Lecture 4 = Skull, Face, and Scalp Lecture Flashcards
What’s the neurocranium and what bones does it have?
Cranial bones to protect the brain. Bony case of brain and meninges, it contains the proximal portions of the cranial nerves and the vasculature of the brain. It consists o the calvaria (skull cap) and cranial base.
It has 8 bones:
- 4 singular midline bones - frontal (development of a right and left half of the frontal bone results in a midline suture anterior to bregma = metopic suture), ethmoidal, sphenoidal and occipital bones
- 2 paired bones - temporal and parietal bones united by sutures (developmentally these are synchrondroses joints filled with hyaline cartilage)
What’s the viscerocranium and what bones does it have?
facial bones to protect airway and alimentary canal. Facial bones that develop from mesenchyme from the pharyngeal arches, supports anterior cranium and defines, mouth, nose, and most of the orbits.
15 bones comprise the cranial base:
- 3 singular midline bones - ethmoid, vomer, and mandible
- 6 paired bones - maxilla, inferior nasal concha (turbinate), zygomatic, palatine, nasal, and lacrimal - there are responsible for the bilateral symmetry of the face
What is the mandible not a bone of the face?
it’s the lower jaw bone and articulate with the face at the TMJ - b/c of this the bone is with the oral cavity and is not a bone of the face.
What is the pterion and why can it be bad if you are hit here?
is a point where the bones can be broken readily since 4 sutures come together at this point. And there is a major vessel, the middle meningeal artery, that runs right behind it so if you get hit at this point, that artery can break and there can be a massive internal bleeding.
What is vertical orientation?
this defines the three different branches of trigeminal nerves - V1, V2, and V3.
What are the features of the Maxilla and mandible?
- both have alveolar process = sockets for teeth
- mandible has mental foramen
- maxilla has infraorbital formamina
- coronoid process
- condyloid (condylar) process (TMJ)
- head, neck, and ramus, body and angle
- mandibular notch, foramen
- mylohyoid groove
- mental spines or genial tubercles (superior and inferior)
*frontal bones have supraorbital foramina/notches and all 3 foramina line up
What are the boundaries of the orbit?
- frontal bone = roof
- zygomatic bone = lateral wall
- maxilla bone = floor and part of the medial wall
- lacrimal and ethmoid bones = rest of medial wall
- sphenoid bone = posterior wall
What are the features of the orbit?
- supraorbital foramen/notch: in superciliary arch
- optic cana (foramen): in medial wall
- superior orbital fissure: in medial wall
- inferior orbital fissure: in floor
- lacrimal groove (nasolacrimal canal) - communicates with nasal cavity
What are the boundaries of the nasal cavity?
- nasal bones, frontal sinus, ethmoid, sphenoid sinus: roof
- maxillary bones: floor and lateral wall
- palatine horizontal plate: floor
- vomer and perpendicular plate of ethmoid bones: medial wall
- nasal septum: medial wall
What are the features of the nasal cavity?
-nasal conchae: projections from lateral wall
-superior nasal conchae: ethmoid bone
-middle nasal conchae: ethmoid bone
-inferior nasal conchae: separate bones
-conchae = turbinates
The nasal cavity is line by a nasal mucosal membrane (respiratory epithelium).
Most bony features have a mucosal covering on them.
Oral mucosa vs. respiratory mucosa
What does the anterior cranial fossa hold?
holds the frontal lobes
What does the middle cranial fossa hold?
holds the temporal lobe
What does the posterior cranial fossa hold?
holds the cerebellum and brainstem
What are the features of the paranasal sinuses?
- are air spaces within the skull bones
- we have 4 pairs of theses
- these are internal bony features that are apparent on CT, MRI, etc
- make bones lighter
- add resonance to voice
- all lines by mucosal membranes
- all continuous with nasal cavity
What are the paranasal sinuses?
frontal sinuses - in frontal bones (2) ethmoid air cells - in ethmoid bone (3-13 cells) - on both sides of the face sphenoid sinuses - in sphenoid bone (2-5 cells) maxillary sinuses - in maxilla (2)
Where are the foramen of the skull?
- there are 13 foramen of the skull
- allow vessels and cranial nn. to exit cranial vault
- a nerve might enter one foramen on the skull and exit through a completely different foramen on the skull
What does the cribriform plate transmit?
olfactory nerve (CN I)
What does the optic canal transmit?
optic nerve (CN II) and the ophthalmic a.
what does the superior orbital fissure transmit?
CN III (Oculomotor), IV (Trochlear), VI (Abducens), and ophthalmic (CN V1)
What does the foramen rotundum transmit?
