Pharyngeal Apparatus Development Flashcards
Where are pharyngeal grooves or clefts?
-external and covered by ectoderm
What are pharyngeal arches?
- 6 bilateral ridges form in cranial to caudal sequence
- neural crest cell migration
- support lateral walls of pharynx
- forms the face, nasal cavities, mouth, larynx, pharynx and neck
Where are pharyngeal pouches?
- internal and lined by endoderm
- 4 are well define with the 5th being rudimentary or absent
What are pharyngeal membranes?
- separating the grooves from the pouches
- ectodermal/endodermal double-layered membrane
- resemble fish at this stage
What is the stomodeum?
-slight external depression indicating location of future mouth
What is the oropharyngeal membrane?
bilaminar membrane separating stomodeum from pharynx
- external surface covered by ectoderm - internal surface lined by endoderm - ruptures and opens passage into forgut
What forms the core of pharyngeal arches?
mesenchyme
What is the mesenchyme in pharyngeal arches formed by and what does it therein form?
- formed by neural crest cells
- forms all CT and smooth mm
- mm derived from somites
What covers the surfaces of pharyngeal arches?
ectoderm = external surface endoderm = internal surface
What does each pharyngeal arch contain?
- cartilaginous rod = skeletal structures
- mm component = somites
- sensory/motor nn. = neuroectoderm
- pharyngeal arch a. = truncus arteriosus
What does pharyngeal arch 1 (Mandibular arch) give rise to?
- malleus & incus - dorsal part
- sphenomandibular ligament and ant ligament of malleus - perichondrium of middle portion
- mandibular prominence - forms mandible - forms by intramembranous ossification
- maxillary prominence forms maxilla, zygomatic and temporal bone
- maxiallary prominence
What does pharyngeal arch 2 (Hyoid arch) give rise to?
- stapes and styloid process of temporal bone - from dorsal part
- stylohyoid ligament - from perichondrium of middle portion of cartilage
- lesser cornu and superior body of hyoid - from ventral portion of cartilage
What does pharyngeal arch 3 give rise to?
-greater cornu and inferior body of hyoid
What does pharyngeal arch 4&6 give rise to?
- fuse to form laryngeal cartilages
- thyroid, cricoid, arytenoids, corniculate, cuneiform
- EXCEPTION: epiglottis
- forms from hypopharyngeal eminence on floor of pharynx
What does pharyngeal arch 5 form?
Rudimentary = no structures!
What are the corresponding nerves for pharyngeal arch 1?
V2(maxillary) and V3(mandibular) of CNV (trigeminal)
What mm do the nerves that correspond to pharyngeal arch 1 innervate?
-mm of mastication, mylohyoid, ant belly of digastric, tensor tympani, tensor veli palatini
What are the corresponding n to pharyngeal arch 2?
CNVII (facial)
What mm are innervated by the nerves of pharyngeal arch 2?
mm of facial expression, stapedius, post belly of digastric, stylohyoid.
What is the corresponding n to pharyngeal arch 3?
CNIX (glossopharyngeal)
What mm do the nerves of pharyngeal arch 3 innervate?
stylopharyngeus
What is the corresponding n to pharyngeal arch 4?
CNX (vagus)
What mm do the n that correspond to pharyngeal arch 4 innervate?
-pharyngeal constrictors, cricothyroid, levator veli palatini
What is the corresponding n of pharyngeal arch 6?
CNX (vagus)
What mm are innervated by the corresponding n of pharyngeal arch 6?
intrinsic mm of the larynx, striated mm in the upper esophagus
Where do the pharyngeal arch aa. originate from?
truncus arteriosus
- aortic sac persists as most of the arch of the aorta and brachiocephalic a.
Where do pharyngeal arch aa. terminate in?
dorsal aorta on the ipsilateral side
What does the arch a. 4 on the left contribute to?
arch of aorta
What does the arch a. 4 on the right form?
proximal parts of the R subclavian
What does arch a. 5 form?
NOTHING!
What does arch a, 6 on left persist as?
left pulmonary a. and ductus arteriosus
- left recurrent laryngeal n. hooks around ductus arteriosus
What does arch a. 6 on right persist as?
right pulmonary a.
- right recurrent laryngeal n hooks around R subclavian a.
What does the pharyngeal pouch 1 expand into?
tubotympanic recess
- elongates to form pharyngotympanic (Eustachian) tube
What does the cavity of the lateral end of the Eustachian tube become?
the tympanic cavity of the middle ear
What forms at the 1st pharyngeal membrane?
tympanic membrane
What does the pharyngeal pouch 2 form?
tonsillar fossa which will contain the palatine tonsil
What does pharyngeal pouch 3 give rise to?
