Download Document

Fascial Compartments of the Neck
The orbital region
Meninges (review)
Dural venous sinuses (review)
BAAB
23/05/2016

Fascial spaces (also termed fascial tissue spaces or tissue
spaces) are potential spaces that exist between the fasciae
and underlying organs and other tissues.

The fascial spaces are different from the fasciae
themselves, which are bands of connective tissue that
surround structures, e.g. muscles.

Fascia is a layer of fibrous tissue that surrounds muscles,
vessels and nerves.

In the neck, there are several layers of fascia, which act
to support and compartmentalise the structures present.

The spaces filled with loose areolar connective tissue
may also be termed clefts.

Other contents such as salivary glands, blood vessels,
nerves and lymph nodes are dependent upon the
location of the space. Those containing neurovascular
tissue (nerves and blood vessels) may also be termed
compartments.

Boundaries of the Neck
The superior boundary of the neck is demarcated by the
superior nuchal line of the cranium and the lower margin
of the mandible.

The inferior boundary of the neck is demarcated by the
suprasternal notch, the clavicle and the first rib.

Clearly, these boundaries are irregular and difficult to
define precisely, because of the continuity of structures
running from one region to another (i.e. between thorax
and neck and between neck and head).

The neck is conveniently thought of as the tissue
surrounding the 7 cervical vertebrae.

Fascial Compartments of the Neck are divided into
superficial and deep parts.

The superficial fascia (tela subcutanea) surrounds the
entire neck, but does not contribute to the
compartmentalization.

The superficial cervical fascia lies between the
dermis and the deep cervical fascia.
Fig; The platysma muscle, located within the superficial cervical
fascia

The superficial cervical fascia contains various
structures:
◦
◦
◦
◦
◦

Neurovascular supply to the skin
Superficial veins (e.g the external jugular vein)
Superficial lymph nodes
Fat
Platysma muscle
In obese individuals, extra fat is deposited in the
superficial fascia, creating the ‘double chin’.

The platysma muscle is situated on the
anterior aspect of the neck.
◦ It has two heads, which originate from the fascia of the
pectoralis major and deltoid.
◦ Fibres from the two heads cross the clavicle, and meet in the
midline, fusing with the muscles of the face.
◦ Motor innervation to the platysma is via the cervical branch
of the facial nerve.

The deep cervical fascia is located underneath the
superficial fascia, and is organised into several
layers. These layers act like a shirt collar, supporting
the structures and vessels of the neck.

The deep fascia also has a superficial and a deep
fasciae.
1. One superficial layer of deep fascia is called
investing fascia, surrounding the whole neck.
Fig: Transverse section of the neck. The investing layer of fascia in
highlighted in blue. Note how the fascia completely envelopes the
SCM and trapezius.


It surrounds all the structures in the neck. Where it
meets the trapezius and SCM muscles, by splitting into
two, completely surrounding them.
The investing fascia can be thought of as a tube; with
superior, inferior, anterior and posterior attachments:
◦ Superior: attaches to the external occipital protuberance and
the superior nuchal line.
◦ Anterior: attaches to the hyoid bone.
◦ Inferior: attaches to the spine and acromion of the scapula,
the clavicle, and the manubrium of the sternum.
◦ Posterior: attaches along the ligamentum nuchae.

There are four layers of deep fascia that separate the neck
into compartments.
2. The prevertebral layer (yellow in the fig), which
surrounds muscles attached to the vertebral column.

The prevertebral fascia surrounds the vertebral column and
its associated muscles (scalene, prevertebral, and deep
muscles of the back). It has attachments along the
antero/posterior and supero/inferior axes:

Superior: attaches to the base of the skull.

Anterior: attaches to the transverse
processes and vertebral bodies of the vertebral column.

Posterior: attaches along the ligamentum nuchae.

Inferior: fuses with the endothoracic fascia of the
ribcage.

The anterolateral portion of prevertebral fascia forms
the floor of the posterior triangle of the neck. It also
surrounds the brachial plexus and subclavian artery as
they leave the neck, forming the axillary sheath. The
axillary sheath continues from the prevertebral layer
and surrounds the brachial plexus

Transverse section of the neck. The carotid sheaths and
prevertebral sheaths are highlighted.
3. The pretracheal or visceral layer (red), which is
found surrounding the anterior organs.
 The pretracheal layer of fascia is situated anteriorly in
the neck. It spans between the hyoid bone and the
thorax, where it fuses with the pericardium.
 The trachea, oesophagus, thyroid gland and infrahyoid
muscles are enclosed by the pretracheal fascia. It can be
anatomically divided into two parts:
 Visceral – encloses the thyroid gland, trachea and
oesophagus.
 Muscular – encloses the infrahyoid muscles.
 The posterior aspect of the muscular fascia is formed
by contributions from the buccopharyngeal fascia (a
fascial covering of the pharynx).

