• There are three large paired glands:
1. Parotid
2. Sublingual
3. Submandibular
• The salivary glands are distinguished by the number of serous, mucous and combined secretory units
• The glands differ further in terms of type and number of ducts

1.1 The Parotid gland

• Is surrounded by a dense connective tissue capsule
• Septae from the capsule divide the gland into lobules
• In the septae fat and lymphocytes are found
• The parotid is a compound tubulo-alveolar gland which is 100% serous
• It contains prominent intralobular secretory ducts

Plate 67 (Fig. 1)
Ross and Romrell p. 413

The Submandibular gland

• Surrounded by a dense connective tissue capsule that sends septae into the gland which divide it into lobes.
• This gland is a compound tubulo-alveolar gland with mixed secretory units:
1. 1. Serous secretory units - 80%
2. 2. Mucinous secretory units - 20% (also contains serous demilunes)
• Prominent duct systems are visible

Plate 66 (Fig. 1)
Ross and Romrell p. 411

The Sublingual gland

• Does not contain a distinct connective tissue capsule, but prominent tissue septae are present in the gland
• This gland is a compound tubulo-alveolar gland with mixed secretory units:
1. 1. Serous secretory units - 20%
2. 2. Mucinous secretory units - 80% (also contains serous demilunes)

Plate 68 (Fig. 1)
Ross and Romrell p. 415

Fig 13.17
Wheater p. 246

Serous Secretory Units

• The cells of the units appear triangular while the units themselves are round
• The nuclei are round and located close to the cell bases
• The cytoplasm is basophilic near the base (where the nucleus is located) and the rest is acidophilic (due to the secretory vesicles)
• The units are surrounded by myoepithelial cells which are located between the cells of the unit and the basement membrane
• The lumen of the unit is small and inconspicuous

Plate 67 (Fig. 2)
Ross and Romrell p. 413

Mucinous Secretory Units

• The units appear larger and paler and in cross-section the cells of the units appear more tubular than round
• The nuclei are flattened and located against the bases of the cells
• The cytoplasm is pale staining due to the mucus that washes out during the preparation of the specimen
• The lumens of the units are large and prominent

Plate 66 (Fig. 2)
Ross and Romrell p. 411

Mixed Secretory Units

• These units consists of serous and mucinous alveoli or a combination thereof mucinous-serous alveolus
• The latter consists of a mucinous alveolus with a serous demilune which secretes into the lumen of the mucinous alveolus via intercellular ductules

Plate 68 (Fig. 2)
Ross and Romrell p. 415

• These special cells have processes that encircle the unit
• The cells lie between the bases and the basement membrane of a unit
• The nuclei are situated in the centre of the cells
• The cytoplasmic processes are contractile and forces the secretion into the lumen of the unit

Intralobular Duct

• Intra - inside the lobules
• There are two different intralobular secretory ducts
• The lumens of these ducts are prominent and their cytoplasm stain acidophilic
• The intralobular ducts originate in the lobules and continue as the interlobular ducts

• Intercalated ducts
  
  • These ducts originate in the alveolus of the secretory units
  • They consist of simple cuboidal epithelium that changes into simple squamous epithelium
  • These ducts are well developed in the parotid, shorter in the submandibular and absent in the sublingual glands
• Striated ducts
  
  • These ducts are the continuation of the intercalated ducts
  • They are larger and lined with simple columnar epithelium
  • The basal part of these cells have a striated appearance due to the intricate folding of the cell membrane

Fig. 15.21
Ross and Romrell p. 397

Interlobular Ducts

• Inter - between the lobules
• The interlobular ducts are found outside the lobules in the connective tissue septa
• The epithelium begins as simple cuboidal and changes to simple columnar and/or pseudostratified epithelium.
• Eventually the epithelium changes to the same epithelium that covers the surface at its opening into the oral cavity
• The interlobular ducts join to form the main secretory duct