H&N exam 1

Viscerocranium

Face

Neurocranium

Cranial base and calvaria

Coronal suture

Joins frontal and parietal bones

Sagittal suture

Joins the two parietal bones along the midline.

Lamdboid suture

Joins the occipital bone with the parietal bones at the posterior of the skull.

Paired bones

Pariteal and temporal

Unpaired bones

Fronta, occipital, sphenoid, ethmoid

Fontanelles

Gaps between incompletely joined bones in infants

Pterion

Region in temporal fossa where many skull bones meet

• Middle meningeal artery travels deep to the pterion

A fracture in this region can cause a epidural hematoma (blood btwn skull and dura mater)

Pterion

• because it damages the middle meningeal artery

Hypophyseal fossa (pit in the sella turcica)

Houses the pituitary gland

Dorsum sellae

Posterior boundary of the sella turcica.

Petrous ridge

Part of the temporal bone separating the middle and posterior cranial fossae.

Foramen magnum

Large opening in the occipital bone

Occipital condyles

 Articulate with the atlas (C1)

CN VII nerve route

• enters the internal acoustic meatus

• passes through the facial canal in the temporal bone

• its motor branches exit via the stylomastoid foramen.

CN XI

has spinal roots that enter the skull through the foramen magnum before exiting through the jugular foramen

Layers of scalp superficial to deep

·       S — Skin

·       C — Connective tissue (dense)

·       A — Aponeurosis

·       L — Loose connective tissue

·       P — Periosteum

Dense connective tissue

Contains major nerves and blood vessels supplying the scalp

Aponeurotic layer

Aponeurotic layer

Loose connective tissue

Allows movement of the superficial scalp

Periosteum

Covers the skull bones

Outside to inside of the skull

• Scalp

• Calvarial bone

• Meningeal vessels

• Meninges

• Subarachnoid space

• Cerebral arteries

Structure of the Cranial Vault

Outer compact table: Hard, dense bone

Diploë: Spongy bone containing diploic veins

Inner compact table: Hard, dense bone

Emissary veins:

Veins that pass through openings in the skull and connect veins outside the skull with intracranial venous sinuses.

3 meningeal layers

• Dura mater

• Arachnoid mater

• Pia mater

2 Layers of the Dura mater

1.      Periosteal layer: Outer layer attached to the skull.

2.      Meningeal layer: Inner layer that forms the dural folds.

When the two layers separate, they create dural venous sinuses.

Epidural space

• Between skull and dura

• potential space in the cranial cavity

Subdural space

• Between dura and arachnoid

• Potential space

Subarachnoid space

• Between arachnoid and pia

• contains CSF and major cerebral blood vessels

Dural fold

• Dural folds are formed by the meningeal layer of dura mater.

• They divide the cranial cavity into smaller compartments and help support the brain.

Dural fold: Falx cerebri

Separates the right and left cerebral hemispheres

Tentorium cerebelli

Separates the cerebrum from the cerebellum

The superior sagittal sinus travels along..

the superior attachment of the falx cerebri.

Dural venous sinus

Dural venous sinuses are endothelium-lined spaces formed between the periosteal and meningeal layers of dura mater.

They receive:

• Venous blood from the brain, scalp and other connected regions

• CSF through arachnoid granulations (villi)

Superior sagittal sinus

Confluence of sinuses

Transverse sinus

Sigmoid sinus

Arachnoid granulations

• allow CSF to return to venous circulation.

• CSF passes from the subarachnoid space into the dural venous sinuses.

The cavernous sinus is located

on either side of the sella turcica.

why is CN VI (Abducens nerve) vulnerable to damage in the cavernous sinus

because it travels directly beside the internal carotid artery

structures in the cavernous sinus

Structure	Location
CN III — Oculomotor	Lateral wall
CN IV — Trochlear	Lateral wall
CN V1 — Ophthalmic	Lateral wall
CN V2 — Maxillary	Lateral wall
CN VI — Abducens	Within sinus
Internal carotid artery	Within sinus

2 arterial systems that supply blood to the brain

Anterior: internal carotid

Posterior: vetebral arteries

Pathway 1: Internal carotid arteries (anterior)

• Common carotid artery

• Internal carotid artery

• Enters skull through carotid canal

• ACA

• Anterior cerebral artery

• MCA

• Middle cerebral artery

• The internal carotid artery also gives off the posterior communicating artery and ophthalmic artery.

Pathway 2: Vertebral arteries (posterior)

• Right and left subclavian arteries

• Right and left vertebral arteries

• Travel through transverse foramina C6–C1 and enter the foramen magnum

• One basilar artery

• Formed when the two vertebral arteries join; travels along the pons

• Right and left posterior cerebral arteries (PCA)

Anterior cerebral arteries (ACA)

Right and left branches of the internal carotid system.

