Oral Cavity

Introduction

This document pertains to the detailed lecture on the oral cavity presented by Dr. Jonathan Hakim at the University of Sydney. The information discussed in this lecture draws from the foundational textbook "Anatomy Descriptive and Surgical" by Henry Gray (1858), which serves as a significant reference for anatomical studies.

Lecture Objectives

• Describe the regions and distinct features of the oral cavity as well as the oropharynx, emphasizing their roles in digestion and respiration.

• List the anatomical boundaries of the oral cavity proper and vestibule, underscoring their clinical significance.

• Describe the surface features associated with the oral and pharyngeal parts of the tongue, including their roles in taste and swallowing.

• Describe the extrinsic muscles of the tongue and the supporting structures that form the floor of the oral cavity, discussing their functional relevance.

• List the bones constituting the hard palate and identify the muscles that comprise the soft palate, relating these to their functions in phonation and deglutition.

Anatomy of the Nasal and Oral Cavities

• Nasal Cavity: This cavity serves as the anterior part of the respiratory system, warming and filtering the air before it reaches the lungs. It is lined with mucous membranes and contains turbinates that help trap debris.

• Oral Cavity: Positioned superior to the larynx and pharynx, it plays an essential role in the initial stages of digestion, enabling the mechanical breakdown of food through chewing and mixing with saliva.

Pharynx Regions:

• Nasopharynx: Located posterior to the nasal cavity, it is responsible for the passage of air and is equipped with the Eustachian tubes that connect the middle ear.

• Oropharynx: Positioned posterior to the oral cavity, it is crucial for both respiratory and digestive functions, allowing the passage of food and air.

• Laryngopharynx: Found posterior to the larynx, this region directs food into the esophagus and air into the larynx.

The Vestibule and Oral Cavity Proper

Vestibule

• The vestibule is located inside the lips and cheeks, superficial to the teeth and alveolar arches. It is a critical space that allows for the movement of food and aids in the initial stages of mastication.

• It comprises labial (related to the lips) and buccal (related to the cheeks) sulci, which are essential for proper speech and swallowing mechanisms.

Oral Cavity Proper

• Boundaries:

  • Anterolateral: Defined by the alveolar processes, this structure supports the teeth and aids in their alignment.

  • Posterior: The oropharyngeal isthmus, bounded laterally by the palatoglossal folds, delineates the transition to the oropharynx.

  • Superior: Comprised of the hard palate and soft palate, these structures not only separate the oral cavity from the nasal cavity but also assist in speech production.

  • Inferior: Formed by the tongue, including the root and mylohyoid muscle, facilitating movements necessary for swallowing and manipulation of food.

Oropharynx

• The entrance to this region is termed the oropharyngeal isthmus or fauces, integrating both respiratory and digestive pathways.

• The borders are defined by the palatoglossal and palatopharyngeal folds, which play a significant role in controlling the flow of air and food.

Tongue Anatomy

Surface Features

• Dorsal Surface:

  • Anterior 2/3: Known as the oral part, it is involved in taste perception and food manipulation.

  • Posterior 1/3: Referred to as the pharyngeal part, it is separated by palatoglossal folds and includes the lingual tonsils, playing a role in immune response.

  • Grooves:

    • Sulcus terminalis: This V-shaped depression marks the boundary between the anterior and posterior parts of the tongue.

    • Foramen caecum: This remnant of the embryological thyroid duct provides insight into developmental anatomy.

• Ventral Surface:

  • Comprises the body (oral part), apex (tip), and root (connected to the hyoid bone), crucial for movement and control during speech and swallowing.

Lingual Papillae

• Types:

  • Fungiform: Mushroom-shaped, associated with taste buds, distributed throughout the anterior part of the tongue.

  • Filiform: Conical in shape and devoid of taste buds, they provide texture and grip.

  • Vallate: Larger papillae found in the posterior part of the tongue, containing numerous taste buds.

  • Foliate: Ridges along the sides of the tongue, associated with taste perception, especially in young individuals. (do NOT possess tastebuds)

Muscles of the Floor of the Oral Cavity

• Mylohyoid Muscle:

  • Extending from the mandible to the hyoid bone, this muscle plays a vital role in swallowing and speech articulation. It forms a muscular floor that supports the oral cavity.

• Geniohyoid Muscle:

  • From the genial tubercle to the hyoid bone, this muscle assists in swallowing and plays a part in depressing the mandible, thus enabling proper oral function.

Extrinsic Muscles of the Tongue

• Genioglossus Muscle: Responsible for protruding and deviating the tongue, facilitating speaking and swallowing actions.

• Hyoglossus Muscle: Functions to depress the sides of the tongue, helping with food manipulation during mastication.

• Styloglossus Muscle: Lifts the tongue upwards and backwards, contributing to the swallowing process.

• Palatoglossus Muscle: Elevates the posterior part of the tongue, relevant during swallowing and to separate the oral cavity from the oropharynx.

Hard and Soft Palate

Hard Palate

• Comprised of the palatine process of the maxilla and the horizontal plate of the palatine bone, it forms the bony structure in the anterior part of the mouth.

• The hard palate features:

  • Incisive foramen: A small opening located behind the front teeth.

  • Greater and lesser palatine foramina: Allow the passage of nerves and blood vessels.

Soft Palate

• Composed of muscle and mucosa, functioning in speech and swallowing. Its dynamic movement aids in closing off the nasal passages during these processes.

• Key muscles: Include levator palati, tensor palati, palatoglossus, palatopharyngeus, and the uvula, collectively playing a role in regulating airflow and food passage.

Teeth

Types:

• There are 20 primary (milk) teeth and 32 permanent (adult) teeth. Understanding their types is essential for pediatric and adult dental care.

Surface Terminology:

• Labial: The anterior tooth surface facing the lip, essential for aesthetics and function.

• Buccal: The posterior tooth surface closest to the cheeks, significant for occlusion.

• Lingual: The surface opposite the tongue, involved in the transition of food during chewing.

• Mesial: Surface closest to the midline of the dental arch.

• Distal: Surface furthest from the midline, important for distinguishing tooth positioning.

• Occlusal: The chewing surface of posterior teeth, crucial for food grinding.

• Incisal: The cutting edge of anterior teeth, essential for initiating the mastication process.