3. The viscerosensory and visceromotor innervation of the head and neck. The fibers of the connective tissue, the extracellular matrix. The development of the viscerocranium.

3 Dec

3. The viscerosensory and visceromotor innervation of the head and neck. The fibers of the connective tissue, the extracellular matrix. The development of the viscerocranium.

Flash Cards:

CN IX, XI - Glossopharyngeal, Accessory n

CN IX, XI - Glossopharyngeal, Accessory n


p1040104

CN X Vagus n & branches


p1040109

Autonomic n. and PNS ggl


p1040110

SNS ganglia in Head & Neck


p1040111

PNS ggl and SNS/PNS relations to them

Anatomy:The viscerosensory and visceromotor innervation of the head and neck.

This topic consists of mainly CN IX, X, and Autonomic innervation of Head & Neck. Yes, some of these cranial nerves also have SM/SS function, but they are very important inVS/VM function.  Other CN also add innervation of VS/VM in the body.  If you want to know all the branches of CNs, please refer to the cards above.

Viscerosensory of Head & Neck:

Viscerosensory innervation of the head and neck have to do with the special sensation function of the cranial nerves. There is a main sensory function we have to look at: taste

Taste:

CN VII – Facial n

covered mostly in last topic, but know that Chorda Tympani n provides VS innervation to ant 2/3 of tongue

  • has motor and sensory roots,
  • Pathway: IAM –> petrous part of temporal bone (through auditory canal) —> exit skull via stylomastoid foramen

Pathway of Chorda Tympani = in desc facial canal –> tympanic membrane –> b/w malleus & incus of middle ear –> thru Petrotympanic fissure –> joins lingual n —> submandibular ggl –> 3 places

  • VM = submandibular, sublingual, lingual glands (discussed in more detail later)
  • VS = ant 2/3 tongue, soft palate
  • cxn w/ geniculate ggl & otic ggl

CN IX – Glossopharyngeal n

  • exit = Jugular foramen,
  • Pathway: from jugular foramen –> follow stylopharyngeus &  passes b/w sup/mid constrictor m. of pharynx –> oropharynx & tongue.
  • Location = Find this n. in parapharyngeal space, behind int carotid, CN XII, CNX, on post surface of stylopharyngeus m
  • innervates structures from 3rd branchial arch
  • receives VS sensation  from parotid gland, carotid body, carotid sinus, pharynx, middle ear

Branches of CN IX that provide VS/VM:

  • Tympanic n
    • forms tympanic plexus around wall of middle ear (w. SNS fibers from int carotid plexus, br from genu ggl of CN VII)
    • SM = tympanic cavity, mastoid antrum, mastoid air cells, auditory tubes, ext ear
    • VM = provides pre-ggl fibers to otic ggl
  • Lingual branches
    • provides VS innervation to post 1/3 of tongue, & vallate papillae for taste sensation, as well as SS to same area

CN X – Vagus n

  • exit = jugular foramen,
  • Pathway: from foramen –> makes connections w. CN IX, CN XI, SNS sup cervical ggl –> goes thru carotid sheath –> thorax
  • innervates structures from 4th & 6th branchial arches
  • receives VS  from base of tongue, pharynx, larynx, trachea, bronchi, heart, esophagus, stomach, & intestine

Branches of CN X that provide VS/VM in head & neck:

  • Mainly VM = will discuss soon

Visceromotor of Head & Neck:

Mainly comes from autonomic innervation. In the head & neck, visceromotor basically means the autonomic innervation of glands, as well as some muscle of the eye.  The four main glands we have to consider are: lacrimal, parotid, submandibular, sublingual, and as well we have to consider the glands of the nasal and oral mucosa & skin. The innervations are primarily run with PNS and SNS ganglia.

If you want to see the information sorted by ganglia, or by PNS v SNS, please refer to flash cards above.

