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- motor fibers to striated, skeletal muscle of the head & neck which has developed embyrologically from the branchial/pharyngeal arches (NOT from somites).
- These muscles include the muscles of facial expression, muscles of mastication, and muscles of the pharynx & larynx (in addition to a few others).
- This component is also called “Special Visceral Efferent” or SVE.
- Do not confuse this with the ANS or VE fibers.
First Branchial Arch
- CN V (Trigeminal)
- muscles of mastication, mylohyoid, ant. belly diagastric, tensor villi palatini, & tensor tympani
- malleus, incus, & mandible
Second Branchial Arch
- CN VII (Facial)
- muscles of facial expression, post. belly diagastric, stylohyoid, & stapedius
- stapes, styloid, & part of hyoid
Third Branchial Arch
- CN IX (Glossopharyngeal)
- part of hyoid
Fourth & Sixth Branchial Arches
- CN X (Vagus)
- muscles of pharynx, larynx, & palate
Lymphatics of the Head & Neck
- lymph from the head and neck drains into 3 groups of lymph nodes:
- (1) pericervical collar nodes,
- (2) superficial cervical nodes (which comprise a number of different lymph node groups), and
- (3) deep cervical nodes.
- From the deep cervical nodes, lymph drains into the thoracic duct (on the left side) and right lymphatic duct (on the right side).
- Both the thoracic duct and right lymphatic duct drain into the venous system at the junction of the internal jugular and subclavian veins.
Pericervical Collar (Groups of) Nodes:
- 1. occipital nodes
- 2. mastoid nodes (retroauricular)
- 3. parotid nodes
- 4. buccal nodes
- 5. submandibular nodes
- 6. submental nodes
Superificial Cervical Nodes
- 1. external jugular nodes
- 2. anterior jugular nodes
- 3. accessory nodes
Deep Chain of Lymph Nodes
surround the internal jugular vein (which is deep to the SCM)
- General Pattern of HN Lymph Drainage
- Lymph drains into the pericervical collar of nodes & superficial cervical node groups.
- From these groups, it then drains into the deep cervical chains (of nodes) and then into the venous system via the thoracic duct (left side) and right lymphatic duct (right side).
- These two ducts are located at the junctions of the internal jugular vein and subclavian veins.
- Lymph flows from (1) superior to inferior and (2) superficial to deep.
Squamous Cell Carcinoma (Cancer) of the Lip
- usually involves the lower lip.
- Overexposure to sunshine over many years and/or chronic smoking are contributing factors.
- Cancer cells from the central part of the lower lip, floor of the mouth, and apex of the tongue spread to the submental lymph nodes.
- Cancer cells from the lateral parts of the lower lip spread to the submandibular lymph nodes.
posterior part of the eyeball.
- circular area where the sensory fibers & vessels conveyed by the optic nerve enter the eyeball.
- It has no photoreceptors and so it is the “blind spot”.
- Lateral to Optic Disc(blind spot)
- at the center of which is a depression called the “fovea centralis”.
- The fovea is the area of most acute vision.
- responsible for refraction of light that enters the eye.
- It is transparent, avascular, and sensitive to touch.
- It is supplied by the (V1 fibers of the) ciliary nerves.
- a watery solution that fills the anterior & posterior chambers and nourishes the cornea & lens.
- The anterior chamber is anterior to the iris.
- The posterior chamber is posterior to the iris.
- muscular & vascular structure which connects the choroid & iris.
- It also provides attachment for the lens. (zonular fibers)
- Contraction & relaxation of its smooth muscle (the ciliaris muscle) controls the thickness (& thus “focus” or “accommodation”) of the lens.
- The ciliaris muscle is under parasympathetic (VE-para/post) control.
- located posterior to the lens.
- filled with a watery, semi-gelatinous substance called the vitreous humor or body.
- The vitreous body transmits light, holds the retina in place, and supports the lens.
- Brain Stem Nucleus of CN III to Ciliary Ganglion
- VE para pre cell bodies that will innervate Ciliary Body and Sphincter Pupillae
- Brain Stem Nucleus of CN VII to both Submandibular and Pterygopalatine Ganglia
- Submandibular targets include Submandibular and Sublingual Glands
- Pterygopalatine targets include Lacrimal Gland, Nasal, Pharyngeal, and Palatal Mucus Glands
Brain Stem Nucleus of CN IX to Otic Ganglion targets Parotid Gland
Sensory Ganglion of CN VII within the petrous bone