Embryology- Head and Neck, Cranial Nerves Flashcards
What tissues are the pharyngeal arches derived from?
What do they interact with
General Mesoderm; they interact with neural crest cells
Glands and mucosae, original tissue and what they interact with
Endoderm, interact with neural crest ectoderm
Brain, embryologic origin tissue
Ectoderm
Cranial nerves, origin
ectoderm
Placodes
What are they? What tissue are they derived from?
- Discs that appear on ectoderm, sensory specialization occurs here
- Later form eye lens, ear spaces, nasal cavity, neurogenic structures
- All derived from ectoderm
Head somites
What are they (specific m.m.)?
What tissue are they derived from?
Derived from head mesoderm
- eg. eye muscles, tongue, SCM, trapezius
What tissues make up the skull? What to they become? What is the embryologic tissue they are derived from?
All derived from mesoderm. Different precursors eventually become bone.
Endochondral cartilages (later bone replaces it)- make up anterior and posterior neurocranium- vertebrae, ethmoid, nasal conchae, central sphenoid
Intramembranous ossification desmocranium (dermal bones)- interact with neural crest cells- make frontal, parietal, occipital, and zygomatic bones
Notochord (makes basisphenoid and basioccipital bones), vertebrae, endochondral cartilages mix
How does endochondral cartilage in skull become bone?
Bone tissue comes above and below it, later bone fills in
The notochord makes part of which bones?
Basisphenoid and basioccipital bones
- Neurocranium is also involved with formation of these bones
Which cranial nerves are associated with placodes?
I- Olfactory
II- Optic
VII- Vestibulocochlear
-They are all sensory nerves–> “special afferent”
Which cranial nerves are associated with head somites and somitomeres?
III- Oculomotor IV- Trochlear VI- Abducens XI- Accessory XII- Hypoglossal
-They are all motor nerves–> all are general somatic efferent AND CN III is also general visceral efferent
Which cranial nerves are associated with pharyngeal arches?
V- Trigeminal
VII- Facial
IX- Glossopharyngeal
X- Vagus
- These are “mixed” nerves, sensory and motor component
- -> All are special afferent (SA), General somatic afferent (GSA), General visceral afferent (GVA), , General visceral efferent (GVE), Special visceral efferent (SVE)
What does the nasal placode form?
Mucosa of nasal capsule
What does the lens placode form?
Lens of the eye
What does the otic placode form?
Vestibular and cochlear parts of the ear?
What do the neurogenic placodes form?
Parts of the cranial nerves
What embryologic precursor are the pharnygeal pouches derived from?
Paraxial mesoderm
What is cranial nerve zero?
the Vomeronasal organ
Which pharnygeal arches are associated with what cranial nerve?
Arch 1 (Meckel’s Cartilage): Trigeminal nerve (V)
Arch 2 (Reichert’s Cartilage): Facial nerve (VII)
Arch 3 (Carotid arch): Glossopharyngeal nerve (IX)
Arch 4 (Systemic arch): Vagus nerve (X), ONLY superior laryngeal branch
Arch 6 (Pulmonary arch): Vagus nerve (X), ONLY recurrent laryngeal branch
Which pharnygeal arches are associated with what arteries?
Arch 1 (Meckel’s Cartilage): Artery mainly gone- remnants of maxillary and part of external carotid
Arch 2 (Reichert’s Cartilage): Stapedial artery
Arch 3 (Carotid arch): Internal and external carotid arteries
Arch 4 (Systemic arch): Parts of aorta and right subclavian artery
Arch 6 (Pulmonary arch): Proximal part of pulmonary arteries
Which cranial nerves are associated with which muscles?
III, IV, VI- Eye muscles
XI- SCM, Trapezius
XII- Intrinsic tongue muscles
What main structures are derived from pharyngeal arch 1?
- Incus and malleus bones of middle ear
- Some muscles of mastication
What main structures are derived from pharyngeal arch 2?
- Stapes (ear bone)
- Stylohyoid ligament
- Some muscles of facial expression
What main structures are derived from pharyngeal arch 3?
- Main part of hyoid bone (greater horn, lower part of body) and cartilage
- Stylopharyngeus (pharyngeal muscle)
What main structures are derived from pharyngeal arch 4?
- Laryngeal cartilages, e.g. cricoid cartilage
- Laryngeal m.m., cricothyroid m., constrictors of pharynx
What main structures are derived from pharyngeal arch 6?
Same as arch 4
- Laryngeal cartilages, e.g. cricoid cartilage
- Laryngeal m.m., cricothyroid m., constrictors of pharynx
What structures do the pharyngeal grooves become?
1st- External auditory canal
2nd, 3rd, 4th- Often closed up, occasionally replaced by cervical sinus
What structures do the pharyngeal pouches form?
The glands! Generally
1st- Auditory canal, middle ear
2nd- Palatine tonsil
3rd- Inferior parathyroid (and Thymus per Dr. Solunias)
4th- Superior parathyroid
How does thyroid migrate during development?
-Starts in tongue, specifically in foramen cecum, cells migrate down to where pharyngeal pouch 3,4 are developing into parathyroid glands
