HEAD AND NECK
Skull, Scalp, Superficial Face
>Before studying the detailed anatomy of the Head and Neck, examine the following bones of the skull:
Major Bones of the Skull
|Lateral aspect of the mandible:
- inferior border
- posterior border
- coronoid process
- head of condyle
- neck of condyle
- mandibular notch
|Other items of lateral skull:
- temporomandibular joint
- external auditory meatus
- zygomatic arch
Air Sinuses of the Skull
| Several of the bones of the skull have
developed air spaces that are lined with mucous membrane. It is this mucous
membrane that becomes infected in sever cases of sinusitis. It is also
irritation of the mucous membrane that results in excessive fluid production
that can fill the air spaces and give you a stuffed nose feeling. Since
these sinuses are embedded in bone, they cannot be seen easily on regular
skull preparations and usually require sawing into the bone to see them.
Some believe that the function of the sinuses are twofold: 1) makes the
skull lighter to carry around and 2) serve as resonating chambers during
speech. The figures below were taken from a specially prepared skull.
Once you have learned some of
the bones of the skull, you should then try to visualize some areas as
they project to the skin. In the following diagrams, you can see some areas
of the skull as they project onto the skin of the face.
In cadaver dissections, the skin is removed carefully and the muscles of facial expression are identified. This is no easy task since the skin is very thin and with very little fatty tissue beneath it. The motor nerves to the muscles of facial expression and the muscles themselves are just beneath the skin. Up until now you have studied muscles that have had 2 bony attachments. The muscles of the face may have a bony attachment but the insertion is into the skin. This
is how we can make facial expressions of happiness, sadness, anger or disapproving. Most of us understand these expressions well.
|The sensory nerves of the face enter the face through a series of foramina:
Identify the following on the anterior skull and face
- 1 supraorbital (supraorbital nerve & vessels) Deep to frontalis m.
- 2 infraorbital (infraorbital nerve & vessels) Deep to levator labii superioris m.
- 3 mental (mental nerve & vessels) deep to the platysma m.
- 4 zygomaticofacial (zygomaticofacial nerve)
- superciliary arch
- canine fossa
- alveolar processes
- anterior nasal spin
Once the skin is removed and the muscles cleaned, you can start to name them. In the following images, the muscles are identified.
MUSCLES OF THE FACE
Muscles of facial expression (image 1):
- orbicularis oculi
- orbital portion
- palpebral portion
Image 2 displays the buccinator and the masseter muscles. The masseter is a muscle of mastication, not facial expression but it is superficial in the face.
- zygomaticus major
- levator labii superioris alequae nasii
- levator anguli oris
- orbicularis oris
- depressor anguli oris
- depressor labii inferioris
You might notice that the muscles of facial expression are arranged around the orifices of the face: orbit, nasal cavity, mouth and ear (although you wont examine these).
Muscles around the mouth include:
Muscles around the orbit are:
- zygomaticus major (3)
- levator labii superior alequae nasii (4)
- levator anguli oris (5)
- orbicularis oris (6)
- risorius (7)
- depressor anguli oris (8)
- depressor labii inferioris (9)
- frontalis (1)
- orbicularis oculi (2)
TO THE FACE
|The motor innervation to the muscles of facial expression is Cranial Nerve VII (Facial) (yellow
in the diagram)
It leaves the skull through the stylomastoid foramen on the base of the skull and immediately turns forward to enter the substance of the parotid gland (pink in the image). While within the gland, it divides into 5 major divisions:
Another nerve enters deep in the buccal area where the buccal branches of the facial nerve are found but it is a purely sensory branch of the mandibular branch of Cranial Nerve V (Trigeminal).
It supplies the mucous membrane inside the cheek and to the skin in this area. The parotid duct (white) can be seen crossing the masseter muscle on it way to penetrate the buccinator muscle. It opens into the mouth opposite the upper 2nd molar tooth. It forms a small swelling (papilla)
inside the oral cavity that can be easily seen. The partotid gland is one of three salivary glands in the head and neck.
- T -- temporal
- Z -- zygomatic
- B -- buccal
- M -- mandibular
- C -- cervical
The transverse facial artery (red) runs just above the parotid duct and is a branch of the superficial temporal artery.
|The arterial and venous supply to the face is seen in the diagram. They are the:
The facial vein is important clinically because it has a direct connection to the ophthalmic vein and then to a deep venous sinus within the cranial cavity, the cavernous sinus. Bacteria can enter the facial vein and gain access to internal cranial structures resulting in infection there. This is probably the reason our mothers always said not to squeeze our pimples.
- Facial artery
- inferior labial
- superior labial
- Facial vein
- Superficial temporal artery
- Superficial temporal vein
FEATURES OF THE ORBITAL REGION
|Inspect and palpate the living eye. To the right are a few items that can easily be seen:
- palpebral commissures
- medial & lateral angles (7,8)
- sclera (3)
- iris (2)
- pupil (1)
- lacrimal caruncle (4)
- lacrimal punctum (5)
- openings of tarsal glands (6)
|Under the lacrimal caruncle (4) is located the medial palpebral ligament to which the orbicularis oculi muscle attaches and beneath which is the lacrimal sac (7) which empties into the lacrimal duct (8) that enters the nose.
Tarsal cartilages are found in each eye lid and add rigidity to the lids. These can be seen if the eyelid is inverted so that the conjuntival side is exposed.
Structures of the External Ear
|On yourself or a lab partner, identify the following parts of the external ear:
- 1 concha
- 2 crus of helix
- 3 helix
- 4 scaphoid fossa
- 5 antihelix
- 6 antitragus
- 7 tragus
Sensory Nerves of the Face
|The sensory nerves of the face are terminal branches of the three divisions of the trigeminal nerve (cranial nerve V)
Opthalmic division (V1)
- external nasal
Maxillary division (V2)
Mandibular division (V3)
The skin of the scalp continues from t he front and lateral side of the face into the occipital region of the skull posteriorly. The makeup of the scalp is important clinically because
trauma to the scalp is frequent and it is up to the clinician to determine by palpation and observation just how serious the trauma is.
|The scalp is made of 5 layers and they spell scalp:
The blood vessels travel through the dense connective. The connective tissue has a special relationship with the arteries in this area. When an artery is severed, the connective tissue fibers around the vessel contract and pull the artery open. This results is more hemorrhage than in other places. With scalp hemorrhage, compression must be used to stop the bleeding. Blood vessels and nerves come into the scalp from three different regions: 1) anterior (supraorbital), 2) lateral (superficial temporal), 3) posterior (occipital). There is free anastomoses from side
to side. With all of this blood supply, lacerations of the scalp are usually profuse and because of the nerve supply, very sensitive.
- S -- skin
- C -- dense Connective tissue
- A -- aponeurosis
- L -- loose connective tissue
- P -- periosteum
The loose connective layer of the scalp will allow bacteria or fluid to pass freely from the posterior aspect of the scalp into the eyelids in front. Trauma in the back of the head can result in blood showing up in the eyelids and should make you suspect something going on in the back of the head.
Major Sutures and Anthropological Landmarks of the Skull
Finally, take a look at some of the skull structures you have identified thus far but through a radiographic image.
|The major sutures to identify are the:
Major anthropological points:
- coronal suture
- frontal sinus
- ethmoid sinus
- nasal cavity
- inferior concha
- maxillary sinus
- ramus of mandible
- body of mandible
- nasal septum
- mastoid air cells
- sphenoid sinus
- hypophyseal fossa
Summary of items in this lesson
Table of Contents for Head & Neck
Practice Practical Exam
Practice Written Exam
||Copyrightę1999 by Wesley Norman, PhD