muscle anatomy
What skeletal muscle consist of? What about contracts?
Muscles can get quite complex anatomy ... and that's without even mentioning the physiology of muscle contraction! This article breaks into several sections of skeletal muscle and examine the smallest fascinating process that brings about all of our movement ...
Each one of 430 bodies of skeletal muscle consisting of muscle tissue, connective tissue, nerves and blood vessels. A fibrous fascia covering called epimysium every muscle and tendon. Connected abdominal muscle tendons to bone and bone periosteum attached to them - more connective tissue covering all bones. Contraction of the abdominal muscles pull on tendons and, in turn, was attached to the bone.
muscle anatomy
Limb muscles (like biceps brachii in the upper arm) has two attachments to the bone. The proximal attachment or origin is closest to the trunk. Distal attachment or insertion is farthest from the trunk. Trunk muscle (such as the rectus abdominus in the stomach) also has two attachments - superior (closer to the head) and inferior (more distant from the head).
A closer look at muscle anatomy shows that each muscle belly of the muscle cells or fibers. muscle fibers are grouped into bundles (up to 150 fibers) called fasciculi. Each fasiculus or bundles surrounded by connective tissue called perimysium. Fiber in each bundle is surrounded by a network of more tissue called endomysium.
Each individual fiber consisting of membrane (sarcolemma) and can be further broken down into hundreds or even thousands of myofibrils. Myofibrils are surrounded by sarcoplasm and together they form a contractile component of muscle. See diagram below:
Muscle anatomy diagrams
Sarcoplasm contain glycogen, fat particles, enzymes and mitochondria. The myofibrils were wounded consisted of two types of protien filaments or myofilaments. They are the actin and myosin.
muscle anatomy
Myosin and actin filaments run parallel to each other along the muscle fibers. Myosin has a small round head protruding from it periodically. This is called cross bridges and plays an important role in muscle action. For more details, see the article on the sliding filament theory.
muscle anatomy
Each myofibril is organized into several sections along its length. Each section is called sarcomere and they are repeated right along the length of the muscle fibers. This is similar to how the ruling meter is divided into centimeters and millimeters. Just as the millimeter is the smallest function of the ruler, sarcomere is the smallest contractile part of muscle fibers.
sarcomere is often divided into different zones to show how to behave during the muscle action. See diagram below:
Sarcomere diagram
muscle anatomy
Sarcomere Z-lines separating each. H-zone is the center of sarcomere and M-line is where the myosin filaments anchor adjacent to one another. In the diagram above the dark A-band where myosin filaments align and light I-band where actin filaments align. When muscles contract the H-zone and I-band both decrease as the z-lines drawn to each other. See diagram below:
muscle anatomy
Actin and myosin diagram
Muscle anatomy examination would not be complete without taking a closer look at how the muscles contract ...
muscle anatomy