Muscles of the Body Flashcards
Muscle Tissue Types
Skeletal Muscle:
Features: Multinucleated, striations (due to the arrangement of actin and myosin filaments), muscle fiber tissue. Voluntary control, attached to bones via tendons, responsible for movement and posture. Contains myofibrils, which are composed of sarcomeres.
Detailed Components: Sarcomeres (basic contractile units), actin (thin filaments), myosin (thick filaments), Z-lines (boundaries of sarcomeres), and the sarcoplasmic reticulum (stores and releases calcium ions).
Function: Enables voluntary movements, maintains posture, and stabilizes joints.
Cardiac Muscle:
Features: Intercalated discs (gap junctions for rapid communication between cells), branching, striations. Involuntary control, found in the heart, responsible for pumping blood.
Detailed Components: Cardiomyocytes connected by intercalated discs, which contain desmosomes (structural support) and gap junctions (electrical coupling). Abundant mitochondria for continuous energy production.
Function: Pumps blood throughout the body with rhythmic contractions.
Smooth Muscle:
Features: Glycogen (energy storage), single nucleus in each muscle cell. Involuntary control, found in the walls of internal organs (e.g., digestive tract, blood vessels), responsible for various functions such as peristalsis and vasoconstriction.
Detailed Components: Lack striations, contain actin and myosin filaments, but not arranged in sarcomeres. Dense bodies anchor actin filaments, allowing contraction. Controlled by the autonomic nervous system, hormones, and local factors.
Function: Controls involuntary movements such as digestion, blood pressure regulation, and pupil dilation.
Motion Terms
Dorsiflexion: Lifting toes up (decreasing the angle between the foot and the shin).
Plantarflexion: Moving toes down (increasing the angle between the foot and the shin).
Inversion: Sole of foot points inward (medially).
Eversion: Sole of foot points outward (laterally).
Protraction: Moving anteriorly (e.g., shoulders, mandible).
Retraction: Moving part posteriorly (e.g., shoulders, mandible).
Elevation: Raising part superiorly (e.g., shoulders).
Depression: Lowering part (e.g., opening mouth).
Rotation: Pivoting on an axis; shaking head “no”; rotating head and shoulder. Can be medial (internal) or lateral (external).
Circumduction: Drawing a circle with body part; shoulder, head. A combination of flexion, extension, abduction, and adduction.
Pronation: Turning hands downward (lying prone is on stomach). Radius rotates over ulna.
Supination: Refers to arms; wanting a bowl of soup. Radius and ulna are parallel.
Flexion: Decreasing the angle between body parts. Bending at a joint.
Extension: Increasing the angle between body parts. Straightening at a joint.
Abduction: Moving away from the midline. Raising arm to the side.
Adduction: Moving toward the midline. Lowering arm to the side.
Specific Movements
Eversion: Sole of foot moves laterally.
Inversion: Sole of foot moves medially.
Supination: Radius and ulna are parallel. Palm faces anteriorly.
Pronation: Radius rotates over ulna. Palm faces posteriorly.
Lateral Rotation: Rotation away from the midline. Also known as external rotation.
Medial Rotation: Rotation toward the midline. Also known as internal rotation.
Mandible Motions
Protraction: Moving mandible forward (anteriorly).
Retraction: Moving mandible backward (posteriorly).
Elevation: Raising the mandible (closing the mouth).
Depression: Lowering the mandible (opening the mouth).
Muscles of Facial Expression
Frontal belly (of occipitofrontalis): Raises eyebrows, wrinkles forehead.
Depressor anguli oris: Pulls the corner of the mouth down (frowning).
Zygomaticus (major & minor):
Major: Elevates and abducts the corner of the mouth (smiling).
Minor: Elevates the upper lip.
Levator labii superioris: Elevates the upper lip (sneering).
Orbicularis oculi: Closes the eyelids, wrinkles around the eyes.
Temporalis: Elevates and retracts the mandible (chewing).
Orbicularis oris: Closes and protrudes lips (kissing, whistling).
Depressor labii inferioris: Pulls the lower lip down (pouting).
Mentalis: Elevates and protrudes the lower lip, wrinkles the chin.
Epicranial aponeurosis: Connective tissue sheet between the frontal and occipital bellies of the occipitofrontalis muscle.
Occipital belly (of occipitofrontalis): Retracts the scalp.
Splenius: Extends and laterally flexes the neck.
Trapezius: Elevates, depresses, retracts, and rotates the scapula; extends the head.
Masseter: Elevates the mandible (chewing).
Risorius: Draws the corner of the mouth laterally (grinning).
