Pharynx

PHARYNX

Definition Dimensions Boundaries Parts Laryngopharynx Structure Muscles Structures Between Muscles Nerve Supply Blood Supply Lymphatic Drainage
01

Definition

  • Pharynx (Latin: throat) is a wide muscular tube situated behind:
    • Nose
    • Mouth
    • Larynx
  • Clinically, it is a part of the upper respiratory passages where infections are common.
  • Upper part of pharynx → transmits only air.
  • Lower part (below the inlet of larynx) → transmits only food.
  • Middle part → common passage for both air and food.
  • Nasopharynx is connected to the middle ear through the pharyngotympanic tube.
02

Dimensions of Pharynx

Length

About 12–14 cm.

Width

Upper Part

Widest (3.5 cm) and non-collapsible.

Middle Part

Narrow.

Lower End

Narrowest part of the gastrointestinal tract, except for the vermiform.

03

Boundaries

Superiorly

Base of skull, including:

  • Posterior part of the body of sphenoid
  • Basilar part of occipital bone

These are in front of the pharyngeal tubercle.

Inferiorly

  • Pharynx is continuous with the oesophagus at the level of the 6th cervical vertebra.
  • This corresponds to the lower border of the cricoid cartilage.

Posteriorly

  • Pharynx glides freely on the prevertebral fascia.
  • This fascia separates it from the cervical vertebral bodies.

Anteriorly

Communicates with:

  • Nasal cavity
  • Oral cavity
  • Larynx

Therefore, the anterior wall of the pharynx is incomplete.

On Each Side

  • Auditory tube
  • Styloid process and muscles attached to it
  • Common carotid, internal carotid and external carotid arteries
  • Last four cranial nerves.
04

Parts of Pharynx

The cavity of pharynx is divided into:

1. Nasal Part

Nasopharynx

2. Oral Part

Oropharynx

3. Laryngeal Part

Laryngopharynx

05

Laryngeal Part of Pharynx

  • It is the lower part of the pharynx situated behind the larynx.
  • Extends from the upper border of the epiglottis to the lower border of the cricoid cartilage.

Anterior Wall

Presents:

  1. Inlet of the larynx
  2. Posterior surfaces of the:
    • Cricoid cartilage
    • Arytenoid cartilages

Posterior Wall

  • Supported mainly by the:
    • 4th and 5th cervical vertebrae
  • Partly by:
    • 3rd and 6th cervical vertebrae
  • In this region, the posterior wall of the pharynx is formed by:
    • Superior constrictor
    • Middle constrictor
    • Inferior constrictor

Lateral Wall

  • Presents a depression called the piriform fossa.
  • There is one piriform fossa on each side of the inlet of the larynx.
  • It is bounded:
    • Medially → aryepiglottic fold
    • Laterally → thyroid cartilage and thyrohyoid membrane
  • Beneath the mucosa of the fossa lies the internal laryngeal nerve.
  • Removal of foreign bodies from the piriform fossa may damage the internal laryngeal nerve.
  • This may lead to anaesthesia in the supraglottic part of the larynx.
06

Structure of Pharynx

The wall of the pharynx consists of 5 layers from within outwards:

1. Mucosa

2. Submucosa

3. Pharyngobasilar Fascia / Pharyngeal Aponeurosis

4. Muscular Coat

5. Buccopharyngeal Fascia

1. Mucosa

Forms the innermost layer.

2. Submucosa

Lies external to the mucosa.

3. Pharyngobasilar Fascia / Pharyngeal Aponeurosis

  • It is a fibrous sheet internal to the pharyngeal muscles.
  • It is thickest in the upper part where it fills the gap between:
    • Upper border of superior constrictor
    • Base of skull
  • It is also thick posteriorly where it forms the pharyngeal raphe.

Attachments

Superiorly, the fascia is attached to:

  • Basiocciput
  • Petrous temporal bone
  • Auditory tube
  • Posterior border of medial pterygoid plate
  • Pterygomandibular raphe

Inferiorly:

  • It is closely attached to muscles and hardly extends beyond the superior constrictor.

4. Muscular Coat

Consists of:

Outer circular layer → three constrictors:

  1. Superior
  2. Middle
  3. Inferior

Inner longitudinal layer → three muscles:

  1. Stylopharyngeus
  2. Salpingopharyngeus
  3. Palatopharyngeus

5. Buccopharyngeal Fascia

  • Covers the outer surfaces of the constrictors of the pharynx.
  • Extends forwards across the pterygomandibular raphe to cover the buccinator.
  • Like the pharyngobasilar fascia, the buccopharyngeal fascia is best developed in the upper part of the pharynx.
  • Between the buccopharyngeal fascia and muscular coat are the:
    • Pharyngeal plexus
    • Veins
    • Nerves.
07

Muscles of Pharynx

Constrictors of the Pharynx

  • The muscular basis of the wall of the pharynx is formed mainly by three pairs of constrictors:
    1. Superior
    2. Middle
    3. Inferior
  • Inferior constrictor consists of two parts:
    1. Thyropharyngeus
    2. Cricopharyngeus

Median Raphe

  • All constrictors of the pharynx are inserted into a median raphe on the posterior wall of the pharynx.
  • Upper end of the raphe reaches the base of the skull.
  • It is attached to the pharyngeal tubercle on the basilar part of the occipital bone.
  • Origins of the constrictors are situated anteriorly in relation to the posterior openings of:
    • Nose
    • Mouth
    • Larynx
  • From their origins, fibres pass into the lateral and posterior walls of the pharynx.
  • Fibres of the two sides meet in the middle in a fibrous raphe.
08