Fig – Transverse section of the neck, showing the pretracheal fascia in red.

4. The carotid sheath (green), which is formed by
condensation of the investing fascia , prevertebral and
pretracheal layers, surrounds the carotid artery, the jugular
vein and the vagus nerve.

The carotid sheaths are paired structures.

The contents of the carotid sheath are :

The carotid fascia is organised into a column, which runs
from the base of the skull to the thoracic mediastinum. This
is of clinical importance as a pathway for the spread of
infection.
◦ Common carotid artery (which bifurcates within the sheath into
the external and internal carotid arteries).
◦ Internal jugular vein.
◦ Vagus nerve.
◦ Cervical lymph nodes.
Fig: The carotid sheaths (green)
Clinical Relevance: Spread of Infections

The neck fascia compartmentalises the
structures within the neck. These layers of
tough fascia define where infection can
spread (e.g a superficial skin abscess is
prevented from spreading further into the
neck by the investing fascia).
Introduction
Bones of the orbit
Boundaries
Contents
Structures associated
Clinical correlates

Introduction:
◦ The orbit is a bonny pyramidal cavity or bonny socket of
the facial skull in which the eye and its appendages are
situated.
◦ it has a base in front and the apex behind.
◦ In the adult human, the volume of the orbit is 30 mL, of
which the eye occupies 6.5 mL.
Bones of the orbit:
There are seven bones that form the orbit:
Frontal bone
Lacrimal bone
Ethmoid bone
Zygomatic bone
Maxillary bone
Palatine bone
Sphenoid bone
Nasal bone (illustrated but not part of the orbit)
The seven bones that form the orbit:
yellow = Frontal bone
green = Lacrimal bone
brown = Ethmoid bone
blue = Zygomatic bone
purple = Maxillary bone
aqua = Palatine bone
red = Sphenoid bone
teal = Nasal bone (illustrated but not part of the orbit)


Borders:
The base, which opens in the face, has four
borders. The following bones take part in their
formation:
◦ Superior margin: frontal bone and sphenoid
◦ Inferior margin: maxilla, palatine and zygomatic
◦ Medial margin: ethmoid, lacrimal bone, and
maxillary bone
◦ Lateral margin: zygomatic and sphenoid
◦ The roof (frontal and sphenoid bones)
◦ lateral wall: zygomatic and sphenoid bones
◦ The floor: maxilla, zygomatic, and palatine bones
◦ medial wall: ethmoid, lacrimal, and frontal bones

Contents of the orbit are grouped into
◦ Nerves: Ophthalmic nerve, Oculomotor, trochlear
and abducent nerves (III, IV, VI), Optic nerve.
◦ Vessels: Ophthalmic vessels
◦ Muscles: Muscles of eyeball (extraocular muscles)
◦ Eyelids
◦ Conjunctiva
◦ Lacrimal apparatus
Ophthalmic nerve the first division of the trigeminal
(fifth cranial) nerve
 afferent nerve that supplies the globe and
conjunctiva, lacrimal gland and sac, nasal mucosa
and frontal sinus, external nose, upper eyelid,
forehead, and scalp
◦ It passes through the superior orbital fissure and
traverse the orbit.

The oculomotor (third cranial) nerve supplies
all the muscles of the eyeball except the
superior oblique and the lateral rectus
muscles.
• pass through the superior orbital fissure within the
common tendinous ring
• It passes through the superior orbital fissure within
the common tendinous ring
• The nerve also conveys preganglionic
parasympathetic nerve fibers to the orbit

The trochlear (fourth cranial) nerve supplies
only the superior oblique muscle of the eyeball
• It passes through the superior orbital fissure just
superior to the tendinous ring.

The abducent (sixth cranial) nerve supplies
only the lateral rectus muscle of the eyeball.
• It passes through the superior orbital fissure within
the common tendinous ring.
The ciliary ganglion is the peripheral ganglion of the
parasympathetic system of the eye.

Optic nerve

The optic (second cranial) nerve is the nerve of sight
◦ it extends from the eye to the optic chiasm.
◦ Developmentally, it may be considered as a tract between
the retina (a derivative of the brain) and the brain
◦ It is surrounded by meningeal sheaths continuous with those
of the brain, and also by the subarachnoid space.
◦ is pierced by the central vessels of the retina, and passes
through the optic canal to enter the middle cranial fossa.

