Anatomy: Skeletal Muscles (Locations & Functions) Flashcards
Sarcolemma
Function: Encloses the muscle fiber and conducts action potentials.
Origin: Derived from the plasma membrane of muscle cells.
Location: Surrounds each muscle fiber (cell).
Sarcoplasm
Function: Site of metabolic processes and contains organelles and myofibrils.
Origin: The cytoplasm of muscle cells.
Location: Inside the muscle fiber.
Mitochondrion
Function: Produces ATP through aerobic respiration.
Origin: Organelle found in eukaryotic cells.
Location: Scattered throughout the sarcoplasm of muscle fibers.
Sarcoplasmic Reticulum
Function: Stores and releases calcium ions (Ca²⁺) during muscle contraction.
Origin: Specialized form of endoplasmic reticulum in muscle cells.
Location: Surrounds myofibrils within the muscle fiber.
Myofibril
Function: Contains the contractile elements (sarcomeres) responsible for muscle contraction.
Origin: Composed of myofilaments (actin and myosin).
Location: Runs parallel within the muscle fiber.
Nucleus
Function: Contains genetic material and regulates cellular activities, including protein synthesis.
Origin: Found in all eukaryotic cells.
Location: Typically located at the periphery of the muscle fiber.
Striation
Function: Indicates the organized arrangement of muscle fibers and contractile proteins.
Origin: Result of alternating thick (myosin) and thin (actin) filaments.
Location: Visible across myofibrils and muscle fibers under a microscope.
Triad
Function: Facilitates rapid transmission of action potentials and calcium release.
Origin: Formed by two terminal cisternae and one transverse tubule.
Location: At the junction of the A and I bands in the myofibrils.
Terminal Cisternae
Function: Stores calcium ions and releases them during muscle contraction.
Origin: Extensions of the sarcoplasmic reticulum.
Location: Flank the T-tubules in the triad structure.
Transverse Tubule (T-tubule)
Function: Transmits action potentials deep into the muscle fiber.
Origin: Extensions of the sarcolemma.
Location: Penetrates into the muscle fiber at the junction of the A and I bands.
Endomysium
Function: Surrounds and supports individual muscle fibers.
Origin: Layer of connective tissue.
Location: Within a muscle, surrounding each muscle fiber.
Perimysium
Function: Surrounds and organizes bundles of muscle fibers (fascicles).
Origin: Connective tissue layer.
Location: Between individual fascicles within a muscle.
Epimysium
Function: Surrounds the entire muscle, providing support and protection.
Origin: Outer layer of connective tissue.
Location: Envelops the entire muscle.
Fascicle
Function: A bundle of muscle fibers that allows for organized structure and efficient force generation.
Origin: Group of muscle fibers surrounded by perimysium.
Location: Found within a muscle, grouped together to form the muscle.
Synergist
Function/Action: Assists the prime mover (agonist) by providing additional force or by reducing undesirable movements.
Definition: A muscle that works together with another muscle to enhance its effect.
Example: The brachialis acts as a synergist to the biceps brachii during elbow flexion.
Fixator
Function/Action: Stabilizes the origin of the agonist so that it can act more efficiently.
Definition: A muscle that prevents unwanted movement at a joint.
Example: The rotator cuff muscles stabilize the shoulder during arm movements.
Antagonist
Function/Action: Opposes or reverses a particular movement of the agonist.
Definition: A muscle that acts in opposition to the agonist.
Example: The triceps brachii is an antagonist to the biceps brachii during elbow flexion
Agonist (Prime Mover)
Function/Action: The main muscle responsible for a specific movement.
Definition: A muscle that is primarily responsible for movement.
Example: The biceps brachii is the agonist during elbow flexion.
Epicranius (Occipitofrontalis)
Function/Action: Raises eyebrows and wrinkles the forehead.
Temporalis
Function/Action: Elevates and retracts the mandible (closes the jaw).
Origin: Temporal fossa.
Insertion: Coronoid process of the mandible.
