Development of Pharyngeal Arches and Pouches in Head and Neck
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Questions and Answers

What is the origin of the muscular components of each pharyngeal arch?

  • Epithelium of endodermal origin
  • Paraxial and lateral plate mesoderm (correct)
  • Neural crest cells
  • Surface ectoderm

    • Which part of Meckel's cartilage disappears except for two portions at its dorsal end?

  • Maxillary process
  • Mandibular process
  • The entire cartilage (correct)
  • None of the above

    • What is the relationship between the pharyngeal pouches and the pharyngeal gut?

  • Pharyngeal pouches are located along the lateral walls of the pharyngeal gut (correct)
  • Pharyngeal pouches are derived from the surface ectoderm
  • Pharyngeal pouches are located outside the pharyngeal gut
  • Pharyngeal pouches penetrate the surrounding mesenchyme

    • What is the origin of the thymus?

    <p>Third pharyngeal pouch</p> Signup and view all the answers

    How do the pharyngeal arches and clefts develop?

    <p>They appear in the 4th and 5th weeks of development</p> Signup and view all the answers

    What is the fate of the dorsal portion of the first pharyngeal arch?

    <p>It forms the maxillary process</p> Signup and view all the answers

    How do the pharyngeal arches consist of?

    <p>A core of mesenchyme covered on the outside by surface ectoderm and on the inside by epithelium of endodermal origin</p> Signup and view all the answers

    What is the origin of the parathyroid glands?

    <p>Third and fourth pharyngeal pouches</p> Signup and view all the answers

    Which pharyngeal arch gives rise to the lesser horn of the hyoid bone?

    <p>2nd pharyngeal arch</p> Signup and view all the answers

    What is the origin of the cartilages of the larynx?

    <p>4th and 6th pharyngeal arches</p> Signup and view all the answers

    What is the fate of the epithelial lining of the 1st pharyngeal cleft?

    <p>Forms the middle ear cavity</p> Signup and view all the answers

    When does the palatine tonsil begin to be infiltrated by lymphatic tissue?

    <p>During the 3rd and 5th months</p> Signup and view all the answers

    Which pharyngeal pouch is involved in the formation of the parathyroid glands?

    <p>4th pharyngeal pouch</p> Signup and view all the answers

    What is the origin of the stapes bone?

    <p>2nd pharyngeal arch</p> Signup and view all the answers

    What is the fate of the epithelial lining of the pharyngeal pouches?

    <p>Gives rise to a number of organs</p> Signup and view all the answers

    What is the origin of the stylohyoid ligament?

    <p>2nd pharyngeal arch</p> Signup and view all the answers

    What forms the anterior two-thirds of the tongue?

    <p>The lateral lingual swellings and tuberculum impar</p> Signup and view all the answers

    What is the name of the groove that separates the anterior two-thirds from the posterior third of the tongue?

    <p>Terminal sulcus</p> Signup and view all the answers

    What is the result of extensive cell degeneration in the floor of the mouth?

    <p>The formation of the frenulum</p> Signup and view all the answers

    From which pharyngeal arches does the posterior part of the tongue originate?

    <p>The 2nd, 3rd and part of the 4th pharyngeal arches</p> Signup and view all the answers

    What is ankyloglossia also known as?

    <p>Tongue-tie</p> Signup and view all the answers

    At what week do facial prominences appear?

    <p>The 4th week</p> Signup and view all the answers

    What type of tissue forms the facial prominences?

    <p>Neural crest-derived mesenchyme</p> Signup and view all the answers

    What is the result of the frenulum extending to the tip of the tongue in ankyloglossia?

    <p>The tongue is tied to the floor of the mouth</p> Signup and view all the answers

    What is the origin of the external auditory meatus?

    <p>The dorsal part of the 1st cleft</p> Signup and view all the answers

    What is the remnant of the cervical sinus?

    <p>Lateral cervical cyst</p> Signup and view all the answers

    What is the result of a rupture of the membrane between the 2nd pharyngeal cleft and pouch?

    <p>Internal branchial fistula</p> Signup and view all the answers

    What is formed from the epithelial lining of the 1st cleft?

    <p>Eardrum</p> Signup and view all the answers

    What is the location of the lateral cervical cyst?

    <p>On the lateral aspect of the neck</p> Signup and view all the answers

    What is the role of neural crest cells in development?

    <p>Formation of the craniofacial region</p> Signup and view all the answers

    What is the consequence of disruption of neural crest cell development?

    <p>Severe craniofacial malformations</p> Signup and view all the answers

    What is the effect of compounds such as alcohol and retinoic acid on neural crest cells?

    <p>Killing of crest cells</p> Signup and view all the answers

    What is the significance of the ultimobranchial body in the development of the thyroid gland?