Inferior parathyroid gland
Thymus
Epithelium in what part of the 3 pouch forms the inf parathyroid gland?
dorsal part
Epithelium in what part of the 3 pouch forms the thymus?
ventral part
Does the thymus remain bilobed after fusion in midline?
yes
What happens to the thymus and parathyroid gland in relation to the pharynx?
lose their connection
What are the derivatives of pharyngeal pouch 4?
superior parathyroid gland
ultimopharyngeal body
How is the superior parathyroid gland formed?
epithelium in the dorsal part of the pouch proliferates to form this gland
- loses connection to pharynx and becomes associated with thyroid gland
How is the ultimopharyngeal body formed?
epithelium in ventral prat of pouch proliferates to form this structure
What are parafollicular cells? where are they formed?
calcitonin producing cells in thryoid
from the ultimopharyngeal body
What does pharyngeal groove 1 become?
external aucoustic meatus
What does the pharyngeal membrane 1 become?
the tympanic membrane
What does pharyngeal arch 2 overgrow?
arches 3-4 and grooves 2-4
What does arch 2 form?
cervical sinus
How common is an external branchial sinus?
uncommon
An external branchial sinus is due to what?
failure of pharyngeal groove 2 and cervical sinus to obliterate
Where does the sinus remain open in an external branchial sinus?
along the anterior border of SCM in inferior neck
How is external branchial sinus detected in infancy?
mucous discharge
How common is Internal branchial sinus?
very rare
How does an internal branchial sinus formed?
persistent pharyngeal pouch 2
What is a branchial fistula?
abnormal canal passing from tonsilar fossa through lateral side of neck
- follows course of carotid aa.
How is a branchial fistula formed?
persistence of groove 2 and pouch 2
What are branchial cysts?
spherical remnant of the cervical sinus or groove 2
When are branchial cysts detected?
late childhood or early adulthood
- fluid accumulation
What are branchial vestiges?
cartilage or bony remnants of arch cartilage
In development of the tongue, what is the median lingual swelling (tuberculum impar)?
from arch 1 and forms on pharyngeal floor
does not persist as recognizable component of adult tongue
In terms of tongue development, what is the lateral lingual swellings?
derived from arch 1 on either side of tuberculum impar
form 2/3 of tongue
- lingual septum = fusion
- lingual br of V3 = sensory innervation to this part of tongue
What are portions of the tongue formed by swellings posterior to tuberculum impar?
- copula
- hypopharyngeal eminence
What is the copula?
lingual swelling derived from arch 2
What is the hypopharyngeal eminence?
- lingual swelling derived from arch 3&4
- forms post 1/3 of tongue
- CNIX = sensory innervation
What is the sulcus terminalis?
V-shaped grove on line of fusion b/t ant and posterior portions of tongue
What does thee pharyngeal arch mesenchyme give rise to?
CT and vasculature in tongue
What are derived from occipital mytomes?
mm in tongue
How does CNXII migrate into the tongue?
follows myoblasts as they migrate
Which lingual papillae form first?
vallate and foliate followed by fungiform and filiform
Which nerves supply taste buds?
CNVII = ant 2/3 taste buds CNIX = post 1/3 taste buds
What is glossoschisis?
bifid or cleft tongue due to incomplete fusion of lateral lingual swellings
- deep midline groove
What is ankyloglossia?
short frenulum extending to the apex of the tongue limiting protrusion of the tongue
(tongue tie)
What is the first endocrine gland to develop?
thyroid gland
In terms of the thyroid gland, where does the thyroid primordium develop from?
median endodermal outpouching from the floor of pharynx
- between tuberculum impar and copula
Where does the thyroid gland descend?
neck anterior to hyoid bone and laryngeal cartilages
What is the foramen cecum?
point of origin of original thryoglossal duct
What is the thyroglossal duct?
narrow tubular connection back to tongue
What connects the R and L lobe of the thyroid?
isthmus
What is the predominance of the pryamidal lobe?
50%
What kind of gland is the thyroid?
follicular endocrine gland
Thyroid hormonesT3 and T4 are stored where? and affect what?
stored extracellularly in inactive form
affect basal met, heat production, body growth & development
Where do thyroglossal duct cysts form?
anywhere along the path of thyroglossal duct
- most commonly seen just inf to the hyoid bone
What happens when thyroglossal duct cysts get infected?
usually perforate the skin in median plane to become a sinus
What type of tissues may be ectopic thyroid gland?
lingual thyroid tissue = more common
sublingual thyroid tissue - if present is the only thyroid tissue present.
