Embryology Flashcards
what forms the definitive endoderm and mesoderm?
invagination of the epiblast through the primitive streak
what are the three parts of the mesoderm?
paraxial
intermediate
lateral plate
when do the pharyngeal arches develop?
weeks 4 and 5
what are the five pharyngeal arches?
1 2 3 4 6
what are the three components of the pharyngeal apparatus?
core pharyngeal arch
external pharyngeal cleft
internal pharyngeal pouch
where are clefts and pouches found on the pharyngeal apparatus?
separate the arches
clefts external
pouches internal
what are the two processes formed by the first arch?
maxillary
mandibular
what does the maxillary process of the first arch form?
maxilla
zygomatic bone
what does the mandibular process of the first arch form?
meckel’s cartilage
what does meckel’s cartilage give rise to?
incus
malleus
mandible
squamous portion of temporal bone
what is the cartilage of the second pharyngeal arch?
reichert’s cartilage
what are the skeletal derivatives of the third arch?
greater horn of hyoid
lower part of hyoid bone
what are the skeletal derivatives of arches 4 and 6?
laryngeal cartilages
what nerve supplies arch 1?
trigeminal
what nerve supplies arch 2?
facial
what nerve supplies arch 3?
glossopharyngeal
what nerve supplies arches 4 and 6?
vagus
what is another name for a cervical cyst?
a branchial cyst
what causes a cervical cyst?
the cervical sinus not fully closing by birth
where are cervical cysts usually found?
along the anterior border of the sternocleidomastoid
what does the first pharyngeal cleft form?
the EAM
what do the 2-4th pharyngeal clefts form?
second arch grows over them creating a space called the cervical sinus
disappears by birth
what does the first pharyngeal pouch form?
tympanic membrane
middle ear
eustachian tube
what does the second pouch form?
palatine tonsil
what does the third pouch form?
inferior parathyroids
thymus
what does the fourth pouch form?
superior parathyroid gland
ultimobranchial body
when does the first form of the tongue appear?
the four weeks
what pharyngeal arch forms the initial tongue?
1st
how does the initial tongue appear?
two lateral swellings
one midline swelling
what is the border between anterior and posterior tongue called?
terminal sulcus