    <p>It is incorporated into the thyroid gland and gives rise to parafollicular cells</p> Signup and view all the answers

    Which part of the pharyngeal pouch develops into the thymus?

    <p>Ventral wing of the third pharyngeal pouch</p> Signup and view all the answers

    What is the origin of the palatine tonsil?

    <p>Epithelium of the dorsal wing of the third pharyngeal pouch</p> Signup and view all the answers

    Which parathyroid gland develops from the epithelium of the dorsal wing of the third pharyngeal pouch?

    <p>Superior parathyroid gland</p> Signup and view all the answers

    What is the fate of the ultimobranchial body in the development of the thyroid gland?

    <p>It is incorporated into the thyroid gland and gives rise to parafollicular cells</p> Signup and view all the answers

    Which pharyngeal pouch develops into the middle ear cavity?

    <p>Third pharyngeal pouch</p> Signup and view all the answers

    What is the origin of the inferior parathyroid gland?

    <p>Epithelium of the ventral wing of the fourth pharyngeal pouch</p> Signup and view all the answers

    What is the significance of the ventral wing of the fourth pharyngeal pouch in the development of the thyroid gland?

    <p>It forms the ultimobranchial body</p> Signup and view all the answers

    Study Notes

    Development of Pharyngeal Arches

    • Pharyngeal or branchial arches form in the 4th and 5th weeks of development, characterized by bars of mesenchymal tissue separated by clefts (pharyngeal clefts).
    • Each arch consists of a core of mesenchyme covered by surface ectoderm and epithelium of endodermal origin.
    • The core contains mesenchyme derived from paraxial and lateral plate mesoderm and neural crest cells.
    • Each arch has its own muscular components, cranial nerve, and arterial component.

    First Pharyngeal Arch

    • Dorsal portion forms the maxillary process.
    • Ventral portion forms the mandibular process, which contains Meckel's cartilage.
    • Meckel's cartilage disappears except for two portions at its dorsal end, forming the incus and malleus.
    • Mesenchyme of the maxillary process gives rise to the premaxilla, maxilla, and zygomatic bone.
    • Mandible is formed by membranous ossification of mesenchymal tissue.

    Second Pharyngeal Arch (Hyoid Arch)

    • Cartilage gives rise to the stapes, styloid process of the temporal bone, stylohyoid ligament, and lesser horn of the hyoid bone.

    Third Pharyngeal Arch

    • Cartilage gives rise to the lower part of the body of the hyoid bone and the greater horn of the hyoid bone.

    Fourth and Sixth Pharyngeal Arches

    • Cartilaginous components fuse to form the cartilages of the larynx (thyroid, cricoid, arytenoid, corniculate, and cuneiform).

    Pharyngeal Pouches

    • Human embryo has 4 pairs of pharyngeal pouches, with the 5th pair being absent or rudimentary.
    • Epithelial endodermal lining of the pouches gives rise to a number of organs.

    First Pharyngeal Pouch

    • Forms a stalk-like diverticulum, the tubotympanic recess, which comes in contact with the epithelial lining of the 1st pharyngeal cleft (future external auditory meatus).
    • Distal portion widens to form the middle ear cavity, while the proximal portion remains narrow, forming the auditory (eustachian) tube.

    Second Pharyngeal Pouch

    • Epithelial cells proliferate and form buds that penetrate into the surrounding mesenchyme, forming the palatine tonsil.

    Clinical Correlates

    • Ankyloglossia (tongue-tie): a condition where the tongue is not freed from the floor of the mouth.
    • Branchial fistula: occurs when the 2nd pharyngeal arch fails to grow caudally over the 3rd and 4th arches, leaving remnants of the 2nd and 3rd clefts in contact with the surface by a narrow canal.
    • Lateral cervical cyst: a remnant of the cervical sinus, located just below the angle of the jaw.
    • Palatine tonsil: formed from the 2nd pharyngeal pouch.

    Face Development

    • Facial prominences consisting primarily of neural crest-derived mesenchyme appear at the end of the 4th week.
    • The dorsal part of the 1st cleft penetrates the underlying mesenchyme and gives rise to the external auditory meatus.
    • The epithelial lining forms the eardrum.

    Thymus and Parathyroid Glands

    • Third pharyngeal pouch contains dorsal and ventral wing, with the epithelium of the dorsal wing forming the inferior parathyroid gland and the ventral wing forming part of the thymus.
    • Fourth pharyngeal pouch: epithelium of the dorsal wing forms the superior parathyroid gland, while the ventral part develops into the ultimobranchial body, which is later incorporated into the thyroid gland.
    • Ultimobranchial body gives rise to the parafollicular (C cells), which differentiate from neural crest cells.

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    Development of Pharyngeal Arches PDF

    Description

    This quiz covers the development of pharyngeal arches and pouches in the formation of the head and neck, a key topic in histology and embryology. Learn about the typical features of this process and more.

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