Study Notes on the Human Muscular System
Fundamentals of the Muscular System
Myology Definition:
The study of the structure, function, and diseases of the muscles.
Muscular System Definition:
The organ system encompassing all muscle tissue throughout the body, directly responsible for body movement.
Weight Contribution:
Muscle tissue comprises approximately to of total human body weight.
Physiological Response and Muscle Facts:
Smiling requires the coordinated effort of muscles.
Frowning engages muscles.
When exposed to cold, skeletal muscles contract involuntarily (shivering), initiating an exothermic reaction that produces energy and generates internal heat to warm the body.
Esthetics and Massage Relevance:
A comprehensive knowledge of muscle anatomy enables the design and execution of beneficial, safe facial and body massage techniques.
Proper technique induces client relaxation and improves personal well-being.
In professional massage therapy and esthetics, manipulation strokes are directed from the muscle's insertion attachment toward its origin attachment to work harmoniously with muscle anatomy and function.
Muscle Tissue Classifications and Structural Components
Structural Classifications of Muscle Tissue:
Cardiac Muscle:
Unique tissue structure found solely in the heart.
Operates entirely involuntarily, pumping blood automatically throughout the circulatory system without conscious, intentional desire.
Voluntary or Striated Muscle:
Characterized by striped (striated) appearance under microscopic examination.
Produces movements based entirely on conscious, intentional desire (e.g., actively raising an arm to catch a ball).
Responsible for voluntary movements across the body.
Estheticians are primarily concerned with voluntary muscles located in the head, face, neck, arms, hands, legs, and feet.
Involuntary or Non-Striated Muscle:
Smooth muscle tissue responding automatically to regulate vital bodily processes without conscious thought.
Operates internal organs including the stomach, intestines, and urinary bladder.
Controls autonomic physiological responses, such as increasing respiratory and breathing effort during stress to augment oxygen availability throughout the body.
Three Primary Parts of a Muscle:
1. Origin:
The non-moving, fixed portion of the muscle attached to bone or another non-moving muscle.
2. Belly:
The thick, midsection portion of the muscle located between the origin and insertion.
3. Insertion:
The movable portion of the muscle joined to movable structures such as bones, mobile muscles, or skin.
Connective Tissues:
Tendons:
Tough bands of fibrous tissue that anchor muscle to bone.
Ligaments:
Dense, strong bands of fibrous tissue that bind bones directly to other bones across joints.
Functions of the Muscular System
Body Movement:
Mediated by the voluntary contraction of skeletal muscle tissue upon receiving electrical signals from the nervous system, producing functional motion of the trunk, limbs, and extremities.
Involvement in Other Body Systems:
Essential for maintaining primary physiological functions, including respiration, blood circulation, digestion, and reproduction.
Support of the Skeletal Framework:
Maintains posture and stabilizes skeletal joints through the structural interplay of ligaments, muscles, and associated connective tissues.
Contouring and Body Shape:
The structural arrangement of skeletal attachments paired with the development and tone of muscle bellies defines the external contours and shape of the human body.
Thermoregulation (Heat Production):
Maintains systemic homeostasis during cold exposure; involuntary muscular contractions trigger internal exothermic metabolic reactions, releasing thermal energy to stabilize core temperature.
Directional and Functional Anatomical Terminology
Positional and Spatial Terms:
Anterior: Located in front of or toward the front.
Posterior: Located behind or in back of.
Superior: Located above, higher than, or of larger size relative to an adjacent structure.
Inferior: Located below, lower than, or of smaller size relative to an adjacent structure.
Ventral: Pertaining to the front surface of the body.
Dorsal: Pertaining to the back surface of the body.
Medial: Positioned toward the central midline of the body.
Lateral: Positioned toward the outer side or away from the midline.
Proximal: Located nearest to the point of attachment or trunk.
Distal: Located farthest away from the point of attachment or trunk.
Functional Action Terms:
Levator: A muscle that lifts or elevates a body part upward.
Depressor: A muscle that draws down or depresses a body part.
Dilator: A muscle that opens, enlarges, or expands an orifice or tract.
Flexion: The movement of bending forward that decreases the angle between jointed bones.
Extension: The movement of straightening or bending backward that increases the angle between jointed bones.
Inversion: Turning or bringing inward.
Eversion: Turning or bringing outward.
Pronation:
Hand: Turning the forearm and hand from a palm-up position (palm facing forward) to a palm-down position (palm facing backward).
