Muscular System

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Muscular System:

The muscular system is an organ system consisting of skeletal, smooth and cardiac muscles. It permits movement of the body, maintains posture and circulates blood throughout the body.

The Human Muscular System

What is the muscular system function?

The muscular system is composed of specialized cells called muscle fibers. Their predominant function is contractibility. Muscles, attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction.

Muscular System

What are the 3 main parts of the muscular system?

In the muscular system, muscle tissue is categorized into three distinct types:

• Skeletal---These are what we would typically think of when talking about muscles.  These muscles attach to the skeleton and provide the skeleton with the ability to move. The Skeletal Muscles are classified as voluntary. This is because we have to make a conscious effort or decision to make them move.
• Cardiac---The cardiac muscle, is an involuntary muscle; meaning it operates without any conscious control.
• Smooth---are also considered involuntary – these muscles are found in organs or organs systems such as the digestive or respiratory system.

Each type of muscle tissue in the human body has a unique structure and a specific role. Skeletal muscle moves bones and other structures. Cardiac muscle contracts the heart to pump blood.

Structure of skeletal muscle:

Structure of skeletal muscle

Structure of skeletal muscle fiber

Structure of skeletal muscle fiber

The Muscular System – An Overview

The muscular system is made up of over 600 muscles. The primary purpose for the Muscular system is to provide movement for the body.  The muscles receive their ability to move the body through the nervous system.

There are 5 major properties to the muscular system:

• Excitable or Irritable:  Muscles are Excitable or Irritable. This means that they are capable of receiving stimulation and responding to stimulation from the nerves.
• Contractible:  They are contractible. After receiving stimulation, they are capable of contracting, or shortening.
• Extensible: Being extensible means a muscle can be stretched without damage by the application of force.
• Elasticity: With elasticity, a muscle is able to return to its original resting shape and length after being extended or contracted.
• Adaptability: The muscular system is adaptable in that it can be changed in response to how it is used. For example, a muscle will enlarge, or undergo hypertrophy with increased work; but on the other hand it can go in  atrophy, or waste away if deprived of work.

Types of Muscle Movements:

• Adduction...is the moving of a body part toward the mid-line of the body.
• Abduction…is moving a body part away from the body.
• Flexion…Flexion means bending a joint to decrease the angle between two bones or two body parts.
• Extension…extension is straightening and extending of the joint to increase the angle between two bones or body parts.
• Rotation… and last, rotation involves move a body part around an axis.

Supportive Structures:

Although muscles obviously make up muscle system, there are still some supportive structures we need to look at that are also a necessary part of the system. Tendons and fascia are important supportive structures for the Skeletal muscles.

Simply put,Tendons are what attach a muscle to a bone. Fasciae connect muscles to other muscles. Tendons and Fascia work together with the muscles, which creates the muscular system necessary for movement.

The Nervous System

While not technically part of the same system, the nervous system is intrinsically connected to the muscular system of the body. It is essential to the voluntary skeletal muscles.

If the communication from the nervous system is severed from the skeletal muscles, the skeletal muscles will not be able to produce movement for the body. The body is now in a state of paralysis.  This is known as  quadriplegia.  The only organ that is not directly dependent upon the nervous system is the Cardiac (heart) muscle.

Muscles of the Shoulder Complex:

Muscles from axial skeleton to scapula and clavicle:
• Serratus anterior
• Trapezius
• Rhomboideus major and minor
• Pectoralis minor
• Levator scapulae
• Supraspinatus
• Infraspinatus
• Teres minor
• Subscapularis
• Teres major
• Coracobrachialis
• Biceps brachii (long head)
• Triceps brachii (long head)

Muscles from scapula and clavicle to humerus:
• Deltoid
• Rotator cuff

Muscles from axial skeleton to humerus:
• Latissimus dorsi
• Pectoralis major

Hip and pelvic region:
Posterior muscles:

• Gluteus maximus
• Biceps femoris
• Semitendinosus
• Semimembranosus
• Gluteus medius
• Gluteus minimus
• Tensor fascia latae
• Piriformis

Anterior muscles:

• Rectus femoris
• Sartorius
• Tensor fascia latae
• Iliopsoas
• Pectineus
• Lateral muscles

Medial muscles:

• Adductor magnus
• Adductor longus
• Adductor gracilis
• Adductor brevis
• Pectineus

Knee Extensors:

• Rectus femoris
• Vastus lateralis
• Vastus medialis
• Vastus intermedius

Flexors:

• Biceps femoris
• Semitendinosus
• Semimembranosus
• Gastrocnemius
• Popliteus

Ankle and foot:

• Triceps surae- gastrocnemius- soleus
• Tibialis posterior
• Flexor digitorum longus
• Flexor hallucis longus
• Feroneus longus and brevis
• Tibialis anterior
• Extensor hallucis longus
• Extensor digitorum longus

Muscles of the Elbow and Radioulnar joints:
Elbow flexors:
• Biceps brachii
• Brachialis
• Brachioradialis
• Pronator teres

Elbow extensors:
• Triceps brachii
• Anconeus

Radioulnar supinators:
• Biceps brachii
• Supinator
• Abductor pollicis longus
• Extensor pollicis brevis
• Extensor indicis proprius

Radioulnar pronators:
• Pronator teres
• Pronator quadratus
• Flexor carpi radialis
• Extensor carpi radialis longus

Pectoralis Major:

Large and fan shaped, and is composed of a sternal head and a clavicular head:

Attachments: The distal attachment of both heads is into the intertubercular sulcus of the humerus.

• Clavicular head – originates from the anterior surface of the medial clavicle.
• Sternocostal head – originates from the anterior surface of the sternum, the superior six costal cartilages and the aponeurosis of the external oblique muscle.

Innervation: Lateral and medial pectoral nerves.

Function: Adducts and medially rotates the upper limb and draws the scapula anteroinferiorly. The clavicular head also acts individually to flex the upper limb.

Pectoralis Minor:

The pectoralis minor lies underneath its larger counterpart muscle, pectoralis
major. Both of these muscles form part of the anterior wall of the axilla region.

Attachments: Originates from the 3rd5th ribs and inserts into the coracoid process of the scapula.

Function: Stabilises the scapula by drawing it anteroinferiorly against the thoracic wall.

Innervation: Medial pectoral nerve.

The muscles of the shoulder are associated with movements of the upper limb. They produce the characteristic shape of the shoulder, and can be divided into two groups:

Extrinsic – originate from the torso, and attach to the bones of the shoulder 
(clavicle, scapula or humerus).

Intrinsic – originate from the scapula and/or clavicle, and attach to the humerus.
The extrinsic muscles of the shoulder originate from the trunk, and attach to the bones of the shoulder – the clavicle, scapula, or humerus. They are located in the back, and are also known as the superficial back muscles.

The muscles are organized into two layers – a superficial layer and a deep layer.

Section of Deltoid Point of Origin:

Anterior- The lateral (outside) portion of the clavicle, which is also known as the collarbone.

Medial- The acromion process and the spine of the scapula (shoulder blade). The acromion process is a bony prominence at the top of the shoulder blade, while the spine is a ridge or plate also at the top of the shoulder blade.

Posterior Spine of the Scapula

Sartorius Muscle: Longest Muscle of the body

Origin- Anterior superior iliac spine of the pelvic bone

Insertion- anteromedial surface of the proximal tibia in the pes anserinus

Function- Flexion, abduction, and lateral rotation of the hip, flexion of the knee