Human Anatomy - Kotsan I. Y. 2009

Splanchnology
Digestive System
Salivary Glands

The ducts of the small and large Salivary Glands, which secrete saliva, open into the Oral Cavity.

Saliva is a mixture of secretions from all the salivary glands. It consists primarily of Water (up to 99.5%), salts, Enzymes (amylase, glucosidase), and the bactericidal agent Lysozyme. Saliva moistens the oral mucosa, lubricates food during mastication, and its constituent enzymes break down CARBOHYDRATES into simpler compounds, thereby initiating the chemical Processing of food.

Based on The Nature of their secretion, salivary glands are classified into serous, mucous, and mixed. Serous glands secrete a protein-rich fluid, mucous glands produce mucus, and mixed glands yield a combined secretion.

The minor salivary glands (glandulae salivariae minores) are located within the thickness of the mucosa and submucosa of the oral cavity. They vary in size, ranging from 1 to 5 mm. Topographically, the minor salivary glands are divided into the following groups: labial glands (glandulae labiales); buccal glands (glandulae buccales); molar glands (glandulae molares), which are buccal glands clustered opposite the large molars; palatine glands (glandulae palatinae); and lingual glands (glandulae linguales). The labial, buccal, molar, and anterior lingual glands produce a mixed secretion; the palatine and posterior lingual glands secrete mucus; and the lingual glands situated in the region of the vallate papillae produce a serous fluid.

The major salivary glands (glandulae salivariae majores) are paired structures situated outside the oral cavity, though their ducts open into it. They include the parotid, submandibular, and sublingual glands (Fig. 144).

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Fig. 144. Major salivary glands

1 — parotid gland; 2 — parotid duct; 3 — masseter Muscle (cut); 4 — submandibular gland; 5 — submandibular duct; 6 — mylohyoid muscle; 7 — Mandible; 8 — sublingual gland; 9 — Tongue; 10 — buccinator muscle

The parotid gland (glandula parotidea) is a serous-type gland. It is the largest of the salivary glands, weighing 20–30 g. It occupies the lateral facial region, anterior and inferior to the auricle. Superiorly, the gland reaches the zygomatic arch; inferiorly, the angle of the mandible; and posteriorly, the mastoid process of the Temporal bone and the anterior border of the sternocleidomastoid muscle. The External Carotid Artery, retromandibular vein, facial and auriculotemporal nerves pass through the gland, while deep parotid Lymph Nodes are embedded within its substance.

Structurally, the parotid gland is a compound alveolar gland. It has a soft consistency and a well-defined lobular architecture. Externally, the gland is enclosed in a fascia, from which Connective Tissue septa penetrate its interior, dividing it into lobules. The parotid duct (ductus parotideus), 5–6 cm in length, emerges from the anterior border of the gland, courses forward beneath the zygomatic arch along the superficial surface of the masseter muscle to its anterior margin, where it turns medially, pierces the buccinator muscle, and opens via a small orifice on the buccal mucosa opposite the second upper molar. Occasionally, small glandular lobules are found along the course of the duct, collectively referred to as an accessory parotid gland (glandula parotidea accessoria).

The Blood supply to the parotid gland is provided by Branches of the superficial temporal artery. Venous drainage flows into the retromandibular vein. Lymphatic vessels of the gland drain into the superficial and deep parotid lymph nodes.

Innervation: sensory — parotid branches of the auriculotemporal nerve; parasympathetic — postganglionic fibers within the auriculotemporal nerve originating from the otic ganglion; sympathetic — from the external carotid plexus.

The submandibular gland (glandula submandibularis) is structurally a compound tubuloalveolar gland, and functionally belongs to the mixed group, producing both serous fluid and mucus. It weighs 10–15 g and is located in the submandibular triangle inferior to the mylohyoid muscle. The submandibular duct (ductus submandibularis) hooks around the posterior border of the mylohyoid muscle and opens on the floor of the oral cavity at the summit of the sublingual caruncle, situated laterally to the lingual frenulum.

The blood supply to the submandibular gland is derived from glandular branches of the facial artery. Venous blood drains into the facial vein, and lymphatic vessels empty into the submandibular lymph nodes.

The submandibular gland is innervated by sensory branches of the lingual nerve (from the mandibular division of the Trigeminal nerve); secretory innervation is supplied by parasympathetic fibers from the chorda tympani of the Facial Nerve and sympathetic fibers from the external carotid plexus.

The sublingual gland (glandula sublingualis) is the smallest of the major salivary glands, with a mass of 4–5 g. Structurally, it is a compound tubuloalveolar gland, and functionally it is classified as a mucous gland (producing mucus). The gland lies directly beneath the mucosa of the floor of the oral cavity, on the superior surface of the mylohyoid muscle. Its anterior end reaches the inner surface of the body of the mandible, while its posterior end extends to the submandibular gland. The gland features a major sublingual duct (ductus sublingualis major), which opens either via a common orifice with the submandibular duct on the sublingual caruncle or independently beside it. Approximately 10–12 minor sublingual ducts (ductuli sublinguales minores) open independently into the oral cavity along the sublingual fold.

The sublingual gland receives its blood supply from branches of the lingual and facial Arteries. Venous blood drains via Veins OF THE same name. The lymphatic Vessels of the gland drain into the submandibular and submental lymph nodes.

The gland is innervated by the same nerve branches as the submandibular gland.