Masseter
Function/Action: Elevates the mandible (primary muscle for jaw closure).
Origin: Zygomatic arch and maxilla.
Insertion: Angle and ramus of the mandible.
Frontalis (Frontal Belly of the epicranius)
Action: Elevates eyebrows, pullls scalp forward
Origin: Top of the forehead or forehead area. (cranial aponeurosis).
Insertion: Skin of eyebrows and root of the nose.
Orbicularis Oculi
Function/Action: Closes eyelids; enables blinking and squinting.
Origin: Frontal and maxillary bones.
Insertion: Skin of the eyelid.
Occipitalis (Occipital Belly)
Function: Pulls scalp backwards (raises eyebrows)
Origin: Occipital bone
Insertion: epicranial neurosis
Orbicularis Oris
Function/Action: Closes and protrudes lips (kissing muscle).
Origin: Indirectly from maxilla and mandible.
Insertion: Encircles mouth; inserts into the muscle and skin at the angles of the mouth.
Zygomaticus
Function/Action: Raises lateral corners of the mouth (smiling).
Origin: Zygomatic bone.
Insertion: Skin and muscle at the corner of the mouth.
Levator Anguli Oris
Function/Action: Elevates the angle of the mouth (smiling).
Origin: Maxilla.
Insertion: Lips
Buccinator
Function/Action: Compresses the cheek (as in whistling or sucking).
Origin: Molar region of maxilla and mandible.
Insertion: Cheeks
Risorius
Function/Action: Draws the corner of the lip laterally.
Origin: Fascia of masseter muscle.
Insertion: Skin at the corner of the mouth.
Depressor Labii Inferioris
Function/Action: Lowers the lower lip.
Origin: Mandible.
Insertion: Skin of lower lip.
Depressor Anguli Oris
Function/Action: Draws the corners of the mouth downward (frowning).
Origin: Mandible.
Insertion: Skin and muscle at the angle of the mouth.
Mentalis
Function/Action: Protrudes the lower lip and wrinkles the chin.
Origin: Mandible.
Insertion: Skin of the chin.
Thyrohyoid
Function/Action: Swallowing
Origin: Thyroid cartilage of the larynx.
Insertion: Hyoid bone.
Mylohyoid
Function/Action: Aids in swallowing, elevates the tongue, speech
Origin: Mylohyoid line of the mandible.
Insertion: Hyoid bone.
Sternohyoid
Function/Action: Depresses the hyoid bone after it has been elevated (RESETS the hyoid bone after swallowing or speech to prepare for next action).
Origin: Manubrium of the sternum
Insertion: Hyoid bone.
Splenius Capitis
Function/Action: Extends or hyperextends the head; rotates and bends the head to the same side (helps in LOOKING up)
Origin: Spinous process of cervical
vertebrae
Insertion: Mastoid process of occipital bone.
Sternocleidomastoid
Function/Action: Flexes the neck
Origin: Manubrium of the sternum and medial portion of the clavicle.
Insertion: mastoid process of temporal bone
Scalenes
Function/Action: Flexes and rotates the neck.
Origin: Transverse processes of cervical vertebrae (C2-C7).
Insertion: First two ribs.
Levator Scapulae
Function/Action: Elevates the scapula
Origin: Transverse processes of C1-C4.
Insertion: Superior Angle of Scapula
Pectoralis Minor
Function/Action: Protract the scapula, raises the ribs
Origin: Anterior surfaces of ribs 3-5.
Insertion: Coracoid process of the scapula.
Pectoralis Major
Function/Action: Flexes and rotates the humerus
Origin: Clavicle, sternum
Insertion: greater tubercle
Serratus Anterior
Function/Action: Protracts scapula
Origin: ribs 1-9.
Insertion: medial border of the scapula.
Intercostalis (Intercostal Muscles)
Function/Action: External intercostals elevate the ribs during inspiration; internal intercostals depress the ribs during forced expiration.
Origin: Inferior/Lower border of the rib above (for both external and internal intercostals).
