FATE OF THE PHARYNGEAL REGION
| Germ
Layers Presented |
1st Arch | 2nd Arch | 3rd Arch | 4th
& 5th (6th) Arches |
| Surface Ectoderm |
Epith.
of buccal cavity, jaws & body of ext. auditory meatus & tym- panic membrane |
Epith. part of ext. audit. meatus and cervical sinus |
Epith. around ear | Epith. around ear |
| Neural Ectoderm |
Maxillary
and mandibular divisions of V |
VII nerve | IX nerve | X
nerve and maybe some XI |
| Aortic arches
|
Degenerates | Degenerates | Stem
of internal carotid art. and part of carotid artery) |
4th
arch = arch of aorta & part of rt. subclavian 6th arch = pulmonary arts. & ductus arteriosus |
| Skeleton
|
Maxillary
and mandibular bones Meckel's cart. = malleus, incus, spheno- mandibular ligament |
Reichert's cart. = stapes, styloid process, body and lesser cornua of hyoid and stylohyoid ligament |
body
and greater cornua of hyoid |
Laryngeal cartilages |
| Muscles
|
Masticatory, ant. belly of digastric, tensor tympani, tensor pala- tini, mylohyoid |
Facial
express., stapedius, post. belly of digastric, epicranius, stylohyoideus |
Stylopharyngeus | Pharyngeal
& laryngeal muscles & muscles of palate. |
| Endoderm
of floor
|
Tuberculum impar (body of tongue). Some lateral swelling |
Thyroid (between 1st & 2nd arch) Copula (root of tongue) |
Copula
(root of tongue) |
Root
of tongue, epiglottis & pharynx |
| Endoderm
of Pouches
|
Eustachian (auditory) tube |
tonsillar fossa | Dorsal
= inferior parathyroids Ventral = thymus |
Dorsal
= superior parathyroids (4th) Ventral = accessory thymus? (4th) Ultimobranchial body = calcitonin producing parafollicular cells. (5th) |