Foot: Natural gait dynamic during walking and running where weight shifts onto the outside edge of the foot before rolling back inward toward the big toe.
Supination:
Hand: Turning the forearm and hand from a palm-down position (palm facing backward) to a palm-up position (palm facing forward).
Foot: Rolling motion to the outer edge of the foot during a step cycle, providing structural leverage to assist toe-off.
Abduction: Movement directing limbs away from the midline of the body, or spreading fingers and toes apart.
Adduction: Movement drawing limbs toward or across the midline of the body, or bringing fingers and toes together.
Muscles of the Scalp, Ear, and Face
Muscles of the Scalp (Epicranium):
Epicranium: Encompasses all structures overlying the cranium, including cutaneous tissues, muscles, and connective aponeuroses.
Occipitofrontalis (Epicranius): A broad cranial muscle composed of two distinct muscular bellies interconnected by the epicranial aponeurosis tendon:
1. Frontalis: Extends over the forehead upward to the top of the skull; raises the eyebrows and pulls the scalp forward.
2. Occipitalis: Positioned at the posterior base of the skull at the nape of the neck; draws the scalp backward.
Muscles of the Ear (Auricular Muscles):
Control subtle movements of the auricula (the visible external portion of the ear):
1. Auricularis Anterior: Situated directly in front of the ear.
2. Auricularis Superior: Located directly above the ear.
3. Auricularis Posterior (Auricular Posterior): Positioned directly behind the ear.
Muscles of the Eyes and Nose:
Control precise mechanical movements of the eyelids, eyebrows, and the cutaneous surface over the nasal bridge.
1. Corrugator: Situated between the eyebrows; draws the eyebrows inward and downward, producing vertical forehead furrows.
2. Levator Palpebrae Superioris: Positioned above the upper eyelid; functions to lift and open the eyelid.
3. Orbicularis Oculi: Circular muscle encircling the orbital socket; closes the eye completely.
4. Procerus: Situated between the eyebrows across the upper nasal bone; depresses the brows and produces transverse horizontal wrinkles across the nasal bridge.
5. Nasalis: Extends transversely across the bridge of the nose; flares the nostrils and wrinkles the nasal dorsum.
Internal Nasal Musculature: Four deep muscles regulate nostril dilation and constriction:
Nasalis
Dilator naris posterior
Dilator naris anterior
Depressor septi
Muscles of the Mouth (Oral Region):
Coordinate the complex movements of the lips, cheeks, mouth angle, chin, and nostril borders:
1. Orbicularis Oris (Obicularis Oris): Circular sphincter muscle encompassing the oral aperture; contracts, puckers, and wrinkles the lips (as during kissing or whistling).
2. Quadratus Labii Superioris (Levator Labii Superioris): Composed of three distinct heads positioned above the upper lip; raises the upper lip and dilates the nostrils (conveying distaste).
3. Quadratus Labii Inferioris (Depressor Labii Inferioris): Situated beneath the lower lip; depresses the lower lip downward and outward to the side (expressing sarcasm).
4. Mentalis: Located at the central prominence of the chin; elevates and pushes the lower lip upward while wrinkling the chin skin (signaling doubt).
5. Risorius: Positioned at the oral angles; pulls the corners of the mouth outward and laterally (forming a grin).
6. Caninus (Levator Anguli Oris): Positioned above the corners of the mouth; elevates the oral angle (as seen in snarling).
7. Triangularis (Depressor Anguli Oris): Located below the corners of the mouth; pulls the labial commissures downward (expressing sadness).
8. Zygomaticus (Major and Minor): Extends obliquely from the zygomatic arch toward the corners of the mouth; pulls the mouth corners upward and backward (facilitating laughing).
9. Buccinator: Broad muscle positioned between the jaws and cheek wall; compresses the cheek inward to forcibly expel air (as during blowing).
Muscles of Mastication (Chewing):
Function to elevate, depress, and manipulate the mandible during mastication and speech; intimately tied to cervical and upper dorsal muscle chains.
1. Temporalis: Positioned superiorly and anteriorly to the ear in the temporal fossa; controls elevation and retraction of the jaw.
2. Masseter: Covers the lateral hinge angle of the mandible; primary muscle providing forceful jaw closure for chewing.
Pterygoid Muscles: Located in the upper cheek and deep temporal regions; coordinate mouth opening, closing, and anterior/posterior jaw excursion (protrusion and retrusion).
