Week 10 Flashcards
Jaw, Jaw and Tongue Muscles, & Ultrasound
What are the two main parts of the jaw?
Maxilla (upper jaw, passive articulator)
Mandible (lower jaw)
What is the only movable part of the jaw?
Mandible, crucial for speech and mastication
How many bones is the mandible?
Two bones fused at the mental symphysis
Fuse together in early years
What/where are the landmarks of the mandible? (5)
Body: Lower horseshoe-shaped, holds the lower teeth
Ramus: Vertical part connecting to the skull
Angle: Where the body and the ramus meet
Condyle (posterior) and coronoid (anterior) process: Two protrusions at the top of the ramus
Mandibular notch: Depression between the two processes
What’s the mental protuberance?
A triangular projection on the anterior part of the mandible located at the midline
Basically your chin
What are mental spines?
Bony projections located in the middle on the inner surface of the mandible
Two inferior and two superior (two pairs)
What do the superior mental spines serve as an origin for?
Genioglossus muscle
What do the inferior mental spines serve as an origin for?
Geniohyoid muscle
What is the temporomandibular joint (TMJ)?
Consists of the condyle of the mandible and the mandibular fossa of the temporal bone
Cushioned by a fibrous articulator disk for smooth movement
What does the temporomandibular joint connect?
Mandible to the temporal bone of the skull
What are the two foramen?
Mandibular foramen
Mental foramen
Where is the mandibular foramen located?
Internal surface of the ramus of the mandible
What is the structure of the mandibular foramen?
An opening serves as an entry point for the inferior alveolar nerve and vessels (vessels provide blood to the lower teeth and surrounding bone)
Where is the mental foramen located?
External surface of the mandible
Near the apex of the mandibular premolar teeth
What is the structure of the mental foramen?
A small opening that allows the passage of the mental nerve and blood vessels
What are the jaw muscles critical for?
Mastication and speech
How are the jaw muscles categorized?
Elevators
Depressors
What muscles elevate the jaw?
Masseter muscle
Temporalis muscle
Medial pterygoid muscles
What is the function of the masseter muscle?
Elevates the mandible (jaw closing)
Divided into deep and shallow heads
Deep head is the shortest muscle in the cranial head
What is the origin and insertion of the masseter muscle?
Origin: Zygomatic arch
Insertion: Ramus and angle of the mandible
What is the temporal fossa?
Shallow depression on the lateral side of the skull
What does the temporal fossa serve as an origin to?
Temporalis muscle
What are the bony boundaries of the temporal fossa? (4)
Frontal bone (inferior lateral part)
Parietal bone (inferior portion)
Temporal bone (squamous part)
Sphenoid bone
What is the function of the temporalis muscle?
Elevates and retracts the mandible (fast closing)
What is the origin and insertion of the temporalis muscle?
Origin: temporal fossa
Insertion: Coronoid process of the mandible
What is the function of the fan-like shape of the temporalis muscle?
Allows for wide range of jaw movements
The vertical (anterior) fibres elevate the mandible
The more horizontal (posterior) fibres retract the mandible
*They do not move independently
What are the two pterygoid muscles?
Medial pterygoid
Lateral pterygoid
Mirror the masseter on the inside
Each have two heads on each side
What is the origin and insertion of the medial pterygoid?
Origin: Sphenoid bone, palatine bone and maxilla
Insertion: Inner surface of the mandible
What is the function of the medial pterygoid?
Elevates the mandible (similar to the masseter)
What is the origin and insertion of the lateral pterygoid?
Origin: Sphenoid bone and maxilla
Insertion: TMJ disc and condyle of the mandible
What is the function of the lateral pterygoid?
Controls side-to-side movement of the jaw
Useful for chewing/grinding food
Aids in protrusion of the jaw
*DUH lateral = side
What happens during contraction of the lateral pterygoid?
Contract one side at a time
The side that you contract is the direction that your jaw moves
Fibres run diagonally
What muscles depress the jaw?
Anterior belly of the digastric muscle
Mylohyiod
Geniohyoid
Also stabilize the hyoid bone and assist in tongue movements
What are the tongue muscles essential for?
Various speech movements
Connecting the tongue to surrounding structures, enabling complex motions
What are the 4 major extrinsic tongue muscles?
Genioglossus
Palatoglossus
Hyoglossus
Styloglossus
What is the origin and insertion of the genioglossus (GG)?
Origin: Mental spine of the mandible
Insertion: Throughout the tongue, from tip to root
What is the function of the genioglossus?
Protracts, depresses, and can groove the tongue
What are the function of the 3 sections of the genioglossus?
Anterior: lowers and retracts tongue front
Middle: lowers and pulls forward tongue body; creates groove
Posterior: pulls tongue root forward
What is the origin and insertion of the palatoglossus?
Origin: Palatone aponeurosis
Insertion: Sides of the tongue body
What is the function of the palatoglossus?
Elevates the tongue, assists in uvular constrictions, and narrows the oropharyngeal isthmus (OPI)
What is the origin and insertion of the hyoglossus?
Origin: Greater horn of the hyoid bone
Insertion: Sides of the tongue
What is the function of the hyoglossus?
Pulls the tongue down and back, especially the back of the tongue
What is the origin and insertion of the styloglossus?
Origin: Styloid process of the temporal bone
Insertion: Sides of the tongue, interlocks with intrinsic tongue muscles
What is the function of the styloglossus?
Traditionally through to raise and retract the tongue
It’s role in speech is under review
What types of sound waves do ultrasounds use for imaging?
High-frequency
Are ultrasounds invasive or non-invasive?
Non-invasive, safe, and widely used in medical diagnostics
What are the Hz levels for infrasound?
Below 20 Hz
What are the Hz levels for audible sound?
20 Hz - 20 000 Hz
What are the Hz levels for ultrasound?
20 000 Hz - ~100 MHz
How are the high-frequency sound waves generated?
Handheld probes/transducers
Piezoelectric crystals generate waves
Frequencies range from 2-18 MHz
What are piezoelectric crystals?
Materials that can convert mechanical energy into electrical energy and vice versa
What structures in the body allow waves to pass through?
Soft tissues and fluid-filled organs
What structures in the body reflect sound waves back to the transducer?
Denser structures like bones
What happens at the boundaries of two mediums and why?
Much of the transmitted wave is reflected (bounces back)
Occurs because the wave cannot easily transfer its energy across the impedance boundary
What does the time it takes echoes to return to the transducer tell us about a sound wave?
The strength (amplitude) tells us the distance and characteristics of the tissues encountered
What does the ultrasound use to generate images?
The echoes received by the transducer
What can ultrasound images show?
Size, structure and any pathological lesions within the organs and tissues
How are ultrasounds used in speech?
Mostly used for studying tongue shapes
What do ultrasounds show us in speech?
Tongue shapes/fronting/retraction in vowels
Tongue root advancement/retraction in vowels
Tongue shape in bunched vs retroflex
