Download THE PHARYNX

THE PHARYNX
By
Prof. Dr. Muhammad Imran Qureshi
Introduction
 The pharynx is the most cranial end of the foregut.
 It extends from the base of the skull down to the
lower border of the cricoid cartilage (C6), where it
continues into the esophagus.
 The internal structure of the pharynx is much like that
of the rest of the gut.



It is lined by a mucous membrane,
has an intermediate muscle layer, and
has an external fibrous layer called tunica fibrosa.

The tunica fibrosa of the pharynx is more often referred
to as Buccopharyngeal membrane or fascia.
Introduction
 However, some differences do exist between the pharynx
and the rest of the gut.
 One of them is the absence of a well defined submucosal
layer except in the region immediately inferior to the skull
base.


Here, a submucosal layer is developed at this site because
here, both side walls of pharynx are devoid of muscle.
This limited submucosal layer of the pharynx is called
pharyngobasilar fascia.
 A second difference is that in the pharynx, the muscle is
striated (not smooth) and is derived from somites
associated with the vagus nerve.
 Finally, at the sites where the embryonic nasal and oral
cavities ruptured into the pharynx, this gut tube misses an
anterior wall.
Introduction
 Posteriorly, both pharynx and oesophagus are in
contact with the prevertebral fascia, which provides a
foundation or basis upon which they can freely slide
during swallowing and movements of the neck.
 The “dead space” between the pharynx and the
prevertebral fascia not only allows for free mobility of
the pharynx and oesophagus, but also permits the
extension of infection from one side of the neck to the
other . It continues below into the posterior
mediastinum.
The Pharyngobasilar Fascia
 Since the muscle does not
extend up to the base of
the skull; here the immobile
wall of the nasopharynx
consists of a rigid
membrane, the
Pharyngobasilar fascia.
 This is simply a dense
thickening of the
submucosa that fills in the
gap between the skull and
the upper border of the
superior constrictor.
The Pharyngobasilar Fascia
 The thickening can be
traced down to the level of
the soft palate, making a
fourth but fibrous cup
stacked inside the other
three.
 Its stiffness keeps the
nasopharynx always open
for breathing, and food
does not enter it.
 We can trace the
attachments of this fascia
as follows:
The Pharyngobasilar Fascia
 Start from the pharyngeal tubercle,
which is a midline thickening. The
pharyngeal raphe is attached to it,
which receives fibres from the
constrictor muscles.
 The attachment of the fascia then
passes laterally, convex forwards
over longus capitis and the back part
of the foramen lacerum to the
petrous part of the temporal bone
just in front of the carotid foramen.
 From this point its attachment is to
the cartilaginous part of the auditory
tube, not to the skull.
 Below the orifice of the auditory tube
it is attached to the sharp posterior
border of the medial pterygoid plate,
down to the hamulus.
The Pharyngobasilar Fascia
 Suspended from the base of the
skull, and sweeping around from
one medial pterygoid plate to the
other, reinforced posteriorly by the
pharyngeal raphe, the
pharyngobasilar fascia makes a
rigid wall that holds the
nasopharynx permanently open for
breathing.
 The lower edge of the
pharyngobasilar fascia lies at the
site of Passavant's ridge, level with
the hard palate, inside the superior
constrictor muscle.
 The ridge acts like a purse string on
the lower free margin of the
pharyngobasilar fascia.
 Below this the mucous membrane
lies on a loose submucosa.
Divisions

1.
Anatomists divide the pharynx into three regions.
The uppermost region lies between the base of the
skull and the palate. Because it opens up into the
nasal cavities, it is called the nasopharynx. The
nasopharynx has no anterior wall

2.
One may consider the back edge of the nasal
septum as all that is left of an anterior wall after the
nasal cavities rupture into the pharynx during
development.
Below the palate and above the epiglottis is a
region of pharynx that opens forward into the oral
cavity. The palatoglossal arches mark the boundary
between this oropharynx and the oral cavity.
Divisions
Divisions


