Sternocleidomastoid Muscle

Sternocleidomastoid Muscle

Sternocleidomastoid Muscle

The sternocleidomastoid muscle, AKA sternomastoid or SCM muscle take its  name from their connection to three bony structures.

  1. The sternum or breastbone
  2. The clavicle or collarbone
  3. Mastoid process of the occipital bone of the skull

Origin: The clavicular division originates at superior medial third of clavicle and the sternal division originates at superior manubrium of sternum. Insertion: Both divisions of sternocleidomastoid muscle insert into  mastoid process of the skull. Action:

  1. Rotate the head to the opposite side
  2. Oblique rotation and lifting the head
  3. Neck Flexion
  4. Assist scalene in inspiration
  5. Cervical plexus nerve of sternocleidomastoid provides proprioception, spacial body orientation in static posture and during movement. 1

Upper Trapezius

upper Trapezius

Upper Trapezius

Origin of upper trapezius: External occipital protuberance, medial third of the superior nuchal line,, ligamentum nuchae, spinous processes of 7th cervical vertebrae.

Insertion: lateral third of the clavicle, medial side of the acromion process.

Actions: Elevates the scapula,  rotates the scapula upward, retracts scapula when contracting with other sections of trapezius muscle.


Pectoralis Major | Origin, Insertion & Action

Pectoralis Major

Pectoralis Major

Origin:  Medial half of the clavicle, sternum, upper costal cartilages (1-7) and the aponeurosis of the external oblique.

Insertion:  Lateral lip of the intertubercular  groove of the humerus,  crest of the greater tubercle of the humerus

Actions: Flex, extend, adduct and medially rotate  the arm at the shoulder.


Human Body Muscles | Three types of muscles in human body

Human Body Muscles

It is easy to become captured by the beauty of human motion and the role skeletal muscles play in  human body muscles. The 700 or so muscles give a surgeon the incredible precision to operate on a brain and they give a world-class powerlifter the strength to lift  a half ton.  The knowledge of human anatomy could inspire great artist like  Leonardo da Vinci 1 and enhance the work for hundreds of years.

It is clear that the knowledge of human body is a necessity for physicians and others in the field of healing and training.  However in our world today with so many suffering from chronic aches and pains related to motion,  a basic knowledge of human body from anatomical point of view could help you at the very least understand how to actually implement the instructions you receive from your physician,  chiropractor, therapist and even your trainer.

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To move with efficiency is the most effective way to get results and reduce chances of injury.  An additional benefit of basic anatomy of human muscle is actually saving time. Many of the motions your perform are redundant motions. You can eliminate these movements and save time. You can also focus on true variety that brings balance to your body. A basic knowledge of human anatomy cold help you recognize these redundancies. As I said it is easy to get lost in the amazing skeletal muscles of human body. But before we go to far let’s cover the other muscles responsible for your digestive system and blood vessels to work and the muscles of the heart that are unique. Human body muscles are in three general categories.

  1. Visceral Muscle. You can find these inside your organs, your stomach, intestines, and blood vessels.  You don’t even feel them working. You only notice the negative effects of these muscles not working well.  Diarrhea and constipation are two examples.   These muscles are controlled by the unconscious part of the brain that most cannot control directly so they are called involuntary muscles. They are also called  smooth muscles to describe a very smooth, uniform appearance they have  under a microscope in comparison to banded appearance of cardiac and skeletal muscles.
  2. Cardiac Muscle.  Heart is especial in so many ways. It has been called the center of wisdom and superior to brain. Interestingly enough  cardiac muscle are autorhythmic which means that generates its own rhythmic action potentials independent of the nervous system.  No wonder that poetically most of the emotions are expressed in terms of the heart for example heart-broken or heart-felt. Anatomically the muscles of the heart are different. They are designed for continuous work.
  3. Skeletal Muscle. Only skeletal muscle are controlled consciously in healthy individuals.  This voluntary control allows your motions to match your intentions. Can you imagine what happens if you sit when you wanted to walk or your body turns left when you wanted to pick up a glass of water.  As odd as it may sound we are slowly giving up this incredible gift and ability to move voluntary.

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Pectoralis Minor

pectoralis minor

Pectoralis Minor

Origin: Anterior surfaces of 3rd, 4th, and 5th ribs near the costal cartilages

Insertion: Coracoid process of the scapula.

Action: Depresses scapula and rotates scapula downward. Important anterior shoulder stabilizer.

Reversed origin-insertion action: With a fixed scapula, pectoralis minor helps rib elevation during forced inspiration.

Synergists:  Pectoralis major, serratus anterior