Branchia = gill

(term “branchial” not used now since actual gills never form) 

The pharyngeal/branchial apparatus consists of:

• Pharyngeal arches:
  •  
    1. develop in the side walls of the primitive pharynx.
    2. initially they consist of a mesodermal core surrounded by epithelium of endodermal and epidermal origin. 
    3.  The mesodermal core of the branchial arches is pleuripotential in that it can give rise to any number of structures e.g. cartilage, muscles or arteries.
• Pharyngeal clefts:

 These arches are separated by deep grooves known as branchial clefts.

• Pharyngeal pouches:

1.      A number of outpocketings known as the branchial pouches appear on the lateral wall of the pharynx.

2.     These pouches gradually penetrate the surrounding mesenchyme but do not establish an open communication with the exterior.

http://anatome.ncl.ac.uk/tutorials/clinical/arch/text/page1.html

• Paraxial Mesoderm: 

Forms:              1.         Floor of the brain case

2.                  Small portion of the occipital region

3.                  All voluntary muscles of the craniofacial region

4.                  Dermis and connective tissues in the dorsal region of the head

5.                  Meninges caudal to prosencephalon

• Lateral plate Mesoderm:

Forms:              1.         Laryngeal cartilage (artynoid and cricoid)

                       2.         Connective tissue in this region

• Neural crest cells: Derived from neuroectoderm, migrate VENTRALLY into pharyngeal arches and ROSTRALLY around forebrain adn optic cup into facial region

                      Forms:              1.         Mid-facial and pharyngeal arch skeletal structures

                      2.                  Tendon

                      3.                  Dermis

                      4.                  Pia and arachnoid

                      5.                  sensory neurons

                      6.                  Glandular stroma

•  

  Together with cells from ectodermal placodes: neurons of 5^th, 7^th, 9^th, and 10^th cranial sensory ganglia

The foramina are: