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Cranial nerves overview (Segmental trunk nerves (Somatic nervous system…
Cranial nerves overview
Segmental trunk nerves
Somatic nervous system under voluntary control
1=Afferent (sensory)
2-3=Inter-neuron
4=Efferent (motor)
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Autonomic nervous system under involuntary control
1=Afferent (sensory)
2= Inter-neuron
3= Pre-ganglionic efferent
4= Post-ganglionic efferent
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Segmental head nerves
Similar to trunk EXCEPT:
- Autonomic efferent neurons leave via dorsal root
- Dorsal & Ventral roots do NOT unite
- Head has 5th neuronal component (Special visceral efferent)
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Striated muscle arising from lateral plate mesoderm supplies by SPECIAL VISCERAL EFFERENTS leaving via dorsal root
Summary
Segment 1 has no pharyngeal arch so it borrows dorsal root nerve from segment 2 (opthalmic branch of CN V)
Due to development of mouth dorsal root nerve of segment 2 splits into 2 major branches (maxillary & mandibular branches of CN V)
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Segment 6&7 somites unite to form tongue muscles, so do their ventral root nerve (XII)
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Info from Keirans table
Segment
1
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Ventral root nerve: III Occulomotor
- Somite (SE): Most orbital muscle [AE ciliary muscle]
Dorsal root nerve: V Trigeminal (opthalmic)
- Ectoderm (SA): Skin on top of head
2
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Ventral root nerve: IV Trochlear
- Somite (SE): Dorsal oblique
Dorsal root nerve: V Trigeminal (Maxillary & Mandibular)
- Ectoderm (SA): Skin of face, rostral 2/3 of tongue
- Pharyngeal arch (SVE): Chewing muscles/malleus & incus
- Pouches: Middle ear, eustachian tube
3
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Ventral root nerve: VI Abducent
- Lateral rectus & retractor oculi
Dorsal root nerve: VII Facial
- Ecotderm (SA): Negligible (skin on inside of pinna)
- Endoderm (AA): Thyroid gland
- Glands (AE): Mandibular/sublingual salivary, nasal, lacrimal
- Pharyngeal arch (SVE): Facial muscles/stapes and hyoid
- Pouches: Tonsil
4
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Dorsal root nerve: IX Glosso-pharyngeal
- Ecotderm (SA): Negligible
- Endoderm (AA): Pharynx, caudal 1/3 of tongue, carotid body/sinus
- Glands (AE): Parotid salivary gland
- Pharyngeal arch (SVE): Stylo-pharyngeus muscle/hyoid
- Pouches: Thymus, para-thyroid
5
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Dorsal root nerve: X/XI Vagal-accessory complex
- Ectoderm (SA) Negligible
- Endoderm (AA): Rostral larynx, common pharynx
- Glands (AE): GI tract glands
- Pharyngeal arch (SVE): Pharyngeal muscles & cricothyroid muscle/laryngeal cartilages
- Pouches: Thymus, para-thyroid, ultimobranchial body
6
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Ventral root nerve: XII Hypoglossal (shared with segment 7)
- Somite (SE): Somites of 6 AND 7 migrate to form tongue muscles
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7
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Ventral root nerve: XII Hypoglossal (shared with segment 6)
- Somite (SE): Somites of 6 AND 7 migrate to form tongue muscles
Dorsal root nerve: X/XI Vagal-accessory complex
- Endoderm (AA): Caudal larynx, oesophagus, respiratory
- Glands (AE): GI tract glands
- Pharyngeal arch (SVE): Laryngeal muscles/laryngeal cartilages