Podcast
Questions and Answers
What structures are associated with the 4th pharyngeal arch?
What structures are associated with the 4th pharyngeal arch?
What is formed by the 1st pharyngeal pouch?
What is formed by the 1st pharyngeal pouch?
Which structure is derived from the dorsal extension of the 3rd pharyngeal pouch?
Which structure is derived from the dorsal extension of the 3rd pharyngeal pouch?
What complication can arise if the pharyngeal clefts do not close properly?
What complication can arise if the pharyngeal clefts do not close properly?
Signup and view all the answers
Which artery is associated with the 6th pharyngeal arch?
Which artery is associated with the 6th pharyngeal arch?
Signup and view all the answers
Which of the following is found in the space associated with the 2nd pharyngeal pouch?
Which of the following is found in the space associated with the 2nd pharyngeal pouch?
Signup and view all the answers
The 4th pharyngeal arch is responsible for the development of which of the following muscles?
The 4th pharyngeal arch is responsible for the development of which of the following muscles?
Signup and view all the answers
What is the function of the endoderm of the pharyngeal pouches?
What is the function of the endoderm of the pharyngeal pouches?
Signup and view all the answers
Which germ layer is responsible for forming the central nervous system, skin, and sensory organs?
Which germ layer is responsible for forming the central nervous system, skin, and sensory organs?
Signup and view all the answers
What is primarily formed from the paraxial mesoderm during development?
What is primarily formed from the paraxial mesoderm during development?
Signup and view all the answers
Which of the following structures is derived from the first pharyngeal arch?
Which of the following structures is derived from the first pharyngeal arch?
Signup and view all the answers
What type of ossification occurs in the formation of the cranial vault?
What type of ossification occurs in the formation of the cranial vault?
Signup and view all the answers
Which cranial nerve is associated with the second pharyngeal arch during development?
Which cranial nerve is associated with the second pharyngeal arch during development?
Signup and view all the answers
What structure acts as a separator between pharyngeal arches?
What structure acts as a separator between pharyngeal arches?
Signup and view all the answers
The viscerocranium is exclusively formed from which type of cells?
The viscerocranium is exclusively formed from which type of cells?
Signup and view all the answers
What do fontanelles allow for during childbirth?
What do fontanelles allow for during childbirth?
Signup and view all the answers
Which structure is formed from the mesoderm during development?
Which structure is formed from the mesoderm during development?
Signup and view all the answers
What cranial nerve is associated with the development of muscles from the third pharyngeal arch?
What cranial nerve is associated with the development of muscles from the third pharyngeal arch?
Signup and view all the answers
Which part of the skull is primarily formed from endochondral ossification?
Which part of the skull is primarily formed from endochondral ossification?
Signup and view all the answers
Which ossicles are derived from the first pharyngeal arch?
Which ossicles are derived from the first pharyngeal arch?
Signup and view all the answers
What is the primary role of ectodermal placodes during development?
What is the primary role of ectodermal placodes during development?
Signup and view all the answers
The maxillary process of the first pharyngeal arch contributes to the formation of which structures?
The maxillary process of the first pharyngeal arch contributes to the formation of which structures?
Signup and view all the answers
Study Notes
Germ Layers
- Ectoderm: forms central nervous system, skin, sensory organs, teeth, hair, pituitary gland and parts of skull
- Mesoderm: forms muscles, skeletal, blood vessels, connective tissues, urogenital structures
- Endoderm: forms portion of gut tube, respiratory system, glands, and epithelium auditory structures
- Mesenchyme: forms connective tissue
Neural Crest Cells
- Derivatives: cranial nerve ganglia, connective tissue and bones of skull, C cells of thyroid gland, odontoblasts, part of meninges
Ectodermal Placodes
- Form sensory organs and ganglia
- Include CN, lens placode, nasal placode, and otic placode
Mesoderm
- Paraxial mesoderm: forms bones of skull, skeletal muscles, dermis & connective tissue of neurocranium, part of meninges
- Lateral plate mesoderm: forms laryngeal cartilages and connective tissues
Endoderm
- Lines pharyngeal pouches
- Forms thymus gland, thyroid gland, tonsils, parathyroid glands, and tympanic membrane
Skull Development
- Viscerocranium: bones of the face
- Forms from Neural crest cells only
- Neurocranium: bones of the braincase
- Forms from Neural crest cells and paraxial mesoderm
Viscerocranium: Pharyngeal Arches
- Pharyngeal arch 1: forms maxillary and mandibular processes
