Pharynx Anatomy (Parts, Layers, Muscles)

Anatomy of the Pharynx

Overview of the Pharynx

• Meditay introduces the anatomy of the pharynx, following a previous discussion on the oral cavity.

• The video will cover three parts of the pharynx: Nasopharynx, Oropharynx, and Laryngopharynx, along with their anatomical structures and associated muscles.

Structure and Function

• The pharynx is approximately 12 to 15 cm long and consists of three sections:

• Nasopharynx: Connected to the nasal cavity.

• Oropharynx: Associated with the oral cavity.

• Laryngopharynx: Linked to the larynx.

• The pharynx serves as a control point for breathing and swallowing; it closes off during breathing but opens when swallowing occurs.

Detailed Anatomy of Nasopharynx

• The nasopharynx corresponds to levels of the first and second cervical vertebrae, attached to the base of the skull at points called Fornix Pharyngis (vault).

• Important landmarks include:

• Pharyngeal tubercle (occipital bone)

• Petro-occipital fissures (fusion point between occipital bone and temporal bone)

• Inferior border of petrous part of temporal bone

• Medial lamina of pterygoid process

Connection Between Nasal Cavity and Pharynx

• A strict border known as Choanae separates the nasal cavity from the pharynx.

• The auditory tube connects the middle ear to the nasopharynx, playing a crucial role in pressure regulation.

Functionality of Auditory Tube

• The auditory tube stabilizes pressure differences in the middle ear by connecting it to nasopharyngeal space.

• At rest, this tube remains closed but opens during swallowing, relieving pressure in situations like flying or driving through mountains.

Pressure Regulation Mechanism

• Changes in air pressure can cause discomfort due to tympanic membrane movement; swallowing helps equalize this pressure by opening up the auditory tube.

Auditory Tube and Pharyngeal Anatomy

Functions of the Auditory Tube

• The auditory tube serves two main functions: equalizing pressure during swallowing and draining the middle ear to protect against pathogens.

• Broad-spectrum antibiotics, such as amoxicillin with clavulanic acid, may be prescribed if infections produce significant symptoms.

Anatomical Features of the Auditory Tube

• The opening of the auditory tube into the pharynx is called ostium pharyngeum tubae auditivae, where "ostium" means opening in Latin.

• Above this opening is a cartilage structure known as torus tubarius, which acts as a cushion for the auditory canal.

Tonsils in the Nasopharynx

• The nasopharynx contains tonsils including the pharyngeal tonsil (adenoids), which can become inflamed and block the auditory tube.

• Another set of tonsils located behind the auditory tube are referred to as tubal tonsils.

Oropharynx and Laryngopharynx Overview

Structure of Oropharynx

• The oropharynx is situated at the level of the third/fourth cervical vertebrae, bordered by the soft palate and epiglottis. It connects to the oral cavity through an opening called isthmus faucium.

Structure of Laryngopharynx

• Located at levels five to six cervical vertebrae, it continues into the larynx; during swallowing, the epiglottis closes off this area to direct food into the esophagus instead of lungs.

• Key openings include laryngeal inlet and esophageal entrance; also features piriform fossa on either side for anatomical reference.

Layers of Pharyngeal Wall

Mucosal Layer

• The tunica mucosa lines the inner layer of pharyngeal cavity with different epithelial types: respiratory epithelium in nasopharynx (pseudostratified with cilia) versus stratified squamous non-keratinized epithelium in other regions for protection against food pressure.

Submucosal Layer

• Tela submucosa consists mainly of connective tissue along with blood vessels, lymph vessels, and glands that support mucosal function.

Muscular Layer

• Tunica muscularis includes circularly arranged inner muscle fibers and longitudinally arranged outer fibers aiding peristalsis—coordinated contractions facilitating movement within pharynx during swallowing.

Adventitial Layer

• The outermost layer, tunica adventitia, comprises tough collagen fibers providing structural integrity to pharyngeal walls from outside influences.

Muscles Involved in Phonation

Pharyngeal Constrictors

• Muscles are categorized into constrictors (superior, medial, inferior) based on their function:

• Superior Pharyngeal Constrictor: Originates from pterygoid process and mylohyoid line; inserts at pharyngeal raphe.

• Medial Pharyngeal Constrictor: Originates from hyoid bone; inserts at raphe pharyngis.

• Inferior Pharyngeal Constrictor: Originates from thyroid & cricoid cartilages; also inserts at pharyngeal raphe.

Understanding the Muscles Involved in Pharyngeal Elevation

Key Muscles and Their Functions

• The stylopharyngeus muscle originates from the styloid process and inserts at the lateral wall of the pharynx, playing a crucial role in elevating the pharynx during swallowing.

• The palatopharyngeus muscle starts at the aponeurosis of the soft palate and also inserts into the lateral wall of the pharynx, contributing to pharyngeal elevation.

• The salpingopharyngeus muscle originates from the walls of the auditory tube and connects with palatopharyngeus fibers; it assists in opening the auditory tube when swallowing, which is typically closed.

• All these muscles work together to ensure that during swallowing, not only is the pharynx elevated but also that necessary structures like the auditory tube are appropriately managed.