SM_01b: Head Primordia Flashcards
In the head, the head mesenchyme arises from the ____
In the head, the head mesenchyme arises from the neural crest
In the head, ____ flanks the foregut
In the head, pharyngeal (branchial) arch mesoderm flanks the foregult
(nerves to striated muscle derivatives are called branchiomotor)
____ neurons are found in the head and neck
Special sensory neurons are found in the head and neck
(vision, olfaction, hearing, balance, taste, chemoreception)
Olfactory nerve (I) arises from the _____
Olfactory nerve (I) arises from the olfactory placode

Optic nerve (II) arises from the ____
Optic nerve (II) arises from the optic cup

Oculomotor (III), trochlear (IV), and abducens (VI) nerves arise from the ____
Oculomotor (III), trochlear (IV), and abducens (VI) nerves arise from the preotic somitomeres
(eye muscles)

Hypoglossal (XII) nerve arises from the ____
Hypoglossal (XII) nerve arises from the postotic somites
(tongue muscles)

Vestibulocochlear (VIII) nerve arises from the ____
Vestibulocochlear (VIII) nerve arises from the otic placode
(hearing and balance)

Nerves V, VII, IX, and X arise from the ____
Nerves V, VII, IX, and X arise from the pharyngeal (branchial) arches

Ectodermal derivatives include the ___, ___, and ___
Ectodermal derivatives include the neural tube, surface covering of the head and neck, and placodes
- Neural tube: brain, spinal cord, optic cup
- Surface covering of the head and neck: stomodeum and pharyngeal / branchial grooves, sensory innervation is mostly by trigeminal nerve (V)
- Placodes: otic, lens, olfactory

____ is the primordium for the ____ and corresponds to the olfactory nerve (I)
Olfactory placode is the primordium for the olfactory epithelium and corresponds to the olfactory nerve (I)
____ is the primordium for the ____ and corresponds to the optic nerve (II)
Optic cup (around lens placode) is the primordium for the retina and nerve II and corresponds to the optic nerve (II)
____ is the primordium for the ____ and corresponds to the vestibulocochlear nerve (VIII)
Otic placode is the primordium for the inner ear (cochlea/semi-circular canals) and corresponds to the vestibulocochlear nerve (VIII)
Eye develops from the ___, ___, and ___
Eye develops from the lens placode, optic cup, and head mesenchyme
- Lens placode sinks under the surface as the lens vesicle is surrounded by the optic cup
- Head mesenchyme from the neural crest begins to condense around the optic cup to form the connective tissue elements

____ and ____ make up the inner ear
Semicircular canals and cochlea make up the inner ear

Ear develops from the ____, ____, and ____
Ear develops from the otic placode, first pharyngeal groove, and first pouch
(otocyst shapes into the cochlea and semicircular canals)

Mesodermal/mesenchyme primordia includes the ____, which originate from the ____ and ____
Mesodermal/mesenchyme primordia includes the pharyngeal (branchial) arches flanking the foregut, which originate from the somites and head mesenchyme
Pharyngeal (branchial) arches flanking the foregut originate from the ____ and ____
Pharyngeal (branchial) arches flanking the foregut originate from the somites and head mesenchyme
- Somites (somitomeres): some cells migrate into the pharyngeal arches for muscle cells
- Head mesenchyme (from neural crest): makes up most of the pharyngeal arches
___ and ___ arches merge together
4th and 6th arches merge together

Arches are separated by _____ on the outside and _____ on the inside
Arches are separated by ectodermal grooves on the outside and endodermal pouches on the inside

Each arch has an ____, ____, ____, and ____
Each arch has an artery, cranial nerve, piece of cartilage, and mesenchyme that will form muscles

Pretrematic nerves ____
Pretrematic nerves provide extra sensory innervation to the territory preceding the arch of origin

Pretrematic for Arch 1 is ____
Pretrematic for Arch 1 is opthalmic nerve (V1) to the orbit and forehead

Pretrematic for Arch 2 is ____
Pretrematic for Arch 2 is chorda tympani to tongue for taste

Pretrematic for Arch 3 is ____
Pretrematic for Arch 3 is tympanic nerve to middle ear cavity

