Anatomy of Pharynx in a nutshell

Anatomy of Pharynx

Intro:

• Pharynx is a common passageway for the GI tract and the respiratory tract
• A fibromuscular tube,  incomplete anteriorly because nasal cavity and oral cavity open into the pharynx (posteriorly).
• Stretches superiorly from the base of the skull.
• Superiorly attaches to the occipital bone.
  • The highest attachment is the Pharyngeal tubercle on the occipital bone.
• Inferiorly, it is continuous with the esophagus
• Posterior, find the retropharyngeal space
• Palate is the roof of the mouth and the floor of the nasal cavity
• Larynx continuous with the trachea

Pharyngeal wall

• Has mucous membrane as internal lining and a dense connective tissue core as well as muscular tissue.
• Layers of wall: 5 layers

1. 1. Most internal: Mucous membrane
      1. Continuous with mucous membrane of the nasal cavity, oral cavity, and larynx
      2. Characteristics may change with the area
   2. Submucosa: has blood vessels
   3. Pharyngeal Basilar Fascia
      1. Dense Connective Tissue
      2. Unique to the pharynx
      3. Attached superiorly to the skull and acts as CT core to support the muscles of the pharynx
   4. Muscular layer
   5. Buccopharyngeal Fascia:

1. 1. 1. The layer of loose connective tissue
      2. Must be flexible to allow food to pass
      3. Directly adjacent to retropharyngeal space

Divisions of the Pharynx

• Nasopharynx:
  • Stretches from the skull to the level of C2
  • Is posterior to the nasal cavity
  • Part is superior to the palate
• Oropharynx:
  • Posterior to the oral cavity
  • Is adjacent to C2-C4
• Laryngopharynx
  • From C4-C6
  • Posterior to layrngeal cartilages
  • Continuous inferiorly with esophagus

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1 – fornix pharyngis; 2 – septum nasi; 3 – torus tubarius; 4 – m. stylopharyngeal 5 – боковая стенка глотки; 6 – arcus palatopharyngeus; 7 – tonsilla palatina; 8 – epiglottis; 9 – recessus piriformis; 10 – aditus laryngis; 11 – plica aryepiglottica; 12 – isthmus faucium; через который виден radix linguae; 13 – uvula; 14 – arcus palatoglossus; 15 – верхняя поверхность palatum molle; 16 – choana sinistra; 17 – glandula parous; 18 – esophagus; 19 – glangula thyreoidea

Structures of Nasopharynx:

• Tubal Elevation (Torus)
  • On the lateral wall of the nasopharynx
  • A Horseshoe-shaped elevation
  • Is covered over by mucous membrane
  • Cartilaginous end of the auditory tube (Eustachian tube) protruding into the nasopharynx

1. 1. • A tube connects the nasopharynx with the middle ear
      • The tube is lined with a mucous membrane that is continuous with both the nasopharynx and middle ear.
      • This tube is 2/3 cartilage and 1/3 bone (toward the middle ear)

1. • Ostium of the auditory tube is the entrance into the tube within the Tubal elevation.
   • The function of the Auditory Tube:

1. 1. • Equalizes pressure between middle ear and external environment
      • Allows drainage from middle ear (contains mucous membrane that will give off secretions during irritation/inflammation)
      • Is a point of attachment for several muscles (1 of pharynx, 2 of soft palate)
      • Otitis Media: middle ear infection
        1. more common in young children
        2. in children, this tube is more linearly horizontal, thus viruses/bacteria have direct line of migration to middle ear.
        3. Treatment may involve placing a tube through tympanic membrane to allow drainage out of auditory meatus
        4. Angle of auditory tube changes in adults

• Pharyngeal Tonsils (Adenoids)
  • Lymphoid tissue in the nasopharynx
  • Just under the mucous membrane of the pharynx
  • Traps foreign matter as a way of guarding the passageway
  • When enlarged, have difficulty passing air into nasopharynx
• Choanae:
  • the posterior nasal apertures/openings
  • Nares are the anterior openings.
  • Air passes through nares → through nasal cavity → through choanae → into the nasopharynx

Structures of Oropharynx:

• Palatoglossal Arch
  • Guard passageway between oral cavity and oropharynx
  • Is an anterior fold of mucous membrane that covers the Palatoglossus muscle (goes from palate to tongue)
• Palatopharyngeal Arch
  • A more posterior fold of mucous membrane
  • Beneath, find Palatopharyngeus muscle.
• Tonsilar bed with Palantine tonsil
  • Is located right between the two arches
  • Is a collection of lymphoid tissue
  • Tonsils regress in size with age

Structure of Laryngopharynx: Piriform recess

• On the lateral aspect of larynx/adjacent to the larynx
• made when muscles of the laryngopharynx blend with the esophagus

