VMED 5127 Developmental Anatomy and Histology The Pharyngeal Apparatus

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VMED 5127
Developmental Anatomy and Histology
The
Pharyngeal Apparatus Dr. Fakhri Al-Bagdadi
Comparative Biomedical Sciences
College of Veterinary Medicine, LSU Baton Rouge
LA.
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Objectives 1-Discuss the structures of the
branchial apparatus. 2-List the
adult derivatives of the pharyngeal pouches and
branchial grooves.
3-List the
cranial nerves and the skeletal muscle groups
that differentiate from each branchial arch
apparatus.

4-Describe briefly the formation of the facial
features. 5-Understand the formation of the
tongue and thyroid gland.

6-Understand the
malformations presented in the class. Resources M
oore and Persaud.
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The designation branchial apparatus. Branchial
is derived from the Greek word branchia,
gill. I-The pharyngeal apparatus consists of A.
pharyngeal arches B. pharyngeal pouches C.
pharyngeal grooves D. pharyngeal membranes
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Pharyngeal Arches. Second arch growing over the
third and fourth arch
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• Pharyngeal Arches
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  A. Neural
  crest cells migrate into future head and neck.
  
  1.Fifth and
  sixth arches are not visible .
  
  2. Pharyngeal grooves
  separate the pharyngeal arches.
  
  B. First pharyngeal
  arch (mandibular arch) provide two prominences
  
  1.
  Maxillary prominence, provide the maxilla (upper
  jaw).
  2. Mandibular
  prominence forms the mandible (lower jaw).
  
  
  
  

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Guttural Pouch of the Horse originates from the
first Pharyngeal arch
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C. Second pharyngeal arch (hyoid arch).


1. Contributes to hyoid bone formation.

2. Stomodeum, primordial mouth appears as a
depression.

a.
Separated from the primordial pharynx by the
oropharyngeal membrane.

b. Rupturing
the oropharyngeal membrane communicate the
primordial pharynx and the foregut with the
amniotic cavity.
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D. Pharyngeal Arch Components

1.Each consists, of mesenchyme, ectoderm and
endoderm.
2.The mesenchyme
is derived from migrating neural crest cells,
which produce maxillary mandibular prominences.

3. Arches
mesenchyme provides the skeletal musculature and
vascular endothelia.
4.
Fate of Pharyngeal Arches

a. They contribute to the formation of the
1) face, nasal
cavities,
2) mouth, larynx,


3) pharynx, and neck.


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E. Typical pharyngeal arch contains
1.Aortic arch, an artery that
arises from the truncus arteriosus of the
primordial heart to enter the dorsal aorta

2.A cartilaginous rod, forms the
skeleton of the arch

3. Muscular component gives the muscles in
the head and neck

4. Nerve, supplies the mucosa and muscles
derived from the arch

5.Nerves of the arches are derived from
the neuroectoderm of the primordial brain.
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Ectoderm
Pharyngeal Pouches and Aortic Arch
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Cranial region of developing embryo 1.Arch
components and floor of primordial pharynx
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F. Derivatives of Pharyngeal Arch Cartilages
1. Form the primordium
of the mandible.
2. The first arch cartilage ( Mickel
cartilage) ossify to form ear bones, malleus and
incus. 3.The
second arch cartilage (Reichert cartilage) form
the stapes and the styloid process of the
temporal bone. 4.The third arch cartilage form
the greater cornu and part of the body of the
hyoid bone. 5. The fourth and sixth arch
cartilages fuse to form the laryngeal
cartilages. 6.The cartilage of the epiglottis
develops from mesenchyme in the hypopharyngeal
eminence.
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Cartilage location of Pharyngeal arches
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G. Derivatives of Pharyngeal Arch Muscles
1.First pharyngeal
arch muscle forms the muscles of mastication and
others. 2. The
second pharyngeal arch forms the belly of
digastric and facial expression muscles.
3.The third pharyngeal arch forms the
stylopharyngeus muscle.
3.The musculature of
the fourth pharyngeal arch forms the
cricothyroid, levator veli palatini, and
constrictors of the pharynx.