Maxillary nerve (CN V2)
What does the foramen ovale transmit?
Mandibular nerve (CN V3)
What does the foramen spinosum transmit?
middle meningeal artery
What does the foramen lacerum transmit?
internal carotid artery, travels superiorly over it and greater petrosal never association.
-this is a major hole but nothing really passes through it because it’s filled by a fibro-cartilage and is part of the floor of the carotid artery pathway in the carotid canal.
What does the jugular foramen transmit?
internal jugular vein, CN IX (glossopharyngeal), CN X (vagus) and CN XI (accessory)
What does the internal acoustic foramen transmit?
CN VII (facial) and CN VIII (vestibulocochlear)
What does the stylomastoid foramen transmit?
CN VII (facial)
What does the hypoglossal canal transmit?
CN XII (hypoglossal)
What does the foramen magnum transmit?
vertebral arteries, spinal cord, and CN XI (accessory)
What does the carotid canal transmit?
internal carotid artery (this enters the skull through here)
What are the layers of the scalp?
From superficial to deep: -skin -connective tissue (dense) -aponeurotic layer -loose connective tissue -pericranium SCALP
Describe the skin layer on the scalp
it is thin except in the occipital regions. It contains many sweat and sebaceous glands and hair follicles. It has abundant arterial supply, good venous and lymphatic drainage.
Describe the connective tissue layer on the scalp
it forms the thick, dense, richly vascularized subcutaneous layer with many cutaneous nerves (where the vessels and nerves reside). This layer tend to “hold” cut vessels open - allowing profuse bleeding.
Describe the aponeurosis layer on the scalp
aka epicranial aponeurosis. is the strong tendinous sheet that covers the calvaria, serves as the attachment for the frontal and occipital bellies of the occipitofrontalis muscles and the superior auricular muscle. Together, this is called the musculoaponeurotic epicranius.
Describe the loose connective tissue layer on the scalp
it is the sponge-like later. It has potential spaces that may distend with fluid as a result of injury or infection. This layer allows the free movement of the scalp proper (the first 3 layers) over the underlying calvaria.
Describe the pericranium layer on the scalp
a dense layer of CT, forms the external periosteum of the neurocranium and is firmly attached. Parts of the pericranium are continuous with the fibrous tissue in the cranial sutures.
What are scalp lacerations?
superficial wounds into the connective tissue layer tend to bleed profusely. This is due to vascular anastomoses - vascular connections. if unconscious, may bleed to death from a minor injury because the lacerations are held open by the dense CT.
deep wounds into the aponeurosis layer gape widely - deep woulds gape because of the muscles attached to the aponeurotic layer : the frontal and occipitalis mm. The muscles will pull the wound even wider because the muscles are pulling this apart - gaping wound.
What is loose areolar tissue?
is called the danger space of the scalp.
Infections spread easily in this layer b/c travels into the cranial cavity through emissary veins (pass through the calvaria - drains venous blood of the scalp down to the superior sagittal sinus) to meninges (gets into the epidural space) and fluid can move anteriorly into eyelids and root of nose
Loose Ct means potential space for bleeds, edemas and infections.
What are the muscles of the scalp and ears?
occipotofrontalis muscle and
3 auricularis muscles
What is the action of the occipitofrontalis muscle?
moves scalp back and forward
this muscle is a combo of occipitals m. + galea aponeurotica (aponeurosis aka cranial epineurosis) + frontalis m.
What is the action of the auricularis mm?
anterior: protract ear
superior: elevate ear
posterior: retract ears
There 3 are very superficial muscles
What are the muscles of the face?
mm of facial expression:
- all attach to bone or fascia and act by pulling the skin (insert into skin) - literally pull on the skin when they are acting
- also surround the orifices of the face (mouth, eyes, nose) acting as sphincters and dilators
mm of mastication (4 pairs)
the face is the anterior aspect of the head from the forehand to the chin and ear to ear
no deep fascia of the face because of all the muscle attachments of the muscles of facial expression - loose connective tissue
What CN innervates the muscles of facial expression?
CN VII - facial nerve
What are the muscles of the eye region?
frontalis m
corrugator supercilii m - deep muscle, hard to find
orbicularis occuli m - wide band around the eye, has a smaller portion over the upper and lower eyelids and these come in contact when the eye closes
What is the action of frontalis m?
raises eyebrow (surprised)
What is the action of the corrugator supercilii m?
draws eyebrow in (frowning)
What is he action of the orbicularis oculi m?
closes eye (winking)