Anatomy- Head And Neck Development

Question 1

Gastrulaation three layers

Answer 1

• ectoderm: epidermis, nervous system
• endoderm: respiratory, digestive
• mesoderm: MSK, dermis, ardiovascular

Question 2

Promitrive streak/node

Answer 2

• first sign of gastrulation, epiblast cell moveement inward -> becomes the three layers
• diminishes after 4 weeks and becomes sacrum and coccyx

Question 3

Notochord

Answer 3

• triggers neural plate

- goes underneath ectoderm and sends out signal to it to become neural tissue

Question 4

• neural plate

Answer 4

• thickening of ectoerm, CNS
• also signalled by notchord - becomes neural groove - will become brain + spinal chord
• neural crest cells: from ectoderm, nerves (cranials) and connective tissue, muscle, dermis

Question 5

Cranium: foetal stage

Answer 5

• base bones: complex, chunky cranium from cartilaginous origin
• cranium flat bones from mesenchyme origine. Joined by sutures called fontanelles - molding during childbirth

Question 6

Cranium: newborn

Answer 6

• cranium round and large (thin)

- face small because jaw and sinuses have not developped

Question 7

Cranium: postnatal

Answer 7

• growth of cranium continues to 16 yo and then thickens until early 20

Question 8

Clinical issues with cranium

Answer 8

• acrania: cranium absent - death
• craniosysnotosis: prenatal closure of sutures - in particular sagital suture
• holoprosencephaly: single feature, cerebrum (single frontal lobe, cyclopia, single nostril….)

Question 9

Pharyngeal arches

Answer 9

• four main ones
• 5/6 rudimentary
• arches support walls of pharync
• componentsL mesenchyme core, ectoderm, endoderm
• arch has artery, cartilage, muscle, nerves

Question 10

1st pharyngeal arch:

• skeleton
• muscle
• nerve

Answer 10

• skeleton: incus, malleus, maxilla, zygomatic, vomer, mandible, temporal
• muscle: mastication, mylohyoid, anterior digastric, tensor tympani, TVP
• nerve: trigeminal

Question 11

2nd pharyngeal arch

• skeleton
• muscle
• nerve

Answer 11

• skeleton: stapes, styloid process, hyoid
• muscle: facial expression, stylohyoid, posterior digastric, stapedius
• nerve: facial

Question 12

3rd pharyngeal arch

• skeleton
• muscle
• nerve

Answer 12

• skeleton: hyoid
• muscle: stylopharyngeus
• nerve: glossopharyngeal

Question 13

4th/6th pharyngeal arch

• skeleton
• muscle
• nerve

Answer 13

• skeleton: laryngeal cartilages
• muscle: LVP, palatoglossus, palatopharyngeus, pharyngeal constrictors, laryngeal
• nerve: X

Question 14

Pharyngeal pouches: four internal diverticula

Answer 14

• 1st: tympanic cavity, auditory tube
• 2nd: tonsillar fossa, palatine tonsil
• 3rd, 4th: parathyroid gland, thymus

Question 15

Pharyngeal grooves

Answer 15

• four external clefts

1st: external acoustic meatus
- all the others obliterate

Question 16

Pharyngeal membrane

Answer 16

• one floor of grooves

- gives the tympanic membrane

Question 17

Clinical issues concerning the pharyngeal apparatus

Answer 17

• pharyngeal fistula/sinus = cysts (2nd groove)

- 1st arch syndrome: eyes, ears, jaw, palate (neural crest cells)

Question 18

Thyroid gland development

Answer 18

• 1st endocrine gland to develop (4-7 weeks): thickening in pharynx
• descends in neck from tongue: foramen caecum
• connected to tongue via thyroglossal duct around 7 week

Question 19

Clinical issues with thyroid gland development

Answer 19

• thyroglossal duct and cysts

- ectopic thryoid gland

Question 20

Palate development

Answer 20

• 1st median palatal process: anterior maxilla

- 2nd lateral palatal process: primordial hard/soft palate, maxillary prominences, septum from nasal prominences

Question 21

Clinical issues with palate development

Answer 21

• cleft lip/palate: common anomalies
• cleft lip: lips, nostril, maxilla: primary palate issue. Can be unilateral or bilateral
• cleft palate: with or without a cleft lip: hard to soft palate/uvula, 2nd palate issue (no fuse maxillary)