4.The musculature of the
sixth pharyngeal arch forms the intrinsic muscles
of the larynx.
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Arch Nerve Muscles Skeletal structures ligaments
First (mandibular) Trigeminal (CN V) Muscles of mastication Mylohyoid and anterior belly of digastric Tensor tympani Tensor veli palatini Malleus Incus Anterior ligament of malleus Sphenoma-ndibular ligament
Second (hyoid) Facial (CN VII) Muscles of facial expression Stapedius Stylohyoid Posterior belly of digastric Stapes Styloid process Lesser cornu of hyoid Upper part of body of hyoid bone Stylohyoid ligament
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Arch Nerve Muscles Skeletal Structures
Third Glossopharyngeal (CN IX) Stylopharyngeus Greater cornu of hyoid Lower part of body of hyoid bone
Fourth and Sixth Cranial laryngeal branch of vagus (CN X) Recurrent laryngeal branch of vagus (CN X) Cricothyroid Levator veli palatini Constrictors of pharynx Intrinsic muscles of larynx Striated muscles of esophagus Thyroid cartilage Cricoid cartilage Arytenoid cartilage Corniculate cartilage Cuneiform cartilage
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H. Derivatives of Pharyngeal Arch Nerves 1. Each
arch is supplied by a cranial nerve (CN).
2. The facial skin is supplied by the
trigeminal nerve (CN V). 3. The second is
supplied by seventh cranial nerve the facial
nerve (CN VII),
4. The
third is supplied by the ninth cranial nerve
the glossopharyngeal nerve (CN IX),
5. The
fourth is by the vagus nerve (CN X)
6.The
fourth arch is supplied by the superior laryngeal
branch of the vagus (CN X)

7. The sixth arch is
supplied by its recurrent laryngeal nerve. 8. The
nerves of the second to sixth pharyngeal arches
innervate the mucous membranes of the tongue,
pharynx, and larynx.
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I. Pharyngeal Pouches
1.The first pair lies
between the first and second. 2.There are four
pairs of pharyngeal pouches

3. The fifth pair is absent or
rudimentary.
A. The First Pharyngeal Pouch Contributes to the
formation of the tympanic membrane. B. The Second
Pharyngeal Pouch 1. Its endoderm forms the lining
of the tonsillar crypts. C. The Third Pharyngeal
Pouch 1. Forms the inferior parathyroid gland.

2. Thymus which descends into
mediastinum
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D. The Fourth Pharyngeal Pouch
1. Develops the
cranial parathyroid gland.
2. Caudal parathyroid
glands derived from 3rd pouch.

3. Develops the
ultimopharyngeal body.
4. Gives rise to
parafollicular cells, (C cells).
5. C cells
differentiate from neural crest cells in the
fourth pouches.

E. The Fifth Pharyngeal Pouch
1.
Rudimentary pouch participate in the formation of
the ultimopharyngeal body.


F. Pharyngeal Grooves

1. The head and neck has four pharyngeal grooves
on each side.

2. Pharyngeal Membranes

a. First pharyngeal membrane becomes
the tympanic membrane
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Pharyngeal pouches adult derivatives and descent
of the Thyroid gland
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VI. Development of Thyroid Gland 1. First
endocrine gland to develop in the embryo.
2. Pharynx
floor provides thyroid primordiums.

3. They Descends into the
neck.
4. Are connected to
the tongue by thyroglossal duct.
5. The thyroids isthmus
lies ventral to the tracheal rings.
6. Thyroglossal duct normally
disappears.
7.
The opening of the thyroglossal duct persists as
foramen cecum in the tongue.

A. Thyroglossal duct
remnant form Cysts and Sinuses


1. In the tongue

2.
In the neck inferior to the hyoid bone.
B. The cyst may contain some
thyroid tissue.
1. Infected cyst perforate
the skin forming thyroglossal duct sinus.
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Development of the thyroid
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Development of the Thyroid
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C. Ectopic Thyroid Gland
1. Lingual thyroid
tissue is the most common
2. Sublingual thyroid
gland.
3. Accessory
Thyroid Tissue
4. Accessory thyroid tissue may
appear in the thymus.

