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Oral Biology > The Pharyngeal Apparatus > Flashcards

The Pharyngeal Apparatus Flashcards

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1
Q

Lateral view of an embryo: What are the 3 bulges next to the Frontal prominence?

A

The 3 pharyngeal arches

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2
Q

What’s the origin of the neural crest cells?

A
  • Neuroectoderm (1st stem in nervous system development = brain and spinal cord)

Neurulation process: Neural crest cells delaminate from overlying ectoderm and migrate to the peripheries and pharnygeal arches

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3
Q

What are the derivatives or Neural crests?

A
  • CT and bones of the face and skull
  • Cranial nerve ganglia
  • C Cells of the thyroid gland
  • Odontoblasts
  • Dermis in face and neck
  • Spinal (dorsal root) ganglia
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4
Q

What’s a Pharyngeal Apparatus?

A

Consists of paired:

  • Pharyngeal arches
  • Pharyngeal pouches
  • Pharyngeal grooves
  • Pharyngeal membranes
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5
Q
  • What’s a Pharyngeal arch?
A
  • Series of externally visible anterior tissue bands lying under the early brain (1/2/3/4/6)

Each arch has:

  • A mesenchymal core (mesoderm & neural crest)
  • A membrane (endoderm and ectoderm)
  • External cleft (ectoderm)
  • Mesenchymal core contains: Blood vessel/nerve/muscular cells/cartilage
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6
Q

What are the cranial nerves associated with the pharyngeal arch?

A

Arch 1: CN V (Trigeminal)
Arch 2: CN VII (Facial)
Arch 3: CN IX (glossopharyngeal)
Arch 4: CN X (Superior laryngeal branch of vagus)
Arch 6: (Recurrent laryngeal branch of vagus)

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7
Q

At the start of embryonic development, how many arches are there?

A

6

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8
Q

What happens to the 5th arch?

A
  • Regresses soon after forming
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9
Q

What happens to the 1st Pharyngeal arch (mandibular arch)?

A
  • Associated with the 1st aortic arch; develops into part of the maxillary artery
  • Innervated by the TRIGEMINAL NERVE (CN V)
  • Splits into an upper MAXILLARY PROMINENCE and a lower MANDIBULAR PROMINENCE
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10
Q

What are the derivatives of the 1st arch (somitomeric mesoderm)?

A

Somitomeric mesoderm:

  • Artery: Terminal portion of the Maxillary artery (branch of the external carotid)
  • Muscle (Max. prom):
    + None
- Muscle (Mand. prom):
\+ Muscles of mastication
\+ Mylohyoid
\+ Ant belly of digastric
\+ Tensor veli palatini
\+ Tensor tympani
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11
Q

What are the derivatives of the 1st arch (Neural Crest)?

A

Neural Crest:

Bone or Cartilage:
- Maxillary Prom (dorsal portion):
\+ Maxilla
\+ Zygomatic bone
\+ Squamous temporal bone
\+ Palatine bone
\+ Vomer
- Mandibular Prom (ventral portion):
\+ Mandible
\+ Incus
\+ Malleus
\+ Associated with Meckel's cartilage
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12
Q

What happens to the 2nd Pharyngeal arch (hyoid arch)?

A
  • Associated with the 2nd aortic arch; develops into the STAPEDIAL ARTERY
  • Innervated by FACIAL NERVE (CN VII)
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13
Q

What are the derivatives of the 2nd arch (somitomeric mesoderm)?

A

Somitomeric Mesoderm:

  • Artery:
    + Stapedial artery
    + Hyoid artery
- Muscles:
\+ Muscles of facial expression
\+ Posterior belly of digastric
\+ Stylohyoid muscle
\+ Stapedius
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14
Q

What are the derivatives of the 2nd arch (Neural Crest)?

A

Neural Crest:

- Bone or Cartilage (Reichert's)/:
\+ Lesser horn of hyoid
\+ Upper half of body of hyoid
\+ Stapes
\+ Styloid process
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15
Q

What happens to the 3rd Pharyngeal arch?

A
  • Associated with aortic arch 3 which contributes to the COMMON CAROTID ARTERY and PROXIMAL SEGMENT OF INTERNAL CAROTID ARTERY
  • Innervated by Glossopharyngeal nerve (CN IX)
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16
Q

What are the derivatives of the 3rd arch (somitomeric mesoderm)?

A

Somitomeric mesoderm:

Artery:

  • Common carotid
  • Proximal interal carotid

Muscle:
- Stylopharyngeus

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17
Q

What are the derivatives of the 3rd arch (Neural Crest)?

