development of the face

Question 1

What is the development of the different prominences?

Answer 1

• At week 4 a small pit at the frontal prominence and the developing cardiac bulge (will eventually become the oral cavity)
  
  • At the same time six little bugles or thickening of the mesoderm sprot from the primitive to become the brachial/pharyngeal arches
  • These arches are symmetrical on both sides and form from the head to the tail
  • Neural crest cells from the mid-brain and he first 2 rhombomeres migrate to the region and infiltrate the mesoderm bumps, supporting the development of embryonic connective tissue needed for craniofacial development called ectomesenchyme
  • Outside of arches=clefts
  • Inside of arches=pockets
  • 1st pharyngeal arch splits into 2 processes (maxillary process and mandibular process)
  • Mandibular processes on either side grow towards each other and fuse very early on

Question 1

What is the development of the palate?

Answer 1

• Most know nose development to understand this
  
  • ….
  • At week 6- Mandibular processes forms mandible and all its teeth and lower. Then fuses with the maxillary process to form the cheek
  • The two medial nasal processes come together, forming the bridge of the nose and the primary palate
  • By week 9- the maxillary processes develop the palatine shelves
  • the palatine shelves grow vertically downwards and fuse with each other and the primary palate. The nasal septum forms and fuses with the secondary palate by week 12
  • Grows vertically downwards on either side of the developing tongue
  • As mandibular process grows the tongue falls backwords giving space for the shelves to go horizontally then grow medially until they fuse with the primary pallet and each other
  • Mesoderm and ectoderm grow down the midline to form the naso sepum which fuses with the secondary palate
  • Finished by the end of week 12

Question 1

What is the development of the nose?

Answer 1

• During week 4- 2 patches of ectoderm on the frontal prominence proliferate to form 2 thickening called the nasal placodes
  
  • During week 5 the mesodermal cells surrounding them proliferate to form a horseshoe-shaped swelling. This is called the nasal process which has the inner half-medical nasal process and outer half=the lateral nasal process
  • At week 6- The region were the nose will develop is called the fronto-naso process
  • Mesoderm proliferates and the Naso-placodes sinks downwards to dorm naso-pits (the base of which are lined by the oro-naso membrane to separate from the primitive oral cavity)
  • The maxillary processes start to proliferate towards the centre, while remaining separated from the lateral nasal process by the naso-optic groove (lateral) and bucconasal groove (medial)
  • By the end of week 6 The maxillary processes fuse with the medial nasal processes on each side, forming the upper lip
  • The two medial nasal processes come together, forming the inter-maxillary segment.
  • The inter-maxillary segment develops into the bridge of the nose, the filtrum, and the primary palate
  • The naso-optic groove gets covered by ectodermal tissue, converting it into the nasal lacrimal duct
  • The lateral nasoprocesses develop into the lateral naso wall
  • Mandibular processes forms mandible and all its teeth and lower. Then fuses with the maxillary process to form the cheek
  • The two medial nasal processes come together, forming the bridge of the nose and the primary palate
  • Even though the whole philtrum is developed from the frontal nasal process the Maxillary process overgrown on the Philtrum so maxillary process covers whole philtrum and upper lip
  • So innervated by the maxillary nerve not ophthalmic

Question 2

What is the development of the nasal cavity?

Answer 2

he nasal pits continue to deepen toward the oral cavity and form substantial cavities themselves
* only a thin oronasal membrane separates the oral cavity from the nasal cavity
* The oronasal membrane soon breaks down, thereby making the nasal cavities continuous with the oral cavity through openings behind the primary palate called nasal choanae
* During weeks 6 and 7 The 2 nasal pits burrow deeper and backwards just above the stomodeum to form the nasal sacs behind the intermaxillary segment
* By week 8 The oronasal membrane disintegrates, forming a primitive coena that connects the nasal and oral cavities.

Question 3

What is the development of the paranasal air sinuses?

Answer 3

• the paranasal sinuses form as outgrowths from the walls of the nasal cavities
  
  • Only the maxillary sinuses begin to form in the prenatal period and are poorly developed at birth.
  • Initially, the maxillary and ethmoid sinuses form from diverticula of the walls of the nasal cavities.
  • The diverticular openings form the orifices of the nasal sinuses
  • Formation of the frontal sinuses and sphenoidal sinuses at approximately 2 years of age.
  • All of the sinuses begin to grow more rapidly in later childhood.
  • The maxillary sinuses are not fully developed until all the permanent teeth have erupted.
  • Growth of the paranasal sinuses alters the size and shape of the face

Question 4

What is the development of the salivary glands?

Answer 4

• The parotid gland develops from a groove-like invagination of ectoderm that forms in the crease between the maxillary and mandibular swellings during week 6.

Question 5

What is macrostomia and microstomia?

Answer 5

• the mouth is reduced to its final width during the second month, as fusion of the lateral portions of the maxillary and mandibular
  
  • swellings creates the cheeks
  • Too little fusion results in macrostomia (a large mouth)
  • Too much fusion results in microstomia (a small mouth)

Question 6

What is a Cleft Lip?

Answer 6

• Bilateral- is malformation results from failure of the medial nasal processes to fuse with the maxillary swellings.
  
  • medial-caused by incomplete merging of the two medial nasal prominences in the midline
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  • Cleft mandible- results from the lack of merging of the distal ends of the mandibular arch. It has been reported in Richieri- Costa -Periera syndrome
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