Dissection of Head and Neck

What is scalp?

The soft structure that covers the skull extending from the eyebrows in front.to the superior nuchal
lines behind.and from one superior temporal line to.the other superior temporal line at the sides.is
known as the scalp. It is the covering of the cranial vault.

Name the layers of the scalp.

It consists of 5.layers:

1. S – Skin
It contains numerous hair follicles and sebaceous glands.
2. C – Connective tissue (superficial fascia)
It is a dense fibro-fatty layer containing abundant vessels and nerves.
3. A – Aponeurosis (epicranial aponeurosis): also known as galea aponeurotica
It is the intermediate tendinous sheet that connects the frontal and occipital bellies of the
occipitofrontalis muscle. It represents the deep fascia of the scalp.
4. L – Loose areolar tissue
It is a very delicate and loose layer forming a potential space for collection of extravasated
blood.
5. P – Pericranium
It is the periosteum of the cranial vault.

Define temporal region or temple.

It is the region on either side of the head which lies between the superior temporal line above.and the
zygomatic arch below.

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Mention the steps of dissection to expose the layers of scalp.

Step 1: A sagittal from the root of the nose along the sagittal suture to the external occipital
protuberance.

Step 2: A coronal incision from the middle of the first incision to the mastoid process.

Step 3: Reflect the skin and and superficial fascia laterally. The superficial fascia contains many
vessels and nerves, but commonly visible are superficial temporal artery and vein.

Step 4: Now we’ll see the third layer of the scalp which contains occipito-frontalis muscle. Frontal
belly lies anteriorly and occipital belly posteriorly. The intermediate portion is the epicranial
aponeurosis.

Step 5: Underneath the third layer there lies a potential space containing loose areolar tissue which
is the fourth layer of scalp.

Step 6: Now a firm layer which is adherent to the bony skull is found and we can separate it from the
bone and reflect laterally. It is the pericranium. Here we observe that the pericranium is tightly
attached to the bone along the suture lines.

https://youtu.be/s7j5JpF1DbA

Which one is the dangerous layer of the scalp and why?

The fourth layer is called the ‘dangerous layer’ of the scalp. As it is a potential space for collection of
extravasated blood and emissary veins open into this layer, any infection from this layer can easily
enter into the intracranial venous sinuses resulting in a very fatal condition.

What is black-eye?

As the frontalis belly has no bony attachment, the potential space of 4th layer of the scalp is
continuous with the root of the nose and the eyelids. For this reason any extravasated blood due to a
blow on the skull slowly tracks down into the eyelids resulting in a blackish discolouration of the
eyelids . It is called black eye.

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What is emissary vein? Give one example.

The veins which establish communication between the extracranial veins and the intracranial venous
sinuses passing through the apertures in the wall of the cranium are called emissary veins. For
example, Parietal.emissary.vein.through the parietal foramen of the parietal bone connects the
superior sagittal sinus with the veins of the scalp.

What are diploic veins?

These are wide venous spaces of the marrow cavities between the outer and inner tables of the flat
bones of the skull. They communicate with the dural venous sinuses, meningeal veins and veins of
the pericranium. They are devoid of values.

Name the muscles of the eyeball.

A. Extra-ocular muscles
a) Voluntary extra-ocular muscles
1. Four recti: superior, inferior, medial and lateral rectus
2. Two oblique: superior and inferior oblique
3. One levator palpebrae superioris

All the voluntary extra-ocular muscles are innervated by oculomotor nerve

except SO4 LR6

b) Involuntary extra-ocular muscles

1. Superior tarsal
2. Inferior tarsal
3. Orbitalis

All the involuntary extra-ocular muscles are innervated by sympathetic nerves

from superior cervical ganglion.

B. Intra-ocular muscles
1. Sphincter pupillae
2. Dilator pupillae
3. Ciliary muscle

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Mention the steps of dissection of face.