Muscles of Pharynx

• Constrictor Muscles:
  • 3 pairs that are circular (or semicircular)
  • Start superiorly at the skull and inferiorly end as are continuous with esophagus
  • Are overlapping, thus making it difficult to differentiate
  • Contract in wave-like action to constrict pharynx to push bolus closer to esophagus
  • Superior Constrictor:

1. 1. • Origin: Pterygomandibular Raphe
        1. Is a line of fascia
        2. stretches from Hammulus (on Medial Pterygoid plate) to Mylohyoid line (on Mandible)
        3. also serves as the attachment point for Buccinator muscle (deep in the face)
      • Stretches posteriorly

• • Middle constrictor:

1. 1. • Origin: Stylohyoid ligament and hyoid bone
      • Overlaps the superior constrictor as it extends posteriorly

1. • Inferior constrictor:

1. 1. • Origin from: Thyroid Cartilage/Cricoid Cartilage
      • Extends posteriorly

1. • All three insert at the Midline Raphe

1. 1. • A connective tissue band on posterior aspect of pharynx
      • Composed of muscles interdigitating on this band

• • • Attaches superiorly at occipital bone (most superior attachment of pharynx)

• • Action: squeezing to push bolus toward esophagus
• Longitudinal Muscles (3 pairs)
  • Salpingopharyngeus:

1. 1. • Origin: Auditory tube
      • Insert: blends with the wall of the pharynx (blends with the constrictors)
      • Is covered by mucous membrane fold called the Salphingopharyngeal Fold

1. • Palatopharyngeus:

1. 1. • Origin: from the soft palate
      • Insert: blends with other muscles of the pharyngeal wall
      • Is covered by the Palatopharyngeal fold of mucous membrane
      • Almost comes together with Salpingopharyngeus as meet with the pharyngeal wall

1. • Stylopharyngeus:

1. 1. • Origin: from the styloid process
      • Insert: blends with the other pharyngeal muscles
      • Innervated by the glossopharyngeal CN IX
      • Is the only muscle that came from the second pharyngeal arch, all other muscles came from the fourth/sixth arches and are thus innervated by the Vagus nerve.

1. • Action:

1. 1. • Raise/Elevate the pharynx which is important for swallowing
      • Helps to keep the pharynx open, thus making it more able to receive the bolus

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1 – m. digastricus (venter posterior); 2, 8, 14 – m. stylopharyngeus; 3 – m. stylohyoideus; 4 – m. pterygoideus medialis; 5, 13 – m. constrictor pharyngis med.; 6 – oshyoideum; 7, 10 – eornu superius et inferius cartilaginis thyreoideae; 11 – esophagus; 12 – m. constrictor pharyngis inferior; 15, 17 – m. constrictor pharyngis sup.; 16 – processus styloideus; 18 – pars basilaris ossis occipitalis; 9, 19 – raphe pharyngis; 20 – fibrous shell of the throat

Innervation of the Pharynx:

• Innervated by the pharyngeal plexus
  • Is a network of nerves in/around the pharynx (found in submucosa/on buccopharyngeal fascia)
  • Has both sensory and motor components as well as autonomics
• The Vagus nerve supplies all motor innervation for muscles of the pharynx with the exception of the Stylopharyngeus (Glossopharyngeal CN IX)
• The Glossopharyngeal nerve supplies sensory information to the mucous membrane
• Sympathetic:
  • from Superior Cervical Ganglion
  • To blood vessels
• Parasympathetic:
  • Going to mucous glands
  • Primarily from the Vagus (possible contributions from Facial nerve)

Blood supply of the Pharynx

• Ascending pharyngeal artery– A branch of the External Carotid
• Branches of Superior Thyroid
• Branches of Inferior Thyroid
• Facial artery gives off Tonsilar Branch to the Tonsilar bed
  • Makes tonsilar bed highly vascularized
  • Having tonsils taken out has the potential for post-op bleeding
• Branches of Maxillary artery

Spinal Accessory Nerve:

• Not the same as the cranial component of the accessory nerve (CN XI)
• The ventral horn of C1-4 has a contribution (cervical contribution) of motor fibers that create the spinal component of CN XI (Accessory Nerve).
• Nucleus Ambiguous: gives the cranial component of CN XI
• For a short time, (in the skull) the two components are together
  • When leaving skull, spinal component leaves to the SCM and Trapezius
  • The Cranial component is distributed with the Vagus nerve (thus, innervation of pharynx muscle is by Vagus but it is using fibers from the Cranial portion of CN XI)

Also read:

1. The Pharynx @ TeachMeAnatomy
2. Practice Anatomy tests for free!
3. Best Anatomy books for Medical students
4. Best Anatomy websites & journals
5. Anatomy syllabus in (CBME) in India
6. Anatomy syllabus in Russia & Other CIS
7. Anatomy syllabus in China

Also Watch:

• Pharynx @ University of Michigan Anatomy