Muscles of the Neck and Back
Functional Role of the Cervical and Dorsal Musculature:
Stabilizes and maintains structural equilibrium through the core (the trunk of the body).
Major Cervical and Dorsal Muscles:
Platysma: Expansive, superficial sheet extending from the inferior mandibular margin down across the clavicle to the upper chest; depresses the lower lip and mouth angle downward and laterally, opening the mouth partially (expressing shock or surprise).
Sternocleidomastoid: Prominent diagonal strap extending along the lateral column of the neck from the mastoid process down to the sternum and clavicle; flexes the head forward and rotates the skull from side to side (as when nodding yes or turning no).
Trapezius: Broad, flat triangular muscle covering the upper cervical spine, posterior neck, and posterior shoulder girdles; elevates, retracts, and stabilizes the scapulae, and aids in extending the head backward.
Latissimus Dorsi: Broad, flat triangular muscle covering the lumbar region and lower half of the thoracic spine; attaches to the humerus to power arm extension and adduction (enabling arm swinging).
Muscles of the Shoulder, Chest, Arm, and Hand
Shoulder, Chest, and Upper Arm Muscles:
Group of large skeletal muscles coordinating voluntary gross motor movements of the upper extremity:
1a. Pectoralis Major: Broad fan-shaped muscle covering the superior anterior chest; adducts, flexes, and medially rotates the humerus, assisting in arm swing.
1b. Pectoralis Minor: Deep anterior chest muscle situated beneath pectoralis major; depresses and stabilizes the scapula.
2. Serratus Anterior: Muscle group situated under the axilla along the lateral thoracic wall; anchors the scapula, assists in raising the arm, and aids in forced respiration.
3. Deltoid: Thick, triangular muscle capping the shoulder joint; abducts, elevates, and rotates the arm.
4. Biceps (Biceps Brachii): Prominent anterior muscle of the upper arm; flexes the forearm at the elbow joint and supinates/rotates the palm.
5. Triceps (Triceps Brachii): Large muscle running the entire posterior length of the upper arm to the olecranon of the ulna; extends the elbow and controls forward reaching motions of the forearm.
Hand and Forearm Muscles (Gross and Fine Motor Controls):
High concentrations of specialized intrinsic hand muscles cross the digits and joints to facilitate fine motor dexterity, grip strength, and delicate mechanical manipulation.
1. Thenar Eminence: Group of three distinct muscles situated at the radial base of the palm beneath the thumb; governs thumb opposition and movement.
2. Hypothenar Eminence: Group of three distinct intrinsic muscles along the ulnar margin of the palm at the base of the little finger; controls fifth-digit motion.
3. Brachialis: Upper arm muscle lying deep to the biceps brachii; provides powerful elbow flexion.
4. Brachioradialis: Muscle spanning from the distal lateral humerus across the elbow to the radial forearm; flexes the forearm.
5. Pronator Teres: Situated obliquely on the anterior palmar side of the proximal forearm beneath the elbow; rotates the radius inward to turn the hand palm-down (pronation).
6. Palmaris Longus: Slender central anterior forearm muscle situated between the flexor carpi ulnaris and flexor carpi radialis; flexes the wrist.
7. Flexor Digitorum Profundus: Deep lateral/volar compartment forearm muscle; flexes the phalanges of the fingers.
8. Extensor Digitorum: Posterior forearm muscle extending from the lateral epicondyle down toward the dorsal carpal ligaments; extends the fingers.
9. Flexor Carpi Ulnaris: Medial anterior forearm muscle running along the ulna; flexes and adducts (deviates inward) the wrist.
10. Flexor Carpi Radialis: Lateral anterior forearm muscle running along the radius; flexes and abducts (deviates outward) the wrist.
11. Extensor Carpi Radialis Longus: Intermediate lateral posterior forearm muscle; extends and abducts the wrist joint.
Muscles of the Leg and Foot
Functional Classifications of Lower Limb Musculature:
Provide structural balance, posture support, shock absorption, and propulsion.
Intrinsic Foot Muscles: Originate and insert entirely within the boundaries of the foot; control fine motor articulation of the digits.
Extrinsic Foot Muscles: Originate on the lower leg and insert into foot bones via long tendons; control gross movements such as plantar flexion, dorsiflexion, inversion, and eversion.
