Face and Scalp Flashcards
(12 cards)
PARIETAL BONE
The two parietal bones form most of the cranial roof and sides of the skull. The temporal fascia is attached to the superior line or arch, and temporalis is attached to the inferior line or arch. The epicranial aponeurosis lies above these lines, and part of the temporal fossa lies below. Posteriorly, close to the sagittal (superior) border, an inconstant parietal foramen transmits a vein from the superior sagittal sinus and sometimes a branch of the occipital artery.
The internal surface is concave and marked by impressions of cerebral gyri and by grooves for the middle meningeal vessels.
FRONTAL BONE
The frontal bone is like half of a shallow, irregular cap forming the forehead or frons. It has three parts and contains two cavities, the frontal sinuses.
ZYGOMATIC BONE
Each zygomatic bone forms the prominence of a cheek, contributes to the floor and lateral wall of the orbit, and the walls of the temporal and infratemporal fossae, and completes the zygomatic arch.
MAXILLA
The maxillae are the largest of the facial bones, other than the mandible, and jointly form the whole of the upper jaw. Each bone forms the greater part of the floor and lateral wall of the nasal cavity, and of the floor of the orbit; contributes to the infratemporal and pterygopalatinfossae; and bounds the inferior orbital and pterygomaxillary fissures. Each maxilla has a body and four processes, namely: the zygomatic, frontal, alveolar and palatine processes.
PALATINE BONE
The palatine bones are posteriorly placed in the nasal cavity, between the maxillae and the pterygoid processes of the sphenoid bones. They contribute to the floor and lateral walls of the nose, to the floor of the orbit and the hard palate, to the pterygopalatine and pterygoid fossae, and to the inferior orbital fissures. Each has two plates (horizontal and perpendicular), arranged as an L-shape, and three processes (pyramidal, orbital and sphenoidal)
Le Fort I fractures (Guerin’s fracture)
Le Fort I fractures consist of a horizontal fracture line above the level of the floor of the nose involving the lower third of the nasal septum. The mobile segment consists of the palate, the alveolar process and the lower thirds of the pterygoid plates.
Le Fort II fractures (pyramidal fracture)
Le Fort II fractures are pyramidal fractures involving the maxillary bones. From the nasal bridge, the fracture enters the medial wall of the orbit to involve the lacrimal bone and then crosses the inferior orbital rim, usually at the junction of the medial third and lateral two-thirds, and often involves the infraorbital foramen. The fracture line then runs beneath the zygomaticomaxillary suture, traversing the lateral wall of the maxillary sinus to extend posteriorly and horizontally across the pterygoid plates. The zygomatic bones and arches remain attached to the skull base.
Le Fort III fractures
Le Fort III fractures run parallel with the base of the skull, separating the entire midfacial skeleton from the cranial base. The fracture extends through the nasal base and continues posteriorly across the ethmoid bone. The fracture then crosses the lesser wing of the sphenoid and, on occasion, involves the optic foramen. Usually, however, it slopes down medially, passing below the optic foramen to reach the pterygomaxillary fissure and pterygopalatine fossa. From the base of the inferior orbital fissure, the fracture runs laterally and upwards, separating the greater wing of the sphenoid from the zygomatic bone, to reach the frontozygomatic suture. It also extends downwards and backwards across the pterygopalatine fossa to involve the root of the pterygoid plates. The zygomatic arch is usually fractured
at the zygomaticotemporal suture.
Open reduction and internal fixation are conducted through aesthetically favourable incisions in the hairline, upper eyelid, oral cavity and lower eyelid (subciliary and transconjunctival).
Condylar process
The condyle is protected from direct injury by the zygomatic arches. Fractures occur usually by the transmission of force following a blow to the front of the mandible or to the contralateral body. Fractures are seen at all levels of the condyle. Except in children, most condylar fractures are not intracapsular, and occur in the neck. They usually run obliquely downwards and backwards from the mandibular notch. Th- condyle is usually displaced anteromedially (because of the attachment of lateral pterygoid to the temporomandibular joint disc, capsule and anterior border of the neck of the condyle). Nowadays, most condylar fractures are managed by open reduction and early mobilization.
Angle of mandible
Th- majority of fractures of the mandible run posteriorly and inferiorly
from the alveolar bone to the angle. The presence of a third molar tooth
produces a line of weakness, and a fracture line will pass through its
socket. Th- unopposed pull of the powerful elevator muscles (masseter,
medial pterygoid and temporalis) will typically displace the posterior
fragment superiorly, anteriorly and medially.
Ramus and coronoid process
Fractures at the ramus exhibit very little displacement as a consequence of the splinting activity of medial pterygoid medially and masseter laterally, the pterygomasseteric sling; their wide attachments to the ramus
extend across the fracture lines. Similarly, the coronoid process is rarely displaced significantly because it is splinted by the tendinous insertion of temporalis.
Body of mandible
Most fractures of the body of the mandible occur as the result of direct trauma and tend to be concentrated in the first molar or canine region. The more anterior the site of the fracture, the more the upward displacement of the elevators is countracted by the downward pull of geniohyoid and the anterior belly of digastric. When teeth are present, displacement is limited by the dental occlusion (i.e. further displacement is resisted by the lower and upper teeth), whereas displacement may be considerable in an edentulous patient.