Constrictor Muscles of Pharynx

Muscle Origin Insertion
Superior constrictor
  1. Pterygoid hamulus
  2. Pterygomandibular raphe
  3. Medial surface of mandible at the posterior end of mylohyoid line
  4. Side of posterior part of tongue
  1. Pharyngeal tubercle on base of skull
  2. Median fibrous raphe
Middle constrictor
  1. Lower part of stylohyoid ligament
  2. Lesser cornua of hyoid bone
  3. Upper border of greater cornua of hyoid bone
 Median fibrous raphe
Inferior constrictor – Thyropharyngeus
  1. Oblique line on lamina of thyroid cartilage
  2. Tendinous band between inferior tubercle of thyroid cartilage and cricoid cartilage
 Median fibrous raphe
Inferior constrictor – Cricopharyngeus Cricoid cartilage Median fibrous raphe
09

Longitudinal Muscle Coat

The pharynx has three muscles that run longitudinally:

  1. Stylopharyngeus
  2. Palatopharyngeus
  3. Salpingopharyngeus.

Longitudinal Muscles of Pharynx

Muscle Origin Insertion Nerve Supply
Stylopharyngeus Styloid process Posterior border of lamina of thyroid cartilage Glossopharyngeal nerve
Palatopharyngeus Arises by two fasciculi (anterior and posterior) from upper surface of palatine aponeurosis Posterior border of lamina of thyroid cartilage; few fibres run posteriorly to form Passavant’s ridge Cranial root of 11th cranial nerve
Salpingopharyngeus Lower part of cartilage of auditory tube Posterior border of lamina of thyroid cartilage Cranial root of 11th cranial nerve

Action of Longitudinal Muscles

  • Elevate the larynx.
  • Shorten the pharynx during deglutition.
  • All these muscles are inserted on the posterior border of the lamina of thyroid cartilage.
  • These muscles elevate the larynx and shorten the pharynx during swallowing.
10

Structures Between Pharyngeal Muscles

Gap Between Superior Constrictor and Base of Skull

  • The large gap between the upper concave border of the superior constrictor and the base of the skull is semilunar.
  • It is known as the sinus of Morgagni.
  • It is closed by the upper strong part of the pharyngobasilar fascia.

Structures Passing Through This Gap

  1. Auditory tube
  2. Levator veli palatini muscle
  3. Ascending palatine artery
  4. Palatine branch of ascending pharyngeal artery.

Gap Between Superior and Middle Constrictors

Structures passing through:

  1. Stylopharyngeus muscle
  2. Glossopharyngeal nerve

Gap Between Middle and Inferior Constrictors

Structures passing through:

  1. Internal laryngeal nerve
  2. Superior laryngeal vessels

Gap Between Lower Border of Inferior Constrictor and Oesophagus

Structures passing through:

  1. Recurrent laryngeal nerve
  2. Inferior laryngeal vessels.
11

Nerve Supply of Pharynx

  • Pharynx is supplied by the pharyngeal plexus of nerves.
  • The plexus lies chiefly on the middle constrictor.

Formation of Pharyngeal Plexus

1. Pharyngeal Branch of Vagus

Carries fibres of the cranial accessory nerve.

2. Pharyngeal Branches of Glossopharyngeal Nerve

3. Pharyngeal Branches of Superior Cervical Sympathetic Ganglion

Motor Fibres

  • Derived from the cranial accessory nerve through the branches of the vagus.
  • Supply all muscles of the pharynx except stylopharyngeus.
  • Stylopharyngeus is supplied by the glossopharyngeal nerve.
  • Inferior constrictor receives additional supply from:
    • External laryngeal nerve
    • Recurrent laryngeal nerve

Sensory Fibres

  • Sensory fibres / general visceral afferent from the pharynx travel mostly through the glossopharyngeal nerve and partly through the vagus.
  • Nasopharynx is supplied by the maxillary nerve through the pterygopalatine ganglion.
  • Soft palate and tonsil are supplied by:
    • Lesser palatine nerves
    • Glossopharyngeal nerve

Taste Sensation

  • Taste sensations from the vallecula and epiglottic area pass through the internal laryngeal branch of the vagus.

Parasympathetic Secretomotor Fibres

  • Parasympathetic secretomotor fibres to the pharynx are derived from the lesser palatine branches of the pterygopalatine ganglion.
12

Blood Supply of Pharynx

Arterial Supply

The pharynx is supplied by:

  1. Ascending pharyngeal branch of external carotid artery
  2. Ascending palatine and tonsillar branches of facial artery
  3. Dorsal lingual branches of lingual artery
  4. Greater palatine, pharyngeal and pterygoid branches of maxillary artery.

Veins

  • Veins form a plexus on the posterolateral aspect of the pharynx.
  • The plexus receives blood from:
    • Pharynx
    • Soft palate
    • Prevertebral region
  • It drains into:
    • Internal jugular veins
    • Facial veins.
13

Lymphatic Drainage of Pharynx

Lymph from the pharynx drains into:

  • Retropharyngeal lymph nodes
  • Deep cervical lymph nodes.
Pharynx — Study Notes