- Maxillary process: forms the maxilla, zygomatic, palatine, lacrimal, vomer, nasal, inferior nasal concha, and squamous temporal
- Mandibular process: forms the mandible, malleus, and incus
- Pharyngeal arch 2: forms the styloid process, stapes, and hyoid
Bone Development
- Cartilaginous: forms from mesenchyme to cartilage to bone
- Membranous: forms from mesenchyme to bone
Viscerocranium Bone Development
- Cartilaginous: ear ossicles, styloid process, hyoid, laryngeal cartilages
- Membranous: everything else
Neurocranium
- Endochondral ossification: base of neurocranium
- Neural crest: ethmoid, sphenoid
- Paraxial mesoderm: parts of temporal bone, occipital base
- Intramembranous ossification: cranial vault
- Neural crest: frontal, sphenoid, temporal
- Paraxial mesoderm: parietal, occipital
Sutures and Fontanelles
- Sutures: where two bones meet
- Fontanelles: where 3+ bones meet
- Allow movement of skull bones during birth
- Remain open for brain growth
Fontanelles and Closure Dates
- Anterior: Frontals and Parietals – closes between 13-24 months
- Posterior: Parietals and Occipital – closes between 1-2 months
- Mastoid: Parietal, Temporal, and Occipital – closes between 6-18 months
- Sphenoid: Sphenoid, Parietal, Temporal, Frontal – closes between 6 months
Fontanelles and Landmarks
- Bregma: where the anterior fontanelle closes and the sagittal and coronal sutures meet
- Lambda: where the posterior fontanelle closes and the sagittal and lambdoid sutures meet
- Pterion: where the sphenoid, parietal, temporal and frontal bones meet (bilateral)
- Asterion: where the parietal, occipital and temporal bones meet (bilateral)
Pharyngeal Structures: Pharyngeal Arches
- Week 4 of development: five outpocketings of the pharynx form
- Separators: clefts and pouches
- Clefts: between each arch, covered in ectoderm
- Pouches: internal to clefts, covered in endoderm
- Pharyngeal arches have ectoderm on external surface, endoderm on internal surface, and a mesenchyme core ( mostly neural crest cells and mesoderm)
Pharyngeal Arches
- Muscles:
- Arch 1: mastication, suprahyoid, palate
- Arch 2: muscles of facial expression, stylohyoid, posterior belly of digastric, stapedius
- Arch 3: stylopharyngues
- Arch 4: musculus uvulae, levator veli palatini, pharyngeal constrictors, salpingopharyngeus, palatoglossus, cricothyroid
- Arch 6: laryngeal muscles
- Cartilage: forming from mesenchyme to cartilage during development
- Arch 1: forms Meckel's cartilage
- Arch 2: forms Reichert cartilage
- Arch 3: forms parts of the hyoid bone
- Arch 4 & 6: form larynx cartilages
- Arteries:
- Arch 1: forms maxillary artery
- Arch 2: forms stapedial artery
- Arch 3: forms internal carotid artery and part of common carotid artery
- Arch 4: forms part of the aortic arch and right subclavian artery
- Arch 6: forms ductus arteriosus and part of pulmonary arteries
- Cranial nerves:
- Arch 1: Trigeminal nerve (CN V)
- Arch 2: Facial nerve (CN VII)
- Arch 3: Glossopharyngeal nerve (CN IX)
- Arch 4 and 6: Vagus nerve (CN X)
1st Pharyngeal Arch
- Two prominences: Maxillary and Mandibular
- Muscles:
- Mastication muscles: temporalis, masseter, medial and lateral pterygoids
- Suprahyoid muscles: mylohyoid, anterior belly of digastric
- Palate muscles: tensor veli palatini, tensor tympani
- Skeleton:
- Ear ossicles: malleus, incus
- Sphenomandibular ligament
- Viscerocranium
2nd Pharyngeal Arch
- Also called the Hyoid arch
- Forms Reichert cartilage
- Muscles: muscles of facial expression, stylohyoid, posterior belly of digastric, stapedius
- Artery: stapedial artery
- Cranial Nerve: Facial nerve (CN VII)
3rd Pharyngeal Arch
- Forms parts of the hyoid bone
- Muscles: stylopharyngeus
- Artery: internal carotid artery and part of common carotid artery
- Cranial nerve: Glossopharyngeal nerve (CN IX)
4th and 6th Pharyngeal Arches
- Form laryngeal cartilages
- Muscles:
- Arch 4: musculus uvulae, levator veli palatini, pharyngeal constrictors, salpingopharyngeus, palatoglossus, cricothyroid
- Arch 6: laryngeal muscles
- Arteries:
- Arch 4: part of the aortic arch and right subclavian artery
- Arch 6: ductus arteriosus and part of pulmonary arteries
- Cranial nerve: Vagus nerve (CN X)
Pharyngeal Pouches
- Internal invaginations between arches
- Four pairs, covered in endoderm
- Form glands: thymus, thyroid, and parathyroid
1st Pharyngeal Pouch
- Forms the tubotympanic recess
- Middle ear cavity (ossicles)
- Pharyngotympanic (eustachian) tube
- Tympanic membrane
- Makes contact with cleft ectoderm
2nd Pharyngeal Pouch
- Forms the tonsillar fossa
- Endoderm proliferation forms the primordium of the palatine tonsils
3rd Pharyngeal Pouch
- Forms dorsal and ventral extensions
- Dorsal extension: forms inferior parathyroid gland
- Ventral extension: forms thymus, migrates to thorax
Pharyngeal Clefts
- Four external clefts covered in ectoderm
- The first pharyngeal cleft contributes to the formation of the tympanic membrane
- Other clefts form the transient cervical sinus
- Can become an issue if closure is not proper.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