Insertion: Superior border of the rib below.
Rectus Abdominis
Function/Action: Flexes the vertebrae.
Origin: Pubic bones
Insertion: Costal Cartilage of inferior ribs
Internal Oblique
Function/Action: Compresses abdominal contents, flexes and rotates the trunk.
Origin: Iliac Crest
Insertion: pubic bone, Inferior/last 3 ribs
Transversus Abdominis
Function/Action: stabilizes the vertebrae and abdomin
Origin: Illiac crest
Insertion: Pubic Bone
External Oblique
Function/Action: Compresses abdominal cavity, aids in trunk rotation and lateral flexion.
Origin: Inferior 8 ribs
Insertion: Illiac crest, pubic bone
Infraspinatus
Function/Action: Rotates the humerus laterally; stabilizes the shoulder joint.
Origin: Infraspinous fossa
Insertion: Greater tubercle of the humerus.
Trapezius
Function/Action: Elevates, retracts, rotates, and stabilizes the scapula; extends the neck.
Origin: Cervical Vertebrae
Insertion: Spine of the scapula
Supraspinatus
Function/Action: Abducts the arm; stabilizes the shoulder joint.
Origin: Supraspinous fossa of the scapula.
Insertion: Greater tubercle of the humerus.
Subscapularis
Function/Action: Medially rotates the humerus.
Origin: Subscapular fossa of the scapula.
Insertion: Lesser tubercle of the humerus.
Teres Major
Function/Action: Extends, adducts, and medially rotates the humerus.
Origin: Posterior inferior scapula
Insertion: Intertubercular sulcus of the humerus.
Rhomboid Major
Function/Action: Retracts the scapula
Origin: Spinous processes of T2-T5.
Insertion: Medial border of the scapula.
Latissimus Dorsi
Function/Action: Extends, adducts, and medially rotates the humerus.
Origin: Inferior Thoracic vertabrae & Lumbar Vertabrae
Insertion: Bicipital groove of the humerus.
Deltoid
Function/Action: Abducts, flexes, and extends the arm.
Origin: Lateral clavicle, and scapula
Insertion: Deltoid tuberosity of the humerus.
Triceps Brachii
Function/Action: Extends the forearm; the long head also aids in adducting the shoulder.
Origin: Posterior shaft of humerus
Insertion: Olecranon process
Biceps Brachii
Function/Action: Flexes the forearm and supinates the forearm.
Origin: Short head - coracoid process of the scapula; long head - supraglenoid tubercle of the scapula.
Insertion: Radial tuberosity
Pronator Teres
Function/Action: Pronates the forearm and assists in flexion of the elbow.
Origin: Medial epicondyle of the humerus and coronoid process of the ulna.
Insertion: Lateral radius
Brachialis
Function/Action: Primary flexor of the forearm.
Origin: Diaphysis of humerus
Insertion: Coronoid process of the ulna.
Supinator
Function/Action: Supinates the forearm.
Origin: Lateral epicondyle of the humerus and proximal ulna.
Insertion: Proximal end of the radius.
Brachioradialis
Function/Action: Flexes the forearm, especially in a mid-pronated position.
Origin: distal humerus
Insertion: Distal radius.
Flexor Carpi Radialis
Function/Action: Flexes wrist and hand
Origin: Medial epicondyle of the humerus.
Insertion: Metacarpals 2 & 3
Flexor Carpi Ulnaris
Function/Action: Flexes and ADDUCTS the wrist/hand.
Origin: Medial epicondyle of the humerus
Insertion: 5th metacarpal
Palmaris Longus
Function/Action: Flexes the wrist and tenses the palm.
Origin: Medial epicondyle of the humerus.
Insertion: Connective tissue in palm of hand
Extensor Carpi Radialis Longus
Function/Action: Extends and abducts the wrist/hand.
Origin: lateral lower diaphysis of humerus
Insertion: Base of the second metacarpal.
