The Muscles (Functions)One of the most amazing things about the human body is the incredible range of movement and mobility it has. This day to day activity is accomplished by our muscles through the extraordinary and fascinating ability of converting chemical energy, energy stored in nutrients, into mechanical energy, energy of movement. Muscles are often viewed as the "machines" of the body. They help move food from one organ to another, and carry out our physical movement.
Muscle TypesThere are three different kinds of muscles in our body: cardiac, smooth, skeletal1. Cardiac Cardiac muscles are involuntary and found only in the heart. They are controlled by the lower section of the brain called the medulla oblongata, which controls involuntary action throughout the body. The heart cells come in long strips, each containing a single nucleus, one of the key factors in determining which of the three classes any particular muscle is. The fibers of cardiac muscle are branching fibers. Cardiac muscle is striated in appearance but like a smooth muscle in its action. Its movement cannot be consciously controlled. Located at the walls of the heart, its main function is to propel blood into circulation. Contraction of the cardiac tissue is caused by an impulse sent from the medulla oblongata to the SA nerve located at the right atrium (link-circulatory).
-2. Smooth Smooth muscles, also called involuntary or visceral muscles, are those muscle fibers which move our internal organs such as the digestive tract, blood vessels, and secretory ducts leading from glands. We have no conscious control over these muscles. They are called smooth because they have no dark or light fibrils in their cytoplasm. Smooth muscle forms sheets of fibers as it wraps around tubes and vessels. Unlike cardiovascular muscles, smooth muscles are generally spherical, as most other human cells are, and each contains one nucleus.
-Skeletal The skeletal muscles are the only voluntary muscles of the body, and make up what we call the muscular system. They are all the muscles that move bones and show external movement. Unlike either of the other two classes, skeletal muscles contain multiple nuclei because of their large size, being in strips up to a couple of feet long.
-They are also called voluntary or striated muscles. We have conscious control over the activity of this type of muscle. Striated muscle fibers (cells) have a pattern of dark and light bands, or fibrils, in their cytoplasm. A delicate membrane called sarcolemma surrounds each skeletal muscle fiber. Skeletal muscle fibers are arranged in bundles. Fibrous tissue that envelopes muscles is called fascia.
Muscle-Bone Interactions Lever SystemA lever is a rigid bar on which a given load is moved with supporting help from a fulcrum. A fulcrum is a fixed point on which lever can move in different ways or angles. The whole muscular system interacts in this kind of way with the skeletal system-hyperlink. Given a load the muscles pull the bone up or in any direction against the load. Our joints-hyperlink usually seem to be the fulcrum on which we move the lever or bone.
-Skeletal muscles can be broken down into groups based upon the type of movement they portray. The movement of the muscle is based upon the type of joint (hyperlink-Skeletal system) upon which the muscle works. Skeletal muscles cant expand, or make themselves longer, but they can contract, or make themselves shorter, so they generally work in pairs. One contracts, and in doing so stretches the other, and reverses its effects on the joint. For example, when we contract our major arm muscle, which is called the biceps, in return the lower arm muscle, called the triceps, extends. So as we contract one muscle the other one extends. These effects can be broken down into groups of their own: flexors, extensors, adductors, and abductors. Flexors and extensors become plantarflexors and dorsiflexors, respectively, when located within either the wrist or ankle joints.
Flexors Flexors bend at the joint, decreasing theinterior angle of the joint. The «bracius»humorous, or biceps, is a flexor of the elbowjoint, bringing the fist towards the shoulder. Ifa flexor appears in either the wrist or anklejoints, it becomes a plantarflexor.
Extensors Opposites of flexors, extensors unbend atthe joint, increasing the interior angle. The«tracius» humorous, or triceps, is an extensorof the elbow joint, taking the fist farther awayfrom the shoulder. If an extensor is found inthe wrist or ankle joints, it becomes adorsiflexor.
Abductors Abductors take away from the body, likelifting the arm to the side. Abd- means to takeaway, like abduct and abdicate. Spreading outyour fingers uses abductors, because you aretaking away your fingers from an imaginaryline running down your arm «graphic».
Adductors• Adductors, the opposites of abductors, move toward the body. Add- means to increase or include. By lowing an arm raised to the side, or moving our fingers together while keeping them straight, our muscles are adducting.
Actions of Skeletal Muscles* Flexion - Decreasing the angle between two bones: bending a limb;* Extension - Increasing the angle between two bones: straightening out a limb;* Abduction - Movement away from the midline of the body;* Adduction - Movement toward the midline of the body
Actions of Skeletal Muscles* Rotation - Circular movement around an axis* Dorsiflexion - Decreasing the angle of the ankle joint so that the foot bends backward;* Plantar flexion - The motion that increases the angle in the ankle joint as when pointing the toes or extending the foot toward the ground;* Supination - Facing upward as applied to the hand, the palm moves from a posterior to an anterior position;* Pronation - Facing downward; as applied to the hand, the palm moves from an anterior to a posterior position.