NOTE: SNS fibers only GO THRU ggl (is not part of them, do not synaspe in PNS ggl) – their ggl are the cervical ggl, they are merely hitchhiking with the PNS nerves, and then they run w/ arteries to targets

Cranial Nerves VM innervation:

  • CN III = PNS to sphincter pupillae m & ciliary m –> constrict pupil, help lens of eye
  • CN VII = PNS to submandibular  & sublingual glands, lacrimal glands, glands of nose & palate
  • CN IX = PNS to parotid gland
  • CN X = PNS to smooth m of trachea,  bronchi, digestive tract,  & cardiac m of heart

Lacrimal gland

* Pterygopalatine ggl = in pterygopalatine fossa, where held in place by branches of V2, just ant to opening of pterygoid canal , and below V2

PNS pathway:

  • Greater petrosal n comes from CN VII @ geniculate ggl, and exits out of petrous part of temporal bone
    • Gtr petrosal n has taste fibers that can go to the palate from ggl
  • joins deep petrosal n. which carries SNS fibers @ foramen lacerum
  • these two together become n of pterygoid canal –> pterygopalatine fossa
  • PNS fibers synapse in pterygopalatine ggl
  • post ggl fibers from ggl run to lacrimal gland via zygomatic br of V2 & lacrimal n of V1
  • also supplies glands of nasal mucosa (via post nasal n) and palate ( Gr palatine n = hard palate, Lsr Palatine n = soft palate)

SNS pathway:

  • SNS post ggl fibers are from the superior cervical ggl
  • these fibers run with deep petrosal n.
    • deep petrosal n is from plexus on int. carotid ggl

Submandibular & Sublingual gland & glands of Oral Mucosa

*Submandibular ggl = lies on surface of Hyoglossus m inf to submandibular duct

PNS pathway:

  • Chorda Tympani, comes from CN VII just above stylomastoid foramen
  • the nerve cross medial to malleus and passes thru petrotympanic fissure
  • joins lingual n of V3 in Infratemporal fossa
  • PNS fibers synapse in submandibular ggl
  • post ggl fibers from ggl run w/ arteries to supply Submandibular gland, Sublingual gland, & glands of Oral mucosa,

SNS pathway:

  • SNS post ggl fibers are from superior cervical ggl
  • these fibers run thru, BUT DO NOT SYNAPSE  in submandibular ggl,
  • then run with PNS post ggl fibers

Parotid Gland

* Otic ggl = located b/w tensor veli palatini & V3, inf to foramen ovale

PNS pathway:

  • Tympanic n arises from CN IX and emerges from jugular foramen
  • n enters the middle ear via the tympanic canaliculus in petrous part of  temporal bone
  • tympanic n forms the tympanic plexus — and lesser petrosal n emerges from this plexus
  • lesser petrosal leaves skull via foramen ovale
  • PNS fibers from it synapse in otic ganglion
  • post ggl fibers from ggl RUN W/ auriculotemporal n (from V3) to supply parotid gland

SNS pathway:

  • SNS post ggl fibers are from superior  cervical ggl via a plexus around middle meningeal a
  • post ggl fibers run w/ PNS post ggl fibers on auriculotemporal n
  • help supply a/v of parotid gland

Orbital region

*Ciliary ggl = b/w optic n and lateral rectus m.

PNS pathway:

  • CN III and its divisions run to ciliary ggl
  • post ggl fibers from ciliary ggl pass to ciliary m & sphincter pupillae m
  • constrict pupil of eye, help with lens of eye

SNS pathway:

  • post ggl fibers from sup cervical ggl  form a plexus around  int carotid a
  • and then run with PNS post ggl fibers  to dilater pupillae and tarsal m.
  • dilate pupil of eye & a/v of eye

Animation: PNS innervation of Head ===Check it out!!

Histology: The fibers of the connective tissue, the extracellular matrix.

