Branchial arches and pouches (dave's notes) Flashcards
How do the branchial arches develop?
Mesoermal condensations develop in the side walls of the primitive pharynx to form branchial arches.
How to the developing branchial arches grow?
These grow ventrally towards each other fusing in the midline (forming horse shoe shapes)
How many branchial arches develop? What descends with this?
As the pericardium drops, 6 arches develop, but 4 and 5 combine hence there are only 4 pouches (internal) or clefts (external)
What layers do the branchial arches keep?
Ecto -meso- endodermal layers
What develops from the 1st branchial arch?
Mandible and mouth
What develop from the 2nd branchial arch?
?Hyoid
What develops from the 3rd branchial arch?
??hyoid?
What develops from branchial arches 4,5,6?
The cartilages of the larynx
What is associated with each arch?
An artery and a cranial nerve. The vascular supply varies, but the nerve supply is constant
Except for the ………. , each pouch grows laterally into a …… and ……. ……….. . The …… pouch regresses but probably gives rise to ………….. .. ……. .
Frist, dorsal and ventral diverticulum. Fifth pouch regresses but probably gives rise to parafollicular c-cells
What does the cervical sinus arise from?
From the second arch descending down over the others. The imprisoned ectoderm normally disappears, but may persist as a branchial cyst -> fistula
Where may a branchial cyst /fistula develop?
As a tract from the tonsil, between the external and internal carotid arteries to the skin at the lower SCM
Ventral derivatives: The epithelium of the tongue is formed form buds of which arches?
1st, 3rd, 4th arches
Where may a thyroglossal duct develop?
A thyroglossal duct evaginates ventrally between the 1st and 2nd arches
How and where does the trachea develop?
In the ventral wall of the oesophagus a groove appears, limited above by the furcula. A gutter begins to form a tube ->trachea
