组织学与胚胎学英文课件------e24

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---distal portion: widen into a sac-like structuremiddle ear cavity, the branchial membrane form tympanic membrane or eardrum
---proximal part: remain narrow to form the pharyngotympanic or Eustachian tube
---dorsal portion: differentiates into inferior parathyroid gland
---ventral part: cells differentiates and form two cell cords, fuse with each other behind the thorax to give rise to the promordium of the thymus
Chapter 24
Development of digestive and respiratory system
* digestive and respiratory system derived from primitive gut /foregut /midgut /hindgut
---epi. of digestive and respiratory system derived from endoderm
④ Fourth pharyngeal pouch:
---dorsal portion: forms superior parathyroid gland
---ventral portion: degenerates ⑤ Fifth pharyngeal pouch:
---gives rise to the ultimobranchial body, immigrate into thyroid and differentiate into parafollicular cells
---CT and MT of digestive and respiratory system derived from splanchnic or visceral mesoderm
1. Development of digestive system
1) derivatives of pharyngeal pouch ---pharyngeal pouch:
---thyroglossal duct: a narrow canal connecting primitive pharynx with thyroid primordium, by the 6th week, becomes solid and disappears.
---foramen caecum:
---with the descent of the heart Baidu Nhomakorabeand lungs, it lengthens rapidly
---muscular coat, formed by surrounding mesenchyme
/striated in upper two-thirds
/smooth in lower one-third
② development of stomach ---by 4th week, appears as a fusiform
dilation of foregut
---greater and lesser curvatures: by the 5th week, posterior part of stomach grow faster than the anterior portion
---thyroglossal cyst and fistula: a cystic remnant of the thyroglossal duct, may be found at any point along the migratory path followed by the thyroid gland; sometimes a thyroglossal cyst is connected to the outside by a fistulous canal, called thyroglossal fistula
2) development of esophagus and stomach ① development of esophagus
---derived from primitive gut extending from the laryngotracheal diverticulum to stomach
② Second pharyngeal pouch: ---distal portion: obliterated ---remaining part proliferate and
primordium of the palatine tonsil
form
③ Third pharyngeal pouch:
*development of thyroid gland
---thyroid primordium: by the 4th week, endodermal proliferation of the floor of primitive pharynx, then descends in front of the primitive pharynx as a bilobed diverticulum
/outpocketings of endodermal lining of the primary pharynx (extends from the buccopharyngeal membrane to the tracheobronchial diverticulum) /5 pairs
---derivatives of pharyngeal pouch: ① First pharyngeal pouch:
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