Muscles of the Lower Leg:
1. Tibialis Anterior: Covers the anterior surface of the shin; dorsiflexes the foot upward and inverts it inward.
2. Gastrocnemius (Calf Muscle):
Prominent superficial posterior calf muscle attaching via the calcaneal tendon to the rear of the heel; exerts powerful downward plantar flexion.
3. Soleus: Deep posterior muscle originating from the superior fibular shaft below the knee, merging into the heel; assists in plantar flexion of the foot.
4. Peroneus Longus: Originates from the upper two-thirds of the lateral fibula; exerts downward plantar flexion while everting the foot and ankle outward.
5. Peroneus Brevis: Originates on the lower third of the lateral fibular shaft; coordinates downward bending and outward eversion of the foot.
6. Flexor Digitorum Longus: Positioned on the medial posterior compartment of the lower leg; curls digits two through five downward.
7. Extensor Digitorum Longus: Positioned along the lateral anterior lower leg; dorsiflexes the foot upward while extending the toes.
8. Achilles Tendon (Calcaneal Tendon): The thickest and strongest tendon in the human body; anchors the posterior calf muscles (gastrocnemius and soleus) directly to the calcaneus (heel bone).
Intrinsic Muscles of the Plantar Surface (Underside of the Foot):
1. Flexor Digiti Minimi Brevis: Positioned along the plantar base of the small fifth toe; flexes the proximal fifth digit.
2. Flexor Digitorum Brevis: Situated centrally beneath the plantar fascia spanning across the ball of the foot; flexes the lateral four toes.
3. Abductor Hallucis: Runs along the medial border of the plantar surface; abducts the big toe (hallux) away from the second toe.
4. Abductor Digiti Minimi: Extends along the lateral border of the foot from the calcaneus to the fifth phalanx; abducts the smallest toe outward.
Knowledge Assessment and Review
Question 1: Anterior Definition
Prompt: TRUE/FALSE: Anterior is a term that means "behind or in back of."
Answer: FALSE.
Explanation: Anterior denotes a position located in front of a structure; posterior is the anatomical term for "behind or in back of."
Question 2: Thenar Eminence Anatomy
Prompt: TRUE/FALSE: The group of muscles that control the movement of the thumb is called the thenar eminence.
Answer: TRUE.
Explanation: The thenar eminence comprises three intrinsic muscular structures localized at the base of the thumb in the radial palm.
Question 3: Definition of Myology
Prompt: Myology is the study of the structure, function, and diseases of the ________.
Answer: Muscles.
Explanation: Derived from anatomical roots, myology specifically investigates muscular biology and pathology.
Question 4: Muscle Origin
Prompt: The non-moving portion of the muscle attached to bone or another fixed muscle is the ________.
Answer: Origin.
Explanation: The origin acts as an anchor, remaining stable while the belly contracts and pulls the insertion.
Question 5: Ligament Identification
Prompt: The dense, strong bands of fibrous tissue that connect bones to other bones are ________.
Answer: Ligaments.
Explanation: Ligaments bridge articular joint spaces to bind skeletal bones together, distinct from tendons which connect muscle to bone.
Question 6: Joint Angle Reduction
Prompt: To bend forward and make the angle smaller is called ________.
Answer: Flexion.
Explanation: Flexion reduces the spatial angle between adjacent articulating segments.
Question 7: Digit Adduction
Prompt: To bring the fingers or toes together is called ________.
Answer: Adduction.
Explanation: Adduction pulls digits toward each other or draws limbs toward the central midline.
Question 8: Brow and Nasal Bridge Manipulation
Prompt: The muscle that is responsible for drawing down the brow and wrinkling the area across the bridge of the nose is the ________.
Answer: Procerus.
Explanation: The procerus pulls the medial brow downwards and creates transverse furrows across the nasal bridge.
Question 9: Smile and Laugh Muscle
Prompt: The muscle that is located outside the corners of the mouth and draws the mouth up and back, as in laughing, is the ________.
Answer: Zygomaticus.
Explanation: Composed of zygomaticus major and minor, these muscles pull the oral angles upward and backward into a smile or laugh.
Question 10: Peroneus Longus Action
Prompt: The muscle that bends the foot and ankle down and out is the ________.
Answer: Peroneus Longus.
Explanation: Originating along the outer fibula, the peroneus longus executes plantar flexion and eversion of the foot.