development of the face Flashcards
what day does neural plate formation occur at
day 17 -
what day does the formation of the neural folds, neural groove occur on
day 18
why does spina bifida happen?
because the posterior neuropore of the neural tube doesn’t close. why it doesnt close is becaause of a lack of folate. folate is KEY in the closing of the ant and post neural tube
folate: folic acid (vit B9)
when do the neuroporesclose (which order)
ant neuropore closes at day 24
post neuropore closes at day 26
what are the basic steps of neuralation
- ectodermal proliferation
- neural plate formation due to the formation of the neural folds and grooves
- neural crest cell formation at edges of neural folds
- neural tube formation
- closing of the ant and post neuropores
how does the neural tube form?
edges of the neural folds fuse with one another, neural grove moves down (invaaginates) so now this tube becomes underneath the ectoderm and within the mesoderm.
neural crest cells sit on top of the neural tube underneath the ectoderm
what end of the neural tube is the anterior neuropore at?
cranail end
what end of the neural tube is the posterior neuropore at?
caudal end
where is the notochord developed from?
mesoderm cells form it after gastrulation is complete
what membrane forms the oral cavity
buccopharangeal membrane
what does the ectoderm form in the pharyngeal apparatus
pharyngeal clefts
what does the mesoderm form in the pharyngeal apparatus?
pharyngeal arches
what does the endoderm form in the pharangeal apparatus
pharangeal pouches
what is the stomodeum
gap between developing face of the embryo and the first pharyngeal arch
where is the buccophaarangeal membrane located
within the stomedeum
when and how does the developing embryo fold?
the embryo will start folding so that the caudal and cranial end almost meet at 4 weeks
what structures are in each pharangeal arch?
artery
cartilage
nerve
which nerves innervate every pharangeal arch
PA1 = TRIGEMINAL
PA2 = FACIAL
PA3 = GLOSSOPHARANGEAAL
PA4 = VAGUS
PA6 = RECCURANT LARANGEAL NERVE
how does the ectomesenchyme form
neural crest cells migrate to the mesoderm forming the ectomesenchyme ->which is an important connective tissue for different structures
function of the ectomesenchyme?
form of mesenchyme , consisting of neural crest cells -> this forms the tissues of the head and neck including: bone, cartilage, connective tissue and dentine
what does the first pharyngeal arch form
mandible
maxilla
what tissues of the tooth do ectomesenchyme cells make
all tissues except enamel
what pharyngeal arch is affected by failure of neural crest cell migration
First arch syndromes are congenital defects caused by a failure of neural crest cells to migrate into the first pharyngeal arch. They can produce facial anomalies. Examples of first arch syndromes include Treacher Collins syndrome and Pierre Robin syndrome.
what is treacher collins syndrome and what is it caused by
- autosomal dominant condition
- caused by a mutation in the TCOF1 gene
- this gene is required to make a protein (treacle) that plays a critical role in formation of bone and tissues of the face
what are the characteristics of treacher collins syndrome?
Is characterised by downward-slanting eyes, micrognathia, absent or malformed ears and clefts of the lips and palate
what is micronathia?
abnormality when the mandible is reduced in size
what week would first arch syndromes occur
during week 4 of intrauterine life
what is Pierre Robins sequence and what does it result in babies
recessive condition
causes micrognathia, glossoptosis - displacement of the tongue which causes respiritory distress and difficulty feeding due to velopharangeal insuffieicenty and clefts of the lip and palate
facial features of FAS
fetal alcohol spectrum disorder:
- small eye openings
-smooth philtrum
-small upper lip
what week does the tongue develop?
week 4 of intrauterine life
what develops the mucosa of the anterior 2/3rds of the tongue?
lateral lingual swellings and tubercular Impar
BOTH FROM 1ST PHARANGEAL ARCH
what develops the mucosa of the posterior 1/3 of the tongue
copula
from the 2nd, 3rd and 4th pharyngeal arch
what develops the epiglottis and from which pharyngeal arch
epiglottic swelling from the 4th pharyngeal arch
name the lingual and 3 medial swellings of the tongue
> lateral lingual swelling
tubercular impar
copula
epiglottic swelling
what forms the muscles of the tongue
The intrinsic and extrinsic muscles of the tongue are derived from occipital somites, which are segments of mesoderm in the region of the upper neck.
The somites migrate from the neck anteriorly to give rise to the muscles of the tongue.
how are somites formed? what are somatocoels?
mesoderm -> from paraxial mesoderm, these form cavity and split into sections -> which are called somites
somatoceols are cavities within the somites
how do somites further differentiate?
the somatocoels split into sections:
1.dermatomyotome
2. scleratone
the dermatomyotome further differentiates into:
1. dermatome
2. myotome
3. sclerotome
