CLASSIFICATION OF ORGAN-SYSTEMS 



39 



system is usually considered as including only the individual or 

 voluntary muscles of the skeleton and skin. 



(4) The nervous system comprises the central nervous system 

 (the brain and spinal cord) and the peripheral nervous system, 

 the latter consisting of the paired cranial and spinal nerves with 

 their associated ganglia and the autonomic nervous system. The 

 last is made up of a pair of ganglionated sympathetic trunks, with 

 two series of ganglia, collateral and peripheral, interposed 

 between these and the visceral organs, and of a set of visceral 

 ganglia and nerves (parasympathetic system) connected with the 

 cranial and sacral regions. Associated with the nervous system 

 are the special sense organs of the head belonging fundamentally 

 in part to the nervous system and in part to the surface layers of 

 the body. 



Fig. 20. Schematic representation of the chief organ-systems of a 

 generalized vertebrate as seen in a transverse section of the abdominal 

 region: 



Integument — int. 



Skeleton— V, vertebral body; av, vertebral arch; cv, vertebral canal. 



Muscular system —sm, skeletal muscle; vm, visceral muscle. 



Nervous system — ms, spinal cord, with the central canal, and the dorsal 

 (posterior) and ventral (anterior) roots^of the spinal nerves; grp, ganglion 

 of the posterior root; re, ramus communicans to sympathetic trunk; rma 

 and rmp, ventral and dorsal rami of a spinal nerve; ts, sympathetic 

 trunk. 



Digestive system — i, intestine. 



Vascular system — ao, aorta. 



Urinogenital system— k, kidney; go, gonad (ovary "or testis). 



Serous cavity— cp, general coelom, pleuroperitoneal, or peritoneal 

 cavity; pv and pp, visceral and parietal parts of the serous tunic — visceral 

 and parietal peritoneum; mes, mesentery. 



