embryology - clinical conditions Flashcards
what is an example of a 1st arch syndrome?
Treacher-Collins Syndrome
what is Treacher-Collins syndrome?
an autosomal dominant condition
failure of colonisation of 1st Ph Arch with NEURAL CREST CELLS (many organs derive from neural crest cells)
skeletal derivative of 1st Ph A?
Meckels cartilage = mandible, malleus, incus
what does Treacher-Collins syndrome result in?
hypoplasia of mandible and facial skeleton
along with defects in development of ears and palate
(Meckels cartilage = mandible, malleus, incus)
what is Di George’s syndrome?
failure in development of 3rd + 4th Ph pouches
what causes Di George’s syndrome?
deletion on chromosome 22
derivative of 3rd pharyngeal pouch?
inferior parathyroid
thymus
derivative of 4th pharyngeal pouch?
superior parathyroid
C cells of thymus (secrete PTH, Ca2+ regulation)
What does Di George’s syndrome cause?
abnormal development of neural crest (under epidermis - ectoderm)
Function of neural crest cells?
give rise to a diverse cell lineage—including:
melanocytes (skin), craniofacial cartilage and bone, smooth muscle, peripheral and enteric neurons and glia (nerves)
what are the symptoms of Di George’s syndrome?
CATCH 22:
Cardiac problems (e.g. tetralogy of Fallot)
Abnormal facies
Thymic aplasia (from 3rd pouch = no thymus)
Cleft palate
Hypocalcaemia (no C cells to regulate Ca2+: 4th pouch)
how does a branchial cyst / fistulae come about?
initially 4 pharyngeal clefts, but only 1st cleft remains
as 2nd proliferates to overlap 3rd + 4th
occurs if obliteration of cervical sinus not complete
what does the Ph 1 cleft become?
EAM
how do branchial cysts present?
lumps along border of SCM
below angle of jaw
how can cleft lip form?
with improper formation + fusion of palatal shelves (of maxillary prominence - forms secondary palate)
what is lateral cleft lip?
failure of fusion of MEDIAL nasal prominences (primary palate) and maxillary prominence (palatal shelves)
(primary palate doesn’t fuse with secondary)
what is cleft lip and palate?
combined failure of cleft lip (medial nasal + maxillary) AND failure in palatal shelves to meet in midline
(primary doesn’t meet secondary AND secondary not complete - doesn’t fuse in middle)
why is cleft lips a problem?
can cause an inability to feed and speak properly
what do common chromosomal abnormalities have associated with?
associated external ear anomalies
what are placodes?
an area of thickening of epithelium in the embryonic head ectoderm layer, that gives rise to neurons and other structures of the sensory nervous system
why does foetal alcohol syndrome occur?
alcohol cross placenta freely (small molecule)
what is sensitive to alcohol in the foetus?
neural crest migration (nervous system) and development of brain (CNS)
how does foetal alcohol syndrom epresent?
growth, mental + physical problems
e.g. flat short philtrum, small lower jaw
what is a condition related to FAS?
alcohol-related neurodevelopmental delay (ARND)
what is ARND?
(mild form of FAS)
slight developmental delay / slow progression due to alcohol comsumption
what is charge syndrome?
CHD7 heterozygous mutation
why is CHD7 heterozygous mutation a problem?
CHD7 essential for production of multipotent neural crest cells
function of neural crest cells in H+N?
NC should migrate just as the neural tube closes to drive the normal development of H+N structures
what is the neural tube?
a hollow structure from which the brain and spinal cord form
what are the symptoms of Charge syndrome?
C - coloboma H - heart defects A - chonal atresia R - growth and development Retardation G - Genital hypoplasia E - Ear defect
what is coloboma?
a hole in one of the structures of the eye:
e.g. iris, retina, choroid, or optic disc
what is choanal atresia?
congenital disorder: back of the nasal passage (choana) is blocked
usually by abnormal bony or soft tissue (membranous) due to failed recanalization of the nasal fossae during fetal development