Due to the oblique disposition of
the epiglottis, the oropharynx is
taller in front than in back. Like the
nasopharynx, the oropharynx has
not much of an anterior wall.
However, it must be remembered
that the dorsum of tongue is a
curved structure. Its anterior two
thirds faces superiorly, but its
posterior one third faces backward.
Thus, just above the hyoid bone,
the oropharynx has an anterior wall
composed of the posterior third of
the tongue.
Divisions
3. Below the oropharynx is the laryngopharynx.
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In embryonic life the laryngotracheal diverticulum
formed as an outpocketing of the anterior wall of the
foregut at the lower end of the pharynx.
The opening into this laryngotracheal diverticulum
was the primitive laryngeal aperture.
The diverticulum grew downward into the chest,
hugging the anterior wall of the esophagus along the
way.
The cranial part of the laryngotracheal diverticulum
becomes the larynx.
Divisions

During its development, “the
larynx” pushes backward
and upward into the lower
part of the pharynx, raising
the laryngeal aperture so
that it lies behind and partly
above the hyoid bone, and
causing the anterior wall of
the lower pharynx to curve
around the sides of the
larynx (hence the pyriform
recesses).
Divisions
Nasopharynx
Oropharynx
Laryngopharynx
Pharyngeal Muscles

The Pharyngeal muscles comprise of:
1. The Constrictors:

1.
2.
3.
The lateral and posterior walls of the pharynx are
composed primarily of the three pharyngeal
constrictor muscles:
Superior Constrictor,
Middle Constrictor, and
Inferior Constrictor.
Pharyngeal Muscles
2.
Supplementing small muscles:
1.
2.
3.
Stylopharyngeus,
Palatopharyngeus, and
Salpingopharyngeus
Attachments of Pharyngeal Muscles
 Let us revise some of the osteology
before the study of the superior,
middle, and inferior constrictor
muscles.
 The diagram shows a few relevant
features of the inferior aspect of the
skull as seen from the side.
 Identify the mastoid process (MP),
zygomatic arch (ZA), external
auditory meatus (EAM), lateral
pterygoid lamina (LPL), medial
pterygoid lamina (MPL) (visualized
through LPL), pterygoid hamulus
(PH) (literally "a little hook", of the
MPL).
Attachments of Pharyngeal Muscles
 Identify also the styloid process (SP),
hyoid bone with its body (B), lesser
horn (LH), and greater horn (GH),
The thyroid cartilage (T) has a
superior horn (SH), an inferior horn
(IH), and an oblique line (OL) on
each lamina. The inferior horn
articulates with the lamina of the
cricoid (ring like) cartilage (CC) to
form the cricothyroid joint (CTJ).
 Before introducing fibrous connective
tissue structures, identify the
pterygopalatine fossa (PF) and the
posterior wall of the maxillary sinus
(PWMS) which forms the anterior
wall of the pterygopalatine fossa
(PF).
Attachments of Pharyngeal Muscles

There are four connective
tissue structures of significance
to understanding the three
constrictors:
1.
2.
3.
4.
The pterygomandibular ligament
(PL);
The stylohyoid ligament (SL);
The pharyngeal raphe (PR);
A tendinous arch (TA) extending
between the inferior tubercle on
the oblique line of the thyroid
cartilage and the arch of the
cricoid cartilage.
Attachments of Pharyngeal Muscles
 The Pterygomandibular ligament
(PL) is attached to the pterygoid
hamulus (PH) of the medial
pterygoid lamina and to the
posterior end of the mylohyoid
line (ML) of the mandible.
 Although the mylohyoid line is on
the medial side of the mandible it
is superimposed on the lateral
view of the bone as though the
bone were transparent.
 Two muscles are intimately
related to this pterygomandibular
ligament:


