Embryology I Flashcards
What system are helped to develop by the pharyngeal arteries?
Brian
CVS - heart and great vessels
Special sensory organs (eye, nose ear)
What are pharyngeal arches?
- They are compromised of a system of mesenchymal proliferation’s in the neck region of the embryo.
- 5 in total, numbers 1-6 (5 not formed in humans)
- Together with FNP (frontonasal prominence) they constitute the building blocks for the head and neck region.
Which cranial nerve is associated with which of the brachial arteries?
All the mixed sensory and motor ones.
1 = CN V 2 = CN VII 3 = CN IX 4-6 = CN X CN XII
These nerves supply the derivatives of the pharyngeal system.
What arch derives the muscles of mastication?
Pharyngeal arch 1
What arch derives the muscles of facial expression?
Pharyngeal Arch 2
What muscles are derived from pharyngeal arch 3?
Stylopharyngeus
What muscles are derived from pharyngeal arch 4?
Crycothyroid
Levator palantini
Constrictors of the pharynx
Wha muscles are derived from pharyngeal arch arch 6?
Intrinsic muscles of the larynx
What cartilage is formed from each of the pharyngeal arches?
Ph A 1 = Meckel’s cartilage: malleus and incus and a template for formation of the mandible.
Ph A 2 = Reichert’s: stapes plus upper part of the hyoid bone.
Ph A 3 = remainder of hyoid bone
Ph A 4 & 6 = Cartilages of the larynx
What happens to aortic arches?
1 and 2 - disappear
3 - internal carotid
4 - left arch of aorta and right brachiocephalic artery
6 - pulmonary arch
Where are the recurrent laryngeal nerves positioned?
Right - under right subclavian
Left - under aortic arch
What are the pharyngeal pouches? And what is made form them?
Endoderm lined pockets in the pharynx.
First pouch is the largest and becomes the tympanic cavity (ear stuff).
Development results in formation of palatine tonsils and parathyroid glands and the thymus.
What happens to the pharyngeal clefts?
Only the first one is left. This becomes the external acoustic meatus.
2nd arch grows down to cover others, obliterating all other clefts.
Branchial cysts (hard mass) or fistula (opening to surface of the neck) can occur if there are remnants.
Branchial cyst would sit anterior to SCM
What drives development of the face?
Expansion of the cranial neural tube
Appearance of a complex tissue system associated with cranial gut give and outflow of the developing heart.
Development of the sense organs also occurs and they need to separate the respiratory tract from the GI tract.
What are the embryological components of the face?
Stomatodeum - buccopharyngeal membrane
Frontonasal prominence
1st pharyngeal arch - maxillary prominence and madibular prominance
What parts of the face are made from the FNP?
Forehead
Bridge of nose.
Nose
Philtrum (upper lip dip)
WHat parts of the phase are made from the maxillary prominence?
Cheeks
Lateral upper lip
Lateral upper jaw
What parts of the face are made form mandibular prominence?
Lower lip and jaw
How does the nose begin to develop?
Nasal placoderms appear on frontonasal prominence
Then sink to become the nasal pits
Medial and lateraled nasal prominence form on either side of the pits.
Maxillary prominences grow medically, pushing the nasal prominences close together in the midline.
Maxillary prominences fuse with medial nasal prominences.
Medial nasal prominences then fuse in the midline.
How do the nasal and oral cavities separate?
Mandible grows large enough to allow the tongue drops
Palatial shelves grow towards each other and fuse in the midline.
Nasal septum develops as a midline down-growth and ultimately fuses with palatial shelves.
How does cleft lip / palate occur?
Lateral cleft lip - failure of fusion of medial nasal prominence and maxillary prominence.
Cleft lip and palate - combined with failure of palatial shelves to meet in the midline.
Where does the external acoustic meatus develop from?
1st Pharyngeal cleft
Where do the middle ear cavity and ossicles develop from?
1st pharyngeal pouch and cartilages of 1st and 2nd arches respectively.
How do the auricle develop?
Auricles develop from proliferation within the 1st and 2nd pharyngeal arches surrounding the meatus.
How do the ears end up on the side of the head?
External ears develop initially in the neck
As mandible grows, the ears ascend to the side of the head to lie in line with the eyes.
All common chromosomal abnormalities have associated external ear abnormalities.
Why can pregnancy people not drink alcohol?
Embryo and foetus sensitive to small concentrations of alcohol.
Most effects of alcohol seen in the head and neck region as the facial skeleton is derived from neural crest cells and the migration of these cells and development of the brain is extremely sensitive to alcohol.
What is foetal alcohol syndrome?
Facial skeleton is developed from neural crest cells - make cartilaginous bars.
Neural crests are extremely sensitive to alcohol.
Seen is significant high conc. of alcohol during pregnancy
Occur 1 in 100 births.
Facial features - small head, flat mid face, thin upper lip, small eye opening, short nose, low nasal bridge, underdeveloped jaw ect.