A

Neural Crest:

Bone or Cartilage:

  • Greater horn of hyoid
  • Lower half of body of hyoid
18
Q

What happens to the 4th Pharyngeal arch?

A
  • Associated with aortic arch 4; contributes to PROXIMAL SEGMENT OF RIGHT SUBCLAVIAN ARTERY and ARCH OF AORTA
  • Innervated by SUPERIOR LARYNGEAL BRANCH OF VAGUS NERVE
19
Q

What are the derivatives of the 4th arch (somitomeric mesoderm)?

A

Somitomeric mesoderm:

Artery:

  • Proximal right subclavian
  • Arch of aorta

Muscle:

  • Muscles of soft palate (except tensor veli palatini)
  • Muscles of the pharynx (except stylopharyngeus)
  • Cricothyroid
  • Cricopharyngeus
20
Q

What are the derivatives of the 4th arch (Neural Crest)?

A

Neural Cest:

Bone or cartilage:

  • Thyroid cartilage
  • Cricoid cartilage
  • Arytenoid cartilage
  • Corniculate cartilage
  • Cuneiform cartilage

(4th and 6th arches contribute to these Laryngeal cartilages)

21
Q

What happens to the 6th Pharyngeal arch?

A
  • Associated with aortic arch 6; contributes to proximal segments of pulmonary arteries & ductus arteriosus (becomes ligamentum arteriosum)
  • Innervated by RECURRENT LARYNGEAL BRANCH OF VAGUS NERVE
22
Q

What are the derivatives of the 6th arch (somitomeric mesoderm)?

A

Somitomeric mesoderm:

Artery:

  • Ductus arteriosus
  • Proximal pulmonaries

Muscles:

  • Intrinsic laryngeal muscles (EXCEPT CRICOTHYROID)
  • Skeletal muscle of esophagus
23
Q

What are the derivatives of the 6th arch (Neural Crest)?

A

Neural Crests:

Bone or Cartilage:

  • Thyroid cartilage
  • Cricoid cartilage
  • Arytenoid cartilage
  • Corniculate cartilage
  • Cuneiform cartilage

(4th and 6th arches contribute to these Laryngeal cartilages)

24
Q

What are the Pharyngeal pouches?

A
  • Endodermal-lined pockets that form on the inside of the pharynx between the arches
25
Q

What happens to the 1st Pharyngeal Pouch?

A
  • Develops into the AUDITORY TUBE & MIDDLE EAR CAVITY
  • Expands to form the Tubotympanic recess = tympanic cavity + auditory tube & mastoid antrum
  • Comes into contact with the 1st groove which forms the EXTERNAL AUDITORY MEATUS
26
Q

What happens to the 2nd Pharyngeal Pouch?

A
  • Epithelial lining of the pouch invade the surrounding mesenchyme; forming numerous infoldings that become the CRYPTS OF THE PALATINE TONSIL (PREMORDIUM OF THE PALATINE TONSIL)
  • Later, lymphocytes infiltrate the underlying lamina propria to establish the definitive PALATINE TONSIL
  • Part of the pouch remains as TONSILLAR SINUS OR FOSSA
27
Q

What happens to the 3rd Pharyngeal Pouch?

A
  • Divides into a superior (DORSAL) and inferior (VENTRAL) portion

Dorsal:
+ Forms the INFERIOR PARATHYROID GLAND - chief and oxyphil cells are derived from the endodermal lining of the pouch

Ventral:
+ Forms the THYMUS
- The epithelial reticular cells are derived from the endodermal lining of the pouch
- T cell progenitors from bone marrow infiltrate the cortex to ESTABLISH DEFINITIVE THYMUS

  • Primordia of THYMUS & PARATHYROID LOSE THEIR CONNECTIONS WITH PHARYNX and MIGRATE INTO NECK (anterior mediastinum)
28
Q

What happens to the 4th Pharyngeal Pouch?

A
  • Divides into a DORSAL and VENTRAL portion?

Dorsal:
- Contributes to the SUPERIOR PARATHYROID GLANDS

Ventral:
- Forms a diverticulum (outpouching of a hollow tube) called ULTIMOBRANCHIAL BODY, the cells of which migrate into the thyroid and differentiate into PARAFOLLICULAR CELLS of the THYROID GLAND

29
Q

Anomalous development of the derivatives of pouch 3 and/or 4 can result in?

A

Ectopic or absent of:
+ Parathyroid
+ Thymic
+ Parafollicular thyroid tissue

30
Q

What’s DiGeorge syndrome?

A
  • Disorder caused by deletion of the long arm of chromosome 22
  • Results in hypoplasia of 2nd and 3rd pharyngeal pouch derivatives
31
Q

What are the symptoms of DiGeorge syndrome?

