90 



ANATOMY FOR NURSES 



[Chap. VII 



Fig. 65. — Dia- 

 GRA.M OF Muscle 

 Fibre with Sar- 

 coLEM.MA At- 

 tached. 



which are attached to the skeleton, and voluntary because it is 

 nearly always under the control of the will. It is composed of 

 long, slender fibres measuring on an average gj^ 

 inch (0.050 mm.) in diameter, but having a length 

 of an inch or more. 



Each fibre consists of three distinct elements : — 



(1) Contractile substance, forming the centre and 

 making up most of the bulk of the fibres ; 



(2) Nuclei, which lie scattered upon the surface 

 of the contractile substance ; 



(3) The sarcolemma, a thin, structureless tube 

 which tightly encloses the contractile substance 

 and the nuclei. 



As each fibre is developed from a single cell and 

 contains a number of nuclei, we may regard it as 

 a multinuclear cell of elongated form. The muscle 

 fibres lie closely packed, their ends lapping over 

 on to adjacent fibres and forming bundles. A 



delicate connective tissue penetrates between 



the fibres, surrounds the small bundles and 



groups them into larger bundles. Connective 



tissue also surrounds the larger bundles and 



forms a covering for the whole muscle. Thus it 



will be seen that connective tissue forms a sup- 

 porting framework for muscular tissue. 



All of the muscles described in this chapter 



are striated or skeletal. 



Non-striated or plain muscular tissue. — This 



tissue is called plain or non-striated because it 



does not exhibit parallel transverse strice or 



stripes. It is also called visceral because it 



constitutes a large portion of the substance of 



many of the viscera, and involuntary because it 



is usually withdrawn from the control of the 



will. It is composed of elongated fibre-cells 



containing a single elongated nucleus. These 



fibre-cells are always shorter than the fibres of 



striated tissue. They lie side by side or lay over one another at 



the ends and are joined together by a small amount of cement 



Fig. 66. — Fibre- 

 cells OF Plain 

 Muscular Tissue. 

 (Highly magnified.) 