Extracellular Matrix:

Ground Substance:

  • transparent, shapeless, colorless extracellular matrix
  • high water content
  • supports and surrounds CT and its cells and fibers
  • loads of Glycosaminoglycans,  glycoproteins, proteoglycans

Matrix glycoproteins:

  • most molecule binding cells
  • cells bind via integrin receptors: has Arg-Lys-Asp-R group
  • regulate function of cells: proliferation, migration, etc
  • interconnect cells & collegen fibers
    • ex/ Laminin – bound collagen IV in basal lamina (integrin)
    • hemidesmosomes in epithelial cells
  • Ex/ fibronectin, tenasin, osteonectin, etc

Glycoaminoglycans (GAGs):

  • polysaccharides, disaccharides, like hexosamine + hexuronic acid
  • strong polyanions
    • bind lots of H2O
  • Ex/ Hyaluronic acid, heparine, chondrolitine-sulfate, keratin-sulfate, dermatin-sulfate, heparin-sulfate

Proteoglycans (PGs):

  • fibrular core proteins w/ 1 GAG side chains
  • heparin found intracellularly
  • Physiochemical properties = decided by GAG side chains
  • Ex/ Syndecan: heparin-sulfacte side chains, membrane-intergrated, receptor function

Fibers of CT:

  • Collagen Fibers

    • 3 tropocollagen helical units –> collagen fibrils
    • amino acids = Hydroxylated Proline (OH-Pro), Hydroxylated Lysine (OH-Lys), about 40% glycine

      • provide mechanical resistance due to OH-aa (Hydroxylate amino acids)
    • amount of glycosylation variable
    • look stratified in microscope
    • broken down by collagenases
    • >20 types, only 3 types  can form fibers themselves w/o aid of others = I,II,III
      • I = skin, bone, ligaments, tendons
      • II = cartilage
      • III = reticular
      • From Avi Sayag Biochem notes: One = Bone, 2 = CarTWOlage, 3 = ReThreecular
    • acidophillic, stain pink with eosin
    • stain well w/ AZAN (blue), H&E (red), Van Geison (spermatic cord)
  • Reticular Fibers
    • glycosylated collagen fibers = III
    • made by reticular cells
    • low mech resistance
    • filled w/ CARBS
    • forms supporting meshwork of organs
    • stains well w/ Ag impregnation (black), PAS + (magenta, like in sublingual glands), AZAN (blue)
  • Elastic fibers
    • made of tropoelastin & fibrillin
    • high amount of Gly, Val, Ala, & Pro
    • has hydroxylated-Pro, but not OH-Lys
    • have short amino acid side chains
    • can be extended due to presence of special cross bond –> higher mech resistance
    • broken down by elastases
    • stains well w/ Resorcin-Fuchsin, Orcein (brown)

Embryology: The development of the viscerocranium.

  • skeletal system develops from paraaxial, lateral plate mesoderm, & neural crest
  • Paraxial mesoderm forms somites,t hat split into somitomeres, dermatomes, & myotomes
  • @ 4th week -sclerotomes –> become mesenchyme (embryonic CT)
  • Mesenchyme can form many things, like osteoblasts = bone forming cells
  • Neural crest cells in head region can also become mesenschyme
  • 2 types of bone formation:
    • (Intra)membranous ossification – mesenchyme of dermis is converted right to bone
    • Endochondral ossification – mesenchyme –> hyaline cartilage –> ossified by osteoblasts
  • Viscerocranium

    • Viscerocranium = bones of the face, like nasal, lacrimal, etc
    • formed mainly from the first 2 pharyngeal arches
    • 1st arch =
      • dorsal portion that becomes maxillary process —> becomes maxilla, zygomatic bone, part of temporal bone
      • ventral portion that becomes mandibular process –> Meckel’s cartilage
    • Mesenchyme around Meckel’s cartilage ossifies via membranous ossification *see previous topic for how this works* —> becomes mandible
    • Meckel’s cartilage completely disappears except for sphenomandibular ligament
    • Dorsal tip of mandibular process = becomes incus, malleus, stapes = bones of inner ear
    • The rest of facial bones formed from neural crest cells
    • Bones and paranasal sinuses continue to grow through puberty.
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