   Anterior communicating artery (ACom)

 Connects the right and left anterior cerebral arteries.

   Internal carotid arteries

 Contribute to the anterior circulation.

Posterior communicating arteries (PCom):

Connect the internal carotid arteries to the posterior cerebral arteries.

 Posterior cerebral arteries (PCA):

Arise from the basilar artery and contribute to the posterior portion of the circle.

Anastomosis:

A connection between blood vessels.

Collateral circulation:

Alternate circulation that allows blood to travel around an obstructed vessel.

structures that pass through Optic canal

CN II and ophthalmic artery

structures that pass through Superior orbital fissure

CN III, IV, V1, VI and superior ophthalmic vein

structures that pass through Inferior orbital fissure

Maxillary nerve (V2) and inferior ophthalmic vein

structures that pass through Anterior/posterior ethmoidal foramina

Ethmoidal neurovascular structures

structures that pass through Nasolacrimal canal

Nasolacrimal duct

Branches of V1 associated with the superior orbital fissure

•  Frontal nerve

• Lacrimal nerve

• Nasociliary nerve

Orbital adipose tissue

·       Protection of orbital structures

·       Support of eye movement

Orbital septum

·       Preseptal space: Contains eyelid, skin, and fascia.

·       Postseptal space: Located behind the orbital septum.

The postseptal space is further divided into

·       Intraconal space: Within the muscle cone.

·       Extraconal space: Outside the muscle cone.

Medial palpebral commissure

Medial junction of upper and lower eyelids

Lateral palpebral commissure

Lateral junction of upper and lower eyelids

Palpebral fissure

Opening between the eyelids

Sclera

White outer covering of the eye

Cornea

Transparent anterior covering

Iris

Colored portion of the eye

Pupil

Opening in the center of the iris

Conjunctiva

Mucous membrane covering portions of the eye and eyelids

• Palpebral conjunctiva: Lines the inner surface of the eyelids.

• Bulbar conjunctiva: Covers the anterior sclera.

Levator palpebrae superioris

• raises upper eyelid

• Inn: CN III

Superior tarsal muscle

• assists upper eyelid elevation

• Inn: sympathetic

Orbicularis oculi

• Closing eyes or blinking

• CN VII

 lacrimal apparatus

produces and drains tears

Lacrimal gland

• Located in the superolateral portion of the orbit.

• Secretes lacrimal fluid (tears).

• Receives parasympathetic innervation associated with CN VII (facial nerve).

Tear drainage pathway

1. Lacrimal gland

2. Produces tears

3. Conjunctival sac / surface of eye

4. Tears move medially across the eye

5. Lacrimal puncta

6. Lacrimal canaliculi

7. Lacrimal sac

8. Nasolacrimal duct

9. Inferior meatus of nasal cavity

Outer fibrous layer

Sclera and cornea

Middle vascular layer

Choroid, ciliary body and iris

Inner neural layer

Retina

Choroid

• Pigmented, vascular layer.

• Supports the retina.

Ciliary body

•  Anterior continuation of the choroid

• Connected to the lens through zonular fibers.

• Contains the ciliary muscle.

Retina

• Neural layer of the eye.

• Contains rods and cones (photoreceptors).

• Associated with the optic nerve (CN II).

Anterior chamber

Between cornea and iris

Posterior chamber

Between iris and lens

Aqueous humor

anterior and posterior chambers

Vitreous humor

large cavity behind the lens.

Superior rectus

• Elevation; also adduction and intorsion

• CN III

Inferior rectus

• Depression; also adduction and extorsion

• CN III

Medial rectus

• Adduction (eye moves medially)

• CN III

Lateral rectus

• Abduction (eye moves laterally)

• CN VI

Superior oblique

• Intorsion; also depression and abduction

• CN IV

• Adducted eye looks down

Inferior oblique

• Extorsion; also elevation and abduction

• CN III

• Adducted eye looks up

Intorsion (Adduction)

Top of the eye rotates toward the nose.

Extorsion (ab-duction)

Top of the eye rotates away from the nose.

H test: Rectus muscles

test vertical movement when eye is abducted.

H test: Oblique muscles

 test vertical movement when eye is adducted

CN III somatic motor

moves and lifts eyeball

Innervates:

·       Superior rectus

·       Inferior rectus

·       Medial rectus

·       Inferior oblique

·       Levator palpebrae superioris

CN III parasympathetic

Controls pupil size and helps the eye focus on nearby objects.

parasympathetic functions:

Ciliary muscle	Changes lens shape to focus on nearby objects (accommodation)
Sphincter pupillae	Constricts the pupil (makes it smaller)