A
  • Hypoplasia of the hyoid
  • Thymic hypoplasia (immunodeficiency due to lack of T-cells)
  • Hypoparathyroidism (missing or hypoplastic inferior parathyroid glands)
32
Q

What can Hypoplasia of the 2nd and 3rd arches cause?

A
  • 1st arch disruption, leading to:

+ Micrognathia (reduced jaw)
+ Cleft palate
+ Hearing loss

33
Q

What are the Pharyngeal clefts?

A
  • Ectodermal-lined recesses that appear on the OUTSIDE of the Pharynx between the arches (Cleft 1 is between Arch 1 & 2; etc)
34
Q

What happens to the 1st Pharyngeal cleft?

A
  • Develops into the EXTERNAL AUDITORY MEATUS (remember, corresponding pouch develops into the auditory tube and the intervening membrane develops into the tympanic membrane)
  • Defects in this can result in PREAURICULAR CYSTS and/or FISTULAS
35
Q

What happens to the 2-4 Pharyngeal clefts?

A
  • Overgrown by expansion of the 2nd pharyngeal arch and are usually obliterated
  • Remnants can appear along the anterior border of the sternocleidomastoid muscle in the form of cervical cysts or fistulas
36
Q

What’s the Thyroid gland?

A
  • 1st endocrine gland to develop (day 24)
  • Makes 2 hormones:
    + Thyroxine (T4)
    + Triiodothyronine (T3)
  • Influences cellular metabolism
37
Q

Outline the development of the Thyroid gland?

A
  • NOT DERIVED FROM A PHARYNGEAL POUCH
  • Develops from the median endodermal thickening in the floor of the primordial pharynx; these cells differentiate into the FOLLICULAR CELLS of the THYROID GLAND
  • ENDODERMAL CELLS OF the ULTIMOBRANCHIAL BODY migrate into the gland and give rise to the PARAFOLLICULAR CELLS of the THYROID
  • Differential growth of the embryo leads to DIVERTICULUM ELONGATION, but remains connected to the forming tongue by the THYROGLOSSAL DUCT (later obliterated)
  • Site of the opening of the THYROGLOSSAL DUCT IS the FORAMEN CECUM which is found in the midline at the TERMINAL SULCUS OF THE TONGUE
38
Q

What are the anomalies of the Thyroid gland?

A
  • Can result in ECTOPIC THYROID TISSUE and/or CYSTS present along the course of the THYROGLOSSAL DUCT
  • Abnormal shape = Pyramidal lobe
  • Anomalies of position = Lingual thyroid
39
Q

How does the Anterior 2/3 of the tongue develop? (incl innervation)

A
  • Anterior 2/3 derived from median (tuberculum impar) and lateral lingual swellings develop on each side of the median tongue buds that arise from the floor of the 1st pharyngeal arch
  • Distal tongue buds increase in size, merge together and overgrow the median bud to form the anterior 2/3rd of the tongue
  • The median tongue bud DOES NOT form any part of the adult tongue
  • CT and vasculature: derived from arch masenchyme

Innervation:

  • Sensory of mucosa: Lingual branch of trigeminal nerve
  • Taste: Chorda tympani branch of facial nerve
  • Motor of intrinsic skeletal muscle: Hypoglossal nerve
40
Q

How does the Posterior 1/3 of the tongue develop? (incl innervation)

A
  • Appearance of Copula due to fusion of Ventromedial part of 2nd pair of arches
  • Hypopharyngeal eminence (prominence) appears due to proliferation of mesenchyme from 3rd & 4th pharyngeal arches
  • Hypopharyngeal eminence overgrows the Copula
  • Posterior 1/3 of the tongue develops from the rostral part of the Hypopharyngeal eminence

(POSTERIOR 1/3 OF TONGUE IS DERIVED FROM 3+4TH ARCH - NO CONTRIBUTION FROM 2ND ARCH)

Innervation:
+ Sensory of mucosa: Mostly glossopharyngeal + some vagus

+ Taste: Mostly glossopharyngeal + some vagus

+ Motor of intrinsic skeletal muscle: Hypoglossal

41
Q

Development of the tongue: When do the Papillae and Taste buds appear?

A
  • End of week 8
  • Taste buds develop during week 11 to 13 - via inductive interaction between epithelial cells and invading gustatory nerve
42
Q

What’s 1st arch syndrome?

A

x2 types:
- Treacher Collins Syndrome - caused by autosomal dominant gene - underdevelopment of zygomatic bond and defective eyelids and ears

Pierre Robin Syndrome - underdevelopment of mandible - cleft palate and defects of the eye and ear

Oral Biology (33 decks)

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