ANATOMY CH 11: MUSCLES OF THE BODY

origin

• location where muscle attaches to the immovable bone

insertion

• location where muscle attaches to the movable bone

circular (sphincter)

• fascicle arrangement

• cocentric rings

• surrounds external body openings

  • ex. obicularis oculi

convergent

• fascicle arrangement

• origin is broad

• fascicles go towards tendon of insertion

• triangular or fan shaped

• muscle fibers extend length form origin to insertion

  • ex. pectoralis major

fusiform

• fascicle arrangement

• parallel

• expanded central belly

• muscles extend length from origin to insertion

• wide range of motion, shortens over long distance

  • ex. biceps brachii

straplike

• fascicle arrangement

• parallel

• flat and long

• wide range of motion, shortens over long distance

  • ex. sternocleidomastoid

pennate

• fascicle arrangement

• short fascicles

• attaches obliquely to tendon that runs muscle length

• can be multi (all sides of tendon)

  • ex. deltoid

• can be bi (both sides of tendon)

  • ex. rectus femoris

• can be uni (one side of tendon)

  • ex. extensor digitorum longus

prime mover (agonist)

• muscle with major responsibility for a certain movement

• opposite of antagonist

antagonist

• muscle with an opposite movement or reverses the movement of a prime mover

synergist

• muscle that helps prime mover

• adds extra force

• adds undesirable movement

  • FIXATOR: holds bone firmly in place

flexion

• muscle crosses joint anteriorly

  • ex. pectoralis major

extension

• muscle crosses joint posteriorly

  • ex. latissimus dorsi

abduction

• muscle crosses joint laterally

  • ex. deltoid

adduction

• muscle crosses joint medially

  • ex. teres minor

muscle compartments

• dense fibrous CT divides limb muscles into regions

• same region → similar actions/synergist

• opposing region → agonist/antagonist pair

• each region innervated by a single nerve

arm compartment

• ANTERIOR COMPARTMENT:

  • biceps brachii, brachialis, coracobrachialis

  • flex arm at shoulder or flex forearm at elbow

  • NERVE: musclulocutaneous nerve

• POSTERIOR COMPARTMENT:

  • triceps brachii

  • extend elbow

  • NERVE: radial nerve

forearm compartments

• ANTERIOR COMPARTMENT

  • wrist and digital flexors/pronators

  • NERVE: median or ulnar nerve

• POSTERIOR COMPARTMENT

  • digital and carpal extensors

  • NERVE: radial nerve

thigh compartments

• POSTERIOR COMPARTMENT

  • hamstrings

  • extend hip and flex knee

  • NERVE: tibial branch of sciatic nerve

• ANTERIOR COMPARTMENT

  • vastus muscles (lateral, intermediate, medial), rectus femoris

  • flex hip and extend knee

  • NERVE: femoral nerve

• MEDIAL COMPARTMENT

  • adductors

  • adduction movement

  • NERVE: obturator nerve

leg compartment

• LATERAL COMPARTMENT

  • fibularis muscles

  • eversion and plantar flexion

  • NERVE: superficial fibular nerve

• ANTERIOR COMPARTMENT

  • tibialis anterior, digital extensors, and dorsiflexors

  • dorsiflexion and extension of toes

  • NERVE: deep fibular nerve

• POSTERIOR COMPARTMENT

  • triceps surae

  • digital and plantar flexors

  • NERVE: tibial nerve

location, action, direction, shape, number of origins, origins and insertions, relative size

• how muscles are named

• a LAD SNORing

neck anterior triangle

• submental triangle

• submandibular triangle

• carotid triangle

• mandibular triangle

• hyoids and pharyngeal constrictors

neck posterior triangle

• occipital triangle

• subclavian triangle

Digastric

• O: lower margin of mandible; mastoid process of temporal bone.

• I: hyoid bone via intermediate tendon.

• A: opens mouth and depresses mandible; elevates hyoid and steadies it.

• N: mandibular branch of trigeminal (V), anterior belly; facial nerve (VII), posterior belly.

Stylohyoid

• O: styloid process of temporal bone.

• I: hyoid bone.

• A: elevates and retracts hyoid, elongating floor of mouth during swallowing.

• N: facial nerve (VII).

Mylohyoid

• O: medial surface of mandible.

• I: hyoid bone and median raphe.

• A: elevates hyoid and floor of mouth.

• N: mandibular branch of trigeminal (V).

Geniohyoid

• O: inner surface of mandibular symphysis.

• I: hyoid bone.

• A: elevates and protracts hyoid; shortens floor of mouth.