Step 1: A longitudinal incision in the median plane from the hair line through the nasion upto the
symphysis menti encircling the nostrils and oral orifice.

Step 2: Two incisions encircling the eyes on both sides.

Step 3: One horizontal incision on each side of the face from the medial angle of the eye upto the
tragus of the ear.

Step 4: Another horizontal incision on each side of the face from the angle of the mouth upto the
angle of mandible.

Step 5: Now the skin of the face is divided into three flaps on each side of the face and those flaps
are reflected laterally.

Now the fibres of the superficial muscles of the face, vessels, nerves and parotid duct are exposed.

https://youtu.be/pyivZZLRFis

What is the boundary of face?

The face is extended from the adult hair-line above upto the chin below and from one auricle to the
other auricle at the sides. The forehead stands therefore common to the face and scalp.

Identify the following muscles in the cadaver.

• Frontalis
• Orbicularis oculi: orbital part, palpebral part and lacrimal part
• Orbicularis oris
• Zygomaticus major
• Mentalis
• Buccinator
• Masseter
• Platysma
• Facial artery

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 • Facial vein
• Parotid gland and its duct
• Facial nerve and its branches
• Sternocleidomastoid muscle

Name the muscles around the orifice of the eye.

1. Orbicularis oculi
2. Corrugator supercilii
3. Frontalis
4. Levator palpebrae superioris

Name the muscles around the nasal cavity.

1. Procerus
2. Nasalis
3. Depressor septi

Name the muscles around the mouth.

1. Orbicularis oris
2. Nine Muscles Converging Around the Mouth:
a) Levator labii superioris alaeque nasi
b) Levator labii superioris
c) Levator anguli oris
d) Zygomaticus major
e) Zygomaticus minor
f) Depressor labii inferioris
g) Depressor anguli oris
h) Risorius
i) Buccinator

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Name the muscles of facial expression.

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Whice nerve gives the motor supply of face?

Facial nerve

Name the branches of facial nerve.

There are five branches of facial nerve:

1. Temporal
2. Zygomatic
3. Buccal: upper buccal and lower buccal
4. Marginal mandibular
5. Cervical

Which nerve gives the sensory supply of face?

Trigeminal nerve

Name the branches of trigeminal nerve.

There are three branches of trigeminal nerve:

1. Ophthalmic
2. Maxillary
3. Mandibular

Arterial supply of face

1. Facial artery
2. Transverse facial artery
3. Arteries that accompany the cutaneous nerves

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Why facial artery is tortuous?

To facilitate its extension during movements of temporomandibular joint.

Name some other tortuous arteries?

1. Splenic artery
2. Uterine artery
3. Testicular artery

Venous drainage of face

1. Facial vein.
2. Retromandibular vein

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What is the dangerous area of face and why?

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The facial vein and its communications are devoid of valves in their lumens. Since facial vein rests
directly on the muscles of facial expression, the movements of these muscles may facilitate the
spread of septic emboli from infected area of the lower part of the nose, upper lip, and adjoining
part of the cheek in retrograde direction through deep facial vein, pterygoid venous plexus, and
emissary vein into the cavernous sinus leading to meningitis and cavernous sinus thrombosis. For
this reason, this portion of the face is called dangerous area of the face.

What type of gland is parotid gland?

It is an exocrine gland secreting saliva.

What are the structures present within the parotid gland?

1. Facial nerve
2. Retromandibular vein
3. External carotid artery

Where and how does the parotid duct open?

Parotid Duct (Stenson’s Duct), about 5 cm long, emerges from the middle of the anterior border of
the gland and pierces buccal pad of fat, buccopharyngeal fascia, and buccinator muscle to open into
the vestibule of the mouth opposite the crown of upper second molar tooth.

How triangles of the neck are divided?

