Ocular anatomy Orbit and eyebrows

7 bones of the orbit

frontal, zygomatic, maxilla, palatine, sphenoid, ethmoid, lacrimal

The orbit contains

the globe, extraocular muscles, orbital nerves, blood vessels, and fat

The roof of the orbit is formed by what bones?

Frontal bone and the lesser wing of the sphenoid bone

The floor of the orbit is formed by what bones?

palatine, zygomatic, and maxillary bones

Why is the floor the weakest wall of the orbit?

The infraorbital groove/canal and maxillary sinus

What bones form the medial wall of the orbit?

ethmoid, maxillary, lacrimal, and sphenoid (body)

Sinus infections can easily pass into the orbit from what sinus?

Ethmoid sinus (thin walls)

What passes through the optic canal?

Optic nerve (CN II)

Ophthalmic artery

What passes through the superior orbital fissure and through the annulus of zinn (inferior half of superior orbital fissure)?

Superior and inferior division of oculomotor nerve (CN III), Nasociliary nerve (CN V-1), and abducens Nerve (CN VI)

What passes through the superior orbital fissure and above the annulus of zinn (superior half)?

Superior opthalmic vein, Trochlear nerve (CN IV), Lacrimal nerve (CN V-1), and Frontal nerve (CN V-1)

What are the branches of the trigeminal nerve (CN V)?

V-1 opthalmic N (frontal, lacrimal, nasociliary nn) V-2 maxillary N (zygomatic, infraorbital nn)

What passes through the inferior orbital fissure?

Inferior opthalmic vein, zygomatic nerve (CN V-2), infraorbital nerve (CN V-2), artery, and vein

Where is the lacrimal fossa (for the lacrimal gland)?

Located in the frontal bone temporally

Where is the lacrimal fossa (for the lacrimal sac)?

Located medially, formed by the lacrimal bone adn frontal process of the maxillary bone

What sits in the nasolacrimal canal and what does it do?

Nasolacrimal duct, drains tears into the nose

What passes through the superior orbital foramen/notch?

Supraorbital nerve (CN V-1), artery, and vein

What passes through the superior trochlear foramen/notch?

Supratrochlear nerve (CN V-1), artery, and vein

Where is the superior trochlear foramen/notch located?

In the frontal bone medial to the supraorbital foramen

What passes through the infraorbital foramen?

The infraorbital nerve (CN V-2), artery, and vein

What are the 3 tunics of the eye?

Outer fibrous layer, middle vascular layer (uvea), and inner neural layer

What is in the outer fibrous layer of the eye?

cornea and sclera

What is in the middle vascular layer of the eye?

iris, ciliary body, and choroid

What is in the inner neural layer of the eye?

retina

What is tenon's capsule? (aka bulbar fascia)

a sheet of dense connective tissue that covers the sclera

Whitnall's ligament

Transverse dense connective tissue in the superior orbit that courses from the lateral orbital wall to medial orbital wall

Lockwood's ligament

Transverse dense connective tissue in inferior orbit that courses from lateral orbit wall to medial orbit wall

Medial check ligament

Transverse dense connective tissue that is an expansion of the sheath of the medial rectus, attaches to the lacrimal bone

Lateral check ligament

Transverse dense connective that is an expansion of the sheath of the lateral rectus, attaches to the zygomatic bone

What is the purpose of the check ligaments?

To prevent overaction of the lateral rectus muscle

Orbital septal system

web of interconnecting connective tissue septa that organizes the orbital space. Anchors and supports EOMs, nerves, and blood vessels

What are the 6 nerves of the orbit?

Optic nerve (CN II), Oculomotor nerve (CN III), Trochlear nerve (CN IV), Opthalmic nerve (CN V-1), Maxillary nerve (CN V-2), and abducens nerve (CN VI)

What are the blood vessels of the orbit?

the opthalmic artery and its branches, superior and inferior opthalmic vein and its branches

Extraocular muscles

Recti muscles (medial, lateral, superior, and inferior rectus), oblique muscles (superior and inferior obliques)

Eyelid retractor muscles

Levator palpebrae, Muller;s muscle, capsulopalpebral fascia

Where are the eyebrows located?

Between the superior orbital rim (margin) and superior nuchal line

What are the layers of the eyebrows?

Skin, dense connective tissue, muscle, loose connective tissue, and periosteum

What is the main type of cell in the epidermis and what do they do?

Keratinocytes, produce the fibrous protein keratin, which provides structure and water-resistant properties

What layer of the epidermis do the keratinocytes undergo mitosis?

Stratum basale

What is desquamation?

The process of keratinocytes being continually pushed up through the layers of the epidermis, dying, and being shed.

What do langerhans cells do?

In epidermis, play a role in immune response (WBC)

What do Merkel cells do?

Attach to nerve ending to form light touch receptors

What does the basement membrane do?

Connects epithelial cells to underlying dermis, serves as a partial barrier allowing only water and small molecules to pass into the dermis

What is connective tissue composed of?

fibroblasts, collagenous fibers, elastic fibers, adhesive proteins, ground substance (water, GAGs, proteoglycans)

Dermis is composed of:

Connective tissue plus WBCs and adnexal structures (sebaceous glands, hair follicles, hair, sweat glands)

What do fibroblasts do?

produce collagen and elastin

What is the hypodermis composed of?

adipose and loose connective tissue

Dense connective tissue

connects skin to underlying muscle and contains arteries, veins, and nerves supplying the eyebrows

frontalis muscle origin and insertion

origin: high on the scalp

insertion: supraorbital margin

frontalis muscle insertion

near supraorbital margin

What does frontalis muscle do?

raises eyebrows (surprise)

Corrugator muscle origin and insertion

origin: supraciliary arch

insertion: medial forehead

What does corrugator muscle do?

Draws the eyebrow down and wrinkles the forehead vertically (look of trouble or concentration)

Procerus muscle origin and insertion

Origin: nasal bones.

Insertion: medial forehead.

what does the procerus muscle do?

-Pulls medial component of the brow inferiorly and creates furrows over the nose

-muscle of menace or aggression

Orbicularis oculi origin and insertion

Origin: medial orbital rim

insertion: lateral palpebral ligament

What does the orbicularis oculi do?

depresses brows and closes eyelids

what are the 4 eyebrow muscles innervated by?

CN VII (facial nerve)

Why is the loose connective tissue associated with the eyebrow considered the danger zone?

pus and blood can spread easily and infections can pass into the cranial cavity through veins

Osteogenic cells

stem cells that differentiate into osteoblasts

osteoblasts

bone forming cells