Tendons and LigamentsMuscles alone cant do the job. At every joint, tendons and ligaments also help out. Muscles wouldnt be very useful alone because they dont directly connect to the bone, so even if they contract, they wouldnt be moving anything. Instead, muscles are connected to tendons, when themselves are connected to the bones. When the muscles contract, they pull on the tendons, which in turn pull on the muscles, and that causes movement.But without ligaments, that movement wouldnt be too useful because it would not be directed movement. Without ligaments, instead of bones bending or rotating about each other when muscles contract, they would slide by each other. Ligaments are what hold the bones together. They connect at the ends of muscles and keep them from slipping and sliding, and force them to bend.
Major Skeletal MusclesThe muscular body is divided into ten different areas where muscles can be found:1. facial,2. neck,3. shoulder,4. arm,5. forearm,6. thorax,7. abdomen,8. hip,9. pelvis/thigh,10. leg.
Facial MusclesFacial muscles are all the muscles that move the face. Orbicularis oculi-sound are the two muscles that move the eyes. Frontalis-sound and Temporalis-sound are the two muscles which move the forehead and sides of the head. Zygomaticus-sound and Masseter-sound are the two muscles that work in conjunction to move the jaw and upper lip area. Orbicularis oris-sound is the muscle which moves the lips.
Neck• The neck area is almost entirely moved by the sternohyoid-sound and Sternocleidomastoid- sound. These muscles allowthe neck to move your head left and right. They work with the platysma muscle to control how far you can move your head left and right. What allows your head to move up and down is the trapezius-sound. The trapezius is so large that it extends down to the shoulder and thorax area. The trapezius is a good example of how some muscles are named by their shape. the trapezius looks just like a trapezoid.
Shoulder• A group of muscles all work together to move the whole shoulder area. This group takes into account the trapezius-sound, deltoid- sound, infraspinatus-sound, teres major- sound, and the rhomboid major-sound. The rhomboid major is called so because its shaped like the geometric shape of a rhombus. Along with the help of the ball and socket joint- hyperlink in the shoulder, these gruops of muscles allow ther arm to throw a ball, pick things over our head, and give our arms a good stretch early in the morning.
Arm• Most known is the arm area. The famous biceps brachii-sound is the muscle that allows us to bring our forearm close to our body. The triceps brachii-sound and brachialis-sound are the two other muscles located in the arm region. These muscles allow a person to do push-ups!
ForearmA majority of the muscles in the forearm help control a part of the arm. Amongst these are the Berachiodialis major-sound, palmaris longus- sound, and Flexor carpi radialis-sound. The name of the flexor carpi radialis is a good example of how muscles are named by their function and location. This muscle is named carpi because of the bones that it helps move, the carpals. Also, the name of radialis is made by the bone that its attached to, the radius.
ThoraxThe muscles of the thorax consist of the intercostals and diaphragm. The intercostal muscles are arranged as three layers (external layer, internal layer and an incomplete innermost layer) between the ribs. The diaphragm closes the thoracic outlet and separates the thoracic cavity from the abdominal cavity. The three layers of the intercostal muscles are:• external layer -- external intercostal• internal layer -- internal intercostal• innermost layer -- transversus thoracic (anterior), innermost (lateral) and subcostal (posterior)• The diaphragm is the most important muscle of the thoracic wall. During normal respiration, this muscle is the primary component. As you can see, the innermost layer is split into three differently named muscle groups. The transversus thoracis, innermost intercostal and subcostal muscles make up the deepest layer of muscles from anterior to posterior, respectively.
AbdomenThe abdominal area consists of the muscles that allow us to bend down and move our waist from side to side. The internal oblique-sound and external oblique-sound are the muscles that move our body from left to right. The transversus abdominus-sound and rectus abdominus-sound, along with the trapezius- sound and latissimus dorsi-sound allow us to bend down and grab objects.
HipOnly two muscles make up the hip area. These are the gluteus medius-sound and gluteus maximus-sound. Probably the laziest muscles in the whole system the gluteus set of muscles are used only to sit down on.
Pelvis/ThighAn overlapping of muscles is what makes this area so firm. The pelvis area is usually referred to as the upper part of the leg. Muscles like the pectineus-sound and illiopsoas-sound , which help support the upper leg area are known as pelvic muscles. Thigh muscles are very rich in capillaries and support the whole body. The upper thigh muscles are abductor longus- sound, gracilis-sound, sartorius-sound, and tensor fasciae latea. The lower thigh muscles are rectus femoris-sound, vastus lateralis-sound and medialis- sound. Located in the back of the leg are the hamstrings-sound. These muscles help us run, jump, and walk!
LegHelping the thigh region support the body is the Leg region. These muscles like the gastrocnemius- sound, soleus-sound, porenius longus-sound, and tibialis anterior-sound, which absorb the impact when one walks and runs. They also give better coordination for moving. The thigh region thrusts the body forward while the leg region coordinates where it should be thrust and where it should stand.