The Superior Constrictor and
The Buccinator.
Attachments of Pharyngeal Muscles
 The stylohyoid ligament
(SL) extends from the tip
of the styloid process to
the lesser horn of the
hyoid bone.
 With the greater horn of
the hyoid bone, the
stylohyoid ligament and
lesser horn form an osseotendinous angle from
which arises the middle
constrictor muscle.
Attachments of Pharyngeal Muscles
 The pharyngeal raphe
drops vertically from the
pharyngeal tubercle on the
basiocciput of the skull
base.
 All three constrictors
attach to the raphe.
Attachments of Pharyngeal Muscles
 The oblique line, the
tubercle at its inferior end
and the tendinous arch (TA)
between the inferior
tubercle of the oblique line
and the cricoid cartilage
serve as attachments for
the inferior constrictor
muscle of the pharynx.
Attachments of Pharyngeal Muscles
 The tendinous arch (TA)
bridges across one of the
intrinsic muscles of the larynx,
the cricothyroid.
 Contraction of the cricothyroid
approximates the anterior
portion of the two cartilages
and tenses the vocal cords.
Movement occurs at the
cricothyroid joint (CTJ) on each
side.
Attachments of Pharyngeal Muscles
 All of the skeletal elements to which the constrictor
muscles are attached (e.g., mandible, hyoid bone,
thyroid cartilage) are open posteriorly except the
cricoid cartilage.
 The portion of the inferior constrictor which is
attached to the tendinous arch is called the
cricopharyngeus muscle.
 If it goes into spasm, swallowing can be difficult or
impossible because it applies lateral pressure
against the posterior surface of the cricoid
cartilage and closes this part of the pharynx.
Attachments of Pharyngeal Muscles
 The arrangement of the
three pairs of constrictor
muscles of the pharynx are
likened to three flower pots
fitted one inside the other.
OR
 These muscles overlap
posteriorly, being
telescoped into each other
like three stacked cups
Attachments of Superior Constrictor
 The anterior attachment (origin) of
the Superior Constrictor is to the
lower part of the posterior edge of
the medial pterygoid lamina, the
pterygoid hamulus,
pterygomandibular ligament, and
posterior end of the mylohyoid line
(ML).
 From these origins the fibers pass
posteriorly to their insertion into
the pharyngeal tubercle (PT) and
raphe (PR).
Attachments of Middle Constrictor
 The anterior attachment (origin)
of the Middle Constrictor is to
the stylohyoid ligament, the
lesser horn, and the greater
horn of the hyoid bone, where
these three structures meet to
form an acute angle.
 From this attachment they pass
posteriorly to insert into the
pharyngeal raphe.
Attachments of Inferior Constrictor
 Anteriorly the Inferior Constrictor
arises from the oblique line of the
thyroid cartilage and the
tendinous arch between the
inferior tubercle of the oblique line
and the cricoid cartilage (this
arches over the cricothyroid
muscle).