Describe the arch cartilage derivatives
Arch cartilage derivatives
- Arch 1: malleus, incus, stapes (auditory ossicles)
- Arch 2: stapes, styloid process, stylohyoid ligament
- Arch 3: greater cornu (horn) of the hyoid bone
- Arch 4/6: thyroid cartilage, cricoid cartilage

___ migrate to form the tongue and eye muscles
Head somites migrate to form the tongue and eye muscles

____ migrates out of the mesoderm to form the face muscles
Arch 2 migrates out of the mesoderm to form the face muscles

___ muscles form from Arch 1
Jaw muscles form from Arch 1

____ muscles form from Arch 2
Facial expression muscles form from Arch 2

____ and ____ muscles form from Arch 4/6
Larynx and pharynx muscles form from Arch 4/6

Describe endodermal derivatives in the head and neck
Endodermal derivatives in head and neck
- Foregut tube gives rise to pharynx, larynx, trachea, and thyroid gland
- Pharyngeal pouches (endodermal extensions of pharynx between pharyngeal arches) give rise to the middle ear, palatine tonsils, thymus, and parathyroid glands
Endodermal foregut extends to the ___
Endodermal foregut extends to the stomodeum

____ and ____ flank the stomodeum
Frontonasal process and maxillary/mandibular parts of the first pharyngeal arch flank the stomodeum

Frontonasal process forms the ____, ____, and ____
Frontonasal process forms the forehead, nose, and part of the upper lip

____ is the only origin for all sympathetics
Thoracolumbar outflow (T1-L2) is the only origin for all sympathetics
(cranial nerves do not exit brain with sympathetic fibers)

Postsynaptic sympathetics leave the ____ and follow ____ into the head to their targets
Postsynaptic sympathetics leave the cervical sympathetic ganglia and follow arteries into the head to their targets

Accessory (XI) nerve arises from the ____
Accessory (XI) nerve arises from the somitic mesoderm
(for neck muscles)
Parasympathetics are characterized by ____ from the CNS
Parasympathetics are characterized by craniosacral outflow from the CNS
(CN III, VII, IX, X, V)

Describe the craniosacral outflow for parasympathetics
Craniosacral outflow for parasympathetics
- Presynaptics leave the brain with nerves III (oculomotor), VII (facial), IX (glossopharyngeal), and X (vagus)
- They synapse in ganglia and join branches of V (trigeminal) to their targets

____ arises from the olfactory placode
Olfactory nerve (I) arises from the olfactory placode

____ arises from the optic cup
Optic nerve (II) arises from the optic cup

____, ____, and ____ arise from the preotic somitomeres
Oculomotor (III), trochlear (IV), and abducens (VI) nerves arise from the preotic somitomeres
(for eye muscles)

____ arises from the postotic somites
Hypoglossal nerve (XII) arises from the postotic somites
(for tongue muscles)

____ arises from the somitic mesoderm
Accessory nerve (XI) arises from the somitic mesoderm
(for neck muscles)

____ arises from the otic placode
Vestibulocochlear nerve (VIII) arises from the otic placode
(for hearing and balance)

____, ____, ____, and ____ arise from the phayngeal (branchial) arches
Nerves V, VII, IX, and X arise from the phayngeal (branchial) arches

Describe the functions of the cranial nerves

Describe the special sensory nerves and their primordia
Special sensory nerves and their primordia
- I (olfactory) - olfactory placode (olfaction)
- II (optic) - optic cup (vision)
- VIII (vestibulocochlear) - otic placode (hearing and balance)
Describe the somatomotor nerves
Somatomotor nerves
- III (oculomotor) - preotic somites (for eye muscles)
- IV (trochlear) - preotic somites (for one eye muscle)
- VI (abducens) - preotic somites (for one eye muscle)
- XII (hypoglossal) - postotic somites (for tongue muscles)
Describe branchial arch nerves (mixed nerves)
Branchial arch nerves (mixed nerves)
- V (trigeminal) - Arch 1
- VII (facial) - Arch 2
- IX (glossopharyngeal) - Arch 3
- X (vagus) - Arches 4/6
XI (spinal accessory nerve) arises from the ____
XI (spinal accessory nerve) arises from the somite mesoderm by arch 6
