Post on 24-May-2015
ANATOMY BY
Dr. THAAER MOHAMMED DAHER ALSAADSPECIALIST IN GENERAL SURGERY
M.B.Ch.B. (MBBS) F.I.B.M.S. )Ph.D.)SENIOR LECTURER
IMS MSU
Salivary Glands
glandulae salivariae
Salivary Glands
• Introduction
• Minor salivary glands
• Major salivary glands
• Relation of facial nerve
Introduction
• Parotid space (area) boundaries:• Anteriorly : • masseter muscle, ramus of the mandible and medial pterygoid muscle.
• Posteriorly :• mastoid process, sternosleidomastoid muscle and facial nerve.• Superiorlty:
• external auditory meatus, and tempromandibular joint.• Inferiorly :• sternocleidomastoid muscle, and posterior belly of diagastric muscle.
• Laterally: • investing layerof the deep cervical fascia, skin, and platysma muscle.
• Medially:• investing layer of deep cervical fascia, styloid process, internal jugular
vein, internal carotid artery, and pharyngeal wall.
MINOR SALIVARY GLANDS
• The mucosa of the oral cavity contains approximately 450 minor salivary glands.
• They are distributed in the mucosa of the lips, cheecks, palate, floor of the mouth and retromolar area.
• These minor salivary glands also appear in other areas of the upper aerodigestive tract including the oropharynx, larynx and trachea as well as the sinuses.
• They contribute to 10% of the total salivary volume.
The surface anatomy of the neck
• In the midline, from above down, can be felt :
1. the hyoid bone—at the level of C3;
2. the notch of the thyroid cartilage—at the level of C4;
3. the cricothyroid ligament—important in cricothyroidpuncture;
4. the cricoid cartilage—terminating in the trachea at C6;
5. the rings of the trachea, over the second and third of which can be rolled the isthmus of the thyroid gland;
6. the suprasternal notch.
The surface anatomy of the neck
• Note that the lower border of the cricoid is an important level in the neck; it corresponds not only to the level of the 6th cervical vertebra but also to:
1. the junction of the larynx with the trachea;
2. the junction of the pharynx with the oesophagus;3. the level at which the inferior thyroid artery and the middle thyroid vein
enter the thyroid gland;
4. the level at which the vertebral artery enters the transverse foramen in the 6th cervical vertebra;
5. the level at which the superior belly of the omohyoid crosses the carotid sheath;
6. the level of the middle cervical sympathetic ganglion;
7. the site at which the carotid artery can be compressed against the transverse process of C6 (the carotid tubercle
The triangles of the neck.
The parotid gland
• This is the largest of the salivary glands,
• lying wedged between the mandible and sternocleidomastoid and overflowing both these bounding structures.
The parotid and its surrounds in a schematic horizontal section—the facial nerve is the most superficial of the structures traversing the gland. (The line of section is shown in the inset head.)
Relations
• Above—lie the external auditory meatus and temporomandibularjoint.
• Below—it overflows the posterior belly of digastric.• Anteriorly—it overflows the mandible with the overlying masseter.
• Medially — lies the styloid process and its muscles separating the parotid from the internal jugular vein, internal carotid artery, last four cranial nerves and the lateral wall of the pharynx.
• The gland itself is enclosed in a split in the investing fascia, lying both on and below which are the parotid lymph nodes.
• Antero-inferiorly, this parotid fascia is thickened and is the onlystructure separating the parotid from the submandibular gland
• (the stylomandibular ligament).
Traversing the gland (from without in) are
1. the facial nerve;
2. the retromandibular (posterior facial) vein, formed by the junction of the superficial temporal and maxillary veins.
3. the external carotid artery, dividing at the neck of the mandible into its superficial temporal and maxillary terminal branches
The parotid duct (of Stensen)
• The parotid duct (of Stensen) is 2in (5cm) long.
• It arises from the anterior part of the gland,
• runs over the masseters a finger’s breadth below the zygomatic arch to pierce the buccinator and
• open opposite the second upper molar tooth.
• The duct can easily be felt by a finger rolled over the masseter if this muscle is tensedby clenching the teeth.
THE RELATIONS OF THE FACIAL NERVE TO THE PAROTID
• The facial nerve is unique in traversing the substance of a gland, a fact of considerable importance .
• This coexistence is explained embryologically; the parotid gland develops in the crotch formed by the two major branches of the facial nerve.
