Name the three common things that occur in week 4

1.  
   1. embryonic folding
   2. foregut
   3. midgut and hindgut

Describe the layers that form the long hollow tube which forms the furture digestive tract in order

embryonic folding turns the endoderm into a tube with these three layers

  

1. endoderm-inside
2. ectoderm-outside
3. mesoderm-middle

Discs fold into the embryo establishing the human axis and placing the tissue in their proper positions for further embryonic development.  Forming the hollow digestive tract

posterior portion of the tube, form the rest of the pharynx, as well as the remainder of the digestive tract

1.  
   1. Mesoderm – gives rise to muscle coats, connective tissues, vessels supplying tissues and organs, and other tissues. 
   2. Ectoderm – from epiblast layer.  Gives rise to the epidermis of the skin, the nervous system, and other structures.
   3. Endoderm – from hypoblast layer.  Gives rise to the epithelial linings of the respiratory passages and digestive tract, including some glandular organ cells.

four well defined pairs of endodermal evginations

(balloonlike structure) between the branchial arches

Describe the four pouches that make up the pharyngeal pouches

Cleft palate

•  
  • occurs with failure of fusion of the palatal shelves with the primary palate
  • isolated forms of cleft palate are less common than cleft lip, and are more common in females

begins as a triangular median swelling

tuberculum impar (median tongue bud)

•  
  •  
    • midline
    • floor of primitive pharynx

• lateral lingual swelling of distal taste buds on each side of the tuberculum impar

• the two swelling fuse and encompass the tuburculum impar to form the anterior 2/3, or body of the tongue

a third median swelling even farther posterior to the copula, that marks the most posterior region of the tongue and of the future epiglottis

Definitive Tongue –

the copula merges with the swellings of the tongue body, which is superficially demarcated by the Sulcus Terminalis in the mature tongue.  This inverted V-shaped groove marks the the border between the base of the tongue and its body

Foramen Cecum

the beginning of the thyroglossal duct which is the origin of and pathway showing the thyroid gland’s migration into the neck region

•  
  • Future oral cavity proper.
  • Origin/method: ectodermal depression that is enlarged by the disintegration of the Oropharyngeal Membrane. 
  • Enlargement allows access to the Primitive Pharynx

another specialized group of cells develop from neuroectoderm.  Involved in the development of many face and neck structures, such as the branchial arches.