• N: first cervical spinal nerve via hypoglossal nerve (XII).

Sternohyoid

• O: manubrium and medial end of clavicle.

• I: lower margin of hyoid bone.

• A: depresses larynx and hyoid if mandible is fixed.

• N: C1-C3 via ansa cervicalis.

Sternothyroid

• O: posterior surface of manubrium.

• I: thyroid cartilage.

• A: depresses larynx and hyoid bone.

• N: C1-C3 via ansa cervicalis.

Omohyoid

O: superior surface of scapula. I: hyoid bone, lower border. A: depresses and retracts hyoid bone. N: C1-C3 via ansa cervicalis.

Thyrohyoid

O: thyroid cartilage. I: hyoid bone. A: depresses hyoid or elevates larynx if hyoid is fixed. N: first cervical nerve via hypoglossal.

Pharyngeal constrictors

O: anterior attachments to mandible/medial pterygoid plate, hyoid, and laryngeal cartilages. I: posterior median raphe of pharynx. A: constrict pharynx during swallowing. N: pharyngeal plexus, branches of vagus (X).

Sternocleidomastoid

O: manubrium of sternum and medial clavicle. I: mastoid process and superior nuchal line. A: flexes and laterally rotates head. N: accessory nerve (XI); cervical spinal nerves C2-C3.

Scalenes

O: transverse processes of cervical vertebrae. I: anterolaterally on first two ribs. A: elevate first two ribs; flex and rotate neck. N: cervical spinal nerves.

Splenius

O: ligamentum nuchae and spinous processes C7-T6. I: mastoid process and transverse processes C2-C4. A: extends head; unilateral action rotates/bends head toward same side. N: cervical spinal nerves, dorsal rami.

Iliocostalis

O: iliac crests; inferior ribs 6-8; ribs 3-6 and cervical transverse processes. I: angles of ribs and cervical transverse processes. A: extends/laterally flexes vertebral column; maintains erect posture. N: spinal nerves, dorsal rami.

Longissimus

O: transverse processes of lumbar through cervical vertebrae. I: transverse processes of thoracic/cervical vertebrae and ribs; capitis to mastoid. A: extends/laterally flexes vertebral column; capitis extends and rotates head same side. N: spinal nerves, dorsal rami.

Spinalis

O: spines of upper lumbar and lower thoracic vertebrae. I: spines of upper thoracic and cervical vertebrae. A: extends vertebral column. N: spinal nerves, dorsal rami.

Semispinalis

O: transverse processes C7-T12. I: occipital bone and spinous processes of cervical/thoracic vertebrae. A: extends vertebral column/head and rotates them to opposite side. N: spinal nerves, dorsal rami.

Quadratus lumborum

O: iliac crest and lumbar fascia. I: transverse processes of upper lumbar vertebrae and lower margin of rib 12. A: laterally flexes vertebral column; maintains upright posture; fixes rib 12. N: T12 and upper lumbar spinal nerves.

External intercostals

O: inferior border of rib above. I: superior border of rib below. A: pull ribs toward one another; aid inspiration and forced expiration. N: intercostal nerves.

Internal intercostals

O: superior border of rib below. I: inferior border/costal groove of rib above. A: pull ribs toward one another; aid inspiration or forced expiration depending on location. N: intercostal nerves.

Diaphragm

O: inferior internal rib cage/sternum, costal cartilages of ribs 6-12, lumbar vertebrae. I: central tendon. A: prime mover of inspiration; flattens on contraction. N: phrenic nerves.

External oblique

O: outer surfaces of lower eight ribs. I: linea alba via aponeurosis; pubic crest/tubercle and iliac crest. A: flexes vertebral column and compresses abdominal wall; trunk rotation and lateral flexion. N: intercostal nerves T7-T12.

Internal oblique

O: lumbar fascia, iliac crest, inguinal ligament. I: linea alba, pubic crest, last 3-4 ribs and costal margin. A: flexes vertebral column and compresses abdominal wall; trunk rotation/lateral flexion. N: intercostal T7-T12 and L1.

Transversus abdominis

O: inguinal ligament, lumbar fascia, cartilages of last six ribs, iliac crest. I: linea alba and pubic crest. A: compresses abdominal contents. N: intercostal T7-T12 and L1.

Rectus abdominis

O: pubic crest and symphysis. I: xiphoid process and costal cartilages of ribs 5-7. A: flexes/rotates lumbar region; fixes/depresses ribs; stabilizes pelvis; increases intra-abdominal pressure. N: intercostal T6 or T7-T12.

