🥇 ANATOMÍA DE LA FARINGE 1/2, (Músculos, Inervación). Fácil y Sencillo

Anatomy of the Pharynx

Introduction to the Pharynx

• Juan José Sánchez introduces the topic of pharyngeal anatomy, noting that it will be divided into two videos for comprehensive coverage.

• The pharynx is described as a muscular tube primarily composed of striated muscle, forming a hollow space behind the oral and nasal cavities.

Anatomical Boundaries

• The superior limit of the pharynx is at the base of the skull, specifically where it articulates with the sphenoid and occipital bones.

• The inferior boundary corresponds to vertebra C6, marking where it transitions into the esophagus.

Structural Complexity

• The pharynx serves as a junction between two major body systems: respiratory and digestive.

• A posterior view shows its connections to both nasal and oral cavities, as well as its relationship with the larynx below.

Muscular Relationships

• The lower border of the cricoid cartilage indicates where the pharynx ends and esophagus begins; lateral relationships include muscles like stylopharyngeus and stylohyoid.

• A transverse section at C2 reveals anatomical relationships with cervical vertebrae and prevertebral muscles.

Neurovascular Connections

• The pharynx's posterior-lateral relations include internal carotid arteries, jugular veins, vagus nerve, and thyroid gland.

Divisions of the Pharynx

Major Divisions Explained

• The pharynx has three main divisions: nasopharynx (or rinofaringe), oropharynx (or bucofaringe), and laryngopharynx.

Nasopharynx vs Oropharynx

• Nasopharyngeal terminology varies by culture; Greeks referred to it as "nasolana," while Latins use "rinofaringe."

Transition to Esophagus

• Laryngopharyngeal region leads directly into esophagus after cricoid cartilage.

Histological Structure of Pharyngeal Layers

Mucosal Layer Description

• The innermost layer is termed mucosa; it's epithelial tissue that lines the interior surface of the pharynx.

Fibrous and Muscular Layers

Anatomy of the Pharynx

Structure and Layers of the Pharynx

• The pharynx consists of a fibrous structure behind the stylohyoid ligament, forming its skeletal framework.

• The outermost layer is the adventitia, made up of buccopharyngeal aponeurosis that encases both oral and pharyngeal muscles.

• The buccopharyngeal aponeurosis connects to both the buccinator muscle in the mouth and the constrictor muscles of the pharynx.

• A diagram illustrates various layers: epithelial lining, muscular layer with fibrous insertions, and external adventitial layer.

• The adventitia continues posteriorly to cover structures like the esophagus.

Epithelial Types in Different Regions

• The mucosal layer varies by region; respiratory epithelium is cylindrical, pseudo-stratified, and ciliated in areas primarily for air passage.

• Nasal cavity and nasopharynx share this respiratory epithelium due to their function in air conduction.

• In contrast, oropharynx and laryngopharynx have stratified squamous non-keratinized epithelium suitable for both air and food passage.

• "Plana" (flat) and "escamoso" (scaly) are interchangeable terms used in anatomy to describe this type of epithelium.

Functional Implications of Epithelial Differences

• The shared structure between digestive and respiratory systems allows for dual functionality in oropharynx and laryngopharynx while maintaining distinct roles for nasopharynx as purely respiratory.

Muscular Composition of the Pharynx

• Two groups form the muscular layer: external circular muscles (three constrictors), which contract circularly, and internal longitudinal muscles that run vertically.

• Starting with superior constrictor muscle origins from pterygoid hook, maxilla, lateral tongue border; some sources also cite pterygomaxillary raphe as an origin point.

• This superior constrictor inserts into buccopharyngeal fascia at tubercle on occipital bone's basilar portion.

• All circular constrictors attach at a central tendinous raphe known as median pharyngeal raphe.

Additional Muscles Involved

Anatomy of the Pharyngeal Muscles

Overview of Pharyngeal Muscle Structure

• The hyoglossus muscle obscures the origin of other muscles; a medial view of the pharynx reveals its structure within the oral cavity.

• The inferior constrictor muscle originates at the angle formed by the lesser and greater horns of the hyoid bone, alongside the stylohyoid ligament.

• The middle constrictor muscle connects to the greater horn and inserts into the midline tendinous raphe, crucial for understanding pharyngeal anatomy.

Functionality and Importance of Constrictor Muscles

• The inferior constrictor has two origins: one from the oblique line of thyroid cartilage and another from the dorsal side of cricoid cartilage, forming part of a circular layer.

• The cricopharyngeal portion is significant as it contributes to forming the upper esophageal sphincter, which keeps the esophagus closed when not in use.

• Both oblique (thyropharyngeal fibers) and transverse (cricopharyngeal fibers) components reach both pharynx and upper esophagus.

Additional Pharyngeal Muscles

• The palatopharyngeus muscle originates from hard palate's dorsal side, inserting into lateral walls of pharynx and thyroid cartilage.

• Salpingopharyngeus arises from Eustachian tube (auditory tube), also known as salpingotympanic tube, inserting into lateral walls of pharynx.

• Stylo-pharynges originate from styloid process on temporal bone, positioned between superior and middle constrictors.

Innervation Details

• These muscles primarily facilitate swallowing; stylopharynges are key elevating muscles along with tensor veli palatini aiding in elevation during swallowing.

• Sensory innervation comes from glossopharyngeal nerve, responsible for reflex actions like gag reflex due to tactile sensations in pharynx.

Plexus Formation and Motor Control

• Glossopharyngeal nerve provides sensory input while vagus nerve controls motor functions for most pharyngeal muscles through plexus formation.

• Accessory nerve (XI cranial nerve), particularly its cranial branch joining vagus, plays a role in forming most fibers within this plexus.

Inervation and Irrigation of the Pharynx

Inervation Details

• The pharynx is innervated by both the vagus nerve's pharyngeal plexus and the superior laryngeal nerve.

• The external branch of the superior laryngeal nerve specifically innervates the cricothyroid muscle, which is part of the larynx.

• The inferior constrictor muscle receives dual innervation, highlighting its complex neural control.

Vascular Supply

• The primary blood supply to the pharynx comes from branches of the facial artery, including the ascending palatine artery and tonsillar branch.

• Additionally, the ascending pharyngeal artery, a branch of the external carotid artery, contributes to irrigating the pharynx.

• Important vascular contributions also come from branches of the subclavian artery, particularly emphasizing the role of the inferior thyroid artery.

Additional Insights on Blood Supply

• The inferior laryngeal artery, although not depicted in provided images, plays a significant role in supplying blood to both laryngeal and pharyngeal structures.