• As the gland enlarges it overlaps these nerve trunks, the superficial and deep parts fuse and the nerve comes to lie buried within the gland.
• The facial nerve emerges from the stylomastoidforamen, winds laterally to the styloid process and can then be exposed in the inverted V between the bony part of the external auditory meatus and the mastoid process.
• This has a useful surface marking, the intertragic notch of the ear, which is situated directly over the facial nerve.
• Just beyond this point the nerve dives into the posterior aspect of the parotid gland and bifurcates almost immediately into its two main divisions (occasionally it divides before entering the gland).
THE RELATIONS OF THE FACIAL NERVE TO THE PAROTID
• The upper division divides into temporal and zygomatic branches;
• the lower division gives the buccal, mandibular and cervical branches.
• These two divisions may remain completely separate within the parotid, may form a plexus of intermingling connections,
• The branches of the nerve then emerge on the anterior aspect of the parotid to lie on the masseter, thence to pass to the muscles of the face.
• No branches emerge from the superficial aspect of the gland,
THE RELATIONS OF THE FACIAL NERVE TO THE PAROTID
◊The named branches of the facial nerve which traverse the parotid gland
The submandibular gland• The submandibular gland is made up of a large superficial and a
small deep lobe which connect with each other around the posterior border of the mylohyoid.
• The superficial lobe of the gland lies at the angle of the jaw, wedged between the mandible and the mylohyoid and overlapping the digastric muscle .
• Posteriorly it comes into contact with the parotid gland,
• separated only by a condensation of its fascial sheath (the stylomandibular ligament).
• Superficially, the gland is covered by platysma and by its capsule of deep fascia, but it is crossed by the cervical branch of the facial nerve (VII) and by the facial vein.
• Its deep aspect lies against the mylohoid for the most part,
• but posteriorly the gland rests against the hyoglossus muscle and herecomes into contact with the lingual (V) and the hypoglossal nerve (XII), both of which lie on hyoglossus as they pass forward to the tongue.
The facial artery also comes into close relationship with the gland, approaching it posteriorly, then arching over its superior aspect (which it grooves), to attain the inferior border of the mandible and thence to ascend on to the face in front of the masseter.
From the medial aspect of the superficial part of the gland projects its deep prolongation along the hyoglossus.
• The submandibular duct (Wharton’s duct)
• arises from this deep part of the gland and runs forward, beneath the mucosa of the floor of the mouth along the side of the tongue,
• to open immediately at the side of the frenu-lum linguae .
The submandibular gland
• The sublingual gland lies immediately lateral to the submandibular duct.
• The lingual nerve reaches the tongue by passing from the lateral side of the duct below and then medial to it—thus ‘double-crossing’ it.
• The submandibular lymph nodes lie partly embedded within the gland and partly between it and the mandible.
The submandibular gland
The sublingual gland
• This is an almond-shaped salivary gland lying immediately below the mucosa of the floor of the mouth and immediately in front of the deep part of the submandibular gland.
• Laterally, it rests against the sublingual groove of the mandible while• Medially it is separated from the base of the tongue by the
submandibular duct and its close companion, the lingual nerve.
• The gland opens by a series of ducts into the floor of the mouth and also in the submandibular duct.
• The sublingual gland produces a mucous secretion, the parotid a serous secretion and the submandibular gland a mixture of the two.
• As well as these main salivary glands, small accessory glands are found scattered over the palate, lips, cheek, tonsil and tongue.
• These glands are occasional sites for development of a mixed salivary tumour.
Innervation
• Salivary glands are innervated, either directly or indirectly, by the parasympathetic and sympathetic arms of the autonomic nervous system.
• Both result in increased amylase output and volume flow.• Parasympathetic innervation is carried via cranial nerves.
• The parotid gland receives its parasympathetic input from the glossopharyngeal nerve (CN IX) via the otic ganglion,
• while the submandibular and sublingual glands receive their parasympathetic input from the facial nerve (CN VII) via the submandibular ganglion.
• Direct sympathetic innervation of the salivary glands takes place via
preganglionic nerves in the thoracic segments T1-T3 which synapse in the superior cervical ganglion with postganglionic neurons
• The sympathetic nervous system also affects salivary gland secretions indirectly by innervating the blood vessels that supply the glands.
Arterial Blood Supply
• External carotid artery
• Parotid gland ;• Transverse facial artery (branch of maxillary
artery, branch of the external carotid artery.
• Submandibular gland:
• Glandular branch of the facial artery.