13. Oral cavity proper - walls The hard and soft palate The oropharyngeal isthmus PDF

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13. Oral cavity proper - walls. The hard and soft palate. The oropharyngeal isthmus. The mucous membrane. Blood supply and nerves. The Mouth (Cavum Oris; Oral Or Buccal Cavity) The cavity of the mouth is placed at the commencement of the digestive tube ; it is a nearly oval-shaped cavity which consists of two parts: an outer, smaller portion, the vestibule, and an inner, larger part, the mouth cavity proper. The Mouth Cavity Proper (cavum oris proprium) is bounded laterally and in front by the alveolar arches with their contained teeth; behind, it communicates with the pharynx by a constricted aperture termed the isthmus faucium. It is roofed in by the hard and soft palates, while the greater part of the floor is formed by the tongue, the remainder by the reflection of the mucous membrane from the sides and under surface of the tongue to the gum lining the inner aspect of the mandible. It receives the secretion from the submaxillary and sublingual salivary glands. Structure.—The mucous membrane lining the mouth is continuous with the integument at the free margin of the lips, and with the mucous lining of the pharynx behind; it is of a rosepink tinge during life, and very thick where it overlies the hard parts bounding the cavity. It is covered by stratified squamous epithelium. The Palate (palatum) forms the roof of the mouth; it consists of two portions, the hard palate in front, the soft palate behind. The Hard Palate (palatum durum) is bounded in front and at the sides by the alveolar arches and gums; behind, it is continuous with the soft palate. It is covered by a dense structure, formed by the periosteum and mucous membrane of the mouth, which are intimately adherent. Along the middle line is a linear raphæ, which ends anteriorly in a small papilla corresponding with the incisive canal. On either side and in front of the raphé the mucous membrane is thick, pale in color, and corrugated; behind, it is thin, smooth, and of a deeper color; it is covered with stratified squamous epithelium, and furnished with numerous palatal glands, which lie between the mucous membrane and the surface of the bone. The Soft Palate (palatum molle) is a movable fold, suspended from the posterior border of the hard palate, and forming an incomplete septum between the mouth and pharynx. It consists of a fold of mucous membrane enclosing muscular fibers, an aponeurosis, vessels, nerves, adenoid tissue, and mucous glands. When occupying its usual position, i. e., relaxed and pendent, its anterior surface is concave, continuous with the roof of the mouth, and marked by a median raphé. Its posterior surface is convex, and continuous with the mucous membrane covering the floor of the nasal cavities. Its upper border is attached to the posterior margin of the hard palate, and its sides are blended with the pharynx. Its lower border is free. Its lower portion, which hangs like a curtain between the mouth and pharynx is termed the palatine velum. Hanging from the middle of its lower border is a small, conical, pendulous process, the palatine uvula; and arching lateralward and downward from the base of the uvula on either side are two curved folds of mucous membrane, containing muscular fibers, called the arches or pillars of the fauces. The oropharyngeal isthmus (or isthmus of fauces or faucal isthmus) is the passage from the mouth to the oropharynx, between the soft palate and the root of the tongue. It is bounded laterally on both sides by the palatoglossal arches. Each palatoglossal arch runs downwards, laterally and forwards, from the soft palate to the side of the tongue. The approximation of the arches shuts off the mouth from the oropharynx, and is essential to swallowing (deglutition). The Palatoglossus muscle closes the oropharyngeal isthmus. The muscle of the soft palate play important roles in swallowing and breathing. Specific muscles include: Muscle Action Nerve levator veli palatini deglutition Vagus nerve via pharyngeal plexus tensor veli palatini

deglutition

mandibular nerve

palatoglossus palatopharyngeus

respiration respiration

Vagus nerve via pharyngeal plexus Vagus nerve via pharyngeal plexus

musculus uvulae

moves uvula

Vagus nerve via pharyngeal plexus

Nerves of the Palate ● The sensory nerves of the palate, which are branches of the pterygopalatine ganglion, are the greater and lesser palatine nerves. ● They accompany the arteries through the greater and lesser palatine foramina, respectively. ● The greater palatine nerve supplies the gingivae, mucous membrane, and glands of the hard

palate. The lesser palatine nerve supplies the soft palate. Another branch of the pterygopalatine ganglion, the nasopalatine nerve, emerges from the incisive foramen and supplies the mucous membrane of the anterior part of the hard palate. Vessels of the Palate ● The palate has a rich blood supply from branches of the maxillary artery. ● ●...