Embryology Of The Pharyngeal Apparatus Flashcards
What are the grooves made of?
Ectoderm
What are the pouches made from?
Endoderm
What are the pharyngeal membranes made of?
Ectoderm from groove
Endoderm from pouch
Mesenchyme from core
What is the core of pahryngeal arches made of?
Mesoderm and Mesenchyme
When do the pharyngeal arches form?
4th week
What do the 1st pair arches form?
Primordial jaws
What is the purpose fo the pharyngeal arches?
Support lateral walls of the primordial pharynx
Give rise to prominences of tissue that contribute to craniofacial development
What does the NCC derived Mesenchyme form from arches?
All CT in head as well as dermis and smooth muscle
What does the paraxial mesoderm do?
Populate each arch to form PA musculature
What does the lateral plate mesoderm do?
Angioplasty to endothelium
What does the Prechordal plate mesoderm do?
Extraocular musculature
What do arch artery arise from? What are they remodeled into?
Truncus arteriosus of primordial heart
Remodeled into great arteries of thorax and head/neck
What is a cervical cyst?
Remnant of cervical sinus (from 2- 4 grooves)
Persists and forms a slowly enlarging, painless, free-lying cyst in neck
Can accumulate fluid and cellular debris derived from desquamation of the epithelial linings
Mobile, typically painless, unattractive, drained or surgically excised
What is a cervical sinus?
How is it detected?
Failure of 2nd pa groove and cervical to go away
Detected due to discharge of mucus
What is a cervical fistula?
Abnormal canal that opens into tonsillar sinus and externally in the side of neck
Persistent of parts of 2nd groove and pouch
How is the thymus formed?
When is it complete?
From PA 3 endoderm (pouch)
Comprised of epithelial cords that grow into surrounding Mesenchyme forming lobules
They then become arranged around a central point forming thymic corpuscles
Thymus growth and development is still going on during childhood
How does the thyroid gland develop?
First endocrine gland to develop
From a median endodermal thickening in the floor of primordial pharynx
Descends into neck with tongue growth
Is conjected to tongue by narrow tube
How is the thyroid conjected to tongue during its descent down the throat?
What will this become?
Thyroglossal duct
Remnant is seen as foramen cecum
What happens to the 3rd pouch?
Caudally migrates due to growth of brain and cardiac regions