Levator ani

O: extensive linear origin inside pelvis from pubis to ischial spine. I: coccyx, opposite levator ani, and structures it penetrates. A: supports/maintains pelvic organs; forms sphincters; lifts anal canal. N: S3-S4 and inferior rectal nerve.

Coccygeus

O: spine of ischium. I: sacrum and coccyx. A: supports pelvic organs; supports coccyx and pulls it forward. N: S4-S5.

Deep transverse perineal

O: ischial rami. I: midline perineal body; some fibers into vaginal wall. A: supports pelvic organs; steadies perineal body. N: pudendal nerve.

External urethral sphincter

O: ischiopubic rami. I: midline raphe. A: constricts urethra; allows voluntary inhibition of urination; helps support pelvic organs. N: pudendal nerve.

Ischiocavernosus

O: ischial tuberosities. I: crus of corpus cavernosum of penis or clitoris. A: retards venous drainage and maintains erection. N: pudendal nerve.

Bulbospongiosus

O: perineal body and midline raphe of penis. I: anteriorly into corpus cavernosum of penis or clitoris. A: empties male urethra; assists erection. N: pudendal nerve.

Superficial transverse perineal

O: ischial tuberosity. I: perineal body. A: stabilizes and strengthens perineal body. N: pudendal nerve.

Pectoralis minor

O: anterior surfaces of ribs 3-5 (or 2-4). I: coracoid process of scapula. A: with ribs fixed, protracts and rotates scapula downward; with scapula fixed, draws rib cage superiorly. N: medial and lateral pectoral nerves C6-C8.

Serratus anterior

O: ribs 1-8 (or 9). I: entire anterior surface of vertebral border of scapula. A: rotates scapula upward; protracts and holds scapula against chest wall; assists arm raising. N: long thoracic nerve C5-C7.

Subclavius

O: costal cartilage of rib 1. I: groove on inferior surface of clavicle. A: stabilizes and depresses pectoral girdle. N: nerve to subclavius C5-C6.

Trapezius

O: occipital bone, ligamentum nuchae, spines of C7 and all thoracic vertebrae. I: acromion, spine of scapula, lateral third of clavicle. A: stabilizes, elevates, retracts, and rotates scapula. N: accessory nerve XI; C3-C4.

Levator scapulae

O: transverse processes C1-C4. I: medial border of scapula superior to spine. A: elevates/adducts scapula; rotates it downward. N: cervical spinal nerves and dorsal scapular nerve C3-C5.

Rhomboids

O: spinous processes C7-T1 (minor) and T2-T5 (major). I: medial border of scapula. A: stabilize/retract scapula; rotate scapulae downward. N: dorsal scapular nerve C4-C5.

Pectoralis major

O: sternal end of clavicle, sternum, costal cartilages ribs 1-6/7, external oblique aponeurosis. I: greater tubercle of humerus. A: flexes, adducts, and medially rotates arm. N: lateral and medial pectoral nerves C5-C8, T1.

Deltoid

O: lateral third of clavicle, acromion, spine of scapula. I: deltoid tuberosity of humerus. A: prime mover of arm abduction; anterior fibers flex/medially rotate, posterior fibers extend/laterally rotate. N: axillary nerve C5-C6.

Latissimus dorsi

O: thoracolumbar fascia, lower six thoracic spines, lumbar vertebrae, lower 3-4 ribs, iliac crest. I: floor of intertubercular sulcus of humerus. A: extends, adducts, and medially rotates arm. N: thoracodorsal nerve C6-C8.

Teres major

O: posterior surface of scapula at inferior angle. I: crest of lesser tubercle of humerus. A: extends, medially rotates, and adducts arm. N: lower subscapular nerve C5-C7.

Triceps brachii

O: long head infraglenoid tubercle; lateral/medial heads posterior humerus. I: olecranon of ulna via common tendon. A: powerful forearm extensor. N: radial nerve C6-C8.

Anconeus

O: lateral epicondyle of humerus. I: lateral aspect of olecranon of ulna. A: abducts ulna during pronation; assists elbow extension. N: radial nerve.

Brachioradialis

O: lateral supracondylar ridge of humerus. I: base of styloid process of radius. A: synergist in forearm flexion; stabilizes elbow. N: radial nerve.

Biceps brachii

O: short head coracoid process; long head supraglenoid tubercle/lip. I: radial tuberosity. A: flexes and supinates forearm. N: musculocutaneous nerve C5-C6.

Brachialis

O: anterior surface of distal humerus. I: coronoid process of ulna and elbow joint capsule. A: flexes forearm. N: musculocutaneous nerve.