THE MUSCULAR SYSTEM Dr Idara

Muscular System Muscles are responsible for all types of body movement 3 basic muscle types are found in the body. They are: Skeletal muscle Cardiac muscle Smooth muscle

Characteristics of Muscles Muscle cells are elongated (muscle cell = muscle fiber) Contraction of muscles is due to the movement of microfilaments All muscles share some terminology Prefix myo refers to muscle Prefix mys refers to muscle Prefix sarco refers to flesh

Muscle histology (cont.) Scaterred throughout the sarcoplasm is the sarcoplasmic reticulum It stores Calcium ions The sarcoplasm contains myoglobin Red pigmented protein related to Hemoglobin that carries oxygen Along entire length are myofibrils Myofibrils made of protein filaments Come in thick and thin filaments

Comparison of Types of Muscle

Types of Muscle, cont

Skeletal Muscle Characteristics Most attach to bones by tendon Cells are multinucleate Striated—have visible binding Voluntary Cells surrounded & bundled by connective tissue

Smooth Muscle Characteristics Picture sub A Has no striations Spindle-shaped cells Single Nucleus Involuntary—no conscious control Found mainly in the walls of hollow organs

Characteristics of Cardiac Muscle Picture sub B Has striations Usually has a single nucleus Joined to another cardiac muscle cell Involuntary Found only in the heart

Functions of Skeletal Muscle Produce Movement Maintain posture Stabilize joints Generate Heat Sites of Muscle Attachment Bones Cartilage Connective tissue coverings Muscle Fibers blend into a connective tissue attachment Tendon—cordlike structure Aponeurosis—sheet-like structure Properties of Muscle Irritability – ability to receive and respond to a stimulus Contractibility – ability to shorten when an adequate stimulus is received Extensibility – ability to lengthen when an adequate stimulus is received Elasticity – ability to return to normal shape

To Note: A muscle cell is also called a muscle Fiber A discrete bundle of muscle cells is called a Fascicle The thin connective tissue that surrounds each muscle cell is called Endomysium The connective tissue that surrounds each Fascicle is called Perimysium The connective tissue surrounding the entire muscle is called Epimysium

Anatomy of a Muscle Cell

Naming Skeletal Muscles

Direction of Muscle Fibers

Location Structure near which muscle is found FRONTALIS = near FRONTAL bone OCCIPITALIS = near OCCIPITAL bone

Size Relative Size of Muscle and location MAXIMUS = largest Gluteus Maximus MEDIUS = middle Gluteus Medius MINIMUS = smallest Gluteus Minimus LONGUS = longest Fibularis Longus BREVIS = short Fibularis Brevis TERTIUS = shortest Fibularis Tertius

Number of Origins Number of tendons of origin BICEPS = Two Biceps Brachii Biceps Femoris TRICEPS = Three Triceps Brachii QUADRICEPS = Four Quadriceps Femoris

Shape Relative Shape of the Muscle DELTOID = triangular shape Δ TRAPEZIUS = trapezoid shape  SERRATUS = saw-toothed ♒ RHOMBOIDEUS = rhomboid shape  TERES = round ○

Origin & Insertion Origin – attachment to an immoveable bone Insertion – attachment to a movable bone ILIO COSTALIS= attaches to the ilium & ribs (costal = ribs)

Types of Muscle--Actions Prime mover (Agonist) – muscle with the major responsibility for a certain movement Antagonist – muscle that opposes or reverses a prime mover Synergist – muscle that aids a prime mover in a movement and helps prevent rotation Fixator – stabilizes the origin of a prime mover

Head & Neck Muscles

Key Muscles of Facial Expression Smiling Muscles Orbicularis Oculi Nasalis Levator Labii Superioris Levator Anguli Superioris Zygomaticus Risorius Frowning Muscles Frontalis Orbicularis Oris Depressor Anguli Oris Depressor Labii Inferioris Mentalis Platysma

Frontalis - Used in frowning Orbicularis Oculi – Surrounds the eye, eyelid and orbit. Used to close the eyes Zygomaticus - Used in smiling Buccinator- A flat muscle of the cheek, draws in the cheek and puffs up the cheeks. Called the Trumpeter’s Muscle. Orbicularis Oris- surrounds the mouth, closes the lips when contracted and used for whistling and kissing. Masseter- Is the Prime mover for jaw closure. Also used for chewing. Temporalis - is the synergist for jaw closure and assists with chewing.

Muscles of the Axial Skeleton

Muscles of the Axial Skeleton Intrinsic Muscles Erector Spinae: maintain posture of back/extension Spinalis Longissimus Iliocostalis Oblique Muscles: rotation of the vertebrae Semispinalis Multifidus Rotatores Muscles of Quiet Respiration Diaphragm External Intercostals Internal Intercostals—deep breaths Abdominal Muscles External Obliques Internal Obliques Transverse Abdominus Rectus Abdominus Quadratus Lumborum – Fixes the lower rib during respiration and cause lateral flexion of the vertebral column.

Diseases and Disorders of the Muscular System Cerebral Palsy: This disorder is characterized by paralysis and or weakened muscles due to loss of muscle tone. It can be caused due to lack of oxygen to the region of the motor region of the cerebrum of the brain which controls conscious control of muscles. This is often attributed to complication during birth.

Others Myalgia: Muscle pain due to strain, tearing of muscle fibers. It also is a symptom of an immune response along with a fever. Myositis: Inflammation of muscle tissue due to injury or disease. Charley Horse (fibromyositis): Inflamation of muscle tissue and the tendons associated with that muscle due to injury (tear or severe bruising- contusion). Cramps: Painful, involuntary muscle contraction, typically caused by fatigue or strain.

Muscular Dystrophy A Series of genetic disorders characterized by the atrophy or wasting away of skeletal muscle. Duchenne Muscular Dystrophy is the most common and affects primarily males. X- linked recessive mutation i.e. mother’s transmit disease to their sons. Onset before 5 years of age. Deletion of the dystrophin gene

Becker’s Muscular Dystrophy Onset in adolesence or early adulthood. Mutated dystrophin gene