Oral Anatomy & Histology (Review: Outcome 10) Flashcards
Osteology
The study of bones
- Bones cover and protect the internal structures
- Bones serve as landmarks for us
Articulation
An area of the skeleton where the bones are joined to each other. They can be either movable or immovable
Sutures
Appear on the skull as “cracks”
- Firm joining of two or more bones
Joint
The moveable junction of two or more bones
Process
An extension of a bone
Fossa
A depression in a bony surface, a place for a joint or muscle attachment to be located
Foramina
Singular = foramen
Number of holes on the cranium
- major blood vessels supply the brain with blood through foramina into the cranium
Examples:
- Mental foramen
- Foramen magnum
- Supraorbital
- Infraorbital foramen
Meatus
Canal-like opening into a bone from outside of the body (external) as in the opening to the ear
How many bones does the cranium have and what are they?
8 bones in total
1) Frontal: single
2) Parietal: paired (2)
3) Occipital: single
4) Temporal: paired (2)
5) Sphenoid: single
6) Ethmoid: single
How many facial bones are there?
14 facial bones
How many bones are in the skull excluding ossicles in the inner ear?
22 bones
Frontal Bone
- Single
- Forms the forehead, part of the floor of the cranium and most of the roof of the orbits
- Contains the 2 frontal sinuses
- Protects the frontal lobe of the brain, which is largely involved with motor and control functions of the body
Parietal Bones
- Paired
- Forms most of the roof and the upper sides of the cranium
- Joined by the sagittal suture at the midline of the skull
- The suture between the frontal bone and the parietal bones is the coronal suture
Occipital Bone
- Single
- Forms the back and base of cranium
- Joins the parietal bones at the lambdoidal suture
- The spinal cord passes through the foramen magnum of this bone, to join with the brain
Temporal Bones
- Paired
- Form the sides and base of cranium
- Enclose the ear and contain the external auditory meatus (bony passage of the outer ear)
- Extend toward the zygomatic bone
- Have a depression, called the glenoid fossa into which the lower jaw articulates
Sphenoid Bone
- Forms the anterior portion of the base of the skull
- It articulates with the temporal bones and the frontal bone to form the back of the eye orbit
Ethmoid Bone
- Forms part of the floor of the cranium, the orbit, and the nasal cavity
List the Facial Bones
14 bones in total
1) Maxilla - paired (2)
2) Zygomatic - paired (2)
3) Palatine - paired (2)
4) Nasal - paired (2)
5) Lacrimal - paired (2)
6) Inferior nasal conchae - paired (2)
7) Vomer - single
8) Mandible - single
Maxilla
- Forms the upper jaw and part of the hard palate
- 2 bones are joined together by the maxillary suture at the midline
- Contain the maxillary sinuses
- Contains the maxillary tuberosity where blood vessels and nerves enter. This is also where much of the growth of the maxilla takes place
Zygomatic Bones
- Also called Malar bones
- Forms the prominence of the cheek, distal walls and floor of the orbit
- Rest of the maxillary bones
- There is a temporal process of the zygomatic bone (that projects backwards) articulates with the zygomatic process of the temporal bone (this forms the zygomatic arch)
Palatine Bones
- Made up of a horizontal plate (hard palate) and a vertical plate
- Horizontal plate: posterior portion
- Vertical plate: lateral walls of the nasal cavity
- It is joined midsagittally at the median palatine suture. This is covered by the tissue of the palatine raphae
Nasal Bones
- 2 bones that are joined
- Articulate with the Frontal bone to make up a small portion of the nasal septum
Lacrimal Bones
- Paired bones found at the inner angle of the eye
- Resemble a fingernail
- Smallest bones of the face
- Located posterior and lateral to the nasal bone
- Contain the lacrimal duct, where tears pass into the nasal cavity and out to the surface
Nasal Conchae
- They are formed from the Ethmoid bone
- The superior and middle nasal conchae are extensions of the Ethmoid
- The inferior is a separate bone
- Extend inward from the maxilla
- Allow for circulation and filtration of air before it goes to the lungs
Vomer
- Single bone
- Triangular shaped
- Forms the inferior and posterior part of the nasal septum
Hyoid Bone
- Does not articulate with any other bones
- It is suspended in the nek and is an attachment point for neck and tongue muscles
- Horseshoe shaped
Auditory Ossicles
- Composed of 6 main bones
- Tiny, highly specialized bones of the inner ear
- 3 per side:
1) Stapes - stirrup
2) Incus - anvil
3) Malleus - hammer
Hard Palate
- Composed of palatine process of the maxilla and the palatine bones
- The right and left sides are joined by the median palatine suture
- Incisive foramen: located at the midline, just behind the upper central incisors
- Greater palatine foramen: located in the palatine bone
Mandible
- Single bone
- Forms the lower jaw
- Moveable bone of the skull
- Alveolar process of the mandible supports the teeth in the mandibular arch
- Composed of 3 parts:
1) Body
2) Alveolar process
3) Ramus
Paranasal Sinuses
1) Maxillary sinuses: largest of the paranasal sinuses
2) Frontal sinuses: located within the forehead, just above both eyes
3) Ethmoid sinuses: irregularly shaped air cells separated from the orbital cavity by a very thin layer of bone
4) Sphenoid sinuses: located close to the optic nerves, where an infection may damage vision
Functions of the sinuses
- Lighten the skull bones
- Act as sound resonators
- Provide mucus for the nasal cavity
Temporomandibular Joint (TMJ)
- A joint on each side of the head that allows for movement of the mandible for speech and mastication
- 3 bony parts:
1) Glenoid fossa of the temporal bone
2) Articular eminence of the temporal bone
3) Condyloid process of the mandible
Capsular Ligament
- A fibrous joint capsule completely encloses the TMJ
- The capsule wraps around the margin of the temporal bone’s articular eminence and articular fossa superiorly
- Inferiorly, the capsule wraps around the circumference of the mandibular condyle, including the condyle’s neck
Articular space
- The area between the capsular ligament and the surfaces of the glenoid fossa and condyle
- Articular disc (meniscus) is a cushion of dense, specialized connective tissue that divides the articular space into upper and lower compartments
(These compartments are filled with synovial fluid, which helps lubricate the joint and fills the synovial cavities)
Jaw movement of the TMJ
1) Hinge action
- first phase of mouth opening
- only the lower compartment of the joint is used
2) Gliding movement
- allows the lower jaw to move forward and backward
- involves both the lower and upper compartments of the joint
- the condyle and articular disc “glide” forward and downward along the articular eminence (projection)
Gliding Movement of TMJ
i. Protrusion: forward movement of the mandible
ii. Retrusion: backward movement of the mandible
iii. Lateral movement of mandible: when internal and external pterygoid muscles on the same side of the face contract together
Rest Position of the TMJ
- Elimination of muscle tension and rest of the TMJ is essential throughout the day
- Clenching and grinding (bruxism) contribute to the tension and eventually lead to TMJ and muscle discomfort
- Rest position of TMJ is achieved with lips together, but teeth slightly apart - carrying the TMJ like this whenever possible will reduce tension and discomfort
Cause of Temporomandibular Disorder (TMD)
- Trauma
- Genetic factors
- Developmental disorders
- Behavioral stresses
- Para-functional habits
- Malocclusion
- Arthritis
Signs and Symptoms of TMD
- Pain
- Stiffness
- TMJ sounds (clicking/popping)
- Internal disc derangement
- Subluxation (locking open)
- Limitation of movement (trismus)
- Malocclusion (shift in the way the teeth align)
