532 BASIC FEATURES OF VERTEBRATE MORPHOGENESIS 



in general, the walls of the coelomic spaces. These two tissues arise directly 

 from the hypomeric mesoderm. 



5. Embryonic Mesenchyme and Its Derivatives 



The mesenchymal cells given off from the mesodermal tubes of the trunk 

 area, namely, (1) sclerotomic mesenchyme, (2) dermatomic mesenchyme, 

 (3) mesenchymal contributions from the lateral plate mesoblast (hypomere) 

 to the gut, skin, heart, and (4) the mesenchyme contributed to the general 

 regions of the body lying between the epidermal tube, coelom, notochord, 

 and neural tube, form, together with the head and tail mesoderm, the general 

 packing tissue which lies between and surrounding the internal tubular struc- 

 tures of the embryo (fig. 254). Its cells may at times assume polymorphous 

 or stellate shapes. This loose packing tissue of the embryo constitutes the 

 embryonic mesenchyme. (See Chap. 15.) 



This mesenchyme ultimately will contribute to the following structures of 

 the body: 



(a) Myocardium (cardiac musculature, etc.) and the epicardium or cover- 

 ing coelomic layer of the heart (Chap. 17), 



(b) endothelium of blood vessels, blood cells (Chap. 17), 



(c) smooth musculature and connective tissues of blood vessels (Chaps. 

 16 and 17), 



(d) spleen, lymph glands, and lymph vessels (Chap. 17), 



(e) connective tissues of voluntary and involuntary muscles (Chap. 16), 



(f ) connective tissues of soft organs, exclusive of the nerve system (Chap. 

 15), 



(g) connective tissues in general, including bones and cartilage (Chap. 15), 



(h) smooth musculature of the gut tissues and gut derivatives (Chap. 16), 



(i) voluntary or striated muscles of the tail from tail-bud mesenchyme 

 (Chap. 16), 



(j) striated (voluntary) musculature of face, jaws, and throat, derived 

 from the lateral plate mesoderm in the anterior pharyngeal region 

 (Chap. 16), 



(k) striated (voluntary) extrinsic musculature of the eye (Chap. 16), 



(1) intrinsic, smooth musculature of the eye (Chap. 16), 



(m) tongue and musculature of bilateral appendages, derived from somitic 

 muscle buds (sharks) or from mesenchyme possibly of somitic origin 

 (higher vertebrates) (Chap. 16), and 



(n) chromatophores or pigment cells of the body from neural crest mesen- 

 chyme (Chap. 12). 