5. It may be functional based on the size
6.
Accessory thyroid tissue originates from
thyroglossal duct.
7. Agenesis
of thyroid Gland
8. Absence of the
thyroid gland, or one lobe, thyroid unilateral
failure of formation, one lobe is absent.
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Sites of Ectopic thyroid tissue. Broken lines,
normal path of thyroid descent
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V. The Tongue
A.
Development

1. A median bud develops rostral to
foramen cecum.

2. Two lateral tongue
swellings develop on each side of the median
tongue bud.
3.
The buds merge and overgrow.

4. Fusion of
the tongue buds is indicated by the median
sulcus of the tongue and internally by the
fibrous lingual septum.

5.The tongue muscles are derived
from the occipital myotomes.

6. The hypoglossal nerve (CN
XII) accompanies the myoblasts and innervates all
the tongue muscles
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Copula connecting part or structure
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B. Nerve Supply of Tongue 1. Sensory supply from
the lingual branch of the mandibular division of
the trigeminal nerve (CN V).

2. The facial nerve supplies the taste buds ,
except for the vallate papillae.

3.The facial
nerve supply the taste buds in the oral part of
the tongue.

4.The vallate papillae are innervated by
the glossopharyngeal nerve (CN IX).

5.The
posterior third of the tongue is innervated by
the glossopharyngeal nerve.

6. Laryngeal branch of the vagus nerve (CN X)
supply the tongue anterior to the epiglottis.

7.The muscles of the
tongue are supplied by the hypoglossal nerve (CN
XII), except for the palatoglossus ,is supplied
by fibers from the vagus nerve (CN X).
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• C. Congenital malformation of the tongue
• 1.Lingual Cysts and Fistulas
• a. Remnants of the thyroglossal duct.
  (difficulty in swallowing).
• b.Fistulas are derived of the thyroglossal duct
  they open
• through the foramen cecum into the oral cavity.
• 2. Ankyloglossia (tied tongue)
• Short lingual frenlum at the ventral surface of
  the tongue.
• b. Make breast nursing difficult. (Frenulum
  mucosal fold)
• 3.Macroglossia
• a. Excessively large tongue.
• b. Due to muscular hypertrophy.
• 4.Microglossia
• a. Abnormally small tongue
• 5. Bifid or Cleft Tongue (Glossoschisis)
• Incomplete fusion of the tongue buds
• Results in a deep median groove.

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• Face Development
  A. Five facial
  prominences around the Stomodeum
• 1. Single frontonasal prominence
• 2. Paired maxillary prominences
• 3. Paired mandibular prominences
• B. Nasal placodes
• 1. Primordia of the nose and nasal cavities.
• 2. Lie in the nasal pits.
• 3. Each is separated from the maxillary
  prominence by nasolacrimal groove.
• 5. Nasolacrimal groove gives nasaolacrimal duct.
  
  6. Its end
  form the lacrimal sac.
  
  C.Intermaxiallary segment which give rise to,
• 1. Philtrum of the upper lip

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Facial development 1.The FNP forms the forehead
and the dorsal and apex of the nose 2.The lateral
nasal prominences form the sides of the
nose 3.Nasal septum is made by nasal prominences

4.The maxillary
prominences form the upper cheek regions and most
of the upper lip 5.The mandibular prominences
give rise to the chin, lower lip, and lower cheek
regions. 6.The upper lip is formed entirely from
the maxillary prominences.
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Frontal Prominence
Maxillary
Mandibular
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Malformation 1.Clefts involving the upper
lip 2.Unilateral cleft lip result from failure of
the maxillary prominence to unite with the medial
nasal prominences.
3.This results with the
lip divided into medial and lateral
parts. 4.Bilateral cleft lip due to failure of
maxillary prominences to meet and unite with the
medial nasal prominences.
5. Cleft palate
leaves the nasal and oral cavities connected.

This causes nursing problem for the new
born.
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Bilateral Facial clefts and bilateral cleft lip
Cleft Upper lip
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Palatogenesis Formation of primary and secondary
palate
Primary palate is formed
Secondary palate is formed