Development of the Head and Neck Flashcards
What are the pharyngeal/brachial arches?
Outpouchings of mesoderm on both sides of developing pharynx
Precursors for = muscles, cartilage, vessels
First seen during 4 week of devel
What structures constitute the building blocks for the head and neck region?
Pharyngeal arches
Frontonasal prominence
What does each pharyngeal arch have associated with it?
Artery
Nerve
Cartilage bar
Which cranial Ns are associated with the pharyngeal arches?
5, 7, 9, 10
Mixed motor and sensory
Outline the muscular derivatives of the pharyngeal arches
Arch 1 = muscles of mastication
Arch 2 = muscles of facial expression
Arch 3 = stylopharyngeus
Arch 4 = muscles of the pharynx
Arch 6 = muscles of the larynx
Outline the cartilage associated with the pharyngeal arches
Arch 1 = mandible
Arch 2 = upper hyoid bone
Arch 3 = lower hyoid bone
Arch 4 = larynx
Arch 6 = larynx
Outline the vessels associated with the pharyngeal arches
Arch 1/2 = disappear
Arch 3 = internal carotid
Arch 4 = arch of aorta, brachiocephalic A
Arch 6 = pulmonary arch
Where do glandular structures start to devel in the head and neck region?
In pharyngeal pouches lined with endoderm on the inside of the developing pharyngeal pouches
What does the 1st pharyngeal pouch become?
Tympanic cavity
What does the 1st pharyngeal cleft become?
External acoustic meatus
How are all the pharyngeal clefts (apart from no.1) obliterated?
2nd arch grows down to cover the others
What processes drive the devel of the nose and face?
Expansion of the cranial neural tube
What embryonic structures make up the face?
Buccopharyngeal membrane = will rupture due to no mesoderm, open into oral cavity
Facial primordia = 1st pharyngeal arch + frontonasal prominence
Primordia of eyes
What does the frontonasal prominence devel into?
Forehead
Bridge of nose
Nose
Philtrum
What does the maxillary prominence devel into?
Cheeks
Lateral upper lip
Lateral upper jaw
What does the mandibular prominence devel into?
Lower lip
Jaw
Briefly outline how the nose forms?
Nasal placodes appear = nasal pits
Medial/lateral nasl prominences form either side of the pits
Maxillary prominences push nasal prominences closer together in the midline
Medial nasal prominence then fuse
How is the nasal and oral cavity separated?
2 palatal shelves fuse to form = secondary palate
Grows into the oral cavity from the maxillary prominences
What is lateral cleft lip?
Affecting the lip alone
Failure of fusion of medial nasal prominence and maxillary prominence
What is cleft lip and cleft palate?
Affecting thew lip and palate
Failure of fusion of medial nasal prominence and maxillary prominence
Combined with failure of palatal shelves to meet in midline
What is a brachial cysts?
Occur due to remnants of pharyngeal clefts that are usually obliterated
Allows tissue fluid to collect – closed cavity
Occur on anterior border of SCM
What is a fistulae in the face neck?
Occur due to remnants of pharyngeal clefts that are usually obliterated
Allows tissue fluid to collect – opening out to the surface of the neck
Occur on anterior border of SCM
Briefly outline the formation of the ear
1st pharyngeal pouch = Tympanic cavity
1st pharyngeal cleft = External acoustic meatus
External ear initially in the neck = mandible grows and ears ascend to side of the head
Outline foetal alcohol syndrome
Neural crest cells that the facial skeleton is derived from = very sensitive to alcohol
Facial features = flat face, small head, smooth philtrum, short nose, small eyes
