The Muscular System

Prepared by Mickelder Kercy, MD - Instructor

Functions of Muscles

O Movement

O Heat production

O Maintain body posture

O Holding bones together

O Breathing,

O Speaking, Eating

O Store and Expel Urine etc….

Types of Muscle Tissue

O Skeletal (Voluntary + Striated)

O Smooth (Involuntary + Non Striated)

O Cardiac (Involuntary + Striated)

Mechanism of muscle contraction

O Muscles break down carbohydrates, fats

and proteins with or without oxygen to

create energy called ATP

O Nerves attached to the muscle release

Ach causing the Sarcoplasmic reticulum

to release calcium in the muscle

O Calcium attaches to certain parts of the

muscle that will use ATP to make the

muscle contract

Structure of Skeletal Muscles

O Epimysium (Covers the muscle)

O Perimysium (Inside of the muscle

dividing it into sections)

O Endomysium (Inside of the muscle

surrounding each muscle cell)

O Tendons (Attach the muscle to the

bones)

Ways to identify Muscles

O Location (eg : Frontalis)

O Direction of fibers (eg : Orbicularis oculi)

O N° of attachments (eg : Sternocleidomastoid)

O Shape (eg : Trapezius)

O Action (eg : Extensor Digitorum)

O Size (eg : Gluteus Maximus, Gluteus Medius,

Gluteus Minimus)

How muscles work together

O Agonism/Prime Mover

O Antagonism

O Synergism

Major Skeletal Muscles

O Muscles that move the Head

*Sternocleidomastoid (Both flex the head

towards the chest, Individually flexes

the head laterally)

O Muscles of the Face

*Frontalis (Raises the eyebrows)

*Orbicularis oris (Closes the mouth,

Purses the lips, Kissing)

*Orbicularis oculi (Closes the eyes,

Wrinkles, Blinks)

O Muscles that move the arm and forearm

*Pectoralis major (Adducts the arm)

*Deltoid (Abducts the arm) ∆

*Biceps Brachii (Flexes the elbow and

moves the forearm)

*Brachialis (Flexes the elbow)

*Triceps Brachii (Extends the elbow)

etc…..

O Muscles that move the wrist, hand and

fingers (key word – carpi / palmaris /

digitorum)

*Flexor carpi radialis

*Flexor carpi ulnaris

*Palmaris longus

*Extensor digitorum etc…..

O Muscles of Respiration

*Diaphragm

*Internal Intercostals

*External Intercostals

O Muscles of the Abdominal Wall

(Key word – Abdominis)

*Transversus abdmoninis

*Rectus abdominis

*Internal and External Oblique

These muscles help in childbirth, urination,

forced expiration and defecation

O Muscle of the Pectoral Girdle/Shoulder

*Rotator cuff muscles

*Deltoid

*Pectoralis Major

*Pectoralis Minor

*Trapezius

*Latissimus Dorsi etc…..

They move the shoulder

O Muscles of the pectoral Girdle/Shoulder

*Extrinsic (Suspend scapula from the trunk. Stabilize

and/or actively moves scapula)

-Trapezius, Levator Scapulae, Rhomboid Major &

Minor, Serratus Anterior, Pectoralis minor

*Intrinsic (Attach scapula to humerus)

-Deltoid, Teres Major

*Rotator Cuff (active stabilization of shoulder joint)

-Supraspinatus, Infraspinatus, Teres Minor,

Subscapularis

*Attach trunk to humerus

-Latissimus dorsi , Pectoralis Major

O Muscles of the back

*Trapezius (adducts the arm)

*Latissimus Dorsi (adducts, extends &

medially rotates the humerus) etc…

O Muscles of the Buttock, Thigh, Leg, Ankle and Foot

*Gluteus maximus, medius and minimus

*Quadriceps Femoris (Rectus Femoris, Vastus

Lateralis, Vastus Medialis and Vastus

Intermedius)

*Gastrocnemius

*Hamstrings (Biceps Femoris, Semitendinosus

and Semimembranosus)

O Sitting and standing are actions performed numerous times

throughout the day by every person. Frail older adults sometimes

have difficulty performing such a fundamental task simply because

they lack the lower body strength. Both sitting down and standing

up require work from the muscles of the lower body as well as

stabilizing work from the upper body. It is important to work the

muscles needed to sit and stand to maintain muscular fitness.

O The quadriceps muscles are on the front of the thigh and are used in

both sitting and standing. They contract to resist gravity when you

lower yourself into a chair. The quadriceps are then contracted to

extend your leg, which allows you to stand

O The hamstring muscles are on the back of the thigh and act to

extend the thigh and flex the knee. The hamstrings are primarily

used to extend your hips when you stand.

O The gluteus muscles are comprised of the gluteus maximus, gluteus

medius and gluteus minimus. The gluteus maximus is the major

extensor of the thigh and is responsible for straightening your hips

as you stand. It also works to control downward movement of the

hips when you lower yourself to the chair. The medius and minimus

help to steady the pelvis when sitting or standing from a chair.

O Calves /The gastrocnemius and plantaris muscles of the calf help to

flex the knee when lowering into a sitting position. These muscles,

along with the soleus, act to stabilize the lower leg when rising to a

standing position.

O The tibialis anterior is located laterally to the shin bone. This

muscle works to prevent hyper-flexion of the ankle when you sit

down. It helps to stabilize the lower leg when standing

O The core consists of the muscles of the abdomen and lower back.

These muscles contract to keep your torso upright throughout the

movements. Failure to use these muscles would result in a hunched

posture and rounded back.

Common Disorders associated with the Muscular System

O Atrophy : Loss of muscle mass and strength

with the disuse of muscles

O Fibromalgia : Musculoskeletal pain and fatigue at

11 or more sites on the body

O Ganglion Cyst : Saclike swelling or cyst

O Lyme Disease : Caused by the bacteria

Borrelia Burgdorferi. Causes rash(erythema

migrans), bell’s palsy, muscle weakness, flu-

like sx etc..

O Muscular Dystrophy : Genetic diseases causing

progressive weakness and degeneration of the

skeletal or voluntary muscles

O Myasthenia Gravis : Chronic autoimmune

neuromuscular disease causing weakness

of the skeletal or voluntary muscles of the

body

O Rotator cuff Tears : Make it difficult for the patient to

reach above their heads and lift with the arms

O Shin Splints : Inflammation of the

periosteum of the extensor muscles of the

lower leg and surrounding tissues

O Sprains : Stretching or tearing of a ligament

O Strain : Stretching or tearing of a muscle or a

tendon

Rupture Achilles Tendon

O Tendonitis : Inflammation of a tendon due to

overuse

O Tetanus : Bacterial Infection causing painful

muscle spasms

The End