Pennate muscle

As Fiederung, we describe a design principle of a skeletal muscle, the force ( lifting force ) and the shortening capacity ( lift height) of a muscle affected. In pinnate muscles, the muscle fibers do not run parallel to the tendon, but set at an angle to it. By this criterion, muscles can be classified into the following groups:

• Simply pinnate muscles (musculus unipennatus )
• Double pinnate muscles (musculus bipennatus )
• Multiple pinnate muscles (musculus multipennatus )

In a doubly pinnate muscle, a tendon splits forked. For multiple pinnate muscles radiate branches of the two tendons in the muscle belly, so that the muscle is penetrated sinewy. Such muscles are pieces of meat of inferior quality because they are very tough.

Lift capacity and lift height

The lifting force of a muscle depends on the cross -section of all muscle fibers perpendicular to its fiber direction ( physiological cross-section). In a featherless ( parallelfasrigen ) muscle of this cross-section is equal to the total by the muscle ( anatomical cross section) and the muscle force is transferred onto the tendon.

The stroke is dependent on the length of the muscle fibers, and this in turn on the number of contraction units ( sarcomeres ). A sarcomere can be up to 3.5 microns long at maximum pre-stretch and shorten during muscle contraction to 1.5 microns in length. This maximum shortening by about 60%, however, does not occur in reality, under physiological conditions, the sarcomere length at optimal pre-stretch about 2-2.2 microns, resulting in a reduction of about 30 % results.

Pennation

By Fiederung can be based on the same muscle thickness, a greater number of muscle fibers to the tendon, the physiological cross-section is therefore greater than the anatomical. The pennation " ( Pennationswinkel ) influences both lifting height and lifting capacity.

The power transmitted to the tendon force ( FS) of a muscle (FM) decreases with increasing pennation ( α ) according to the formula: FS = FM • cos α.

At a 60 ° pennation thus only half the muscular power is transmitted to the pulling direction of the tendon. Due to the higher number of accreting Direction muscle fibers, however, the lifting power of a pinnate muscle is greater.

The lifting height (H ) shall apply in principle to pinnate muscles. At the same long fibers is determined not only by the shortening fraction, but also by the pennation thereby changing: H = l1 • cos α1 - α2 cos • l2, where l1 and α1 fiber length and approach angle before, l2 and α2 are after the contraction.