Muscles of eyeball (extraocular muscles)

The eyeball is moved chiefly by six extrinsic
muscles: four recti and two oblique muscles.



These skeletal muscles arise from the posterior
aspect of the orbit (except for the inferior
oblique muscle) and are inserted into the sclera.
The four recti arise from a common tendinous
ring that surrounds the optic canal and a part of
the superior orbital fissure
The eye is poised in the fascia and fat of the
orbit, and equilibrium is maintained by all the
muscles, none of which ever acts alone.


Moreover, the two eyes move together in unison
(conjugately). Movements may be considered to
be around a vertical axis (abduction and
adduction), a lateromedial axis (elevation and
depression) and even an anteroposterior axis
(extorsion and intorsion).
Paralysis of an extrinsic eye muscle is noted by
• (1) limitation of movement in the field of action of
the paralyzed muscle and
• (2) the presence of two images (diplopia) that are
separated maximally when an attempt is made
to move the eye in the direction of primary
action of the paralyzed muscle.

Eyelids: These are musculofibrous folds in the
anterior part of each orbit.
◦ They are two sets, upper and lower lids
◦ They perform reflex blinking, distribute tears and
prevent drying of the cornea.
◦ The free margin of each lid possesses hairs termed
eyelashes (cilia).
◦ The upper eyelid is composed of skin and subcutaneous
tissue, muscle (the palpebral part of the orbicularis oculi
and the levator palpebrae superioris), fibrous tissue
(including the tarsal plate), and mucous membrane (the
palpebral part of the conjunctiva).


Conjunctiva
The conjunctiva is a connection (conjunction)
between the eyelids, sclera and cornea. It is the
mucous membrane that lines the posterior surface
of the eyelids (palpebral conjunctiva) and the
anterior aspect of the globe (bulbar conjunctiva).
◦ conjunctival sac is the potential space, lined by
conjunctiva, between the lids and the globe.
◦ palpebral fissure is the mouth of the conjunctival sac.
◦ Fornix is the reflection of the conjunctiva from the lid to
the globe; hence, superior and inferior fornices.
◦ Limbus is a junction between the bulbar conjunctiva and
the epithelial lining of the cornea.


Conjuntival innervation and blood supply.
The conjunctiva is supplied by branches of the
ophthalmic nerve. The vessels of the bulbar
conjunctiva are visible. They arise from (1) a
peripheral palpebral arcade and (2) the anterior
ciliary arteries. In acute conjunctivitis (e.g., from
wind exposure or infection) the bulbar conjunctiva
becomes brick-red (a "blood-shot eye"). In deeper
conditions (e.g., diseases of the iris or ciliary body),
in which branches of the anterior ciliary arteries are
dilated, a rose-pink band of "ciliary injection" is
produced around the margins of the cornea.

Lacrimal apparatus:
◦ The lacrimal apparatus comprises (1) the lacrimal gland
and its ducts and (2) associated passages for drainage:
the lacrimal canaliculi and sac and the nasolacrimal duct
◦ it lodges in a fossa anterolaterally at the roof of the
orbit.
◦ the main portion is the orbital part, but a process called
the palpebral part projects into the upper lid
◦ a dozen lacrimal ducts leave the palpebral part to enter
the superior conjunctival fornix where small accessory
lacrimal glands are also found.
◦ tears secreted keep the eye moist and free of foreign
bodies.
◦ the half of the lacrimal secretions that does not
evaporate drains into the lacrimal sac.

Review Questions :
1. Force applied to the rim of the orbit may be transmitted toward the side of the
nose. Which thin bones are likely to be splintered?
2. Which nerve accompanies the ophthalmic artery?
3. Which is the most important branch of the ophthalmic artery?
4. Which cranial nerve is "the weakling of the cranial contents" because of its likely
damage from increased intracranial pressure?
5. Where is the peripheral relay station of the parasympathetic fibers to the eye?
6. Which nerves enter the orbit within the common tendinous ring?
7. Which chief muscles and nerves are concerned with (a) closing the eyelids and (b)
opening them?
8. What are the main features of Horner syndrome?
9. On looking downward and to the right, a patient's left pupil failed to descend.
Which muscle is likely to be paralyzed?
10. On looking upward and to the left, a patient's right pupil failed to ascend.
Which muscle is most likely to be involved?

Lacrimal apparatus Conjunctiva Eyelids Optic
nereve Muscles of eyeball (extraocular
muscles) Oculomotor, trochlear and abducent
nerves (III, IV, VI) Ophthalmic vessels
Ophthalmic nerve