Session 4 - Developmemt and TMJ Flashcards
(39 cards)
What drives development of the face?
Expansion of the cranial neural tube.
Appearance of a complex tissue system associated with - the cranial gut tube, the outflow of the developing heart.
Development of sense organs - and the need to separate the resp tract from GI tract
What week does the neural tube form?
Week 3
What are neural crest cells?
A specialised population of cells that originate within the neuroectoderm.
Cells of the lateral border of the neuroectoderm.
Become displaced and enter the mesoderm.
From what does the facial primordial develop?
1st pharyngeal arch
Frontal nasal prominence
- surrounds ventro lateral part of the forebrain
- primordia of the eyes
What makes up the face?
Stomatadeum - buccopharyngeal membrane
Frontonasal prominence (forehead, bridge of nose, nose, philtrum)
1st pharyngeal arch
- Maxillary prominence (cheeks, lateral upper lip, lateral upper jaw)
Mandibular prominence (lower lip and jaw)
Describe the development of the nose:
Nasal placodes appear on the frontonasal prominence.
They then sink to form nasal pits
Medial and lateral nasal prominences form on either side of the pits.
Maxillary prominences grow medially pushing the nasal prominences closer together in the midline.
Maxillary prominences fuse with medial nasal prominences.
Medial nasal prominences then fuse in the midline
What is the intermaxillary segment and how is it formed?
The intermaxillary segment is formed from the fusion of the medial nasal prominences. The intermaxillary segment has three components:
Labial component - philtrum
Upper jaw - 4 incisors
Palate - primary palate
Describe the development of the palate
The secondary palate which is the main part of the definitive palate is derived from the palatal shelves which are derived from the maxillary prominences. They grow vertically downwards into the oral cavity in a each side of the developing tongue. The mandible grows large enough to allow the tongue to drop. The palatal shelves grow towards each other in the midline and fuse. The nasal septum develops as a midline down growth and fuses with palatal shelves.
Describe the developmental defect that occurs in a lateral cleft lip.
There is a failure of fusion of medial nasal prominence and maxillary prominence.
What is the developmental defect involved in cleft palate?
Failure of the palatal shelves to meet in the midline.
Describe the fates of the following facial prominences:
Frontonasal, medial nasal, lateral nasal, maxillary and Mandibular.
Frontonasal - forehead, bridge of nose, medial and lateral nasal prominences
Medial nasal - philtrum, primary palate, mid upper jaw
Lateral nasal - sides of nose
Maxillary - cheeks, lateral upper jaw, secondary palate, lateral upper lip.
Mandibular - lower jaw and lip
Describe the development of the eyes.
Occurs during the fourth week.
Out pocketings of the forebrain.
Optic vesicle grows toward the surface to make contact with the lens placode.
The lens placode then invaginate and pinches off.
The optic placodes form the lens
The retina is derived for the diencephalon (forebrain)
Originally eye primordia are situated on the side of the head. As facial prominences grow the eyes move to the front of the face.
Describe the development of the external ear
The external auditory measure is developed from the first pharyngeal cleft.
Auricle develop from the 1st and 2nd pharyngeal arches surrounding the meatus.
Initially the external ear develop in the neck. As the mandible grows the ears ascend to the side of the head to lie in line with the eyes.
Describe briefly the development of the inner ear.
Optic placodes im agitates to form auditory vesicles.
These then form a membranous labyrinth of the cochlea and the semi-lunar canal system.
Describe some of the consequences of fetal alcohol syndrome.
Neural crest migration and development of the brain are extremely sensitive to alcohol.
This can result in a small head, small eye openings, low nasal bridge, flat mid face, short nose, smooth philtrum, thin upper lip, underdeveloped jaw.
What is the position of the TMJ?
Anterior and roughly level to the tragus of the ear.
What are the articular surfaces of TMJ
Squamous part of the temporal bone - Mandibular fossa and articular tubercle
Condyle of the mandible
Describe the TMJ capsule, and the articular disc.
Is split into a upper and lower cavity by a fibrocartilaginous articular disc. Capsule is thin any loose which permits movement. The articular disc is thicker at the periphery where is attaches to the capsule. It is thinner centrally can almost be perforated.
What two types of movement are allowed due to the separation of the TMJ cavity into two?
Gliding movement
Hinge movement
As well as separating the cavity into two what is the second function of the articular disc?
Makes the superior and inferior surfaces of the joint congruous.
The superior surface is convexo-concave (Antero-posteriorly) and the inferior surface is condyloid with a superior trajectory.
Describe the superior articular surface of the TMJ in more detail.
Can be split into two the anterior superior articular surface - articular tubercle which is more inferior.
And the posterior superior articular surface which is set more superiorly.
Describe the position of the condyle of the mandible when the jaw is open?
The Mandibular condyle moves forward into the anterior superior articular surface or articular tubercle. This movement is known as translation.
Where is the condyle of the mandible positioned when the jaw is closed?
It articulates with the posterior superior articular surface or mandibuLr fossa.
Where does the fibrous capsule of the TMJ attach?
Superiorly around the circumference of the articular tubercle and mandibular fossa.
Inferiorly around the neck of the condyle of the mandible.