By the sternocleidomastoid muscle the neck is divided into two trinagles:

1. Anterior triangle: in front of the sternocleidomastoid muscle

2. Posterior triangle: behind the sternocleidomastoid muscle

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What are the subdivisions of the anterior triangle of neck?

For convenience of description, the anterior triangle has been subdivided, by the digastric muscle
and superior belly of omohyoid muscle, into the following 3½ triangles:

1. Submental triangle (half only)

2. Digastric (submandibular) triangle
3. Carotid triangle
4. Muscular triangle

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What are the subdivisions of the posterior triangle of neck?

The posterior triangle is subdivided into two parts by the inferior belly of the omohyoid muscle, which
crosses the lower part of the triangle obliquely upwards and forwards:

1. Occipital triangle: larger upper part

2. Subclavian (supraclavicular) triangle: smaller lower part

These parts are so named because they contain occipital and subclavian arteries, respectively.

Give the boundaries of the anterior triangle of neck.

It is a triangular area on each side of the front of the neck.

a) In front: by the midline of the neck extending from the chin to the jugular notch
b) Behind: by the anterior border of the sternocleidomastoid muscle
c) Base: by the base of the mandible and a line joining its angle to the mastoid process
d) Apex: suprasternal notch
e) Roof: investing layer of deep cervical fascia

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Give the boundaries of the posterior triangle of neck.

It is the triangular space on the side of neck behind the sternocleidomastoid muscle.

a) In front: posterior border of sternocleidomastoid muscle

b) Behind: anterior border of trapezius muscle
c) Base: superior aspect of middle third of the clavicle
d) Apex: meeting point of sternocleidomastoid and trapezius muscles at the superior
nuchal line of the occipital bone
e) Roof: investing layer of deep cervical fascia

Steps of dissection of anterior triangle of neck.

Step 1: A longitudinal incision from the jugular notch to the sysmphysis menti along the middle line
of the neck.

Step 2: An oblique incision from the symphysis menti to the angle of the mandible along its base,
then carrying it to the tip of the mastoid process.

Step 3: Reflect the triangular flap of the skin.downwards and laterally up to the anterior margin of the
sternocleidomastoid.

Boundaries of carotid triangle.

1. Superiorly: posterior belly of digastric muscle supplemented by stylohyoid muscle

2. Anteroinferiorly: superior belly of omohyoid muscle
3. Posteriorly: anterior border of sternocleidomastoid muscle
4. Roof: investing layer of deep fascia

Why it is called carotid triangle?

It is so called because it contains all the three carotid arteries – common carotid, internal carotid,
and external carotid.

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Contents of carotid triangle.

1. Carotid arteries
a) Common carotid artery
b) Internal carotid artery
c) External carotid artery and its five branches
2. Carotid sinus and body
3. Internal jugular vein
4. Last three cranial nerves
a) Vagus nerve
b) Spinal accessory nerve
c) Hypoglossal nerve
5. Carotid sheath
6. Ansa cervicalis
7. Cervical part of sympathetic chain
8. Deep cervical lymph nodes

Contents of carotid sheath

1. Internal jugular vein

2. Common carotid artery
3. Internal carotid artery
4. Vagus nerve
5. Ansa cervicalis embedded in its anterior wall

Sternocleidomastoid muscle

Origin

a) Sternal head: superolateral part of the anterior surface of manubrium sterni

b) Clavicular head: medial third of the superior surface of clavicle

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Insertion

a) Lateral surface of the mastoid process (tendinous)

b) Lateral half of the superior nuchal line of the occipital bone (aponeurotic)

Nerve supply

a) Motor: spinal accessory nerve

b) Sensory (proprioception): ventral rami of C2 and C3

Action

a) Individual contraction: same side tilting and opposite side rotation of the head
• Upward sideway glance
b) Simultaneous contraction: forward movement of the head
• Lifting the head from the pillow
• Bending the head during eating

Dr S M Abu Sayeed
Curator, Anatomy Department
Jashore Medical College, Jashore

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