Muscular System

The muscular system makes up nearly half the weight of the human body, this is why when we train we sometimes put on weight instead of losing it. We put on muscle weight.

The muscles provide the forces that enable the body to move. Muscles stretch across joints to link one bone with another and work in groups to respond to nerve impulses.

There are three types of muscle

  • Skeletal Muscle
  • Smooth Muscle 
  • Cardiac Muscle

Skeletal Muscle

  • There are nearly 650 skeletal muscles in the human body
  • Skeletal muscles are attached to the skeleton
  • They work in pairs: one muscle moves the bone in one direction and the other moves it back again
  • Skeletal muscles are voluntary muscles – in other words we think about what movements we want to make (at least, usually!) and send messages via our nervous system to tell the appropriate muscle(s) to contract.
  • Muscle contractions can be short, single contractions, or longer ones.

Smooth Muscle

  • Smooth muscle is found in our internal organs: in our digestive system, our blood vessels, our bladder, our respiratory organs, and, in a female, the uterus. 
  • Smooth muscle can stretch and maintain tension over extended periods 
  • Smooth muscles are involuntary muscles – in other words, we do not have to think about contracting them because they are controlled automatically by the nervous system.

Cardiac Muscle

  • As the name should tell you, cardiac muscle is found only in the heart. 
  • It can stretch, just like smooth muscle, and contract like skeletal muscle. 
  • It is a twitch muscle – it only does short single contractions
  • Like smooth muscle, cardiac muscle is involuntary. It’d be rather dangerous if it were voluntary – we could stop our heart beating any time we wanted!

Muscle Contraction / Movement

Nerve impulses bring about muscle contraction and contraction causes fiber shortening so light and dark fibers become closer together. As contraction of muscle ends, fibers relax and muscle length is once again attained due to increased length of muscle fiber.

Major Skeletal Muscles

The muscular body is divide into ten different areas where muscles can be found: facial, neck, shoulder, arm, forearm, thorax, abdomen, hip, pelvis/thigh, leg.

  • Facial

    In the facial area, one finds all the muscles which move the face. Orbicularis oculi-sound is the two muscles that move the eye are. Frontalis-sound and temporalis-sound are the two muscles that move the forehead and sides of your head. Zygomaticus-sound and Masseter-sound are the two muscles that work in conjunction to move your jaw and upper lip area. Orbicularis oris-sound is the muscle that moves your lips.

  • Neck

    The neck area is almost entirely moved by the sternohyoid-sound and Sternocleidomastoid-sound. These muscles allow the 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 works 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 it’s shaped like the geometric shape of a rhombus. Along with the help of the ball and socket joint-hyperlink in your shoulder, this group of muscles allows your arm to throw a softball, pick things over your head, and give your arms a good stretch early in the morning.

  • Arm

    Most known amongst teenage weight lifters is the arm area. The famous bicep brachii-sound is the muscle that allows you to bring your forearm close to your body and form a huge ball of muscle which catches a lot of attention amongst weight lifters. The tricep brachii-sound and brachialis-sound are the two other muscles located in the arm region. These muscles allow a person to do push-ups!

  • Forearm

    A majority of the muscle 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 carp because of the bones that it helps move, the carpels. Also, the name of the radial is made by the bone that it’s attached to, the radius.

  • Thorax:

     The thorax is the set of muscles that carrying your head, arms, stomach, and any other upper body areas. These muscles are the trapezius-sound and latissimus dorsi-sound. Usually, the majority of the muscles of the thorax can be damaged easily if one does not stretch before exercise, or lifts a heavy load. 

  • Abdomen

    The abdominal area consists of the muscles that allow you to bend down and move your waist from side to side. The internal oblique-sound and external oblique-sound are the muscles that move your body from left to right. The Transversus abdominus-sound and Rectus abdominus-sound, along with the trapezius-sound a latissimus dorsi-sound allow you to bend down and grab objects. 

  • Hip

    Only 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/Thigh 

    An 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 iliopsoas-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 your leg is the hamstrings-sound. These muscles help you run, jump, and walk! 

  • Leg

    Helping 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 absorb the impact when one walks and runs. they also give better coordination for moving. the thigh region trusts the body forward while the leg region coordinates where it should be thrust and where it should stand.

Smallest Muscle

The smallest muscle of the skeleton is the stapedius, which measures 1/20th of an inch. It is the activator of the stirrup that sends vibrations from the eardrum to the inner ear.

Largest Muscle

The largest muscle is the latissimus dorsi. This is the flat muscle of the back that operates during arm movement.

Fastest Muscle

The eye muscle is the fastest reacting muscle of the whole body. It contracts in less than 1/100th of a second.

Longest Muscle

The longest muscle in your body is the sartorius.

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