Sternocleidomastoid: Flexes and rotates the neck.
Muscles of the Neck
Mylohyoid: Elevates hyoid bone and floor of mouth.
Stylohyoid: Elevates and retracts hyoid bone.
Hyoid bone: A U-shaped bone in the neck that anchors the tongue.
Omohyoid (superior belly): Depresses and retracts hyoid bone.
Sternohyoid: Depresses hyoid bone.
Sternocleidomastoid: Flexes and rotates the neck.
Omohyoid (inferior belly): Depresses and retracts hyoid bone.
Anterior belly (Digastric): Elevates hyoid bone and depresses mandible.
Posterior belly (Digastric): Elevates hyoid bone and depresses mandible.
Stylohyoid (cut): Elevates and retracts hyoid bone (cut for demonstration).
Thyrohyoid: Depresses hyoid bone and elevates larynx.
Thyroid cartilage of the larynx: Part of the voice box structure.
Thyroid gland: Endocrine gland that produces thyroid hormones.
Sternothyroid: Depresses thyroid cartilage.
Muscles of the Thorax
Pectoralis major: Adducts, flexes, and medially rotates the arm.
Internal intercostals: Depress the ribs (exhalation).
Pectoralis minor: Depresses and protracts the scapula, elevates ribs.
Serratus anterior: Protracts and rotates the scapula upward (boxing muscle).
External intercostals: Elevate the ribs (inhalation).
Muscles of the Back
Rhomboideus (major & minor): Retract and rotate the scapula.
Trapezius: Elevates, depresses, retracts, and rotates the scapula; extends the head.
Muscles of the Abdomen
External oblique: Compresses abdomen, flexes and rotates trunk.
Rectus abdominus: Flexes vertebral column, compresses abdomen.
Internal oblique: Compresses abdomen, flexes and rotates trunk.
Serratus anterior: Protracts and rotates the scapula upward (boxing muscle).
Muscles of the Shoulder
Supraspinatus: Abducts the arm.
Infraspinatus: Laterally rotates the arm.
Teres minor: Laterally rotates and adducts the arm.
Teres major: Extends, adducts, and medially rotates the arm.
Subscapularis: Medially rotates the arm.
Deltoid: Abducts, flexes, and extends the arm.
Muscles of the Upper Arm
Coracobrachialis: Flexes and adducts the arm.
Triceps brachii: Extends the forearm.
Biceps brachii: Flexes and supinates the forearm.
Brachialis (deep to biceps brachii): Flexes the forearm.
Muscles of the Forearm
Pronator teres: Pronates the forearm.
Brachioradialis: Flexes the forearm.
Flexor carpi radialis: Flexes and abducts the wrist.
Palmaris longus: Flexes the wrist.
Flexor carpi ulnaris: Flexes and adducts the wrist.
Extensor digitorum: Extends the fingers.
Extensor carpi radialis brevis: Extends and abducts the wrist.
Extensor carpi ulnaris: Extends and adducts the wrist.
Extensor carpi radialis longus: Extends and abducts the wrist.
Abductor pollicis longus: Abducts the thumb.
Extensor pollicis brevis: Extends the thumb.
Muscles of the Hip and Thigh
Gluteus medius: Abducts and medially rotates the thigh.
Gluteus maximus: Extends and laterally rotates the thigh.
Adductor magnus: Adducts and extends the thigh.
Gracilis: Adducts, flexes, and medially rotates the thigh.
Iliotibial tract: Stabilizes the hip and knee.
Tensor fascia latae: Flexes, abducts, and medially rotates the thigh.
Pectineus: Adducts and flexes the thigh.
Sartorius: Flexes, abducts, and laterally rotates the thigh.
Quadriceps femoris:
Rectus femoris: Flexes the thigh and extends the leg.
Vastis lateralis: Extends the leg.
Vastus medialis: Extends the leg.
Vastus intermedius: Extends the leg.
Adductor longus: Adducts, flexes, and laterally rotates the thigh.
Hamstrings:
Biceps femoris: Flexes the leg and extends the thigh; laterally rotates the leg when flexed.
Semitendinosus: Flexes and medially rotates the leg and extends the thigh.
Semimembranosus: Flexes and medially rotates the leg and extends the thigh.
Muscles of the Lower Leg
Gastrocnemius: Plantarflexes the foot and flexes the leg.
Soleus (deep to Gastrocnemius): Plantarflexes the foot.
Tibialis anterior: Dorsiflexes and inverts the foot.
Extensor digitorum longus: Extends the toes and dorsiflexes the foot.
Fibularis longus: Everts and plantarflexes the foot.
Fibularis