The part of the Inferior Constrictor
attaching to the tendinous arch is
called the Cricopharyngeus
muscle.
Spasm of these fibers can cause
great difficulty in swallowing
because the cricoid cartilage is a
complete ring.
Gaps between the Constrictors
 There is a space between the upper
border of the superior constrictor and
the base of the skull. Through here
passes the cartilaginous part of the
auditory tube, the tensor & levator veli
palitini muscles and tonsillar branch of
ascending pharyngeal artery. The rest
of the space is closed by the firm
pharyngobasilar fascia.
 There is a gap laterally between the
superior and middle constrictors. This
is plugged by the back of the tongue
and traversed by structures that pass
from outside the pharynx to inside the
mouth, namely stylopharyngeus, the
glossopharyngeal nerve and the lingual
nerve.
Gaps between the Constrictors
 The gap between the middle
and inferior constrictors is
closed by the thyrohyoid
membrane, which joins the
hyoid bone to the thyroid
cartilage and walls in the
laryngeal part of the pharynx
at the piriform recess.
 Passing through this gap by
piercing the membrane are
the internal laryngeal nerve
and superior laryngeal
vessels.
Outer Surface of the Pharynx
 The outer surface of the pharynx is covered by the
delicate epimysium of the pharyngeal constrictors.
 This thin tissue is continuous over the pterygomandibular
raphe with the epimysium over buccinator, so it has been
called the buccopharyngeal fascia.
 The junction between thyropharyngeus and
cricopharyngeus near the midline is a potentially weak
area of the pharyngeal wall, and through this area
(Killian's dehiscence) a pouch of mucosa may become
protruded (pharyngeal diverticulum).
 As it enlarges the pouch hangs down at the side of the
oesophagus, and although it may be called an
“oesophageal” diverticulum the origin is above the
cricopharyngeus.
Lesser Pharyngeal Muscles
 These are the Stylopharyngeus, Palatopharyngeus,
Salpingopharyngeus.
 These three small pharyngeal muscles have common
insertions. Their fibers run more or less longitudinally.
1. The Stylopharyngeus: It is the biggest of all the
three. It arises from the medial surface of the styloid
process (i.e., that surface closest to the pharynx).
The fibers pass medially and downward to contact
the external surface of the lower fibers of the
superior constrictor. The stylopharyngeus then slips
deep to the upper border of the middle constrictor
and continues deep to it and then to the inferior
constrictor all the way to an insertion on the
posterior border of the thyroid lamina and the actual
connective tissue of the pharyngeal wall.
Lesser Pharyngeal Muscles
Lesser Pharyngeal Muscles
2. The palatopharyngeus: It arises from the
connective tissue of the soft palate and descends
almost straight vertically deep to the superior
constrictor (thus, separated by it from the
stylopharyngeus). At the lower border of the superior
constrictor, the palatopharyngeus and
stylopharyngeus meet and pass together to a
common insertion.
3. The salpingopharyngeus: It arises from the medial
end of the cartilaginous auditory tube and descends
almost straight vertically deep to the superior
constrictor to contact the back edge of the
palatopharyngeus and pass with it to join the
stylopharyngeus.
Function of Pharyngeal Muscles
 The pharyngeal muscles play role in swallowing.
 The constrictors are activated in sequence, from top
to bottom, to propel food toward the esophagus.
 The longitudinal muscles elevate the larynx and
pharynx at the initiation of the swallow.
Blood Supply and Lymph Drainage
 Branches of many arteries take blood to the pharynx:
Ascending pharyngeal, ascending palatine, lingual,
tonsillar, greater palatine, the artery of the pterygoid
canal, and the superior and inferior laryngeal arteries.
 Venous blood is largely collected into the pharyngeal
venous plexus which like the nerve plexus is situated
at the back of the middle constrictor; it drains to the
pterygoid plexus or directly into the internal jugular
vein. From the lowest part blood finds its way to the
inferior thyroid veins.
 Lymph drainage
 Lymph passes to retropharyngeal lymph nodes and via
these or directly to upper and lower deep cervical
groups.

Nerve Supply
 For the motor nerve supply of the pharynx the
general statement is that all the muscles are supplied
by the pharyngeal plexus except for stylopharyngeus,
which is the only muscle supplied by the
glossopharyngeal nerve.
 The cricopharyngeus part of the inferior constrictor
may be supplied by the recurrent laryngeal nerve,
or have an additional or even sole supply from the
external laryngeal.
 The cell bodies that supply all six muscles on each
side are in the middle part of the nucleus
ambiguus, no matter by what named nerves they
reach their destination.
Nerve Supply
 The pharyngeal plexus lies on the posterolateral wall
of the pharynx, mainly over the middle constrictor,
and is formed by the union of pharyngeal branches
from the vagus and glossopharyngeal nerves and the
cervical sympathetic.
 The glossopharyngeal component is purely afferent;
 The pharyngeal fibres of the vagus carry some motor
fibres from the cranial part of the accessory nerve as
well as afferent fibres.
 The sympathetic element is vasoconstrictor.
Nerve Supply
 The mucosa of the nasopharynx is supplied from the
maxillary nerve through the pterygopalatine ganglion,
whose pharyngeal branch reaches the nasopharynx
via the palatovaginal canal.
 Most of the oropharynx receives its sensory supply
from the glossopharyngeal nerve, but the vallecula is
supplied by the internal laryngeal nerve, and all the
rest of the pharyngeal mucosa is innervated by the
internal and recurrent laryngeal nerves.