Flexor Digitorum Superficialis
Function/Action: flexes digits and hand
Origin: Medial epicondyle of the humerus
Insertion: Middle phalanges of fingers 2-5.
Extensor Carpi Ulnaris
Function/Action: Extends and adducts the wrist.
Origin: Lateral epicondyle of the humerus
Insertion: Base of the fifth metacarpal.
Extensor Digitorum
Function/Action: extends digits and hand
Origin: Lateral epicondyle of the humerus.
Insertion: phalanges 2-5
Piriformis
Function/Action: Laterally rotates and abducts the thigh.
Origin: Anterior surface of the sacrum.
Insertion: Greater trochanter of the femur.
Tensor Fascia Lata
Function/Action: Abducts, flexes, and medially rotates the thigh; tenses the iliotibial band, stabilizing the knee.
Origin: Iliac crest
Insertion: (IT band).
Gluteus Maximus
Function/Action: Extends and laterally rotates the thigh; assists in thigh abduction.
Origin: Dorsal ilium, sacrum, and coccyx.
Insertion: Gluteal tuberosity of the femur and iliotibial tract.
Biceps Femoris (Hamstrings)
Function/Action: Extends the thigh, flexes the knee, and laterally rotates the leg when the knee is flexed.
Origin: distal half of femur
Insertion: Head of the fibula
Semitendinosus
Function/Action: Extends the thigh, flexes the knee, and medially rotates the leg when the knee is flexed.
Origin: Ischial tuberosity.
Insertion: Medial surface of the proximal tibia.
Adductor Longus
Function/Action: Adducts, flexes, and medially rotates the thigh.
Origin: body of pubis
Insertion: Linea aspera of the femur.
Semimembranosus
Function/Action: Extends the thigh, flexes the knee, and medially rotates the leg when the knee is flexed.
Origin: Ischial tuberosity.
Insertion: Medial condyle of the tibia.
Pectineus
Function/Action: Adducts and flexes the thigh; assists in medial rotation.
Origin: Superior ramus of the pubis.
Insertion: posterior femur
Gracilis
Function/Action: Adducts the thigh, flexes, and medially rotates the leg.
Origin: Inferior ramus and body of the pubis.
Insertion: Medial surface of the tibia just below the condyle.
Sartorius
Function/Action: Flexes, abducts, and laterally rotates the thigh; flexes the knee.
Origin: Anterior superior iliac spine.
Insertion: Medial aspect of the proximal tibia.
Rectus Femoris
Function/Action: Extends the knee and flexes the thigh at the hip.
Origin: Anterior inferior iliac spine and superior margin of the acetabulum.
Insertion: Patella and tibial tuberosity via the patellar ligament.
Vastus Intermedius
Function/Action: Extends the knee.
Origin: Anterior and lateral surfaces of the proximal femur shaft.
Insertion: Patella and tibial tuberosity via the patellar ligament.
Fibularis Longus (Peroneus Longus)
Function/Action: Everts and plantarflexes the foot.
Origin: Head and upper lateral fibula.
Insertion: Base of the first metatarsal and medial cuneiform.
Vastus Medialis
Function/Action: Extends the knee.
Origin: Linea aspera, intertrochanteric line, and medial supracondylar line of the femur.
Insertion: Patella and tibial tuberosity via the patellar ligament.
Vastus Lateralis
Function/Action: Extends the knee.
Origin: Greater trochanter, intertrochanteric line, and linea aspera of the femur.
Insertion: Patella and tibial tuberosity via the patellar ligament.
Tibialis Anterior
Function/Action: Dorsiflexes and inverts the foot.
Origin: Lateral condyle and upper shaft of the tibia.
Insertion: First metatarsal and medial cuneiform.
Extensor Digitorum Longus
Function/Action: Extends toes 2-5 and dorsiflexes the foot.
Origin: Lateral condyle of the tibia
Insertion: Phalanges 2-5
Gastrocnemius
Function/Action: Plantarflexes the foot and flexes the knee.
Origin: Lateral and medial condyles of the femur.
Insertion: calcaneous
