The arrangement of muscle fibers and tendons in two muscles used for growth studies.
The arrangement of muscle fibres and tendons was examined in the soleus muscle of rats from 6 to 175 days post partum. The muscle was seen to change from a simple structure, with mean fibre length of approximately 90% of complete muscle length, to a unipennate structure, with mean fibre length of only about 60% of muscle length. The dog pectineus muscle was also investigated and found to have a bipennate structure throughout postnatal growth. The arrangement of muscle fibres in both these muscles is such that it might be difficult (particularly in the older animals) to cut a transverse section through all the fibres contained in the muscle; some fibres might not enter the plane of section. Results on muscle fibre number in these muscles at different ages may therefore be misleading.
D000375:Aging; D000818:Animals; D004285:Dogs; D006614:Hindlimb; D008297:Male; D024510:Muscle Development; D009132:Muscles / Q000033:anatomy & histology*; D051381:Rats; D013710:Tendons / Q000033:anatomy & histology* / Q000254:growth & development; D013848:Thigh