastebuds
• This is a section of filiform papillae

  
• The filiform papillae all sweep in the same direction and point to the back of the tongue
• The fungiform papillae are found scattered and concentrated on the tip of the tongue. They are non-keratinized, have a narrow base and dome top, they contain taste buds on their apical surface
• Foliate papillae are arranged in rows on the lateral sides of the tongue. They are separated by furrows. They are non-keratinized, have flat tops, there are multiple adjacent to each other, and they have taste buds on their lateral surface
• This slide is showing foliate papillae

  
• Circumvallate papillae are non-keratinized, there are usually around 8-12 of them, they are each surrounded by a circular deep furrow, lingual salivary glands empty into the furrows, and they have taste buds on their lateral surface
• This is a slide of circumvallate papillae

  
• Taste buds are found on fungiform, foliate, and circumvallate papillae. They are seen as light staining ovals in the epithelium. The surface opening of a taste bud is called the taste pore.
• Taste buds are made up of 3 cell types

  • Taste receptor - have microvilli that extend out through the taste pore so that the can interact with molecules in the oral cavity called tasteins
  • supporting cell - support the function of the receptor cells but they can also become receptor cells
  • basal cell - at base of the taste bud, they will proliferate and differentiate into both receptor cells or supporting cells
• Taste receptors are found at the more central part of the taste bud, supporting cells found on the periphery, and basal cells found at the base with a very dark nucleus
• This is an image of a tastebud

  A) taste pore

  B) taste receptor

  C) supporting cell

  D) basal cell

  
• There are 3 major pairs of salivary glands

  • parotid
  • sublingual
  • submandibular
• Salivary glands are compound tubulo-acinar glands
• The secretory portion of the salivary glands secrete mucins, proteins, enzymes and transport of sodium, chloride, water, and IgA

  The duct portion of the salivary gland produces bicarbonate and reabsorbs sodium and chloride
• The largest unit of a salivary gland is a lobe -> lobule
• Secretions in salivary gland begins in acinus -> intercalated duct (intralobular) -> striated duct (intralobular) -> intralobular duct -> interlobular/excretory duct -> lobular duct

  
• Serous acini

  • contribute watery secretions and proteinaceous secretions to saliva
  • contain triangular shaped acini cells - dark staining cytoplasm
  • very round basal nuclei
  • contain apical zymogen granules that are basophilic
  • serous acini can be found in the parotid gland

  
• Mucus acini

  • contribute gel-like secretions, glycoproteins and mucus secretions
  • pale staining cytoplasm (bc of carbohydrates)
  • triangular shaped cells
  • flat basal nuclei
  • filled with granules (carbohydrates) which gives light staining/foamy appearance
  • found in the sublingual gland
• This is a slide of mucus acini

  
• Mixed acini

  • contribute both serous and mucus secretions to saliva
  • mucus cells are closer to ducts (central)
  • serous cells are periphery and form serous demilunes around mucus cells
  • can be found in the submandibular glands

  A) serous demilune

  
• Acini also contain myoepithelial cells that surround them. These cells act like smooth muscle and contract upon stimulation to force the secretions out of the acini into the ducts
• Intercalated duct (intralobular)

  • smallest ducts
  • receive secretions directly from acini
  • low cuboidal epithelium
  • lightly stained

  
• Striated ducts (intralobular)

  • important for ion transport
  • simple cuboidal/columnar (the further down the duct the more columnar they become)
  • have basal striations from infoldings of plasma membrane and rich in mitochondria
  • round central nuclei

  
• Interlobular/excretory duct

  • between different lobules
  • stratified/pseudostratified columnar
  • much larger lumen than the other ducts

  
• Label the salivary gland

  A) intercalated duct

  B) striated duct

  C) serous acini

  D) interlobular/excretory duct

  
• Label these components of a salivary gland

  A) parotid gland

  B) sublingual gland

  C) submandibular gland

  D) intralobular

  E) interlobular

  F) intralobular