Written Examination Part III. (30 pts) - Short Answer (October 27, 2006)

Indicate your understanding (characteristics, importance, function, relationships, boundries and/or contents) of the following.

Parotid Region

from zygomatic arch superior from ear canal and ear posterior superiorly from sternocleidomastoid posterior inferiorly superficial over ramus of mandible posteriorly and masseter anteriorly Relationships The cervical investing fascia extends superficial and deep to the gland. The parotid duct crosses the masseter to pierce the buccinator muscle of the cheek. Number of important structures are “hostage” to the parotid gland.

• The buccal branch of CN VII and the transverse facial artery parallel its course on the face.
• The terminal branches of CN VII are found leaving the free border of the gland.
• These include the proximal branches of the facial nerve, the retromandibular vein, the external carotid artery.
• The auriculotemporal nerve emerges from the superior edge of the gland after traveling from behind the gland.
• The deep portion of the gland wraps around the ramus of the mandible and is in relati to the posterior belly of the digastric and stylohyoid muscle, which separate it from the carotid sheath with the internal jugular vein, vagus n, internal carotid artery in the carotid sheath and also CN’s XII, XI, and IX.

Paranasal Sinuses

Frontal, Maxillary, Sphenoid, Ethmoid Frontal – Opens inferior to middle concha into ethmoid infidibulum or frontal recess (variable) Maxillary – located in the Maxilla, drains high on its medial wall, usually in the infidibulum Ethmoid- Vary in number from 3 approx. 18, 3 groups: anterior- (open in middle meatus), middle – (middle meatus on the surface of ethmoid bulla), posterior – (abuve superior concha). Sphenoid (bilateral inside sphenoid bone) through anterior wall via sphenoid ethmoidal recess. Frontal Sinus only sinus to drain with normal gravitational forces, requiring cilia to actively move mucus to the nasal cavity. Site of infiection.

Arterial Supply to the Cranial Cavity

• Internal Carotid: branch of common carotid travels via carotid canal to foramen lacerum were it opens into the middle cranial fossa
• Vertebral arteries: branch of first part of sublcavian- travels superiorly via C6 to C1 takes a tortuous turn medially before entering the posterior cranial fossa via the foramen magnum.
• Middle Meningeal artery, branch of the maxillary travels into middle cranial fossa via foramen spinosum.
• Accessory Middle Meningeal artery (variable) travels into the middle cranial fossa via foramen Ovale.
• Spenopalatine Artery branch of the maxillary artery, travels into the nasal cavities via the sphenopalatine foramen.

SMALLER LESS SIGNIFICANT SUPPLIES

• Potentially arteries that exit to the face can undergo situations of reverse blood flow supplying the cranial cavity.
• Occipital Branch via the mastoid foramen
• Posterior Meningeal artery via the foramen Magnum.
• Ascending branch of the ascending pharyngeal artery via condylar foramen.
• Meningeal branch of the vetebral artery via the foramen magnum.

Muscular Process of Arytenoid Cartilage

Lever point for the movement of the Arytenoid cartilidge. Serves as a insertion point for two muscles. Posterior Crycoarytenoid the lateral Crycoarytenoid. Structure is opposite the vocal process serving as the site for the vocal cords. Contraction of the Posterior Crycoarytenoid results in abduction of the vocal cords, Contraction of the lateral Crycoarytenoid results in adduction of the vocal cords. Superior to Crycoid cartilage. Oblique Arytenoid originates from Muscular process.

Transverse Process of C6

• Location of carotid tubercle
• Apex of Vertebral Triangle, bordered medially by the longus coli and laterally by the anterior scalene.
• Covered by prevertebral fascia
• Phrenic N travels superficial to it.
• Site of entrance for the vertebral artery into the travsverse process of C6.
• Location of the middle Cervical Ganglion – sympathetic trunk.
• Vertebral Vein normally inferior.

Clinical importance: abnormal tumors of the tubercle can impinge on carotid sheath located superficial to the transverse process of C6 Blockage so vertebral artery at this location can result in parastesia, to associated dermatomes of C345, Blockage bilaterally can affect the Phrenic N. Vagus N. is vulnerable to damage as a result of tumors on the carotid tubercle

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-- ThomasPerrault - 21 Nov 2006